Neptunium: Radiation Protection Guidelines (N C R P Report)

NCRP REPORT NO. 90

Neptunium: Radiation Protection Guidelines Recommendations of the NATIONAL COUNCIL O N RADIATION PROTEC1-ION AND MEASUREMENTS

Issued February 28, 1988 National Council on Radiation Protection and Measurements 7910 WOODMONT AVENUE/BETHESDA, MD. 20814

LEGAL NOTICE This report was prepared by the National Council on Radiation Protection and Measurements (NCRP). The Council strives to provide accurate, complete and useful information in its reports. However, neither the NCRP, the members of NCRP, other persons contributing to or assisting in the preparation of this report, nor any person acting on the behalf of any of these parties (a) makes any warranty or representation, express or implied, with respect t o the accuracy, completeness or usefulness of the information contained in this report, or that the use of any information, method or process disclosed in this report may not infringe on privately owned rights; or (b) assumes any liability with respect to the use of, or for damages resulting from the use of, any information, method or process disclosed in this report, under the Civil Rights Act of 1964, Section 701 et seg. as amended 42 U.S.C. Section 2000e et seg. (Title VII) or any other statutory or common law theory governing liability.

Library o f Congress Cataloging-in-Publication D a t a National Council on Radiation Protection and Measurements. Neptunium: radiation protection guidelines. (NCRP report, no. 90) Bibliography: p. Includes index. 1. Neptunium-Toxicology. 2. Neptunium-Metabolism. mental aspects. 1. Title. 11. Series. RA1231.N37N38 1987 616.9'897 87-11207 ISBN 0-913392-87-1

3. ,Neptunium-Environ-

Copyright O National Council on Radiation Protection and Measurements 1988 All rights reserved. This publication isprotected by copyright. No part of this publication may be reproduced in any form or by any means, including photocopying, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotation in critical articles or reviews.

Preface The NCRP has considered from time to time specific problems associated with individual radionuclides and devoted entire reports to one radionuclide. Examples of this are NCRP Report No. 44 on 85Kr, Report No. 52 on '37Cs, Report No. 62 on 3H, Report No. 75 on '''I, and Report No. 81 on I4C. The present report reviews the current knowledge of neptunium in areas which are important to radiation protection and makes recommendations on radiation protection guidelines. The report briefly reviews the chemical and physical properties of neptunium, the sources of neptunium in the environment, and potential pathways to man. The limited animal data on health effects are also examined. In addition, animal studies that may serve as a basis for predicting the metabolic behavior of neptunium in humans are considered. On the basis of the information examined, recommendations are made on the fraction of ingested neptunium absorbed from the gastrointestinal tract into blood (fi). Finally, the report applies the available data to recommendations on radiation protection guidelines for neptunium. The units used in this report are those of the Systeme International #Unites (SI) but they are followed by the conventional units in parenthesis in accordance with the procedure set forth in NCRP Report No. 82, SI Units in Radiation Protection and Measurements. After this report was completed but before its publication, the ICRP issued its Publication 48, "The Metabolism of Plutonium and Related Elements", which considers neptunium and arrives at conclusions that are generally similar to those set forth in this NCRP report. The two reports agree on the most significant change, i.e., from a value of to a value of lop3for the fraction absorbed from the gastrointestinal tract. Furthermore, values for ALI and DAC which the ICRP might in the future base on the metabolic parameters recommended in ICRP Publication 48 would not differ significantly from those recommended in this NCRP report. This report was prepared by Task Group 13 (Neptunium) of Scientific Committee 57 on Internal Emitter Standards jointly with Scientific Committee 38 on Waste Management. Serving on the Task Group were: Roy C. Thompson. Chairman Battelle Pacific Northwest Laboratory Richland, Washington iii

iv

/

Preface

Maryka H. Bhattacbaryya Argonne National Laboratory Argonne, Illinois

Norman Cohen New York University New York, New York

Maurice F. Sullivan Battelle Pacific Northwest Laboratory Richland, Washington

Robert P. Larsen New Smyrna Beach, Florida

Patricia W. Durbin, Consultant University of California Berkeley, California

Serving as the Chairman of Scientific Committee 38 on Waste Management was Merril Eisenbud. Serving on Scientific Committee 57 on Internal Emitter Standards were: J. Newel1 Stannard, Chairman University of California at San Diego San Diego, California

John A. Auxier Evaluation Research Corporation Oak Ridge. Tennessee

Roger 0.McClellan Lovelace Biomedical and Environment Research Institute Albuquerque, New Mexico

William J. Bair Batklle Pacific Northwest Laboratory Richland, Washington

Chester E. Richmond Oak Ridge National Laboratory Oak Ridge, Tennessee

Bruce B. Boecker Lovelace Biomedical and Environmental Research Institute Albuquerque, New Mexico

Robert A. Schlenker Argonne National Laboratory Argonne, Illinois

Keith J. Eckerman Oak Ridge National Laboratory Oak Ridge, Tennessee

Roy C. Thompson Battelle Pacific Northwest Laboratory

Richland, Washington

NCRP Secretarid-E. Ivan White

The Council wishes to express its gratitude to the members of the Task Group and Scientific Committee for the time and effort devoted to the preparation of this report. Especial thanks are due to Keith Eckerman, Oak Ridge National Laboratory and the dosimetry group at the Laboratory for their calculation of the Annual Limits on Intake and the Derived Air Concentrations given in this report. Warren K. Sinclair President, NCRP Bethesda, Maryland Nou. 20, 1987

Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Chemical and Physical Properties of Neptunium . . . . . 2.1 Oxidation-Fteduction Equilibria . . . . . . . . . . . . . . . . . . . . 2.2 Neptunium (111) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Neptunium (IV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Neptunium (V) and Neptunium (VI) . . . . . . . . . . . . . . . . . 2.5 Biological Inferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Neptunium in the Environment . . . . . . . . . . . . . . . . . . . . . 3.1 Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Pathways to Man . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Metabolism of Neptunium in Mammals . . . . . . . . . . . . . . 4.1 Ingestion (Gastrointestinal Absorption . . . . . . . . . . . . . . . 4.2 Inhalation (Pulmonary Retention and Absorption . . . . . . 4.3 Systemic Distribution. Retention. and Excretion . . . . . . . 5 Health Effects of Neptunium . . . . . . . . . . . . . . . . . . . . . . . . 6 Radiation Protection Guidelines . . . . . . . . . . . . . . . . . . . . 6.1History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix A Supplemental Dosimetric Information . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The NCRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NCRP Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.

. . .

1. Introduction Neptunium, element number 93, is less well understood than some other transuranic elements such as plutonium and americium. It has become of particular recent interest, however, because of the presence in nuclear waste of its long-lived isotope 237Np(half-life, 2.14 x lo6 y), and because of its presumed environmental mobility. This report summarizes present knowledge of neptunium in areas pertinent to the establishment of radiation protection guidelines. Following the Introduction, the second section of the report briefly reviews the chemical and physical properties of neptunium, particularly as these relate to its biological behavior. The third section briefly describes sources of neptunium in the environment, and potential pathways to people. The fourth section reviews the results of animal studies that may serve as a basis for predicting the metabolic behavior of neptunium in humans. The fifth section reviews the limited animal data on health effects. The final section applies these data to the development of radiation protection guidelines for neptunium. This report includes numerous citations of the more recent neptunium literature most pertinent to radiation protection considerations, but does not purport to be an exhaustive review of the subject. A recent review, by R. C. Thompson (1982),has been drawn upon heavily in the preparation of this report and should be consulted for references to the older literature.

2.

Chemical and Physical Properties of Neptunium

Neptunium is the element of atomic number 93, just beyond uranium in the periodic table. Some pertinent nuclear properties of the isotopes of neptunium are presented in Table 2.1. Because of its presence in nuclear waste and its very long half-life, 237Np is the isotope of principal concern from the point of view of radiological protection. Neptunium-237 decays (2.14 x 106y)by alpha emission (=: 4.6 MeV) and soft gamma emission (up to 0.3 MeV) to 233Pa. The chemistry of neptunium is briefly reviewed here, only as a background for radiological protection considerations. For a more detailed coverage of neptunium chemistry see Keller (1971), Bailar et al. (1973), or Burney and Harbour (1974). In the discussion which follows, the chemical behavior of neptunium will be compared with that of the better understood, and somewhat similar actinides, uranium and plutonium. While the chemistry of these elements is critical to the understanding of their overall environmental and metabolic behavior, it must also be recalled that the risk from human inhalation of their very insoluble refractory oxides (probably the predominant form of occupational exposure) will be largely determined by the physical characteristics of the aerosols inhaled. 2.1 Oxidation-Reduction Equilibria

Neptunium is a multivalent element, which, like its adjacent actinides, uranium and plutonium, may exist in one or more of four oxidation states: 111, IV, V, and VI. The particular significance of oxidation state becomes apparent when one considers the wide variation in oxidizing and reducing conditions that exist within a mammal, on both macroscopic and microscopic scales. Oxidizing conditions exist in the lungs while reducing conditions exist in the small intestine; arterial blood is more oxidizing than venous blood; and extracellular fluids are more oxidizing than intracellular fluids. The most oxidizing situation is probably that in the lungs, where neptunium might be expected to exist in the V state; the most reducing situation is probably

2.1

OXIDATION-REDUCTION EQUILIBRIA

/

3

TABLE2.1-Pertinent nuclear characteristics of neptunium isotopesn Mass Number

Half-Life

,

232 233 234 235 236 236 237 238 239 240111 240

14.7 m 36.2 m 4.4 d 396.1 d 22.5 h 1.15 x lOby 2.14 X 106y 2.117 d 2.355 d 7.4 rn

65 m

Principal Decav Mode

EC EC EC EC EC flEC fla

808/

3

!

"From ICRP (1983).

that in the small intestine, where neptunium might be expected to exist in the IV state. Neptunium absorbed to the blood from these two sources may thus differ chemically, and if oxidation or reduction does not occur rapidly, the distribution and retention pattern of neptunium from one source might not be the same as that from the other. Unfortunately, it is difficult to predict the oxidation state(s) existing in a biological system for elements such as neptunium, uranium and plutonium, because of the extensive opportunities for thermodynamically allowed complexation reactions of the various valence states and the unknown kinetics of transformation of the species potentially involved. Some characteristics of neptunium oxidation states of potential interest in biological systems are considered below. 2.2

Neptunium (111)

Neptunium, uranium, and plutonium in the 111state exhibit strongly cationic properties. Each can be precipitated from solution as the hydroxide, fluoride, carbonate, or oxalate; each can be maintained in neutral solution by an excess of a dicarboxylic acid such as citrate; and each forms a very strong complex with chelating agents such as ethylenediaminetetraacetic acid (EDTA), or diethylenetriaminepentaacetic acid (DTPA). In acid solution, e.g., 1 M hydrochloric acid, U(II1) is oxidized to U(1V) by hydrogen ions, Np(II1) to Np(1V) by a mild oxidant such as iron (111), while a comparatively strong oxidant such as elemental bromine is required to oxidize Pu(II1) to Pu(1V). In neutral media the redox potentials of the 111-IV couples are highly positive because complexing by hydroxyl ions is much stronger for the IV state than for the I11 state; and the 111 state of each element is converted to the IV state by reaction with water, producing hydrogen.

4

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2.

CHEMICAL AND PHYSICAL PROPERTIES OF NEPTUNIUM

It is difficult to conceive of Np(III) playing a significant role in biologic systems.

2.3 Neptunium (IV) In the IV state neptunium, like uranium and plutonium, may exhibit either cationic or anionic characteristics, the latter becoming dominant when ligands with which it strongly interacts are present. In media containing sulfate, fluoride, carbonate, dicarboxylates or chelates, the stability of the complex formed with the IV state is much higher than that formed with either the I11 or V state. A particularly important reaction of the IV state is that involving hydroxyl ions, the so-called hydrolytic reactions that lead to the formation of hydrous oxide polymers. The probability of these reactions occurring increases with: (1) decreasing acidity, (2) increasing concentration of actinide, (3) decreasing concentrations of strongly complexing ligands, (4) increasing temperature, and (5) the length of time that the preceding conditions exist.

2.4

Neptunium (V) and Neptunium (VI)

The chemical properties of neptunium, uranium, and plutonium in the V and VI states differ markedly from those of the I11 and IV states. The higher states react only moderately with ligands to form complexes (those formed with the VI state being more stable than those formed with the V state), and neither the V nor VI state is prone to hydrolytic reactions. As a consequence, stable solutions of the V and VI states, with appreciable actinide concentration, can be prepared in media containing a ligand such as bicarbonate. In acid solution the chemical behavior of neptunium differs from that of uranium and plutonium, in that the V state is stable; the redox potential for the neptunium IV-V couple being lower than that for the V-VI couple. The IV and V states of neptunium are thus the oxidation states of interest in biologic systems. The oxidation of Np(1V) to Np(V) and the reduction of Np(V) to Np(1V) in inorganic media are relatively slow reactions, the chemical explanation being that one involves the formation and the other the breaking of covalent bonds. The biologically relevant questions are: How slow are these reactions in biological systems? Will ingested Np(V) be reduced to Np(1V) in the intestine before absorption can occur? Will inhaled Np(1V) be oxidized in the

2.4 NEPTUNIUM (V) AND NEPTUNIUM (VI)

/

5

lung to Np(V)? Will Np(IV), if absorbed in that state, persist in the blood and be distributed differently than Np(V)? 2.5 Biological Inferences

Experimental evidence relative to the thermodynamically stable state(s) of neptunium in natural media is meager. Pentreath and Harvey (1981) have shown that neptunium discharged to the Irish Sea from Windscale is not adsorbed on sea-bed sediments. Since it is known that tetravalent actinides such as Th(1V) and Pu(1V) adsorb strongly to such sediments, it may be inferred that neptunium in sea water is in the V state. The oxidation state of neptunium incorporated in laboratory animals can be inferred to be Np(V), since DTPA therapy is not significantly effective in its removal (Smith, 1972; Morin, et al., 1973). The increased gastrointestinal absorption of neptunium when fed with an oxidizing agent suggests that it is normally reduced in the intestine to Np(IV), except when fed in large mass quantities or when fed following a fast, in which case the intestinal reductants are probably ineffective (Sullivan, 1984a). The increased deposition in liver when relatively massive quantities of neptunium are intravenously injected, suggests that polymerized products of Np(1V) may persist in the blood under these conditions (Thompson, 1982). The much lower deposition in liver under other circumstances might support the assumption that Np(V) is the normal biological form of this element in the blood. The above observations form a reasonably consistent, albeit somewhat limited and certainly speculative picture of neptunium chemistry in biologic systems. The ability of neptunium to exist in either the IV or V state under biologic conditions, and the markedly different chemical behavior of these two states, may, when properly understood, explain many of the anornolous biological observations that have been reported for neptunium.

3. Neptunium in the Environment Neptunium isotopes have not presented unusual problems in occupational radiation protection, nor have they, until recently, been of special environmental concern. Particular attention has recently been directed to the potential of environmental exposure to the long-lived 237Np,which is estimated to be the principal surviving component of high level nuclear waste after ten or twenty thousand years (Cohen, 1982). In this section the potential sources of neptunium isotopes in the environment, and the pathways by which these isotopes might reach man are briefly considered. Such information, while not essential to the derivation of radiation protection guidelines, is necessary for their proper application. Thompson (1982) provides additional information in this area, with references to the early literature. This is, however, an expanding area of much current activity.

3.1 Sources The P-emitting, 2.4-day half-life 239Npis an intermediate product in the production of plutonium. It results from the absorption of a neutron in uranium according to the following reaction.

As such, it was a prominent component of the early fallout from the atmospheric detonation of nuclear devices. It may also be present in the waste streams from nuclear power plants where it is produced according to reaction (1)either within the uranium fuel from which it may leak, or from neutron irradiation of traces of uranium on the fuel cladding or in the reactor cooling water. Although 239Npmay contribute significantly to the radiation dose from early fallout following a nuclear detonation (Perkins and Thomas, 1980), its short half-life precludes any lingering environmental contamination. The neptunium isotope of primary interest is 2"Np. It has a half-

3.1

SOURCES

/

7

life of 2.14 x lo6 years and is produced in nuclear reactors by several neutron-capture nuclear-decay routes.

Z U (n, 2n) 2:iU &'17N 6.7 d

'ZU (n, y ) ,3' ,9U

93

0- 'ZNp + 0+ 24 m 2.4 d

Reactions (2) and (3) are the primary ones involved in the production of '"Np in the fuel from plutonium production reactors; reaction (4) is the primary source of 237Npin the spent fuel from light water and fast breeder reactors, and hence in the wastes generated when these fuels are processed. Due to its formation from the decay of 241Am,the amount of 237Npin these fuels at the time of removal from a reactor is a factor of about 10 lower than it is 1000 years later (Croff et al., 1982). Neptunium-237 has been purposefully separated from the other constituents of spent fuel and irradiated with neutrons to produce ='Pu (Schultz and Benedict, 1972).

The '"Pu so produced is employed as the heat source in the thermoelectric devices that have been used as power sources in space vehicles and in carhac pacemakers. ~h~ 2 3 7 ~ ~ / 2 3 9 + 2 4Pu 0 activity ratio in fallout, as measured in lichens from Sweden, is 2.7 x 10-"Holm, 1981); similar results have been obtained from measurements in soil (Efurd et al., 1984). It is conceivable that "'Np could be accidentally dispersed from a production facility, but the greater concern is associated with its disposal in high-level nuclear waste repositories, and its possible subsequent release and environmental dispersal over future periods of hundreds-of-thousands of years. Based on some recent assumptions

8

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3. NEPTUNIUM IN T H E ENVIRONMENT

as to its biological behavior (ICRP, 1980a), it has been estimated that 237Npmay be the most hazardous remaining constituent of high-level nuclear waste during the interval from about 10,000 years to 30,000,000 years following disposal (Cohen, 1982). 3.2 Pathways to Man Environmental 237Npbecomes a significant hazard only to the extent that it is ingested, inhaled, or otherwise assimilated by man. The environmental pathways by which such assimilation can occur seem generally more permeable to neptunium than to other actinides (Thompson, 1982). In mineral soils, the extractability of neptunium is markedly greater than that of plutonium, americium, or curium in the p H range below 6, while in calcareous soils a second extraction maximum is observed at a pH of 10 (Nishita et al., 1981). Values of the distribution coefficient, Kd [concentration on solid phase (g/g) divided by concentration in liquid phase (g/ml)], for these soil systems ranged from 3 to 900. Extractability and Kd appear to be influenced by soil organic matter and the hydrous oxides of aluminum, iron, and manganese. These data indicate either a persistence of Np(V) in surface soils, or relatively easy oxidation of Np(1V). However, studies by Bondietti and Frances (1979), using suspensions of igneous rock maintained under anaerobic conditions such as might be expected to exist under waste disposal circumstances, demonstrated the rapid reduction of Np(V) to Np(IV), with the latter being strongly sorbed. The prediction of long-term movement of neptunium through geological media is, therefore, somewhat uncertain. The movement of neptunium from soil to plants occurs more freely than does the movement of other actinides. Plant availability of neptunium in soils, CR (concentration per unit dry weight of vegetation divided by concentration per unit dry weight of soil), has been reported to range from to 1 at relatively high soil concentrations of W7Np(Romney et al., 1981; Schreckhise and Cline, 1981; Watters, et al., 1980). More recent studies using 235Np,to permit evaluation of neptunium availability at environmental concentrations, showed CR values ranging from 0.5 to 4 for foliage of forage and seed crops, with seed values lower than leaves by a factor of ten (Cataldo et al., 1987). In the studies of Schreckhise and Cline (1982), five years of weathering in field lysimeters had little effect on the uptake of neptunium by plants (Cline, private communication). Limited data for marine environments indicate that neptunium

3.2 PATHWAYS TO MAN

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9

behaves somewhat similarly to other actinides. At the very low concentrations in which it is present, it exists primarily in the (V)state in filtered waters (Pentreath et al., 1985; Fowler and Aston, 1982). Concentration factors due to uptake/adsorption from water to alga are from 8 to 56, a factor of about 100 less than for other actinides. Concentration factors for lobster tail and claw muscle, of 0.02 to 0.3 vary with season and are comparable to data for plutonium. Reliable data are not available for freshwater systems. Limited animal food chain data show little evidence for enhanced transport of neptunium as compared to other actinides. Transfer to milk by sheep, goats, and rats is generally lower for neptunium than for plutonium, americium, or curium (Thompson, 1982). While these data on environmental availability of neptunium are not essential to the derivation of intake limits, they are essential to the proper application of such limits in terms of derived, environmentally measurable, action levels. This kind of information is largely lacking in the case of neptunium and is of particular importance because neptunium does not seem to fit the environmental behavior pattern of other actinides.

4. Metabolism of Neptunium in Mammals The only measurements of 237Npin humans are those on liver and lung samples from 3 autopsies, which indicated Np/Pu ratios in both organs that are 0.01 to 0.06 times the Np/Pu ratios in weapons-test fallout (Efurd et al, 1984, and personal communication). This observation suggests that neptunium is discriminated against, relative to plutonium, but provides no clue as to where or how this discrimination may occur. In the absence of any substantial human data, our understanding of neptunium behavior in humans must be inferred from information on other actinides, modified by the results from comparative studies with neptunium and other actinides in laboratory animals. For purposes of radiation protection, one is primarily concerned with defining those human metabolic parameters required for dosimetric modeling. Such parameters include the fraction of ingested neptunium that is absorbed from the gastrointestinal tract; the fraction and rate of absorption of inhaled neptunium from the respiratory tract; and the distribution and retention of neptunium in body organs. The more pertinent data bearing on these concerns will be considered in this section.

4.1 Ingestion (Gastrointestinal Absorption) The fraction of ingested neptunium absorbed from the gastrointestinal tract into blood (fl) is currently assumed to be 0.01 by the International Commission on Radiological Protection (ICRP, 1980a). This fraction had previously been set a t 0.0001 by both the ICRP (1960) and NCRP (1959) and the change in 1980 by a factor of 100 was primarily responsible for the current renewed interest in potential health risks from neptunium. Data that formed the basis for the 1980 ICRP fl value of 0.01 are summarized in Table 4.1. The Hamilton (1947) data, derived from only 3 animals, was the basis of the earlier ICRP/NCRP fi value of 0.0001. 10

TABLE 4.1-Pre-1981 Isotope

Species (no.)

Dose' (mg/kg)


data on the gastrointestinal absorption of neptunium by adult animals

Form Administered

Oxidation State

Fed or Fasted

Time of Sacrifice

Fraction Fraction lLetained ( ~ 1 0 ~ ) Absorbedb (X102)

Reference

chloride

N.A.'

N.A.

N.A.

N.A.

c0.05

N.A.

N.A.

24 h

0.8

0.9

Ballou et d.,1962

20 20

"industrial dust" citrate, pH 4 nitrate, pH 1.5 citrate, pH 4 citrate, pH 4 citrate, pH 4

N.A. N.A. VId Vd IVd

N.A. N.A. N.A. N.A. N.A.

24 h 24 h 24 h 24 h 24 h

0.26 0.12 2.3 1.1 0.3

N.A. N.A. N.A. N.A. N.A.

Ballou et al., 1962 Ballou et d.,1962 Ballou et al., 1962 Ballou et al., 1962 Ballou et d.,1962

237Np Rat (5)

40

nitrate, pH 1.5

Fed

24 h

0.24

N.A.

9.

'"Np

Rat (6)

40

nitrate, pH 1.5

VI (86%) V (14%) V (100%)

Fed

24 h

0.18

N.A.

10.

"Np

Rat (5)

40

nitrate, pH 1.5

Mahlum et d., 1963 Mahlum et al., 1963 Mahlum ei al., 1963

11.

239Np

Rat (5)

lo-'

nitrate, pH 1.5

12.

234Np Goat (2)

lo-'

citrate

13.

Z37Np Rat (14)

34

nitrate, pH 1.5

14.

237Np Rat (6)

<1

biologically incorporated in neonatal rats

1.

2S9Np Rat (3)

2.

n7Np

3. 4. 5. 6. 7.

*"Np Rat (6-9) Rat (6-9) mNp 2"Np Rat (6) 237Np Rat (6) 237Np Rat (6)

8.

Rat (6)

0.3 60 60 20

Hamilton, 1947

VI (99%) V (57%) I V (34%) N.A.

Fed

24 h

0.03

N.A.

Fed

24 h

0.05

N.A.

N.A.

Fed

5d

0.04

0.5

Mullen et al., 1977

V (99.3%)

Fed

7d

0.73

1.2

Sullivan, 1980a

N.A.

Fed

7d

0.03

N.A.

Sullivan, 1981

' Calculated where not given, assuming a body weight of 250 g for rats and 50 kg for goats. "Absorbed" is sum of "Retained" plus that excreted in urine. N.A. = information not available. Attributed oxidation state is questionable.

Mahlum et al., 1963

-

a I-

9 3 52

3m 4

5

t'

m

V,

0

9

S

z

\

+ CI

12

/

4.

METABOLISM OF NEPTUNIUM IN MAMMALS

The data of Table 4.1 exhibit a nearly 100-fold range of retention values following gastrointestinal absorption. The ICRP choice of 0.01 was based primarily on the data of Sullivan (1980a), from an experiment that involved a relatively large group of rats, used a wellcharacterized chemical form of neptunium, and reported urinary excretion as well as systemic retention. The data of Table 4.1 suggest, however, that absorption may be lower when a lower mass of neptunium is fed; and the ICRP qualified its choice of the fi value with the words, "However, the fractional absorption of trace quantities of the element may be a factor of ten lower as may be the fractional absorption of neptunium incorporated in food" (ICRP, 1980a). Since the publication of the ICRP fi value of 0.01, many additional experiments on neptunium absorption have been reported. These new data, as determined in adult animals, are summarized in Table 4.2. A wide range off, values is still apparent, but a clear pattern has emerged. High absorption values, of the order of lop2or more, are observed only when the mass fed exceeds 1 mg/kg, or when animals are previously fasted; in the absence of fasting, and when the mass fed is less than 1 mg/kg, absorption is of the order of lop3or less. An explanation for the effect of both neptunium mass and fasting on neptunium absorption has been proposed, based on neptunium oxidation-reduction equilibria in the gastrointestinal tract (Sullivan e t al., 1984a). Data bearing on this point are shown in Table 4.3. Presence of the oxidizing agents quinhydrone, ferric iron, or chlorine enhanced "low-mass" neptunium absorption to levels as high as, or higher than those normally observed only with "high-mass" quantities of neptunium or in fasted animals. Presence of a reducing agent (ferrous iron) reduced the enhanced absorption caused by fasting. It is postulated that the oxidizing agents maintain neptunium in a more readily absorbed (V) oxidation state, which is normally reduced within the intestinal tract to the less well absorbed (IV) state; such reduction is incomplete when neptunium is present a t high mass levels, or when the reducing action of the intestinal contents is minimized by fasting. Other explanations of these data may be possible, but the general observation of decreased absorption under conditions of a smaller ingested mass of neptunium seems clearly established. If we consider the data from Table 4.2 relating only to animals fed normal diets prior to administration of relatively low neptunium mass levels (
TABLE 4.2-Post-1981 data on the gastrointestinal absorption of neptunium by adult a n i d Isotope

Species (no.)

Dose' (mg/kg)

Form Administered

Oxidation

Stateb

Fed or Fasted

Time of Fraction Sacrifice Retained

Fraction

(xlaz)

(~101)

1. 217Np

Rat (6)

43

nitrate, pH 1.5

V

Fed

7d

1.7

2.7

2. *7Np

Rat (6)

24

nitrate, pH 1.5

V

Fed

7d

1.0

1.7

3. =?Np

Rat(6)

22

nitrate, pH 1.5

V

Fed

7d

1.0

1.5

4. n7Np

Rat (6)

10

nitrate, pH 1.5

V

Fed

7d

0.1

0.2

5. *'Np

Rat (6)

5

nitrate, pH 1.5

V

Fed

7d

0.05

0.1

6. 2"Np

Rat (4)

1 x lo-'

nitrate, pH 1.5

V

Fed

7d

0.03

0.06

7. mNp

Rat (10)

2 x lo-? nitrate. pH 2.0

V

Fed

3d

0.04

0.05

8. W7Np

Rat (8)

nitrate, pH 1.5

V

Fed

7d

0.07

0.11

9. U7Np

f i t (25)

nitrate, pH 1.5

V

24 h Fast

7d

0.42

0.65

5 5

10. =Np

Mouse (8)

6 X lom5 nitrate, pH 1.5

V

Fed

7d

0.04

0.06

11. =Np

Mouse (8)

2X

nitrate, pH 1.5

V

24 h Fast

7d

1.0

1.3

nitrate, pH 1.5 citrate, pH 4 nitrate, pH 1.5 citrate, pH 4 citrate, pH 4 citrate, pH 4 citrate. pH 4 citrate, pH 4

V

Fed Fed Fed Fed Fed Fed Fed Fed

7d 7d 7d 7d 7d 7d 7d 7d

0.19 0.19 0.19 0.17 0.17 0.06 0.08 0.04

0.27 0.29 0.28 0.25 0.30 0.12 N.A. NA.

12. 13. 14. 15. 16. 17. 18. 19.

=?Np 237Np *'Np 2J7Np m7Np *?Np 237Np *?Np

Rat (6) Rat (6) Rat (6) Rat (6) Rat (6) Ftat (6) Rat (6) Rat (6)

15 15 15 15 53 26 11

6

V VI

VI V V V V

Reference

Sullivan et d., 1983a Sullivan et aL, 1983a Sullivan et al., 1983a Sullivan et al., 19838 Sullivan et al., 1983a Sullivan et al., 1983a Sullivan et d., 1983a Sullivan et al., 1984a Sullivan et al., 1984a Sullivan et d , 1984a Sullivan et al., 1984a Sullivan et al., 1985 Sullivan et al., 1985 Sullivan et d.,1985 Sullivan et d,1985 Sullivan et d, 1985 Sullivan et al., 1985 Sullivanet d, 1985 Sullivan et aL, 1985

I-. P

cl

5 z

8rn

2 z

i?

*

0

5

2 1

+

Isotope 20. 237Np

'pecies

(no.)

Dose' (mg/kg)

Form Administered

Oxidation

Fed or

Stateb

Fasted

Time Fraction Fraction Sacrifice Itetained (~102) (x~OZ)

Hamster (12)

5

nitrate, p H 1

V

Fed

14 d

0.025

0.052

Hamster (6)

5

citrate (2%)

V

Fed

14 d

0.030

0.062

I

21. 237Np 22. 237Np

34. "'Np

Rat (5)

nitrate, pH 1 citrate (2%) 20 nitrate, pH 1 5x nitrate, pH 1 2 x lo4 nitrate, pH 1 5x nitrate, pH 1 5 x 10- bicarbonate, pH 6.5 2 x lod bicarbonate, p H 6.5 5 x lo-' bicarbonate, pH 6.5 2 x 104 citrate, pH 6.5 phytate, pH 6.5 2x 8x biologically incorporated in liver bicarbonate, pH 6.5 2x

35. 2sNp

Mouse (10)

6 x lod

36. n9Np

Mouse (10)

5x

23. '"Np

24. 25. 26. 27. 28. 29. 30. 31. 32. 33.

237Np '"Np *'Np 239Np -Np '=Np "'Np 2mNp W9Np 239Np

Rat (6) Rat (6) Hamster (5) Hamster (6) Rat (5) Rabbit (5) Hamster (6) Rat (5) Rabbit (5) Rat(5) Rat (5) Rat (6)

37. 237,239NpRat (18) 38. n7;B9Np Rat (18) 39. U7s239NpRat (20) 40. 2 3 7 , 2 3 9p~ Rat (12) 41. 297;239~p Baboon (2)

2

2x

lo4

2.1 2x 3x 4 x 10-' 0.6

0.01 M HC03 1ppm C12 pH 8.2 0.01 M HCO31ppm C12 DH8.2 nitrate nitrate nitrate nitrate nitrate

V

Fed

V

Fed Fed Fed Fed Fed Fed Fed Fed Fed Fed Fed

V V V V V V V V V

N.A. V

8 h Fast

Fbference Harrison & Stather, 1981 Harrison & Stather, 1981

7d 7d 14 d 7d 7d 7d 7d 7d 7d 7d 7d 7d

0.16 0.09 0.02 0.01 0.02 N.A. 0.01 0.11 N.A. 0.10 0.03 0.01

0.26 0.12 0.04 0.02 0.03 0.18 0.02 0.15 0.12 0.14 0.04 0.01

Harrison et aL, 1984 Harrison et al., 1984 Harrison et al.. 1984 Harrison et al., 1984 Harrison et d.,1984 Harrison et al., 1984 Hamson et al., 1984 Harrison et al., 1984 Harrison et al.. 1984 Harrison et al., 1984 Harrison et d.,1984 Harrison et al., 1984

7d

0.18

0.25

Harrison et al., 1984

VI

Fed

3d

0.011

0.027

Larsen et al., 1982a

VI

24 h Fast

3d

0.28

0.35

Larsen et al., 1982a

0.70 0.15 0.13 0.12 0.5

0.98 0.28 0.15 0.17 1.2

Metivier et al., 1983 Metivier et al., 1983 Metivier et al., 1983 Metivier et al., 1983 Metivier et al., 1983

\

g

3

3

m

3 z C Z

3 g K E

p

> s

V

d

5d

V

d

5d

V V

d

V

d

5d 5d 4d

d

tj

V V

d

d

4d 4d

0.04 0.014

0.10 0.048

Metivier et al..1983 Metivier et al., 1984

V

d

4d

0.006

0.062

Metivier et al., 1984

V

d

4d

0.035

0.70

Metivier et al., 1984

46. 237*239N~ Baboon (2)

10-"itrate nitrate (high cereal, low vitamin diet) 8x nitrate (high milk, low cereal diet) 5x nitrate (high fruit, no cereal diet) 9 x lo-' nitrate (wtato diet)

V

d

4d

0.20

0.32

Metivier et al., 1984

47. 237Np

Baboon (1)

2x

0.01 M HC031 ppm CIR pH 8.3

VI

Uncertain Fast

32 d

0.18

0.33

48. w p

Baboon (1)

5 x 10"

0.01 M HC031 ppm C12,pH 8.3

VI

24 h Fast

1d

0.52

0.89

49. mNp

Baboon (3)

3 x 10-",01

M HC031 ppm CI*, pH 8.3

VI

24 h Fast

e

0.60'

1.V

50. =Np

Baboon (1)

2 x lo-'

0.01 M HC031 ppm CI2,pH 8.3

VI

14 h Fast

e

0.31'

0.51'

51. 239Np

Baboon (1)

8 x lo-' 0.01 M HC031 ppm Clz, pH 8.3

VI

Fed

e

0.05'

0.09'

Cohen and Ralston, 1983 and unpublished Cohen and Ralston, 1983 and unpublished Cohen and Ralston, 1983 and unpublished Cohen and Ralston, 1983 and unpublished Cohen and Ralston, 1983 and unpublished

42. m,u9Np Baboon (2) 43. p71asNp Baboon (2) 44.

W7,mNp Baboon (2)

45. ",u9Np

Baboon (2)

2x

"Calculated where not given, assuming a body weight of 2000 g for rabbits, 250 g for rats, 100 g for hamsters, and 25 g for mice. Refers to the oxidation state of the neptunium employed in preparing the gavage solution. This oxidation state may have changed prior to, or subsequent to gavaging the animal, e.g., higher oxidation states of neptunium are not stable in the presence of such agents as citrate, which complex Np (IV). '"Absorbed" is sum of "Retained" plus that excreted in urine (Harrison et al. estimate the fraction excreted in urine, based on separate intravenous injection experiments). Last feeding 1.5hours prior to gavage under anesthesia. 'Animals are not sacrificed. Estimate of fraction absorbed based on comparison of 24 h urinary excretion of neptunium following intravenous and oral administration. Estimate of Fraction Retained is difference between Fraction Absorbed and fraction excreted in urine in 24 h.

TABLE 4.3-Influence of fasting, oxidizing, and reducing agents on the gastrointestinal absorption of neptunium by adult rats and mice' Isotope

1. 2. 3.

4. 5. 6. 7. 8. 9. 10. 11. 12.

13.

"'Np 23?N~ "Np n7Np m N ~ 2a7Np ='Np %Np 235Np =Np "5Np %Np %Np

Species (no.)

Rat (8) Rat (25) Rat (4) Elat (4) Rat (4) Rat (4) Rat (14) Mouse (8) Mouse (8) Mouse (8) Mouse (8) Mouse (8) Mouse (5)

Dose (rng/kg)

5 5 5 5 5 5 5 6x 2 x 10-I 2 x lo-& 2 x lo-5 2x

2 x LO-=

Data from Sullivan, 1984a. htention measured at 7 days post gavage. '"Absorbed" is sum o f "retainedn plus that excreted in urine.

Fed or Fasted

Fed 24 h Fast Fed 24 h Fast Fed 24 h Fast 24 h Fast Fed 24 h Fast 24 h Fast 24 h Fast 24 h Fast 24 h Fast

Oxidizing or Reducing

Agent

None None 350 mg/kg quinhydrone 350 mg/kg quinhydrone 300 mg/kg Fe+++ 300 mg/kg Fe+* 150 mgkg Fe* None None 90 mgkg Fe+++ 130 mg/kg Few+ 100 ppm C1, 130 mg/kg Fe++

Fraction Retainedb

Fraction AbsorW

(XI@)

(~107

0.07 0.42 0.76 1.7 5.5

0.11 0.65 1.1 2.7 7.1 8.0 0.07 0.06 1.3 2.4 6.9

6.5

0.02 0.04 1.0 1.8 6.0 1.9 0.15

2.1

0.4

%

6 t-

E 0

r

3 23 c 2

2 2

g 5

5:

t:

4.1

GASTROINTESTINAL ABSORPTION

/

17

values of 0.0012 and 0.0018. Among seven experiments in which neptunium nitrate was fed to rats, four gave fl values from 0.0003 to 0.0006; the other three, in which the neptunium was administered under anesthesia after a short fast, gave f, values from 0.0017 to 0.0028. Four other experiments in which rats were administered various complexed forms of neptunium led to fl values ranging from 0.0001 to 0.0015. Baboons showed enhanced absorption a t fed masslevels as low as 0.6 mg/kg; at lower mass levels, and when fed normal diets, results from two laboratories indicated fl values of 0.001 or less. Of five pairs of baboons on various diets, only two, on fruit or potato diets, showed fl values higher than 0.001; the highest fi value of 0.007, on the fruit diet, was associated with a very much lower retention value. Taken together, these data might suggest an fl value for adult human populations of 0.001. The United Kingdom's National Radiological Protection Board has recently recommended an fi value of 0.001, both for workers, and for members of the public older than one year of age (NRPB, 1984). The choice of such a value would need to be qualified, however, on several grounds as discussed below.' Effect of Chemical Form: The animal data on gastrointestinal absorption of neptunium were obtained in experiments employing neptunium in various, sometimes ill-defined oxidation states, and in various compound forms (Tables 4.1 and 4.2). Two studies with 237Np in biologically incorporated form seemed to show no enhanced absorption. More extensive studies would be required, however, to establish the range of fraction absorbed for neptunium incorporated into foods. For the establishment of limits for workers, it would also be desirable to have data on industrially relevant compounds of neptunium other than the nitrate, including those that might first be inhaled and subsequently cleared from the respiratory tract and swallowed. Effect of Feeding Regimen:Data from studies conducted in mice or 'After this report was completed but before its publication, the ICRP issued ita Rrblication No. 48. T h e Metabolism of Plutonium and Related Elements", which considera neptunium and amves a t conclusions that are generally similar to those set forth in this NCRP report. The two reports agree on the most significant change, i.e. h m a value of lo-' to a value of lo-' for the fraction absorbed from the gastrointestinal tract. The ICRP report recommends fractions of 0.76,0.15, and 0.10 for distribution of neptunium from blood to bone, liver, and urine, respectively, which are somewhat different from the values in this NCRP report of 0.5, 0.1, and 0.4, for fraction to bone, liver, and urine, respectively. The ICRP report adopts shorter retention half-times of 50 years and 20 years for neptunium in bone and liver, respectively, while this NCRP report retains the older ICRP and NCRP half-times of 100 years and 50 years for bone and liver, respectively. It should be further noted that the modified values of ICRP Publication 48 have not been reflected by ICRP in their values of ALI and DAC, which remain those of ICRP Publication 30. Values for ALI and DAC which the ICRP might in the future base on the metabolic parameters recommended in ICRP Publication 48 would not differ significantly from those recommended in this NCRP report.

18

/

4.

METABOLISM OF NEPTUNIUM IN MAMMALS

rats at three laboratories indicate that fasting may increase neptunium absorption approximately ten-fold (Table 4.2). Similar observations have been reported for plutonium (Sullivan et al., 1979; Stather et al., 1980; Larson et al., 1982b). In studies with plutonium in mice, it has been shown that as little as 2 hours of fasting at the beginning of the active phase (dark cycle) will produce the higher absorption characteristic of the fasting state, whereas fasting initiated after 4 hours of active-phase feeding produces higher absorption only after an 8-hour fast (Larsen et al., 1982b). The applicability of such information to the human is highly uncertain, but it would seem that a worker who skips breakfast might have a substantially higher absorption rate. For the case of nonoccupational exposure, this effect of fasting might be of lesser significance, since intake of neptunium would be expected to occur predominantly in conjunction with meals. An effect of the nature of the diet on neptunium absorption is evident in the data from baboons of Table 4.2 and has also been demonstrated in the case of plutonium (Sullivan et al., 1983b). The possible range of such effects, as applied in the human case, is difficult to predict. Effect of Age: As is true of plutonium and other actinides, the absorption of neptunium is markedly enhanced in the neonate (Table 4.4). Neptunium was earlier thought to be an exception to this rule; when high mass levels of 237Npare fed, little difference is noted in the fraction absorbed by adult and neonatal rats (Sullivan, 1980b). However, low-mass studies with 239Npexhibited the more typical 50-fold enhancement of absorption at 2 days of age, and a 30-fold enhancement at 9 days of age; similar observations have been reported in the hamster and in swine (Table 4.4). The oxidizing agent (Fe+++)has little effect in further enhancing neptunium absorption by the neonate, but the reducing agent (Fe++)reduces absorption to near-adult levels. Neptunium, like other actinides, shows a prolonged retention within the gastrointestinal tract of the neonate (Table 4.4). Thus, as much as 73% of 239Npingested by 2-day-old rats was still present in their gastrointestinal tract a t sacrifice, 4 days later. This phenomenon has been more extensively studied with plutonium, which has been shown, autoradiographically, to be incorporated within the epithelial cells of the intestinal wall (Sullivan, 1980b). Very little of this retained plutonium is absorbed systemically; it is sloughed with the epithelial cells and largely excreted within 10 days. While present within the intestine, however, such a retained actinide might contribute significantly to the radiation dose to the intestinal walls. Enhanced absorption and retention of neptunium by the very young is not relevant to occupational exposure. Whether it is a significant factor in the derivation of exposure standards for general populations

Isotope

Species (no.)

Age

Medium

Dose (mg/kg)

Time of Sacrifice

Fraction Retained Systemically (~103

Fraction Retained in G.I.Tract'

Reference

(x1O2)

"'Np 237Np "'Np "'Np "'Np

Rat Rat Rat Rat Rat

(3) (4) (9) (3) (10)

1d 2d 3d 4d 9d

nitrate, pH nitrate, pH nitrate, pH nitrate, pH nitrate, pH

2 2 2 2 2

425 310 215 185 150

7d 7d 7d 7d 7d

0.75 0.60 0.37 0.64 1.2

15 39 11 13

Sullivan, 1980b Sullivan, 1980b Sullivan, 1980b Sullivan, 1980b Sullivan, 1980b

"'Np %Np "9Np "'Np

Rat (6) Rat (9) Rat (9) Rat(l1)

1d 1d 2d 9d

nitrate, pH nitrate, pH nitrate, pH nitrate, pH

2 2 2 2

168 3 x lo-' 8x 4x

7d 7d 4d 4d

0.43 3.5 1.3 0.9

6 56 73 60

Sullivan et al., 1983a Sullivan et al., 1983a Sullivan et al., 1983a Sullivan et al., 1983a

t

"'Np "'Np

Rat (15) Rat (10)

5d 5d

95 95

7d 7d

0.91 1.1

12

E!

N.A.

Sullivan et d., 1984a Sullivan et al., 1984a

23'Np

Rat (10)

5d

95

7d

1.1

24

Sullivan et al., 1984a

""Np

Rat (9)

5d

95

7d

2.7

N.A.

Sullivan et al., 1984a

237Np

Rat (8)

5d

nitrate, pH 2 nitrate, pH 2 + 50 mg Fec++/kg nitrate, pH 2 + 90 mg Fe+*+/kg nitrate, pH 2 + 175 mg Fe+++/kg nitrate, pH 2 + 190 mg Fe++/kg

95

7d

0.12

N.A.

Sullivan et al., 1984a

m

"'Np

Swine (4)

1d

nitrate, pH 2

20

7d

6.0

4

Sullivan et al., 1982

=Np pgNp 2"Np '"Np

Hamster (6) Hamster (6) Hamster (10) Hamster (10)

2d

nitrate, pH 1 nitrate, pH 1 bicarbonate, pH 6.5 bicarbonate, pH 6.5

7d 7d 7d 7d

1.8

1.0 0.1 0.4 0.6

David and Harrison, 1984 David and Harrison, 1984 David and Harrison, 1984 David and Harrison, 1984

9 9

4d 2d 4d

28

0

%

8 4 Z m m

=!

5r >

2 x 10" 2 x 10"

2x 2x

* Present within walls and contents of G.I. tract at sacrifice.

lo-'

1.6 4.0 1.6

,

20

/

4.

METABOLISM OF NEPTUNIUM 1N MAMMALS

depends upon the magnitude and duration of the effect in humans. The limited data at low neptunium mass levels (Table 4.4) provide no basis for estimating the duration of the effect, even in the rat. More extensive data on plutonium indicate that absorption declines rapidly in the rat, reaching adult levels a t the age of weaning (21 days) (Ballou, 1958). An fi value of 0.01 for the first year of human life would seem a conservative assumption. Application of such age-dependent metabolic parameters in the derivation of age-specific exposure limits is a complex problem, with many ramifications, and quite beyond the scope of this report. Guidance on the subject is provided by Adams (1981) and by the ICRP (1984).The United Kingdom's National Radiological Protection Board has recently recommended an fi value of 0.01 for neptunium during the first three months of life, and an average value for the first year of life of 0.005 (NRPB, 1984). Problems of Extrapolation to Man: Should an fi value based largely on rodent data be applied directly t o the human? Among the actinides, only in the cases of uranium and thorium are there data on gastrointestinal absorption for both humans and laboratory animals. Agreement among the uranium data is not reassuring: an fi value of about 0.1 is reported, based on the balance between dietary intake and urinary output of natural uranium in man (Welford and Baird, 1967); values ranging from 0.005 to 0.05 were measured in four human volunteers fed uranyl nitrate (Hursh et al., 1969); an average value of 0.015 was measured in 10 dogs given a single dose of UOzFzin water (Fish, et al., 1960); and values of 0.0006 were measured in rats gavaged or 900 pg of 233U,as uranyl nitrate (Sullivan, with either 0.5 pg of 1980a). In the case of thorium, on the other hand, the measured fi value from 5 human subjects is 0.0002 (Maletskos et-al., 1969), in close agreement with the value of 0.0003 measured in rats (Sullivan, 1980a), and 0.0006 measured in mice (Sullivan et d.,1983~). There is, in the case of plutonium, indirect evidence that the fi value for humans cannot be much larger than 0.001. This conclusion is derived from the fact that Laplanders of Northern Finland eat large quantities of reindeer liver, which contain a much higher concentration of fallout plutonium than is present in most food; however, their plutonium burdens a t autopsy are not significantly higher than those of Finns in Southern Finland, who have no large dietary intake of plutonium (Mussalo-Rauhamaa, 1981; Mussalo-Rauhamaa et al., 1984). This estimated upper limit on human plutonium absorption is in good agreement with fi values derived from experiments in a variety of animal species. In view of the quite close agreement among low-mass neptunium fi values derived from experiments with mice, rats, hamsters, rabbits,

4.2

PULMONARY RETENTION AND ABSORPTION

/

21

goats, and baboons, there would seem no reasonable basis for making other than a direct extrapolation to the human. 4.2 Inhalation (Pulmonary Retention and Absorption)

For purposes of dosimetric modeling, the ICRP currently assigns all compounds of neptunium to inhalation Class W of its respiratory tract model (ICRP, 1980a). This implies that, for nominal 1 pm A M A D (activity median aerodynamic diameter) particles, 30% of neptunium inhaled will be deposited in the nasal passages (N-Pregion), 8% will be deposited in the trachea and bronchial tree (T-B region), 25% will be deposited in the deep lung ( P region), and the remaining 37% will be exhaled immediately (ICRP, 1979). For particles larger and smaller than 1p m AMAD, apportionment among the regions of the respiratory tract will be somewhat different, as elaborated by lCRP (1980a). According to the ICRP model, 10% of Class W materials deposited in the N-P region will be rapidly absorbed to body fluids and the remaining 90% will be passed to the gastrointestinal tract with a removal half-time of 0.4 day. Of the Class W material deposited in the T-B region, 50% will be rapidly absorbed to body fluids and the other 50% will be cleared by mucociliary action and passed to the gastrointestinal tract with a removal half-time of 0.2 day. Of the Class W material deposited in the P region, 40% will be cleared and passed to the gastrointestinal tract with a removal half-time of 1 day, another 40% will follow the same route but with a half-time of 50 days, 15% will be absorbed to body fluids with a half-time of 50 days, and the remaining 5% will be removed to pulmonary lymph nodes with a halftime of 50 days. From the lymph nodes, Class W material will be totally absorbed to body fluids with a half-time of 50 days. Thus a total of 12% of inhaled Class W material will ultimately be absorbed for systemic distribution, not counting the small fraction that may be absorbed from the gastrointestinal tract. The holdup in lungs and pulmonary lymph nodes is relatively brief. This Class W model is applied by the ICRP to all actinide compounds except the insoluble oxides and hydroxides of thorium, uranium, plutonium, and californium. It is one of 3 models employed for inhaled compounds of all elements; the Class D model provides for greater absorption from, and shorter retention in, the lung; the Class Y model provides for less absorption and longer retention. The pertinent question with respect to neptunium is whether the Class W kinetic model adequately describes neptunium behavior in the respiratory system, or whether there is evidence to justify a modification of these parameters.

22

/

4.

METABOLISM OF NEPTUNIUM IN MAMMALS

The experimental data on deposition and retention of neptunium in the respiratory tract of animals have been reviewed by Thompson (1982). Moskalev et al., (1972, 1979) describe a study in which 237Np citrate was administered intratracheally. Of the administered dose, 80% was retained in the lungs after 1 day; 58.6% remained after 32 days. An elimination half-time of 4 days was estimated for 31% of the neptunium deposited, and a half-time of 133 days for the remainder. These estimates were based on data from groups of 3 rats sacrificed 1, 4,8, 16, and 32 days following administration. A second study, described by Lyubchanskii and Levdik (1972), and later reviewed by Moskalev et al. (1975, 1979), involved inhalation of 237Np(V,V1)nitrate, and 237Np(IV)oxalate aerosols. From (400-1100 Bq 0.01-0.03 &i) were initially deposited in the respiratory tracts of 165 rats, which were sacrificed a t intervals up to 512 days (nitrate) or 650 days (oxalate) postexposure. After an initial rapidly-lost component, 26% of the nitrate deposit was lost with a half-time of 15.4 days and 8.1% with a half-time of 168 days. The oxalate was retained more tenaciously, 43.8% being lost with a half-time of 22.3 days and 22.6% with a half-time of 151 days. A third study (Sullivan, 198413) involved the inhalation of 237Np(V) nitrate aerosols by 75 rats with initial lung deposits of (4000 to 11000 Bq 0.1 to 0.3 pCi). A rapid loss from the lung of 78% of the initial deposit was followed by loss of 21% with a half-time of 28 days. About 0.8% of the initial deposit was retained in the lung with a half-time much longer than the life-span of the rat. The above data are hardly adequate to support a detailed model of neptunium retention in the respiratory tract of the rat. They are, however, similar to the data available in greater abundance for other relatively soluble actinides (ICRP, 1980b),and are in better agreement with the kinetics of Inhalation Class W, than with the kinetics of either Class D or Class Y. While shortcomings of the general ICRP lung model have been pointed out (NCRP, 1985), no clearly superior substitute is currently available. It is therefore concluded that the behavior of inhaled neptunium should be characterized, for radiation protection purposes, by the Inhalation Class W model of the ICRP.

4.3 Systemic Distribution, Retention, a n d Excretion The 1959 NCRPIICRP recommendations included neptunium distribution and retention parameters based on a single report of investigations in the rat (Lanz et al., 1946). The percentages transferred from blood to bone, liver, and kidneys were taken as 45%, 5%, and 3%, respectively. The biological half-life in bone was taken as 200 years, by analogy with plutonium. The biological half-life in liver was

4.3 DISTRIBUTION, RETENTION, AND EXCRETION

/

23

taken as 150 years and that in kidneys as 175 years. For its 1980 recommendations, the ICRP employed neptunium parameters based on a common model for systemic distribution and retention of all transuranic elements. This model was based largely on plutonium data, as summarized in a task group report (ICRP, 1972). It was assumed that 45% of any transuranic element is deposited in bone, 45% in liver, and 10% is rapidly excreted, except for 0.035% deposited in testes or 0.011% deposited in ovaries. The transuranic element in bone is retained with a biological half-life of 100 years, that in liver with a biological half-life of 40 years; no loss is assumed to occur from gonads. The transuranic element in bone is assumed t o distribute itself according to the general ICRP model for bone-surfaceseeking radionuclides (ICRP, 1979). This model assumes that the radionuclide is uniformly distributed on bone surfaces, which are of equal area in trabecular and cortical bone. This distribution pattern serves to maximize dose to the endosteal cells on bone surfaces, the presumed sensitive tissue for cancer induction. This localization of dose is of particular significance for alpha- and low-energy betaemitters, whose particle range in tissue is short. The ICRP decision to base neptunium distribution and retention parameters on a general transuranic model is no doubt explained by the more extensive data available for other transuranic elements, and by the large variability in the data available for neptunium. Thompson (1982), reviewing data from 17 published sources through 1980, found reported liverbone deposition ratios ranging from 0.02 to 2.9. Faced with such a range of values one might understandably conclude that an equal split between liver and bone offered the only reasonable compromise. However, a closer look at these data revealed a general pattern of high liver deposition following intravenous administration of high-mass quantities of neptunium (237Npstudies), and of low liver deposition following administration of low-mass quantities of neptunium, or administration by oral, intraperitoneal, intramuscular, or inhalation routes. This pattern suggests that high liver deposition is a consequence of some form of concentration-dependent neptunium polymerization in the blood. Thompson (1982) concluded that deposition fractions of 0.15 in liver and 0.60 in bone were most appropriate for radiation protection evaluations. More recently, quite extensive data on neptunium distribution have become available from the many studies designed primarily to measure absorption from the gastrointestinal tract. Such data are particularly relevant since in these studies, regardless of the chemical form or quantity fed, neptunium should reach the blood stream in a concentration and chemical form more typical of that resulting from human exposure to environmental or occupational sources. Table 4.5 sum-

24

/

4.

METABOLISM OF NEPTUNIUM IN MAMMALS

TABLE 4.5-Distribution and uriruary excretion of gastrointeztinally absorbed ne~tunium" Species

Rat

Table

4.1 4.2

ir 13 1 2 3 4 5 6 7 8 9 12 13 14 15

,012 .027 .017 .015 .002 .001

16

4.3

-

Fraction of Total Absorbed to: Fraction Absorbed

17 22 23 26 29 31 32 33 34 3 4 5 6 7

,0006 .0005 .0011 .0065 .0027 .0029 .0028 .0025 .0030 .0012 ,0026 .0012 .0003 .0015 .0014 .ooo4

.mo1 .0025 .011 .027 .071 .080 .0007

Mean (n)

Mouse

4.2

10 11 35 36

4.3

10 11 12 13

Liver

Skeleton

.56 .47 .5 1

.59 .45 .40 .25 -40

.4 5 .54 N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. .56 .62 .42 .40 .10 .45 (15)

.02 1 .004

N.A. N.A. N.A. N.A. N.A. N.A. N.A. N.A.

,0005 .0006 .0004 .0002 .0002

N.A. N.A. N.A. N.A. N.A.

.0006 .013 ,0003 .0035 .024 .069

-

4.2

Mean (n)

.39

.36 .04 .33 .45 -50

.50 20 .27 .37 .30 .34 .32 .32 .43 .48

N .A. N.A. N.A. N.A. N.A. N.A. N.A. N.A. .33 .37 .23

.19 .7 1 .35 (21) .33 .26 .57 .21 .25 .12 .32 .63 .34 (8)

Mean (n)

Hamster

Urine

20 21 24 25 28

--

N.A. N.A. N.A. N.A. N.A.

4.3 DISTRIBUTION, RETENTION, AND EXCRETION

/

25

TABLE 4.5-Continued Referenceb Species Rabbit

Table 4.2

Fraction

Fraction of Total Absorbed to:

ivAbsorbed Liver Skeleton

Urine

27 30

N.A. N.A.

-

.0018

.01

N.A. N.A.

Mean (n) Baboon

4.2

41 42 43 44 45 46

Meanc (n)

"Average data from individual treatment groups. Reference is to table and line number in this report. 'Separate means calculated for the two sets of baboon data because of substantially different treatments and results.

marizes distribution data, where available, from the experiments already outlined in Tables 4.1, 4.2, and 4.3. Despite a wide variation in total fraction of neptunium absorbed, the fractions of the absorbed neptunium that deposit in liver and skeleton, and that are excreted in urine; show much less variation. The fraction deposited and retained in liver is clearly much smaller than the 0.45 assumed by ICRP. Data from the rat, hamster, and baboon would suggest a deposition fraction as low as 0.05. The higher value measured in mice, and the fact that mice, rats and baboons lose actinides rather rapidly from the liver, would argue that 0.1 might be a better assumption. A value of 0.5 for the fraction of neptunium deposited in bone seems most reasbnable. It is slightly larger than the mean of the values measured in the rat skeleton, and substantially larger than several values measured for the baboon skeleton. However, low values for the baboon could be due to overestimates of neptunium in urine, considering the difficulty in separating urine from feces with some of the diarrhea-producing diets employed. It also seems desirable that deposition estimates should err on the high side, since there are no data on which to base realistic estimates of minor deposition in tissues other than liver and skeleton. The remaining fraction, 0.4, if assigned to urinary excretion, seems a reasonable compromise of the data from rat, mouse, and baboon. In the absence of usable data on the deposition of neptunium in gonads (Thompson, 1982), the current ICRP (1980a) assumption of 0.035% in testes and 0.011% in ovaries, as derived for plutonium,

26

/

4.

METABOLISM OF NEPTUNIUM IN MAMMALS

would seem appropriate for neptunium. Data on the long-term retention of neptunium are available from only a few experiments in rats (Thompson, 1982), and from studies in progress with baboons (Cohen and Ralston, 1983 and unpublished). Data obtained by in-vivo gamma spectrometry measurements of the skull and whole-bodies of two baboons over a period of 300 days postinjection, indicate that neptunium is retained in bone with a biological half-time of 1 to 2 years. Autopsy tissue data and fecal excretion measurements for times up to 90 days postinjection indicate that neptunium is retained in the baboon liver with a half-time of 40 to 80 days. These baboon data, together with the indication of a markedly decreased Np/Pu ratio in human autopsy material as compared to environmental Np/Pu ratios (Efurd et al., 1984 and personal communication), suggest that the metabolism of neptunium may be substantially different from that of plutonium and other transuranic elements. Until more evidence is obtained, however, it seems appropriate, for radiation protection purposes, to follow ICRP practices and to base neptunium retention parameters on the extensive data available for plutonium. These ICRP retention half-times of 100 years for actinides in bone, and 40 years for actinides in liver, are generally considered to be overestimates but it is beyond the scope of this report to re-evaluate these general actinide parameters. A task group of the ICRP is currently involved in this effort. Some information is available on the microdistribution of neptunium in its principle organs of deposition (Thompson, 1982). This information is relevant to the establishment of neptunium exposure standards primarily as it pertains to the question of distribution in bone. Current ICRP (1980a) limits are based on the assumption that neptunium in bone behaves as a surface-seeker, like plutonium, rather than as a volume-seeker, like uranium. Similarities in the behavior of neptunium to that of the uranyl ion and to that of alkaline earths were noted by Nenot, et al. (1972). Recent detailed autoradiographic studies of the comparative behavior of actinides in the skeleton of the rat (Priest, et al., 1982,1983, and unpublished) indicate a rather typical surface-seeker behavior for neptunium, very similar to that of protactinium and intermediate between that of plutonium and americium. The ICRP assumption of indefinite retention of actinides on bone surfaces is not supported by the available data for neptunium or by the more extensive data for other actinides. The quantitative resolution of this problem must involve a general revision of the bone dosimetry model that will allow for gradual burial of actinides within the total volume of bone (Harley and Pasternack, 1976; Priest and Hunt, 1979; Leggett, 1984). Until such a general revision is undertaken, it seems appropriate to retain the present ICRP assumptions, while noting that they very likely overestimate the retention and the dose.

5 . Health Effects of Neptunium Effects of neptunium exposure have not been described in man. For radiation protection purposes it has been assumed that radiation doses resulting from neptunium deposition in organs and tissues will result in biomedical effects that are similar to those observed following exposure of humans to other sources of ionizing radiation. An evaluation of the risks of cancer and genetic effects has been the primary basis for limits on radiation dose equivalent as employed by NCRP (1971,1987) and ICRP (1977). While the very limited data on neptunium effects in animals provide no directly useful estimates of risk to man, and have played no direct role in establishing neptunium standards, they can nevertheless help to validate these standards through comparisons with other animal studies employing other radionuclides. Such comparisons provide some assurance that neptunium effects are broadly predictable from the more extensive experience with other radionuclides in animals and humans. Except for early effects from nuclear weapons fallout, where shortlived neptunium isotopes may contribute significantly to radiation exposure (Perkins and Thomas, 1980), the neptunium isotope of primary health concern is 237Np.All animal toxicity studies with neptunium have employed this isotope. Because of its low specific activity (0.76 mCi/g) (28 MBq/g), effects due to chemical toxicity are often observed to the exclusion of radiation effects. The published literature on chemical and radiation effects of 237Np has been recently reviewed by Thompson (1982). The rather extensive Soviet data in this area have been collected in a monograph by Moskalev et ad. (1979),which has recently become available in an English translation. The concern here is not with chemical effects, except to note that such effects might be a controlling factor in an acute exposure to 237Np.They would not, however, be an important factor at the usual levels of concern in radiation protection-certainly not at the very low levels of potential environmental exposure. Long-term radiation effects of 237Nphave been studied only in rats and have been reported only in the Soviet literature. Genetic effects have not been studied. Bone cancer has been the predominant longterm effect of low-level injections of 237Np;both lung and bone cancer

28

/

5. HEALTH EFFECTS OF NEPTUNlUM

incidences are elevated following inhalation exposure. As compared t o 237Np results of similarly conducted studies with 2 3 9 Pand ~ 241Am, exhibits a comparable carcinogenicity in lung, and perhaps a somewhat greater carcinogenicity in bone (Thompson, 1982). There is no indication in the available data that neptunium at low exposure levels constitutes a unique health risk unpredictable from its general radiological characteristics.

6. Radiation Protection Guidelines This section reviews past and current standards established for control of exposure to neptunium. It then considers the extent to which current understanding of the biological behavior of neptunium would counsel changes in these standards and makes recommendations in that regard.

6.1 History Recommendations for control of exposure to neptunium were first made in the 1959 reports of NCRP (1959) and ICRP (1960). The dosimetric parameters assumed for the derivation of these standards are summarized in Table 6.1. Based on these parameters, limits were derived in terms of a "maximum permissible burdenn in the total body (MPB), and "maximum permissible concentrations" in water (MPC), and air (MPC),. MPBs and MPCs were calculated in such a manner that the annual dose rate attained after 50 years' exposure t o the radionuclide did not exceed the basic annual exposure limits. These calculations were made separately for the total body and for various organs; the organ implying the smallest value of MPB or MPC became the "critical organ" and the MPB and MPCs based on that critical organ were the controlling values for the radionuclide. Table 6.2 reproduces the 1959 neptunium limits as promulgated by NCRP and ICRP. For '"Np the most restrictive MPB was 2200 Bq (0.06 pCi) based on bone as the critical organ. The corresponding (MPC), was 2.4 Bq/cm3 (9 x lo-' &i/cm3). It would appear that somewhat less restrictive MPCs would apply to "insolublen neptunium; however, these were intended to apply only if more restrictive than the "soluble" limits and, in fact, no basis was ever established for distinguishing between soluble and insoluble compounds. Revised limits for neptunium were recommended by ICRP in 1980. These standards were based on a substantially different dosimetric approach, in which a weighted sum of the committed dose equivalents to all important organs was restricted by basic dose equivalent limits. 29

\

TABLE6.1-Dosimetric parameters for neptunium in man ?'

NCRPPCRP 1959 "Soluble"

Ingestion Parameters' Fraction absorbed to blood Inholotion Parametersc Fraction exhaled Fraction absorbed to blood Fraction(s) retained in lung/(retention half-time) Systemic Parameters Fraction from blood rapidly excreted Fraction from blood/(retention halftime) in skeleton in liver in kidney in ovaries in testes

"insoluble"

0.0001

b

ICRP 1980

NCRP 1987

0.01

0.001

0.37 0.12 O.lO/(ld) 0.10/(50d)

0.37 0.12 O.lO/(ld) 0.10/(50d)

?

E5 0

0.25 0.25 0

0.25 b

0.12/(120d)

0.47

b

0.10

0.40

0.45/(200y) O.O6/(15Oy) O.O3/(175y)

b

0.45/(10Oy) 0.45/(4&)

0.50/(100y) 0.10/(4@)

1.1 X lo4/(@ 3.5 X lo4/(-=)

1.1 x lo-'/(w) 3.5 x lo-4//(-)

z Cd

$ 0

2 z

0

C n b b

Parameters relating to retention within G.I.tract are not included. U I n ~ ~ l u b lcompounds e" were distinguished only with respect to inhalation parameters. 'Parameters relating to passage of inhaled materials through G.I. tract are not included. ICRP 1980 and NCRP entries assume 1 pm AMAD particles inhaled.

5 M

2

%

2

0

%

z

-? w

'-01 x L ‘-01 x z 9-01 X 8

6-01 OOZ

(~m3/!3") "(3dN)

(P3/!3") '(3dM)

1-01 X F v-OI X Z 1-01 c-01 x 9 9-01 X 6

L 8 9

s-OI x ZT-01X ,I-01 x 21-01 X an-01

g-01

f2

‘-01

06 09 06

9-01 X P -01 X Z ,OI x z X

Z

9-01 x Z '-01 x L E-01X Z g-0 I ,-01 X L 9-01 x P '-01 X 8

L-01X Z 11-01 X Z 11-01 x Z rr-O1 X L el-01 X P (em3/!3d) '(3dN)

6-01 x P 009 OOE OOZ 001 r-O1 X P

,-01 p-OT

,-or

9

X

6

X

x

P

1-01 X Z +O1 X 6 (sm3/!3d) '(3dN)

wfilq 0 ) J O ~ I

Taa* Jq 891 106

9'0 S'O 1'0 90'0 *(!3")

b Lpoq ~ B J O ?u! uapanq

alq!sqmrad otnuqwK

alq!smmaad m n ~ x 8 ~

. ~ ~ O ! ~ ~ I ~ U ~ ~ U O J

32

/

6. RADIATION PROTECTION GUIDELINES

The details of this system are described in ICRP Publication 30, Part 1 (ICRP, 1979) and have been discussed a t length in an NCRP report (NCRP, 1985). Table 6.1 compares the basic dosimetric parameters in the 1959 and 1980 reports; changes include the much discussed increase in fraction absorbed from the gastrointestinal tract, the changed respiratory tract model, and changes in systemic distribution and retention parameters. The limits recommended by the ICRP in 1980 were stated in terms of "annual limits on intake" (ALI) via ingestion or inhalation, in units of becquerels (Bq); a "derived air concentration" (DAC) was also given in units of Bq/m3. The DAC is that concentration of a radionuclide in air which, if breathed for 2000h (50 weeks at 40 hours per week), would result in the ALI by inhalation. The DAC is thus conceptually equivalent to the 1959 (MPC),. Table 6.3 reproduces the ICRP recommendations of 1980. Table 6.4 compares, for 237Npand 239Np,the 1959 NCRP/ICRP recommendations with the 1980 recommendations of ICRP. After conversion to common units, the 1959 (MPC), compares directly with the 1980 DAC. The 1959 (MPC), and (MPC),, when multiplied by the annual intakes (assumed 40-hour work week, 50 weeks per year), correspond to ALIs for ingestion and inhalation, respectively. The only change larger than a factor of 2 is that in the ingestion limit for 237Np,which is more restrictive in the 1980 limits by a factor of about 300. This change is attributable in large part to the 100-fold change in the gastrointestinal absorption factor. Gastrointestinal absorption is not a significant factor in the case of 239Np;because of its short physical half-life of 2.3 days, the dose of overriding importance in determining limits is that to the gast.iointestinal tract itself.

6.2

Recommendations

The NCRP has recently considered the merits of the 1979 ICRP system of standards for control of exposure t o internally deposited radionuclides (NCRP, 1985). With certain qualifications, the NCRP has recommended adoption of the new ICRP system in place of the 1959 NCRP/ICRP system. This report is not concerned, therefore, with recommending changes in the system itself, but only with its application in the derivation of neptunium standards. As discussed and justified in earlier chapters of this report, several changes are recommended in dosimetric parameters for neptunium. These changes are summarized in Table 6.1 in the column headed

6.2 R E C O M M E N D A T I O N S

1

33

TABLE 6.3-1980 ICRP neptunium limits" to subsections are to those

(Reproduced from I C R P Publication 30, Part 2. Fteferences in t h a t document.)

--

Oral

Inhalation Class W

Radionuclide ALI

f, = 1 x 1 x loo (2X 109 Bone surf. -

DAC

f, = 1 X

lo-z

9 x 10' (2 x 10)'.

Bone surf. 4 x 10'

ALI DAC

1 X 10" 5 x 10'

ALI DAC

4 x 10'

1x

lo8

5 x 10' (5 x 10')

ALI

Bone surf. DAC ALI

2 x 10'

1x

lo'

2 x 10' Bone surf.

-

DAC ALI

2 x 107 (3 x 10') Bone surf.

DAC ALI

3~ 103 5x109 Bone surf.

-

DAC

1x103

(2 x 103) Bone surf. 4X

lo-'

1 X lo6 (3 x 109

Bone surf. 6 X 10' 2 x lo= (4 x lo=)

Bone surf. 9 X 10-2 3 x lo6 (6 X 10')

ALI

Bone surf. 1x103

DAC ALI

6X

lo7

9 x 10'

(6 X lo7)

LLI Wall DAC

-

ALI DAC 'Values of ALl(Bq) are given for the oral and inhalation routes of entry into the body. It is emphaswxd that the limit for inhalation is the appropriate ALI and that the values of DAC (Bq/m3) for a 40-h working week are given only for convenience and should always be used with caution (Section 3.4, Chapter 3). Values of ALI for inhalation and DAC are for particles with an AMAD of 1 p m . A method of correcting the values for particles of other sizes is described in Section 5.5, Chapter 5 and the required numerical data are given in the Supplement to this Part (ICRP, 1980a). If a value of ALI is determined by the non-stochastic limit on dose equivalent to a particular organ or tissue, the greatest value of the annual intake that satisfies the Commission's recommendation for limiting stochastic effects is shown in parentheses beneath the ALI. The organ or tissue to which the non-stochastic limit applies is shown below these two values. When an ALI is determined by the stochastic limit this value alone is given (Section 4.7, Chapter 4) (ICRP,1980~).

34 .-

I

6. RADIATION PROTECTION GUIDELINES

TABLE 6.4-Comparison of 1980 and 1959 ICRP neptunium limits -Radionuclide

1980 Recommendations* 1959 Recommendationsb -DAC DDAC Oral' Inhal'nd ALI---.--( r C i ) ALl (&i) (rCi/cma) --------AI.1 ( r C i ) ALI ( r C i ) (rCi/cma) - .-

-Ojxrz

-237Np 239Np

0.08 1600

0.005 2400

2x 1x10"

25 1100

0.01 2000

4 x lo-'? 8X10-~

"Converted from SI units. Recommendations for "solublen neptunium compounds, converted to ALIs and DACs to facilitate comparison. ' (MPC), multiplied by ICRP-assumed water intake during 250 work days per year (1100X 250 cm3). (MPC). multiplied by ICRP-assumed air intake during 250 work days per year (10' X 250 cm3).

"NCRP 1987" and include a value of 0.001 for the fraction absorbed to blood from the gastrointestinal tract. Values included for the fraction absorbed from blood to skeleton, liver, and urine are 0.5,0.1, and 0.4, respectively. Values for the fraction moving from blood to gonads are not changed from the numbers recommended by the ICRP in 1980; retention halftimes for neptunium in skeleton and liver are also unchanged. These numbers are not supported by any significant neptunium data but are based on the more extensive data available for plutonium and other actinides. A review of the current status of these actinide data might well result in changes in these parameters, but such a review is beyond the scope of the present report. More accurately descriptive respiratory tract and skeletal models for actinides have also been proposed, but these too would require study in the total actinide context. By applying the changed dosimetric parameters listed in Table 6.1 as corrections to the ICRP neptunium dosimetric data tables published in the Supplement to Part 2 of ICRP Publication 30 (ICRP, 1981), revised values for oral and inhalation ALIs and for DACs for 10 neptunium isotopes were calculated and are listed in Table 6.5. Additional dosimetric data employed in the calculation of these values for ALI and DAC are tabulated in Appendix A. The revised exposure limits of Table 6.5 should be viewed as still somewhat conservative. This is because of the conservatism generally considered to reside in the generic actinide retention parameters, and in the lung and bone models employed in the derivation of these limits. The exposure limits of Table 6.5 constitute the current NCRP recommendations for limiting exposure to neptunium isotopes in the workplace. They are not directly applicable to the protection of general populations. Some of the additional factors to be considered in the protection of general populations have been discussed in this report. A more general consideration has been given by the ICRP (1984).

TABLE 6.5-1987 NCRP recommendations for annual limits on intuke (ALI) and derived air concentrations (DAC) (40 h/wk) for neptunium isotopes" S.I. Units Radionuclides

Half-Life

Emissions

Oral ALI(Bq)

Inhal'n ALI(Bq)

Conventional Units

DAC (Bq/ma)

Oral ALI (pCi)

Inhal'n ALI (pCi)

8 x lo7 (2 x 10')

(6 X lo3)

Bone Surf.

Bone Surf.

2x

3x

8X

=Np

1.15 X 1OSy

EC, 8-

lo7

(6 x lo7)

2 x 10' (3 x lo4)

(2 x lo3)

LLI Wall

Bone Surf.

LLI Wall

Bone Surf.

1 x lo5 (3 x 109

1 x 103 (2 x 103)

Bone Surf.

Bone Surf. 1 x 10s (3 x lo6) Bone Surf.

2X

lo8

2x

lo4

(6

X

104)

5 x 107

2 x 102 (5 x 16)

Bone Surf. 3x106

3

(7) Bone Surf. 4x

lo3

6X

lo-' (2)

Bone Surf. 1 x 103

(7 x 109 Bone Surf. 6 x 10' (6 X 10')

LLI Wall a

65 m

See explanation beneath Table 6.3.

8-

I x lo3

8 X 10' (1 x lo9)

Bone Surf.

"ONp

lo6

3 x 103

1 x 10'

4 x lo7

lo3

9 x lo7

3x (6 X lo-')

Bone Surf. 40 (90)

Bone Surf. 5 x 104 (1 x 10-2)

Bone Surf.

80 (200)

2 x 103 (2 x 10J)

Bone Surf. 2 x lo3

LLI Wall 8 X lo4

DAC (pCi/crnJ)

Appendix A Supplemental Dosimetric Information In this Appendix is tabulated dosimetric data relevant to calculation of secondary limits for isotopes of neptunium. The content and format of the information parallels the presentation given in the Supplement to ICRP Publication 30, Part 2 (ICRP, 1981), and the tables were directly reproduced from the computer code (Watson and Ford, 1980) used to calculate the secondary limits presented in ICRP Publication 30. The supplemental information provides numerical information supporting the calculation of Annual Limit on Intake (ALI) and the Derived Air Concentration (DAC). For each isotope of neptunium the following information is of interest; 1) Number of Nuclear Transformations; 2) Specific Effective Energy; and 3) Committed Dose Equivalent per unit intake, and the ALI and DAC. T o limit the size of the appendix, only those data which differ from that in the Supplement to ICRP Publication 30, Part 2 are presented. The reader wishing to investigate the calculations of the secondary limits presented in Table 6.5 may need to consult the Supplement to ICRP Publication 30, Part 2. Furthermore, the reader is encouraged to consult the discussion in the Supplement to Part 1 for further detailed information on the tabulations.

A. 1 Number of Nuclear Transformations Values are given for the number of transformations, U, that occur in source organs during the 50 years following the ingestion or inhalation of a unit activity of the specified neptunium isotope. Where appropriate, values of U are also given for any radioactive daughters that are formed from transformations of the specified neptunium isotope taken into the body. Nuclear transformation data is presented only for those source organs contributing greater than 1% to the committed dose equivalent in the target organs. Revision of the metabolic model affects not only the numerical values but also the selection of data for presentation.

A.2

Specific Effective Energy

Values of Specific Effective Energy (SEE) in selected target organs from nuclear transformations arising in selected source organs are

APPENDIX A

/

37

given for the specified neptunium isotope and, where appropriate, for any radioactive daughters that are produced from transformations of the neptunium isotope taken into the body. Target organs are selected for inclusion in the table by the 10% rule, i.e., organs are excluded if their weighted committed dose equivalent is less than 10% of the maximum weighted committed dose. Source organs are retained in the tabulation only if they contribute greater than 1% of the committed dose equivalent of the target organs retained in the tabulation. Since the revised metabolic model alters the list of organs surviving the 1% and 10% rules, in some instances it was necessary to include revised tabulations of the SEE values. Note that SEE data are presented here only if the necessary data were not given in the Supplement to Publication 30, Part 2.

A.3 Committed Dose Equivalent per Unit Intake The committed dose equivalent per unit intake for target organ T is computed as H50,T

lo-''

USj SEE(T

= 1-6.

+ S)j,

(A.1)

S j

where the sum extends over all source organs S and all members j of the decay chain, when appropriate. Values of the committed dose equivalent are presented for each organ or tissue surviving application of the 10% rule to the intake of the specified neptunium isotope. The weighted committed dose equivalent, WTHWpT, was tabulated in the Supplement to Part 2; however, since these values are readily obtained from the above definition they are not tabulated here.

A.4 Annual Limit on Intake and Derived Air Concentration The ALI and DAC are tabulated for each neptunium isotope in this appendix for completeness. The numerical data are the same as those present in Table 6.5.

38

/

APPENDIX A

Annual limits on intake, ALI(Bq) and derived air concentrations, DAC(Bq/m3) (40 h/ wk) for isotopes of neptunium Inhalation

-

Radionuclide

232Np

233N~

m N ~ 235N~

Z3RN~ (1.15 x i o 5 ~ )

21BN~ (22.5 h)

-

ALI

DAC ALI D AC ALI DAC ALI DAC A LI DAC ALI

2a7Np

DAC A LI

238N~

DAC ALI

usN~

DAC ALI

UON~

DAC ALI DAC

Oral

Class W

f, = 1 x I O - ~

6 = 1x lo-' -

6 X 10'

8 X 10' (2 x lo8) Bone surface 4 x lo4 1 x 10" 5 x 10' 1 x lo8 4 x 1@ 4 x lo7 (6 X 10') Bone surface 2 x lo4 1 x lo3 (2 x lo3) Bone surface 4 x lo-' 1x lo6 (3 X lo0) Bone surface

3 x 1ol0

-

8 x 10'

-

8 x 10a (1X loo) LLI Wall 1 x lob (3 x lo6) Bone surface

-

2 ~ 108

2 x 10' (6 X 10') Bone surface -

5x

lo7 -

6 X LO7 (6 x lo7) LLI Wall

-

8 ~ 108 -

6 x 1d 2 x lo2 (5 x lo2) Bone surface 8 X lo-' 3x

lo6

(7 x lo6) Bone surface 1 x lo3 9 x lo7 4 x lo4 3 x lo9 1 x lo6

APPENDIX A

/

NUMBER OF NUCLEAR TRANSFORMATIONS OVER 50 YEARS IN SOURCE ORGANS OR TISSUES PER UNIT INTAKE OF ACTIVITY (TRANSFORMATIONSIBa) OF NP-232 ORGAN

ORAL

INHALATION

CLASS W

fi = 1.E-03

GONADS

ST CONTENT

SI CONTENT

ULI CONTENT

CORT BONE

TRAB BONE

7.OE-03 6.43-03 6.1E-03 6.1E-03 6.1E-03 6.1E-03 6.lE-03 6.1E-03 3.93-03 8.2E 00 7.1E-04 9.83-06 8.83-06 8.83-06 8.83-06 8.73-06

39

\

SPECIFIC EFFECTIVE ENERGY ( M e V PER GRAM PER TRANSFORMATION) OF NP-232 SOURCES TARGETS

5

!zu z

*

GONADS

ST CONTENT

SI CONTENT

ULI CONTENT

GONADS

1.3E-02

4.1E-06

4.OE-05

3-93-05

3-83-06

3.83-06

R MARROW

1.4E-05

4-53-06

1.1E-05

9.43-06

1.4E-05

5.OE-05

BONESURF

4.1E-06

2.63-06

3.5E-06

3.1E-06

1.5E-04

1.5E-04

S T WALL

3.2E-06

4-33-04

1.43-05

1.5E-05

2.33-06

2.33-06

ULI WALL

4.4E-05

1.3E-05

9-63-05

4.3E-04

3.OE-06

3.OE-06

PANCREAS

3.OE-06

6.93-05

8-23-06

8.4E-06

3.93-06

3.9E-06

CORT BONE TRAB BONE

SPECIFIC EFFECTIVE ENERGY ( M e V PER GRAM PER TRANSFORMATION) OF U-232 SOURCES TARGETS GONADS GONADS

9.8E 00

R MARROW

l .lE-08

BONE SURF

2.83-09

ST WALL

7.3E-10

SI WALL

7.1E-08

UL I WALL

1.5E-07

PANCREAS

3.9E-10

ST CONTENT

SI CONTENT

UL I CONTENT

CORT BONE TRAB BONE

S P E C I F I C E F F E C T I V E ENERGY ( M e V P E R GRAM P E R T R A N S F O R M A T I O N ) OF TH-228 'C]

'd

m z

SOURCES TARGETS

-.zX

GONADS

ST CONTENT

SI CONTENT

ULI CONTENT

GONADS

1 . OE 01

3.8E-09

1 .2E-07

1 .3E-07

5.6E-09

5.6E-09

RMARROW

4.9E-08

1.3E-08

4.OE-08

3.33-08

1.5E-07

3.6E-02

B O N E SURF

1.3E-08

7.53-09

1 .1E-08

9-83-09

2.3E-01

2.3E-01

S T WALL

5-83-09

2.23-03

3.2E-08

3.5E-08

4-33-09

4-33-09

S I WALL

1.3E-07

2.1E-08

1.4E-03

2.OE-07

5.9E-09

5-93-09

ULI WALL

1.7E-07

3.OE-08

7.73-07

2.5E-03

5.6E-09

5.6E-09

PANCREAS

3.4E-09

1.7E-07

1.5E-08

1.7E-08

7-33-09

7.33-09

CORT BONE TRAB BONE

>

W H

W

h U r4 ti.

VJ W U W 3 0 V1 H v

co

W

Z N 0

c

u

m

-

I

~

N

I

W W l D a

0 I

2 h 0

o 0

e

0

D

C

a

0

7

I

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e

r

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00 0 I

a,

o

r

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0

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a,

l l

0 I

W h

e

r

b 0

W

o

t W a

b

o I W ~ D

o

3

0

a

0

o

I W b

N

b

I W W

9

o

l

b

W b

o

c

I

u

I

APPENDIX A

o

N

f l W a

o

c

I

I W

o

p o

l W m

o

c

I W c n

r

m

o I W m l

-

I W m

u

I

b

n

N

*

o

W W , a o c

0

W

o

O

-

o

r

I W

m

N

I W m

o

N

m

w

I W ~

f

I W

o

W

o W =

F

W

Z

W

h

z

0 ~

l

b

I W

H

N

I 0

n

.

I W Z

o

Z

o

-

a

r

b

~

a

H l

U

O

H

z W

0

~ H

z W H H V J 0 U

b

/

n

c

~

m

I

I

43

~

-. SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORMATION) OF RN-220 SOURCES

3

E

GONADS

ST CONTENT

Sf CONTENT

ULI CONTENT

GONADS

1 - 2 3 01

7.9E-10

1.2E-08

1.6E-08

1.4E-09

1.4E-09

RMARROW

4.1E-09

1.4E-09

3.33-09

2.83-09

4.1E-09

4.23-02

BONE SURF

1.2E-09

8.OE-10

1 .OE-09

9.5E-10

2.6E-01

2.6E-01

S T WALL

l.1E-09

2.53-03

4.53-09

4.83-09

7.7E-10

7.7E-10

SI WALL

1.6E-08

3.53-09

1.6E-03

2.1 E-08

l.lE-09

1.1 E-09

ULIWALL

1.5E-08

4-33-09

3.OE-08

2.8E-03

9.4E-10

9.4E-10

PANCREAS

7.8E-10

2.3E-08

2-73-09

2-43-09

1.2E-09

1.2E-09

TARGETS

5m 3e

CORT BONE TRAB BONE

*

2 P:

Cl

a W

h

S

rn W U

0 IA

:

g

I

W W

I W m

APPENDIX A

I I W W N b m

I I W W I I -

W m

~ P

l

1

l

1

1

1

n

1

r

W ~

-

W l

.

W W W W ~ c o h

-

W h

.

H

.

-

n o . I I W W w

-

1 2 W a

3 0 0 - o m c . - . - - - 0 0 I I I I I W W W W = a m I - r n -

m

.

U

2 0

/

m

I

45

m

% \

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORMATION) OF PB-212 h¶ v

z m

SOURCES GONADS

ST CONTENT

SI CONTENT

UL I CONTENT

GONADS

1.6E-02

2.53-07

5.83-06

6.43-06

4.OE-07

4.OE-07

R MARROW

2.63-06

7.5E-07

2.03-06

1.7E-06

2-23-06

6.1E-05

BONE SURF

7.33-07

4.3E-07

6.OE-07

5-43-07

3-33-04

3.33-04

ST WALL

4.23-07

3.83-04

2.OE-06

2.03-06

3.OE-07

3.OE-07

SI WALL

6.6E-06

1.4E-06

2.4E-04

9.3E-06

4.1E-07

4.1E-07

ULI WALL

6.23-06

1.9E-06

1.4E-05

4.2E-04

3.83-07

3.83-07

PANCREAS

2.53-07

1.OE-05

1.1E-06

1.2E-06

5.33-09

5.33-07

TARGETS

CORT BONE TRAB BONE

B>

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORMATION) OF BI-212 SOURCES TARGETS GONADS

ST CONTENT

CONTENT

UL I CONTENT

CORT BONE TRAB BONE

GONADS

4.1E 00

5.4E-06

5.93-0 7

R MARROW

1.8E-06

1.5E-06

1.9E-06

BONE SURF

5.4E-07

4.7E-07

9.1E-02

ST WALL

5-33-07

3.53-07

SI WALL

6.83-06

4-93-07

ULI WALL

6.4E-06

4-53-07

PANCREAS

4.1E-07

6.23-07

APPENDIX A C

I

0

W m

I-.

C

W

I

0

m

I-.

0 0

0

0

0

0

0 0

r4

a

5 rn

W

m

0

z

APPENDIX A

/ 49

50

/

APPENDIX A

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, DAC, ( 4 0 Hr/Wk) FOR NP-232

QRAL

INHALATION

INHALATION

f , = I .E-03

CLASS W f ,=I .E-03

CLASS W f , = I . E-03

6.E 09

8.E 07 (2.E 08) BONE SURF

4.E 04

NUMBER OF NUCLEAR TRANSFORMATIONS OVER 50 YEARS I N SOURCE ORGANS OR TISSUES PER UNIT INTAKE OF ACTIVITY (TRANSFORMATIONS/Bq) OF NP-233

rn

ORGAN

f , = 1 .E-03

LUNGS S T CONTENT SI CONTENT ULI CONTENT LLI CONTENT

NP-233 U-233 NP-233 U-233 NP-233 U-233 NP-233 U-233 NP-233 U-2 3 3

1.7E 03 8.33-07 1.2E 03 5.7E-06 2.4E 02 2.OE-05 1.6E 01 3.73-05

INHALATION CLASS W f ,=1 .E-03 9.3E 02 4.5E-04 3.5E 01 7.8E-07 2.5E 01 3-23-06 5.1E 00 1.OE-05 3.3E-01 1 .9E-05

52 / APPENDIX A

APPENDIX A

/

-

53

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, D A C , (40 Hr/Wk) FOR NP-233

DRAL

INHALATION

f , = I .E-03

f , = I .E-03

CLASS W

CLASS W f , = 1 .E-03

-

NUMBER OF NUCLEAR TRANSFORMATIONS OVER 50 YEARS SOURCE ORGANS OR TISSUES PER UNIT INTAKE OF ACTIVITY (TRANSFORMATIONS/Bq) OF NP-234

ORGAN

GONADS LUNGS S I CONTENT ULI CONTENT L L I CONTENT LIVER CORT BONE TRAB BONE

ORAL

NP- 2 3 4 U-2 3 4 NP-234 U-234 NP-234 U-234 NP-234 U-234 NP-234 U-234 NP-234 U- 2 3 4 NP-234 U-234 NP-234 U-234

CLASS W f , = 1 .E-03 4.5E 00 1.OE-03 8.9E 04 4.6E-02 5.2E 03 1.1E-04 1.5E 0 4 4.1 E-04 2.5E 0 4 9-53-00 3.9E 03 6.2E-01 9.6E 03 2 - 0 3 00 9.5E 03 2.03 00

5

m I

0

-

-

VIW L n .

4 I4 II U w

APPENDLX A

/

55

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, DAC, (40 H r / W k ) FOR NP-234

Au2.E&l

DAC ( B a / m 3 )

aaaL

INHALAITION

INHALATION

f ,=1 .E-03

CLASS W f ,=I .E-03

f ,=1 .E-03

CLASS W

H H & H 0

a E 4am W O Z I4 A

APPENDIX A

O

.

*

.

r

.

Z Z

W W

r

I

aa=Tm=T;f 0 0 0 0 0 0

0

.

1

m 0 0

W Q

W W W W W W *

* W

. .

at-IOaOhlw

II

H H

z z

Z W W W H H

H

r

r *

-In w

UI

nm

H Z 2 0 0 z o o mm ouua w ~ l m H H 3 G 4

4uu Z Z

o ~ ~ ; r urlw3I44uw

~

/

~

57

o

a

58

/ APPENDIX A

APPENDIX A

/

59

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, DAC, ( 4 0 Hr/Wk) FOR NP-235 ALLmSfl

DAC ( B p / m 3 )

ORAL

fNHALATION

INHALATION

f , = 1 .E-03

CLASS W f ,=I .E-03

f , = I .E-03

8.E 08 ( 1 .E 09) LLI WALL

4.E 07 (6.E 07) BONE SURF

CLASS W 2.E

04

60

/

APPENDIX A

W - 2 3 6 (1.15E 05 v l NUMBER OF NUCLEAR TRANSFORMATIONS OVER 50 YEARS IN SOURCE ORGANS OR TISSUES PER UNIT INTAKE OF ACTIVITY (TRANSFORMATIONS/Bq) O F NP-236 (1.15E 05 y ) P&BL

ORGAN

INHALATION CLASS W

f ,=I .E-03 GONADS

CORT BONE

TRAB BONE

NP-236 U-236 TH-232 RA-228 AC-228 PU-236 U-232 TH-228 RA-224 RN-220 PO-2 16 PB-2 12 BI-212 PO-21 2 NP-236 U-236 TH-232 RA-228 AC-228 PU-236 U-232 TH-228 RA-224 RN-220 PO-2 1 6 PB-2 12 BI-212 PO-21 2 NP-236 U-2 3 6 TH-232 RA-228 AC-228 PU-236 U-232 TH-229 RA-224 RN-220 PO-21 6 PB-212 BI-212 PO-2 12

2.1E 04 1.4E-02 1.2E-11 7.4E-12 7.4E-12 1.7E 03 3.3E 02 2.9E 02 2.9E 02 2.9E 02 2.9E 02 2.9E 0 2 2.9E 0 2 1.9E 02 4.OE 07 2.6E 01 2.OE-08 1.3E-08 1.3E-08 3.2E 06 5.9E 05 5.3E 05 5.3E 05 5.3E 05 5.3E 05 5.3E 05 5.3E 05 3.4E 05 4.OE 07 2.6E 01 2.OE-08 1.3E-08 1.3E-08 3.2E 06 5.9E 05 5.3E 05 5.3E 05 5.3E 05 5.3E 05 5.3E 05 5.3E 0 5 3.4E 05

APPENDIX A

/ 61

62 / APPENDIX A

rnw

rn

57 Ou;

APPENDIX A NUMBER OF NUCLEAR TRANSFORHATIONS OVER 5 0 YEARS I N SOURCE ORGANS OR T I S S U E S PER U N I T I N T A K E 0 1 A C T I V I T Y ITP.ANSPOBttATIONSIBq1 OF N P - 2 3 6 1 2 2 . 5 h )

GONADS

S I CONTENT

U L I CONTENT

L L I CONTENT

CORT BONE

I R A 0 BORE

NP-236 U-216

f,~-l.E-o3 1.2E-02 9.lE-09

CLASS Y f , S I .E-03 9.8E-01 I .Z E - 0 6

PO-212 HP-236 U-216 TH-232 11A-2211 AC-228 PU-236 U-232 TM-228 RA-220 1111-220 PO-216 PB-212 81-212 PO-212 NP-236 U-2 1 6 TH-232 RA-228 AC-228 PU-236 U-232 TH-228 RA-220 nw-220 PO-216 PB-212 POW212 NP-236 U-216 TH-232 AC-228 PU-236 U-212 TH-228 RA-220 UN-220 PO-216 PB-2 1 2 BI-212 PO-2 1 2 NP-236 U-216 TH-232 U-228 AC-128 PU-236 U-212 TH-221 RA-22U RN-220 PO-2 1 6 PB-212 BI-212 PO-212 YP-236 U-236 TH-232 RA-228 AC-228 PU-236 U-212 TH-220 11A-224 11H-220 PO-216 PB-212 .I-212 PO-212

1.7E-09 3.18 04 1.2E-06 5.8e-19

1 .OE-OV 8 . l E 03 2.OE-06 5.3E-18

/

63

(22.5 h )

P

v v

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORMATION) OF NP-236 SOURCES TARGETS

8z P

GONADS

SI CONTENT

UL I CONTENT

LL I CONTENT

GONADS

8.33-03

2.OE-06

2.23-06

3.33-06

RMARROW

1.1E-06

8.33-07

7.1E-07

BONE SURF

3.OE-07

2.4E-07

SI WALL

2-33-06

ULI WALL LLI WALL

CORT BONE TRAB BONE 1.4E-07

1.4E-07

1 OE-06

1 - 1 E-06

3.OE-05

2.23-07

3.2E-07

1.8E-04

1.8E-04

1.2E-04

3.3E-06

1 .8E-06

1 .3E-07

1.3E-07

2.33-06

5.93-06

2.1E-04

8-43-07

1 .2E-07

1.2E-07

3.OE-06

1.5E-06

6.1E-07

.3.4E-04

1 .8E-07

1.8E-07

.

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORMATION) OF U-236 SOURCES TARGETS GONADS

SI CONTENT

UL I CONTENT

GONADS

8.3E 00

4.23-08

5-53-08

R MARROW

4.63- 0 9

7.33-09

4 -63-09

BONE SURF

1.2E-09

1 .8E-09

1.2E-09

SI WALL

4-73-08

1.1E-03

9-83-08

ULI WALL

1.1E-07

6.73-07

2.0E-03

LLI WALL

1.4E-07

8.23-08

9.1E-09

LLI CONTENT

CORT BONE TRAB BONE

P

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORMATION) OF TH-232

E?

zs

SOURCES TARGETS

P

GONADS

SI CONTENT

ULI CONTENT

LLI CONTENT

GONADS

7.4E 00

2.83-08

3.63-08

7-63-08

5.7E-10

5.7E-10

RMARROW

5.93-09

6-63-09

4.63-09

1.1E-08

8.53-08

2.7E-02

BONE SURF

1 .5E-09

1 .7E-09

1 .3E-09

3.OE-09

1 -7E-01

1 .7E-0 1

SI WALL

3.OE-08

1.OE-03

5.93-08

3.23-08

6.8E-10

6.8E--10

ULI WALL

6-53-08

4.23-07

1.8E-03

2.23-08

7.1E-10

7.1E-10

LLIWALL

8.1E-08

5.OE-08

6.1E-09

3.OE-03

1.5E-09

1.5E-09

CORT BONE TRAB BONE

SPECIFIC EFFECTIVE ENERGY ( M e V PER GRAM PER TRANSFORMATION) OF RA-228 SOURCES TARGETS GONADS GONADS

1.5E-03

R MARROW

3.1 E- 1 6

BONE SURF

7.53- 1 7

SI WALL

7.9E-15

ULI WALL

2.53-14

LLI WALL

2.7E-14

SI CONTENT

ULI CONTENT

LLI CONTENT

CORT BONE TRAB BONE

SPECIFIC EFFECTIVE ENERGY ( M e V PER GRAM PER TRANSFORMATION) OF AC-228

k-

m

z

u 2

SOURCES TARGETS

*

GONADS

SI CONTENT

ULI CONTENT

LL I CONTENT

GONADS

4.6E-02

3.OE-05

2.7E-05

5.43-05

3.OE-06

3.OE-06

RMARROW

9.6E-06

7-93-06

6.7E-06

9.83-06

1.OE-05

1.7E-04

BONE SURF

2.9E-06

2.5E-06

2.3E-06

3.3E-06

2.7E-04

3.03-04

S I WALL

3.6E-05

7-03-04

5.OE-05

2,8E-05

2.6E-06

2.63-06

ULI WALL

3-43-05

7-33-05

1.2E-03

1.3E-05

2.43-06

2.43-06

LLI WALL

4.33-05

2-23-05

1.OE-05

1-9E-03

3.3E-06

3.33-06

CORT BONE TRAB BONE

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORMATION) OF PU-236 SOURCES TARGETS GONADS GONADS

1.1E 01

R MARROW

6.7E-09

BONE SURF

1.6E-09

SI WALL

7.4E-08

ULI WALL

1 .6E-07

LLI WALL

2.1E-07

SI CONTENT

ULI CONTENT

LLI CONTENT

CORT BONE TRAB BONE

SPECIFIC EFFECTIVE ENERGY ( M e V PER GRAM PER TRANSFORMATION.) OF U-232

> m

3 i? *

SOURCES TARGETS GONADS

SI CONTENT

ULI CONTENT

LL I CONTENT

GONADS

9.8E 00

6.3E-08

8.OE-08

1.8E-07

1.2E-09

1.2E-09

R MARROW

1.1E-08

1.3E-08

9.1E-09

2.6E-08

1.8E-07

3.5E-02

BONE SURF

2.8E-09

3.4E-09

2.43-09

6.7s-09

2.2E-01

2.2E-01

SI WALL

7.1 E-08

1.3E-03

1.4E-07

7.5E-08

1.3E-09

1.3E-09

ULI WALL

1.5E-07

8.7E-07

2.4E-03

4.9E-08

1.4E-09

1.4E-09

LLI WALL

1.9E-07

l.lE-07

1.4E-08

4.OE-03

3.2E-09

3.2E-09

CORT BONE TRAB BONE

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER TRANSFORHATION) OF TH-228 SOURCES -.

TARGETS GONADS GONADS

1.OE 01

R MARROW

4.9E-08

BONE SURF

1.3E-08

SI WALL

1 .3E-07

ULI WALL

1.7E-07

LLI WALL

2-23-07

SI CONTENT

UL I CONTENT

LL I CONTENT

CORT BONE TRAB BONE

SPECIFIC EFFECTIVE ENERGY ( M e V PER GRAM P E R TRANSFORMATION) OF RA-224

> ; m

z

SOURCES TARGETS

8

>

GONADS

SI CONTENT

UL I CONTENT

LL I CONTENT

GONADS

1.1E01

3.63-07

4.1E-07

6.83-07

2.6E-08

2-63-08

R MARROW

1.4E-07

1 - 1 E-07

9-83-08

1.4E-07

1.2E-07

3.83-02

BONE SURF

4.1E-08

3.53-08

3.1E-08

4-53-08

2.4E-01

2.4E-01

SI WALL

4.2E-07

1.4E-03

5-83-07

3.33-07

2.7E-08

2-73-08

ULIWALL

4.OE-07

8.4E-07

2-53-03

1.5E-07

2.63-08

2.63-08

L L I WALL

5.1E-07

2-53-07

1.1E-07

4.23-03

3.73-08

3-73-08

CORT BONE TRAB BONE

I

l

l

W t

W

l

-

m

W

W m

W

O

W

W b

l

0

m

a

0

n

W

l

W ;

APPENDIX A

W ~

-

I

-

.

c

W

a 0

W N

W

QI

l

W

W

I

7

0

0 I

I

0 I

l

W

l

l

W

0 I

QI

l

U)

W m

I

W

U)

m

SPECIFIC E F F E C T I V E ENERGY ( M e V P E R GRAM P E R TRANSFORMATION) OF PO-216

5

SOURCES TARGETS

+

GONADS

SI CONTENT

ULI CONTENT

LL I CONTENT

GONADS

1.3E 01

5.5E-10

5.3E-10

9.3E-10

5.7E-11

5.7E-11

R MARROW

1.7E-10

1.4E-10

1 .2E-10

1-.7E-10

1 -7E-10

9.53-02

B O N E SURF

5.1E-11

4.4E-11

3.9E-11

5.7E-11

2.8E-01

2.8E-01

SI WALL

6.4E-10

1.7E-03

8.9E-10

5.OE-10

4.7E-11

4.7E-11

ULI WALL

6.OE-10

1.3E-09

3.OE-03

2.3E-10

4.3E-11

4.3E-11

LLI W A L L

7.6E-10

3.8E-10

1.8E-10

5.OE-03

1.8E-11

5.8E-11'

C O R T B O N E TRAB BONE

SPECIFIC EFFECTIVE ENERGY (MeV PER GRAM PER 'RANSFORMATION)

OF. PB.-212

SOURCES TARGETS GONADS

SI CONTENT

ULI CONTENT

LL I CONTENT

GONADS

1 .6E-02

5.8E-06'

6-43-06

1 . I E-05

4.O.E-07

4.OE-07

R HARROW

2.63-06

2.OE-06

1 .7E-06

2.53-06

'2.2E-06

6.1 E-05

BONE' SURF

7.-3E-07

6.OE-07

5.. 4E-07

8.OE-07

3.3E-04

3 ..3E-04

SI WALL

6.6E-06-

2.4E-04

9.3E-06

5.ZE-06

4.1E-0.7

4.1E-0.7.

ULI WALL

6-23-06

1.4E-05

4.23-04

2.3E-06

3.8E-07

3..83-07

LLI WALL

8.OE-06

4.OE-06.

1.7E-06

6,.8E-04

5.63-07.

5.6E-07

CORT BONE TRAB BONE

% 'd L? IF

SPECIFIC EFFECTIVE ENERGY ( M e V PER GRAM PER TRANSFORMATION) OF BI-212

5

m

-z

SOURCES TARGETS

t3 X P

GONADS

SI CONTENT

ULI CONTENT

LLI CONTENT

GONADS

4.1E 00

5.4E-06

5.53-06

9.93-06

5.9E-07

5.9E-07

R MARROW

1.8E-06

1.5E-06

1.2E-06

1.8E-06

1.9E-06

1.5E-02

BONE SURF

5.4E-07

4.73-07

4.23-07

6.1E-07

9.1E-02

9.1E-02

S I WALL

6.83-06

1.2E-03

9.43-06

5.33-06

4.9E-07

4.9E-07

ULI WALL

6.43-06

1.YE-05

2.1E-03

2.5E-06

4.53-07

4.53-07

LLIWALL

8.1E-06

4.1E-06

1.83-06

3.43-03

6.1E-07

6.1E-07

CORT BONE TRAB BONE

rn PI

W U

S 0 Ln

Z

o

a . o

p z . o

U

H z

H W

U

0

A H

3

o

o o

m

W m o

o

o

APPENDIX A

o

o

o

o

I

o

m

m 0

o

/

77

78 / APPENDIX A

APPENDIX A

. Z

W W W r m o

1

79

APPENDIX

H

>I H

3 H

rn I3

au 0

*2 E 0

I

m

mmk

x

a < N

W

>zc4

&

k 0

O H Z

# 4 # V l

W O Z A 4

U Vl a 5 Z;H

z6-

b m b m m m m m 1

1

1

1

N N N N

Ptr4PI4 ZPIZPI

COMMITTED DOSE EQUIVALENT IN TARGET ORGANS OR TISSUES PER INTAKE OF UNIT ACTIVITY ( S v / B q ) OF NP-237

nRAL f , = 1 .E-03 R MARROW 1.7E-06 BONE SURF 2.1E-05

INHALATION CLASS W f , = 1 .E-03 R MARROW 2.OE-04 ( 2 5 , 33, 4 2 ) BONE SURF 2.6E-03 (25, 33, 4 2 )

82

/

APPENDIX A

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, DAC, ( 4 0 Hr/Wk) FOR NP-237 DAC

Au-uSLL DRAL f , = I .E-03

2.E 04 ( 6 . E 04)

BONE SURF

(~a/rn~)

DuAuTDm

INHALATION

CLASS W

CLASS W f , = I .E-03

f , = 1 .E-03

2.E 0 2 (5.E 02) BONE SURF

8. E-02

NUMBER OF NUCLEAR TRANSFORMATIONS OVER 50 YEARS IN SOURCE ORGANS OR TISSUES PER UNIT INTAKE OF ACTIVITY (TRANSFORMATIONS/Bq) OF NP-238

aRGAN

ORAL

INHALATION CLASS W f , = 1 .E-03

GONADS SI CONTENT ULI CONTENT

LLI CONTENT CORT BONE TRAB BONE

NP-238 PU-238 NP-238 PU-238 NP-238 PU-238 NP-238 PU-238 NP-2 38 PU-238 NP-238 PU-238

2.2E 00 1.1E 00 4.4E 03 1.9E-01 1.2E 04 7.7E-0 1 1.7E 04 1.8E 00 4.3E 03 2.2E 03 4.2E 03 2.2E 03

84

/ APPENDIX A

APPENDIX A

/

85

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, DAC, ( 4 0 Hr/Wk) FOR NP-238

f!mL

3;NHALATION

f , = I .E-03

CLASS W f ,=1 .E-03

5.E 07

3 . E 06 (7.E 0 6 ) BONE SURF

INHALATION CLASS W f , = I .E-03 l . E 03

NUMBER OF NUCLEAR TRANSFORMATIONS OVER 50 YEARS IN SOURCE ORGANS OR TISSUES PER UNIT INTAKE OF ACTIVITY (TRANSFORMATIONS/Bql OF NP-239

QRAL

ORGAN

LUNGS SI CONTENT

ULI CONTENT LLI CONTENT CORT BONE TRAB BONE

NP-239 PU-239 NP-239 PU-2 3 9 NP-239 PU-2 3 9 NP-239 PU-2 3 9 NP-239 PU-239 NP-239 PU-239

INHALATION CLASS W f , = I .E-03 5.4E 0 4 2.6E-01 4.6E 03 7.4E-04 1.3E 04 3.OE-03 1.8E 04 6.9E-03 4.9E 03 1.1E 01 4.8E 03 1.1E 01

*eel "0

tl

2

P

m 3 0 a,

h

aoQ

3 m

m a

-

N

n

0

n

cud cu Jcn .

7

APPENDIX A

do,

cud

-

m WI U 7OI N I U I Z I I - 5 1 n . U W W W * W.WI4-Zzr zu, ~m ~ a , W a .

-

m

Y

\O U)

-

/

d 11 3 -0 - A * -a u -ciwom-rn~-rn~~m

87

88

/

APPENDIX A

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, DAC, ( 4 0 Hr/Wk) FOR NP-239

DRAL

f ,=1 .E-03 6.E 07 (6.E 0 7 ) LLS WALL

INHALATION

INHALATION

CLASS W f ,=1 .E-03

CLASS W f , = 1 .E-03

9.E 07

4.E 04

NUMBER OF NUCLEAR TRANSFORMATIONS OVER 5 0 YEARS IN SOURCE ORGANS OR TISSUES PER UNIT INTAKE OF ACTIVITY (TRANSFORMATIONS/Bq) OF NP-240

ORGAN

QRAL

INHALATION

f ,=1 .E-03

f , = 1 .E-03

2.2E 03 2.7E-05 2.5E 03 2.33-04 8.6E 0 2 8.73-04 9.7E 01 1.6E-03 8.43-02 6.23-03 4.9E-02 6.23-03

1.6E 03 1.9E-02 7.8E 01 3-33-05 8.8E 01 1.4E-04 3.1E 01 4.5E-04 3.5E 0 0 8.3E-04 2.8E 01 7.5E-01 1.6E 01 7.5E-0 1

CLASS W LUNGS ST CONTENT SI CONTENT ULI CONTENT LLI CONTENT CORT BONE TRAB BONE

NP-240 PU-240 NP-240 PU-240 NP-240 PU-240 NP-240 PU-240 NP-240 PU-240 NP-240 PU-240 NP-240 PU-240

COMMITTED D O S E EQUIVALENT I N T A R G E T ORGANS OR TISSUES PER I N T A K E OF U N I T ACTIVITY (Sv/Bq) OF NP-240

naBL

INHALATION

%

zu v

2 P

f ,=1 .E-03 GONADS 2.5E-11 ST W A L L 3.8E-10 SI WALL 2.7E-10 UL I W A L L 2.OE-10 LLI WALL 4.3E-11

CLASS W f ,=1 .E-03 LUNGS 1.3E-10 ( 0 , 14, 8 6 ) B O N E SURF 5.5E-11 ( 2 5 , 34, 4 1 )

APPENDIX A

/

91

ANNUAL LIMITS ON INTAKE, ALI, AND DERIVED AIR CONCENTRATIONS, DAC, ( 4 0 Hr/Wk) FOR NP-240

AuLma

DAC ( ~ a / r n ~ )

ORAL

INHALATION

INHALATION

f , = I .E-03

CLASS W f , = 1 .E-03

CLASS W f , = I .E-03

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"The influence of oxidation state on the absorption of plutonium from the gastrointestinal tract," Radiat. Res. 8 0 , 116. SULLIVAN, M. F. (198Oa). "Absorption of actinide elements from the gastrointestinal tract of rats, guinea pigs and dogs," Health Phys. 3 8 , 159. SULLIVAN, M. F. (1980b). "Absorption of actinide elements from the gastrointestinal tract of neonatal animals," Health Phys. 38, 173. SULLIVAN, M. F. (1981). "Actinide absorption from the gastrointestinal tract," page 311 in Actinides in Man and Animals, Wrenn, M. E., ed. (R. D. Press, Salt Lake City, Utah). M. F. A N D GORHAM, L. S. (1982). "Further studies on the absorpSULLIVAN, tion of actinide elements from the gastrointestinal tract of neonatal animals," Health Phys. 43, 509. SULLIVAN, M. F., MILLER,B. M. AND RYAN,J. L. (1983a). "Effect of mass on the gastrointestinal absorption of plutonium and neptunium," Radiat. Res. 94,199. L. S. (1983b). "Nutritional SULLIVAN, M. F., MILLER,B. M. A N D GORHAM, influences on plutonium absorption from the gastrointestinal tract of the rat," Radiat. Res. 96, 580. SULLIVAN, M. F., MILLER,B. M. A N D RYAN,J. L. (1983~)."Absorption of thorium and protactinium from the gastrointestinal tract in adult mice and rats and neonatal rats," Health Phys. 44, 425. SULLIVAN, M. F., RUEMMLER, P. S. A N D RYAN,J. L. (1984a). "Effects of fasting and/or oxidizing and reducing agents on absorption of neptunium from the gastrointestinal tract of mice and adult or neonatal rats," Radiat. Res. 100,519. SULLIVAN, M. F. (1984b). "Gut-related studies of radionuclide toxicity," page 61 in Pacific Northwest Laboratory Annual Report for 1983 to the DOE Office of Energy Research, Part 1, Biomedical Sciences, Report No. PNL-5000 Pt. 1 (Pacific Northwest Laboratory, Richland, Washington). P. S. (1985). uFurther SULLIVAN, M. F., MILLER,B. M. AND RUEMMLER, studies of the influence of chemical form and dose on absorption of neptunium, plutonium, americium, and curium from the gastrointestinal tract of adult and neonatal rodents," Health Phys. 48, 61. R. C. (1982). "Neptunium-the neglected actinide: A review of THOMPSON, the biological and environmental literature," Radiat. Res. 90, 1. WATSON,S. B. A N D FORD,M. R. (1980). A Users Manual to the ICRP CodeA Series of Computer Programs to Perform Dosimetric Calculations for the ICRP Committee 2 Report, Report No. ORNLITM-6980 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). D. N., HAKONSON, T. E., HANSON,W. C., WATTERS,R. L., EDCINCTON, SMITH, M. H., WHICKER, F. W. AND WILDUNC, R. E. (1980). "Synthesis of the research literature," page 1 in Transuranic Elements in the Environment, Hanson W. C., ed. (U.S. Department of Energy, Technical Information Center, Oak Ridge, Tennessee). G. A. A N D BAIRD,R. (1967). "Uranium levels in human diet and WELFORD, biological materials," Health Phys. 1 3 , 1321.

The NCRP The National Council on Radiation Protection and Measurements is a nonprofit corporation chartered by Congress in 1964 to: 1. Collect, analyze, develop, and disseminate in the public interest information and recommendations about (a) protection against radiation and (b) radiation measurements, quantities, and units, particularly those concerned with .radiation protection; 2. Provide a means by which organizations concerned with the scientific and related aspects of radiation protection and of radiation quantities, units, and measurements may cooperate for effective utilization of their combined resources, and to stimulate the work of such organizations. 3. Develop basic concepts about radiation quantities, units, and measurements, about the application of these concepts, and about radiation protection; 4. Cooperate with the International Commission on Radiological Protection, the International Commission on Radiation Units and Measurements, and other national and international organizations, governmental and private, concerned with radiation quantities, units, and measurements and with radiation protection. The Council is the successor to the unincorporated association of scientists known as the National Committee on Radiation Protection and Measurements and was formed to carry on the work begun by the Committee. The Council is made up of the members and the participants who serve on the eighty-two scientific committees of the Council. The scientific committees, composed of experts having detailed knowledge and competence in the particular area of the committee's interest, draft proposed recommendations. These are then submitted to the full membership of the Council for careful review and approval before being published. The following comprise the current officers and membership of the Council: officers President Vice President Secretary and Treasurer Assistant Secretary Assistant Treasurer

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Members

Honorary Members

LAURISTON S. TAYLOR, Honorary

President

WILFRID B. MANN KARL2.MORGAN ROBERTD. MOSELEYJR: ROBERTJ. NELSEN HARALDH. ROSSI WILLIAM C. RUSSELL JOHNH. RUST EUGENEL. SAENCER J. NEWELLSTANNARD HAROLD0. WYCKOFF 'Elected posthumously

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Currently, the following subgroups are actively engaged in formulating recommendations: Basic Radiation Protection Criteria Medical X-Ray, Electron Beam and Gamma-Ray Protection for Energies Up to 50 MeV (Equipment Performance and Use) X-Ray Protection in Dental Offices Standards and Measurements of Radioactivity for Radiological Use Radiation Exposure from Consumer Products Biological Aspects of Radiation Protection Criteria Task Croup on Atomic Bomb Survivor Dosimetry Subgroup on Biological Aspects of Dosimetry of Atomic Bomb Survivors Natural Background Radiation Radiation Associated with Medical Examination Radiation Received by Radiation Employees Operational Radiation Safety Task C ~ o u p2 on Uranium Mining and Milling-Radiation Safety Programs Task Croup 3 on ALARA for Occupationally Exposed Individuals in Clinical Radiology Task Croup 4 on Calibration of Instrumentation Task Croup 5 on Maintaining Radiation Protection Records Task Croup 6 on Radiation Protection for Allied Health Personnel Task Croup 7 on Emergency Planning Task Group 8 on Radiation Protection Design Guidelines for Particle Accelerators Task Croup 9 on ALARA a t Nuclear Power Plants Instrumentation for the Determination of Dose Equivalent Assessment of Exposure of the Population Conceptual Basis of Calculations of Dose Distributions Internal Emitter Standards Task Croup 2 on Respiratory Tract Model Task Croup 5 on Gastrointestinal Models Task Croup 6 on Bone Problems Task Croup 8 on Leukemia Risk Task Croup 9 on Lung Cancer Risk Task Croup 10 on Liver Cancer Risk Task Croup 11 on Genetic Risk Task Croup 12 on Strontium Task Croup 14 on Placental Transfer Task Croup 15 on Uranium Human Radiation Exposure Experience Radon Measurements Radiation Exposure Control in a Nuclear Emergency Task Croup on Public Knowledge About Radiation Task Croup on Exposure Criteria for Specialized Categories of the Public Radionuclides in the Environment Task Croup 5 on Public Exposure from Nuclear Power Task Group 6 on Screening Models Task Croup 7 on Contaminated Soil as a Source of Radiation Exposure

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Task Group 8 on Ocean Disposal of Radioactive Waste Task Group 9 on Biological Effects on Aquatic Organisms Task Group 10 on Low Level Waste Task Group 11 on Xenon SC-65: Quality Assurance and Accuracy in Radiation Protection Measurements SC-66. Biological Effects and Exposure Criteria for Ultrasound SC-67: Biological Effects of Magnetic Fields SC-68: Microprocessors in Dosimetry SC-69: Efficacy of Radiographic Procedures SC-70: ~ u a l i t y~ s s u r a n c ;and Measurement in Diagnostic Radiology SC-71: Radiation Exposure and Potentially Related Injury SC-74: Radiation ~ i e i v e din the ~ e c o n t a k i n a t i o no f ~ u c l e a Facilities r SC-75: Guidance on Radiation Received in Space Activities SC-76: Effects of Radiation on the Embryo-Fetus SC-77: Guidance on Occupational and Public Exposure Resulting from Diagnostic Nuclear Medicine Procedures SC-78: Practical Guidance on the Evaluation of Human Exposures in Radiofrequency Radiation SC-79: Extremely Low-Frequency Electric and Magnetic Fields SC-80: Radiation Biology of the Skin (Beta-Ray Dosimetry) SC-81: Assessment of Exposure from Therapy SC-82: Control of Indoor Radon Study Group on Comparative Risk Task Group on Comparative Carcinogenicity of Pollutant Chemicals Ad Hoc Group on Medical Evaluation of Radiation Workers Ad Hoc Group on Video Display Terminals Task Force on Occupational Exposure Levels

In recognition of its responsibility to facilitate and stimulate cooperation among organizations concerned with the scientific and related aspects of radiation protection and measurement, the Council has created a category of NCRP Collaborating Organizations. Organizations or groups of organizations that are national or international in scope and are concerned with scientific problems involving radiation quantities, units, measurements, and effects, or radiation protection may be admitted to collaborating status by the Council. The present Collaborating Organizations with which the NCRP maintains liaison are as follows: American Academy of Dermatology American Association of Physicists in Medicine American College of Nuclear Physicians American College of Radiology American Dental Association American Industrial Hygiene Association American Institute of Ultrasound in Medicine American Insurance Association American Medical Association American Nuclear Society

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American Occupational Medical Association American Podiatric Medical Association American Public Health Association American Radium Society American Roentgen Ray Society American Society of Radiologic Technologists American Society for Therapeutic Radiology and Oncology Association of University Radiologists Atomic Industrial Forum Bioelectromagnetics Society College of American Pathologists Conference of Radiation Control Program Directors Federal Communications Commission Federal Emergency Management Agency Genetics Society of America Health Physics Society National Bureau of Standards National Electrical Manufacturers Association Radiation Research Society Radiological Society of North America Society of Nuclear Medicine United States Air Force United States Army United States Department of Energy United States Department of Housing and Urban Development United States Department of Labor United States Environmental Protection Agency United States Navy United States Nuclear Regulatory Commission United States Public Health Service

The NCRP has found its relationships with these organizations to be extremely valuable to continued progress in its program. Another aspect of the cooperative efforts of the NCRP relates to the special liaison relationships established with various governmental organizations that have an interest in radiation protection and measurements. This liaison relationship provides: (1) an opportunity for participating organizations to designate an individual to provide liaison between the organization and the NCRP; (2) that the individual designated will receive copies of draft NCRP reports (at the time that these are submitted to the members of the Council) with an invitation to comment, but not vote; and (3) that new NCRP efforts might be discussed with liaison individuals as appropriate, so that they might have an opportunity to make suggestions on new studies and related matters. The following organizations participate in the special liaison program: Commission of the European Communities Commisariat a I'Energie Atomique (France)

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Defense Nuclear Agency Federal Emergency Management Agency Japan Radiation Council National Bureau of Standards National Radiological Protection Board (United Kingdom) National Research Council (Canada) Office of Science and Technology Policy Office of Technology Assessment United States Air Force United States Army United States Coast Guard United States Department of Energy United States Department of Health and Human Services United States Department of Labor United States Department of Transportation United States Environmental Protection Agency United States Navy United States Nuclear Regulatory Commission

The NCRP values highly the participation of these organizations in the liaison program. The Council's activities are made possible by the voluntary contribution of time and effort by its members and participants and the generous support of the following organizations: Alfred P. Sloan Foundation Alliance of American Insurers American Academy of Dental Radiology American Academy of Dermatology American Association of Physicists in Medicine American College of Nuclear Physicians American College of Radiology American College of Radiology Foundation American Dental Association American Hospital Radiology Administrators American Industrial Hygiene Association American Insurance Association American Medical Association American Nuclear Society American Occupational Medical Association American Osteopathic College of Radiology American Podiatric Medical Association American Public Health Association American Radium Society American Roentgen Ray Society American Society of Radiologic Technologists American Society for Therapeutic Radiology and Oncology American Veterinary Medical Association American Veterinary Radiology Society Association of University Radiologists

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Atomic Industrial Forum Battelle Memorial Institute Center for Devices and Radiological Health College of American Pathologists Commonwealth of Penhsylvania Defense Nuclear Agency Edison Electric lnstitute Edwa~dMallidckrodt, Jr. Foundation Electric Power Research Institute Federal Emergency Management Agency Florida Institute of Phomhate Research Genetics Society of America Health Physics Society Institute of Nuclear Power Operations James Picker Foundation National Aeronautics and Space Administration National Association of Photographic Manufacturers National Bureau of Standards National Cancer Institute National Electrical Manufacturers Association Radiation Research Society Radiological Society of North America Society of Nuclear Medicine United States Department of Energy United States Department of Labor United States Envihnmental Protection Agency United States Navy United States Nuclear Regulatory Commission

To all of these organizations the Council expresses its profound appreciation for their support. Initial funds for publication of NCRP reports were provided by a grant from the James Picker Foundation and for this the Council wishes to express its deep appreciation. The NCRP seeks to promulgate information and recommendations based on leading scientific judgment on matters of radiation protection and measurement and to foster cooperation among organizations concerned with these matters. These efforts are intended to serve the public interest and the Council welcomes comments and suggestions on its reports o t activities from those interested in its work.

NCRP Publications NCRP publications are distributed by the NCRP Publications' office. Information on prices and how to order may be obtained by directing an inquiry to: NCRP Publications 7910 Woodmont Ave., Suite 1016 Bethesda, MD 20814 The currently available publications are listed below.

Proceedings of the Annual Meeting No. 1 2 3

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5 6

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Title Perceptions of Risk, Proceedings of the Fifteenth Annual Meeting, Held on March 14-15, 1979 (Including Taylor Lecture No. 3) (1980) Quantitative Risk in Standards Setting, Proceedings of the Sixteenth Annual Meeting, Held on April 2-3, 1980 (Including Taylor Lecture No. 4) (1981) Critical Issues in Setting Radiation Dose Limits, Proceedings of the Seventeenth Annual Meeting, Held on April 8-9, 1981 (Including Taylor Lecture No. 5) (1982) Radiation Protection and New Medical Diagnostic Procedures, Proceedings of the Eighteenth Annual Meeting, Held on April 6-7, 1982 (Including Taylor Lecture No. 6) (1983) Environmental Radioactivity, Proceedings of the Nineteenth Annual Meeting, Held on April 6-7, 1983 (Including Taylor Lecture No. 7) (1984) Some Issues Important in Developing Basic Radiation Protection Recommendations, Proceedings of the Twentieth Annual Meeting, Held on April 4-5, 1984 (Including Taylor Lecture No. 8) (1985) Radioactive Waste, Proceedings of the Twenty-First Annual Meeting, Held on April 34,1985 (Including Taylor Lecture No. 9) (1986)

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Symposium Proceedings

The Control of Exposure of the Public to Ionizing Radiation in the Event of Accident or Attack, Proceedings of a Symposium held April 27-29, 1981 (1982) Lauriston S. Taylor Lectures No.

Title and Author The Squares of the Natural Numbers in Radiation Protection by Herbert M. Parker (1977) Why be Quantitative About Radiation Risk Estimates? by Sir Edward Pochin (1978) Radiation Protection-Concepts and Trade Offsby Hymer L. Friedell (1979) [Available also in Perceptions of Risk, see above] From "Quantity of Radiation" and "Dose" to "Exposure" and 'lbsorbed Dose''-An Historical Review by Harold 0.Wyckoff (1980) [Available also in Quantitative Risks in Standards Setting, see above] How Well Can We Assess Genetic Risk? Not Very by James F. Crow (1981) [Available also in Critical Issues in Setting Radiation Dose Limits, see above] Ethics, Trade-offs and Medical Radiation b y Eugene L. Saenger (1982) [Available also in Radiation Protection and New Medical Diagnostic Approaches, see above] The Human Environment-Past, Present and Future by Merril Eisenbud (1983) [Available also in Environmental Radioactivity, see above] Limitation and Assessment in Radiation Protection by Harald H . Rossi (1984) [Available also in Some Issues Important in Developing Basic Radiation Protection Recommendations, see above] Truth (and Beauty) in Radiation Measurement by John H. Harley (1985) [Available also in Radioactive Waste, see above] Nonionizing Radiation Bioeffects: Cellular Properties and Interactions by Herman P. Schwan (1987)

NCRP Commentaries Commentary Title No. Krypton-85 in the Atmosphere- With Specific Reference 1 to the Public Health Significance of the Proposed Controlled Release at Three Mile Island (1980)

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Preliminary Evaluation of Criteria for the Disposal of Tramuranic Contaminated Waste (1982) Screening Techniques for Determining Compliance with Environmental Standards (1986) Guidelines for the Release of Waste Water from Nuclear Facilities with Special Refereme to the Public Health Significance of the Proposed Release of Treated Waste Waters at Three Mile Island (1987)

NCRP Reports No.

Title Control and Removal of Radioactive Contamination in Laboratories (1951) Radioactive Waste Disposal in the Ocean (1954) Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and i n Water for Occupational Exposure (1959) [Includes Addendum 1issued in August 19631 Measurement of Neutron Flux and Spectra for Physical and Biological Applications (1960) Measurement of Absorbed Dose of Neutrons and Mixtures of Neutrons and Gamma Rays (1961) Stopping Powers for Use with Cavity Chambers (1961) Safe Handling of Radioactive Materials (1964) Radiation Protection in Edmtional Institutions (1966) Medical X-Ray and Gamma-Ray Protection for Energies Up to 10 MeV-Equipment Design and Use (1968) Dental X-Ray Protection (1970) Radiation Protection in Veterinary Medicine (1970) Precautions in the Management of Patients Who Have Received Therapeutic Amounts of Radionuclides (1970) Protection against Neutron Radiation (1971) Basic Radiation Protection Criteria (1971) Protection Against Radiation from Brachytherapy Sources (1972)

Specification of Gamma-Ray Brachytherapy Sources (1974) Radiological Factors Affecting Decision-Making in a Nuclear Attack (1974) Review of the Current State of Radiation Protection Philosophy (1975) Krypton-85 in the Atmosphere-Accumulatwn, Biological Significance, and Control Technology (1975) Natural Background Radiation in the United States (1975)

NCRP PUBLICATIONS

Alpha-Emitting Particles i n Lungs (1975) Tritium Measurement Techniques (1976) Radiation Protection for Medical and Allied Health Personnel (1976) Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies Up to 10 MeV (1976) Environmental Radiation Measurements ( 1976) Radiation Protection Design Guidelines for 0.1-100 MeV Particle Accelerator Facilities (1977) Cesium-137 From the Environment to Man: Metabolism and Dose (1977) Review of NCRP Radiation Dose Limit for Embryo and Fetus i n Occupatiodly Exposed Women (1977) Medical Radiation Exposure of Pregnant and Potentially Pregnant Women (1977) Protection of the Thyroid Gland in the Event of Releases of Radioiodine (1977) Radiation Exposure From Consumer Products and Miscellaneous Sources (1977) Imtrumentation and Monitoring Methods for Radiation Protection (1978) A Handbook of Radioactivity Measurements Procedures, 2nd ed. (1985) Operational Radiation Safety Program (1978) Physical, Chemical, and Biological Properties of Radiocerium Relevant to Radiation Protection Guidelines (1978) Radiation Safety Training Criteria for Industrial Radiography (1978) Tritium in the Environment (1979) Tritium and Other Radionuclide Labeled Organic Compounds Incorporated i n Genetic Material (1979) Influence of Dose and Its Distribution in Time on DoseResponse Relationships for Low-LET Radiations (1980) Management of Persons Accrdentally Contaminated with Radiorulelides (1980) Mamnamography(1980) Radiofrequency Electromagnetic Fields-Properties, Quantities and Units, Biophysical Interaction, and Measurements (1981) Radiation Protection in Pediatric Radiology (1981) Dosimetry of X-Ray and Gamma-Ray Beams for Radiation Therapy in the Energy Range 10 ke V to 50 MeV (1981) Nuclear Medicine-Factors Influencing the Choice and Use

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of Radionuclides in Diagnosis and Therapy (1982) Operational Radiation Safety-Training (1983) Radiation Protection and Measurement for Low Voltage Neutron Generators (1983) 73 Protection in Nuclear Medicine and Ultrasound Diagnostic Procedures in Children (1983) 74 Biological Effects of Ultrasound: Mechanisms and Clinical Implications (1983) 75 Iodine-129: Evaluation of Releases from Nuclear Power Generation (1983) Radiological Assessment: Predicting the Transport, Bioac76 cumulation, and Uptake by Man of Radionuclides Released to the Environment (1984) 77 Exposures from the Uranium Series with Emphasis on Radon and its Daughters (1984) 78 Evaluation of Occupatiod and Environmental Exposures to Radon and Radon Daughters in the United States (1984) Neutron Contamination from Medical Electron Accelera79 tors (1984) Induction of Thyroid Cancer by Ionizing Radiation (1985) 80 81 Carbon-14 in the Environment (1985) 82 S I Units in Radiation Protection and Measurements (1985) The Experimental Basis for Absorbed-Dose Calculations in 83 Medical uses of Radionuclicles (1985) General Concepts for the Dosimetiy of Internally Deposited 84 Radionuclides (1985) Mammography-A User's Guide (1986) 85 86 Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields (1986) 87 Use of Bioassay Procedures for Assessnwnt of Internal Radionuclide Deposition (1986) 88 Radiation Alarms and Access-Control Systems (1987) 89 Genetic Effects of Internally Deposited Radionuclides (1987) 90 Neptunium: Radiation Protection Guidelines (1987) Binders for NCRP Reports are available. Two sizes make it possible to collect into small binders the "old series" of reports (NCRP Reports Nos. 8-30) and into large binders the more recent publications (NCRP Reports Nos. 32-90). Each binder will accommodate from five to seven reports. The binders carry the identification "NCRP Reports" and come with label holders which permit the user to attach labels showing the reports contained in each binder. 71 72

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The following bound sets of NCRP Reports are also available: Volume I. NCRP Reports Nos. 8,16,22 Volume 11. NCRP Reports Nos. 23,25,27,30 Volume 111. NCRP Reports Nos. 32, 33, 35, 36, 37 Volume IV. NCRP Reports Nos. 38,40,41 Volume V. NCRP Reports Nos. 42,44,45,46 Volume VI. NCRP Reports Nos. 47,48,49,50,51 Volume VII. NCRP Reports Nos. 52,53,54,55,56,57 Volume VIII. NCRP Reports No. 58 Volume IX. NCRP Reports Nos. 59,60,61,62,63 Volume X. NCRP Reports Nos. 64,65,66,67 Volume XI. NCRP Reports Nos. 68, 69,70,71,72 Volume XII. NCRP Reports Nos. 73, 74, 75, 76 Volume XIII. NCRP Reports Nos. 77, 78,79,80 Volume XIV. NCRP Reports Nos. 81,82,83,84,85. (Titles of the individual reports contained in each volume are given above). The following NCRP Reports are now superseded and/or out of print: No. 1

Title X-Ray Protection (1931). [Superseded by NCRP Report No. 31 Radium protection' (1934). [Superseded by NCRP Report No. 41 X-Ray Protection (1936). [Superseded by NCRP Report No. 61 Radium Protection (1938). [Superseded by NCRP Report No. 131 Safe Handling of Radioactive Luminous Compounds (1941). [Out of Print] Medical X-Ray Protection Up to Two Million Volts (1949). [Superseded by NCRP Report No. 181 Safe Handling of Radioactive Isotopes (1949). [Superseded by NCRP Report No. 301 Recommendatwns for Waste Disposal of Phosphorus-32 and Iodine-131 for Medical Users (1951). [Out of Print] Radiological Monitoring Methods and Instruments (1952). [Superseded by NCRP Report No. 571 Maximum Permissible Amounts of Radioisotopes in the Human Body and Maximum Permissible Concentrations

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in Air and Water (1953). [Superseded by NCRP Report No. 221 Recommendations for the Disposal of Carbon-14 Wastes (1953). [Superseded by NCRP Report No. 811 Protection Against Radiations from Radium, Cobalt-60 and Cesium-137 (1954). [Superseded by NCRP Report No. 241 Protection Against Betatron-Synchrotron Radiations Up to 100 Million Electron Volts (1954). [Superseded by NCRP Report No. 511 Safe Handling of Cadavers Containing Radioactive Isotopes (1953). [Superseded by NCRP Report No. 211 Permissible Dose from External Sources of Ionizing Radiation (1954) including Maximum Permissible Exposure to Man, Addendum to National Bureau of Standards Handbook 59 (1958). [Superseded by NCRP Report No. 391 X-Ray Protection (1955). [Superseded by NCRP Report No. 261 Regulation of Radiation Exposure by Legislative Means (1955). [Out of Print] Protection Against Neutron Radiation Up to 30 Million Electron Volts (1957). [Superseded by NCRP Report No. 381 Safe Handling of Bodies Containing Radioactive Isotopes (1958). [Superseded by NCRP Report No. 371 Protection Against Radiations from Sealed Gamma Sources (1960). [Superseded by NCRP Report Nos. 33, 34, and 401 Medical X-Ray Protection Up to Three Million Volts (1961). [Superseded by NCRP Report Nos. 33, 34, 35, and 361 A Manual of Radioactivity Procedures (1961). [Superseded b y NCRP Report No. 581 Exposure to Radiation in an Emergency (1962). [Superseded by NCRP Report No. 421 Shielding for High Energy Electron Accelerator Installations (1964). [Superseded by NCRP Report No. 511 Medical X-Ray and Gamma-Ray Protection for Energies Up to 10 MeV-Structural Shielding Design and Evaluution (1970). [Superseded by NCRP Report No. 491 Basic Radiation Protection Criteria (1971). [Superseded by NCRP Report No. 911

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Review of the Current State of Radiatian Protection Philosophy (1975). [Superseded by NCRP Report No. 91.1

Other Documents The following documents of the NCRP were published outaide of the NCRP Reports aeries: "Blood Counts, Statement of the National Committee on Radiation Protection," Radiology 63,428 (1954) "Statements on Maximum Permissible Dose from Television Fkceivers and Maximum Permissible Dose to the Skin of the Whole Body," Am. J. Roentgenol., Radium Ther. and Nucl. Med. 84, 152 (1960) and Radiology 75,122 (1980) X-Ray Protection Standards for Home Television Receivers, Interim Statement of the National Council on Radiation Protection and Measurements (National Council on Radiation Protection and Measurements, Washington, 1968) Specification of Units of Natural Uranium and Natural Thorium (National Council on Radiation Protection and Measurements, Washington, 1973) NCRP Statement on Dose Limit for Neutrons (National Council on Radiation Protection and Measurements, Washington, 1980) Control of Air Emissions of Radionuclides (National Council on Radiation Protection and Measurements, Bethesda, Maryland, 1984)

k

Copies of the s atements published i n journals may be consulted in libraries. A limited umber of copies of t h e remaining documents listed above are available for distribution by NCRP Publications.

INDEX Absorption of neptunium from gastrointestinal tract, 4-5, 11-21, 24-25, 30, 32,34 effect of age, 18-20 effect of diet, 17-18 effect of mass ingested, 5,11-20 effect of oxidation state, 4-5, 11-20 effect of prior fast, 5,11-20 fraction absorbed, f,, 10-21, 24-25, 30, 32,34 Absorption of neptunium from respiratory tract, 21-22 effect of physical and chemical state, 21-22 fraction absorbed, 21-22 Algae, neptunium in, 9 Americium, comparison of chemical and biological behavior with that of neptunium, 8-9,28 Annual limits on intake of neptunium isotopes (ALI), 17,32-35 Blood, oxidation state of neptunium in, 2-

Derived air concentrations for neptunium isotopes (DAC), 17,32-35 Distribution of neptunium among tissues (see specific tissue) Distribution coefficient (solidfliquid), &, 8 Effects of neptunium (='Np), 27-28 chemical effects in experimental animals, 27 radiation effects in experimental animals, 27-28 Environmental neptunium. 6-9 in marine environments, 8-9 in plants, 8-9 in soils and rocks, 8 "Np, 6-9 WP,6 pathways to man, 8-9 sources, 6-8 weathering, effect of, 8 Excretion of neptunium, 17,23-26,30 Extractability of neptunium from soils, 8

5

Bone, neptunium in, 17,22-28,30,34 carcinogenicity, 27-28 deposition and retention parameters, 17,22-26,30,34 microdistribution and dosimetry, 23,26 Carcinogenicity of neptunium, (23'Np), 27-28 Chelation of neptunium, 3,6 Chemistry of neptunium (see also under specific topics), 2-5 Complexing of neptunium, 3-4 Concentration ratio (plant/soil), CR, 8 Critical organ, 29,31 Curium, comparison of chemical and biological behavior with that of neptunium. 8-9 Decay modes of neptunium isotopes, 2,3, 6.7

Fallout following nuclear detonations. =Np in, 6, 27 Feces, excretion of neptunium in, 26 Gastrointestinal tract, neptunium in, 2-5, 12,1&19 absorption from (see under Absorption) oxidation state, 2-5, 12 retention, 18-19 Geologic behavior of neptunium, 8 Gonad (see Ovary or Testes) Half-lives of neptunium isotopes, 2,3,6,7 Hydrolysis of neptunium, 4-5 Ingestion of neptunium (see under Absorption and Gastrointestinal tract) Inhalation of neptunium (see under Absorption and Lung) Intake limits (see Limits)

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International Commission on Radiological Protection (ICRP), recommendations of, 10, 12,17,20-23, 26,29-34 Kidney, neptunium deposition and retention parameters, 22-23,30 Limits for neptunium intake, 9, 17, 29-35 Liver, neptunium in, 5,17, 22-26, 30, a4 effect of mass administered, 5, 23 effect of oxidation state, 5 effect of route of entry, 23 deposition and retention parameters, 17, 22-26, 30,34 Lung, neptunium in, 2-5,21-22.27-28,30 absorption from (see under Absorption) carcinogenicity, 27-28 oxidation state, 2-5 retention and clearance parameters, 2122,30 Lymph node (see Pulmonary lymph node) Maximum permissible burden (MPB), 29, 31-32 Maximum permissible concentration (MPC), 29,31-32 Milk, neptunium in, 9 National Council on Radiation Protection and Measurement (NCRP), recommendations of, 10, 17, 29-32, 34-35 National Radiological Protection Board (England), recommendations of, 17, 20 Neptunium (see specific topics) Ocean waters, neptunium in, 5 , & 9 Ovary, neptunium deposition and retention parameters, 23, 25-26, 30

Oxidation states of neptunium, 2-5, 8-9, 11-20 general, 2-5 in ocean waters, 5,8-9 in organs and tissues, 2-5,ll-20 in soils and rocks, 8 9 Plant accumulation of neptunium, 8-9 Plutonium, 2-5,7-9,18,26,28, 34 comparison of chemical and biological behavior with that of neptunium, 25,8-9, 18, 26, 28,34 2 S B Pproduction ~ from "'Np, 7 Pulmonary lymph node, neptunium in, 21 Respiratory tract (See under Absorption and Lung) Retention of neptunium (see specific organs and tissues) Skeleton (see Bone) Soils, neptunium in, 8 Testes, neptunium deposition and retention parameters, 23, 25-26, 30, 34 Thorium, comparison of chemical and biological behavior with that of neptunium. 20 Uranium, comparison of chemical and biological behavior with that of neptunium, 2-5,20,26 Urine, excretion of neptunium in, 17, 2425 Waste, 1, 2,6-8 "'Np in nuclear, 1, 2,6-8 mNp in nuclear, 6