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NASA Technical Memorandum 4270

Radiation Health Research, 1986-1990

Radiation Health Program,

Life Sciences Division

NASA Office of Space Science and Applications

Washington, D.C.

National Aeronautics and

Space Administration

Office of Management

Scientific and Technical

Information Division

1991

INTRQDUCTION

The present volume is a collection of recent abstracts of radiation research sponsored by

NASA. Its purpose is to make available a concise summary for use by active investigators,

prospective investigators, interested administrators, and the community at large. The period

covered from 1986 to 1990 is somewhat arbitrary. Hopefully, this collection goes back far enough

to yield an adequate perspective of the research effort and yet does not detain the reader at

milestones that already have been achieved.

The research sponsored by NASA and reported here is evidence of a very large return to

the taxpayer for a very minimal investment. Much of this research was made possible by the

existence of an infrastructure developed by other Federal agencies and with marginal resources

riding on other programmatic support. In many cases, this infrastructure no longer exists or is no

longer available, and NASA will have to depend much more on its own resources to conduct

research critical for our mission. That the research reported in this book was possible at all is in no

small measure due to the imagination and farsightedness of a few individuals. Foremost among

these was the late Stuart Nachtwey, who stimulated this research effort with the same grace under

pressure with which he battled to the end against his f'mal illness. Stu's courage and determination

serve as an example to all of us who were privileged to witness them. The work described in this

book is our testimonial.

In 1990 the Radiation Health Program became an independent program of the Life Sciences

Division in the Office of. Space Science and Applications at NASA. This change implements the

recommendations of several advisory committees and the policy decisions to expand the radiation

research program in recognition of the critical importance of radiation protection to the Space

Exploration Inititative. The purpose of the Radiation Health Program is to establish the scientific

basis for the radiation protection of humans engaged in the exploration of space, with particular

emphasis on lunar and planetary space exploration. It supports scientific research into the

fundamental mechanisms of radiation effects on living systems and the interaction of radiation with

cells, tissues and organs, as well as the development of instruments and processes dealing with the

measurement of radiation and its effects. In pursuit of the Radiation Health Program, the Life

Sciences Division supports researchers at universities, NASA centers and national laboratories,

establishes interagency agreements for cooperative use and development of facilities, and operates

a space-based research program centered on the Life Sciences Satellite (LifeSat).

L

111

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It is expected that collections similar to the present one will be published at more frequent

intervals in the future, reflecting the increasing pace of research sponsored by the Radiation Health

Program. The present publication was made possible by the efforts of many people. The principal

investigators took time off from their busy schedules to proofread the reprinted abstracts. T. C.

Yang and D. Morrison, of the NASA Johnson Space Center, helped prepare the bulk of this

volume. M. Jablin, G. Ferraro, R. Teeter, K. Stokes, R. Maggio, and C. Brooks of the l_xx:kheed

Engineering and Sciences Co., Washington D.C., and Janice Wallace, Elizabeth L. Hess, April C.

Roy, and F. Ronald Dutcher of George Washington University, Washington, D.C., were

responsible for proofreading, cross-referencing, and completing the document. Their work is

gratefully acknowledged.

Walter Schimmerling

Manager, Radiation Health Program

iv
•

•

TABLE OF CONTENTS

PHYSICS

1.1. ATOMIC PHYSICS

Journals

Reports/Meetings

1.2. NUCLEAR SCIENCE

Reports/Meetings

1.2.1. THEORY

Journals

Reports/Meetings

1.2.2. EXPERIMENTAL

Journals

Reports/Meetings

1.3. SPACE RADIATION

1.4.

1.5.

1.3.1. COSMIC RAY AND ASTROPHYSICS

Journals

1.3.2. ENVIRONMENTS AND ENVIRONMENTAL MODELS

Journals

Reports/Meetings

1.3.3. SOLAR ACTIVITY AND PREDICTION

Reports]Meetings

1.3.4. EXPERIMENTS

Reports/Meetings

RADIATION TRANSPORT AND SHIELDING

Reports/Meetings

1.4.1. THEORY AND MODEL DEVELOPMENT

Journals

Reports/Meetings

1.4.2. EXPERIMENTAL STUDIES

Journals

Reports/Meetings

INSTRUMENTATION

Journals

BIOLOGY

2.1. MOLECULAR BIOLOGY

Journals

1

5

7

12

14

16

17

18

18

19

20

22

24

30

31

34

35

36

V
,

2.2.

2.3.

2.4.

2.5.

RISK

3.1.

3.2.

TABLE OF CONTENTS

CELLUI_R RADIATION BIOLOGY

Journals

2.2.1. TRANSFORMATION, MUTATION

Journals

2.2.2. LETHALITY, SURVIVAL

Journals

Reports/Meetings

2.2.3. DNA DAMAGE AND REPAIR

Journals

Reports/Meetings

TISSUE, ORGANS AND ORGANISMS

Journals

Reports/Meetings

2.3.1. IN VIVO/IN VITRO SYSTEMS

Journals

Reports/Meetings

2.3.2. CARCINOGENESIS AND LIFE SHORTENING

Journals

2.3.3. CATARACTOGENESIS

Journals

Reports/Meetings

2.3.4. OTHER EFFECTS

Journals

Reports/Meetings

RADIOPROTECTANTS

Reports/Meetings

PLANTS

Journals

ASSESSMENT

RADIATION HEALTH AND EPIDEMIOLOGY

Journals

Reports/Meetings

SPACE FLIGHT RADIATION HEALTH PHYSICS

Journals

Reports/Meetings

38

39

42

45

46

48

49

50

5O

51

52

53

55

61

62

65

66

67

68

69

72

78

vi
TABLE OF CONTENTS

3.3.

3.4.

INTER- AND INTRASPECIES EXTRAPOLATION

Journals

Reports/Meetings

RADIATION LIMITS AND STANDARDS

Journals

Reports/Meetings

4. MICROGRAVITY

4.1. MICROGRAVITY

Journals

Reports/Meetings

KEYWORD INDEX

AUTHOR INDEX

84

87

88

89

91

92

94

99

107

vii
ii

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1. PHYSICS
1.1. ATOMIC PHYSICS

JOURNALS

Khan, F., Khandelwal, G. S., and Wilson, J. W. (1988) Differential oscillator

strengths and dipole polarizabilities for transitions of the helium sequence.

Physical Review A 38: 6159-6164.

Oscillator strengths, Dipole polarizabilities, Radial integrals

The dipole radial integral for an initial discrete ls state and a final continuum state has been

calculated under the screened hydrogenic model. In this model, single-electron hydrogenic wave

functions are employed and the initial and the final states are treated by two different effectivecharge parameters. Numerical values of differential oscillator strengths for transitions from ls 21S

to the continuum for the helium sequence ions are obtained. Also calculated are the dipole

polarizabilities, which are found to be in excellent agreement with the results of other authors.

Khan, F., Khandelwal, G. S., and Wilson, J. W. (1988) Static multipole

polarisabilities and second-order Stark shift in francium. Journal of Physics B

21: 731-737.

Stark effect, Muttipole polarizability

The multipole polarisability of the ground state of francium is calculated by utilizing both the

variational technique of Davison and the quantum defect theory underlying the Bates-Damgaard

method. This approach is also shown to yield reasonable results for other alkali atoms. Secondorder Stark shift for the ground state of francium is presented as a function of field strength for

possible future experimental comparison.

Khan, F., Khandeiwal, G. S., and Wilson, J. W. (1988) Is 2 iS.Is np Ip

transitions of the helium isoelectronic sequence members up to Z = 30. The

Astrophysical Journal 329: 493-497.

Radial integrals, Oscillator strengths, Effective charge

Radial integrals have been calculated under the one-electron hydrogenic model. Two different

values of the effective charge parameter, one for the initial state and the other for the final state, are

retained in these formulae. The model is able to reasonably reproduce the existing dipole oscillator

strength values with little effort. The dipole oscillator strength values are given for many ions for

the first time.

Khan, F., Khandelwal, G. S., and Wilson, J. W. (1990) Moments of dipole

oscillator-strength distribution for the helium sequence. Journal of Physics B:

At Mol Opt Phys 23: 2717-2726.

Oscillator strengths, Helium

The moments S(t.t) for -6 _< _t < 2 and L(I.t) for _=0, 1, and 2 are calculated for the helium

sequence for atomic numbers Z up to 30 under a screened hydrogenic model. In this model, one

describes the atom by single-particle hydrogenic wavefunctions and treats the initial and the final

state as characterized by two different effective charge parameters Zi and Z r, respectively. An

asymptotic expansion is made of the differential oscillator strength of the screened hydrogenic

model. Assuming the value 287.6 for the coefficient of the term z_-7/'z for helium atom as given by

2

PRECEDING PAGE BLANK NOT FILMED
Salpeter and Zaidi, the parameter Zf is determined for the helium sequence. This approach has

resulted in values which are in reasonable agreement with the various moment values of other

authors.

Khandelwal, G. S., Khan, F.,

for dipole oscillator strength

Journal 336: 504-506.

and Wilson, J. W. (1989) Asymptotic expressions

for transitions of He sequence. The Astrophysical

Oscillator strengths, Radial integrals, Excitations

The radial integral for ls 2 1S-ls np 1p transitions of the He isoelectronic sequence is

asymptotically expanded to order n -7 to facilitate calculations of the dipole oscillator strength for

large n. The threshold differential oscillator strength values are obtained for ions up to Z=30

within the screened hydrogenic model.

Khandelwal, G. S., Pritchard, W. M., Grubb, G., and Khan, F. (1989)

Screened hydrogenic radial integrals. Physical Review A 39: 3960-3963.

Hydrogenic, Radial integrals, Electronic transitions

The screened hydrogenic radial integral both for discrete-discrete and discrete-continuum

transitions is expressed in forms suitable for obtaining closed-form expressions for specific

transitions. Two effective charge parameters Z_ and ZI, respectively, for the initial state and for the

final state are retained in these formulas. As examples, explicit expressions for a few transitions

are derived and a method for obtaining a series for a discrete-discrete radial integral, suitable for

large final-state principal quantum numbers, is indicated.

Olsgaard, D. A., Khan, F.,

hydrogenic radial integrals.

2438.

and Khandeiwal, G. S. (1988) Asymptotic screened

Journal of the Optical Society of America B 5: 2437-

Radial integrals, Hydrogen transitions

The screened hydrogenic radial dipole integral for discrete-discrete transitions from initial state n'/'

to final state nl is asymptotically expanded to the lowest order such that the final quantum mumber

n _ 00. The analytical expression obtained is in terms of confluent hypergeometric functions,

and explicit expressions for a few of the specific transitions are derived from them as examples.

Rustgi, M. L., Pandey, L. N., Wilson, J. W., Long, S. A. T., and Zhu, G.

(1988) Distribution of energy in polymers due to incident electrons and protons.

Radiation Effects 105: 303-311.

Polymers, Protons, Coulomb scattering, Electrons, Electronic excitation, Ionization

The recoil spectrum of nuclei in polymers for incident protons below 10 MeV in energy is

calculated by using the Rutherford cross-section with screening corrections. Employing the work

of McKinley and Fesbach on the Coulomb scattering of relativistic electrons by nuclei, the recoil

spectrum of the nuclei is also calculated for electron energies varying from threshold to 10 MeV.

The partitioning of energy between electronic excitation and ionization and nuclear recoil is then

studied to search for possible difference in polymer radiation response as a function of radiation

energy and type.

3
1.1. ATOMIC PHYSICS

REpQRTS/MEETINGS

Khan, F., Khandelwal, G. S., and Wilson, J. W. (1987) ls 2 IS- Is np 1p

transitions of helium isoelectronic sequence members up to z = 30. Abstract

presented at the Annual Meeting of the Virginia Academy of Sciences, Norfolk,

VA, May 20-22, 1987. Virginia Journal of Science 38: 70.

Effective charge, Oscillator strengths

Radial integrals have been calculated under the one-electron hydrogenic model. Two different

values of the effective charge parameter, one for the initial state and the other for the final state, are

retained in these formulae. The model is able to reasonably reproduce the existing dipole oscillator

strength values with little effort. The squares of the radial integral values are given for many ions

for the first time.

Wilson, J. W., Khandelwal, G. S., and Fogarty, N. T. (1988) X.ray Production

in Low Energy Proton Stopping. NASA Technical Memorandum 100619.

X-ray production, Protons, Alloy, Electronic devices

The X-ray yields of stopping protons in an iron-nickel-cobalt alloy are calculated for use in

predicting radiation damage in encased electronic devices.

Xu, Y. J., Khandelwal, G. S., Wilson, J.W. (1986) The maximum momentum

transfer in proton-hydrogen collisions. Physics Letters A 115(1,2): 37.

Hydrogen, Momentum transfer, K-shell electrons, Gas

The upper limit of momentum transfer by a proton to K-shell electrons is calculated in a restricted

three-body classical model. The model shows that the infinite upper limit used in practice, is

generally good except for low energy protons passing through an extremely rarefied gas.

Xu, Y. J., Khandelwal, G. S., and Wilson, J. W. (1989) Charge Exchange

Transition Probability for Collisions Between Unlike Ions and Atoms Within the

Adiabatic Approximation. NASA Technical Memorandum 101559.

Charge exchange, Adiabatic approximation

A simple formula for the transition probability for electron exchange between unlike ions and

atoms is established within the adiabatic approximation by employing the Linear Combination of

Atomic Orbitals (LCAO) method. The formula also involves an adiabatic parameter, introduced by

Massey, and thus the difficulties arising from the internal energy defect and the adiabatic

approximation are avoided. Specific reaction LP + + H + and Be n+ + H == Be 3+ + H + are

considered as examples. The calculated capture cross section results of the present work are

compared with the experimental data and with the calculation of other authors over the velocity

range of 10 7 cm/sec to 10 s cm/sec.

L
1.2. NUCLEAR SCIENCE

REPORTS/MEETINGS

Meador, W. E. and Townsend, L. W. (1988) Local Time Displacement as a

Symmetry of Nature in Flat Space-Time. NASA Technical Memorandum 100610.

Relativity

Local time displacement is shown to be a true symmetry of Minkowskian physics, thereby

demonstrating the empirical equivalence of different choices of the clock synchronization parameter

in generalized Lorentz transformations.

1.2.1. THEORY

Badavi, F. F., Townsend, L. W., Wilson, J. W., and Norbury, J. W. (1987) An

algorithm for a semiempirical nuclear fragmentation model. Computer Physics

Communications 47: 281-294.

Heavy ion fragmentation, Cross sections, Fragmentation model

Interactive program NUCFRAG presents an algorithm for an abrasion/ablation model of heavy ion

fragmentation which includes a second order correction for the surface energy term and addition of

photonuclear dissociation to provide reasonable representation of the present elemental

fragmentation cross sections. Using the Weizsacker-Williams method of virtual quanta, the

photodissociation fragmentation cross sections are calculated and added to the nuclear

fragmentation cross sections generated by an abrasion/ablation model of heavy ion collision. The

photodissociation cross sections are calculated for one nucleon removal only (either a proton or

neutron). The nuclear interaction fragmentation cross sections are not calculated for target

fragments and peripheral collisions with A A< 0.5. On C.D.C. - Cyber/750 at NASA Langley

Research Center, compilation takes about 20-30 seconds, while execution about 60-90 seconds.

Cucinotta, F. A., Khandelwal, G. S., Townsend, L. W., and Wilson, J. W.

(1989) Correlations in an a-a scattering and semi-classical optical models.

Physics Letters B 223: 127-132.

Alpha-alpha correlation, Optical models, Coupled-channel equations

We show the equivalence of semi-classical solutions to optical model coupled-channel equations

derived from Watson's form of the nucleus-nucleus multiple-scattering series to the Glauber

multiple-scattering series. A second-order solution to the semi-classical coupled-channel elastic

amplitude is shown to be nearly equivalent to a second-order optical-phase-shift approximation to

the Glauber amplitude if the densities of all nuclear excited states are approximated by the groundstate density. Using the Jastrow method to model the two-body density we find an average

excited-state density to be of negligible importance in the double-scattering region of a-a scattering.

5
Gross, F., Maung, K. M., Tion, J. A., Townsend, L. W., and Wallace, S. J.

(1989) Pseudoscalar pi.N coupling and relativistic proton-nucleus scattering.

Physical Review C 40: RI0-RI2.

Protons, Elastic scattering, Two-body relativistic equation

Relativistic p-40Ca elastic scattering observables are calculated using relativistic NN amplitudes

obtained from the solution of a two-body relativistic equation. Results at 200 MeV are presented

for three sets of NN amplitudes, two with pure pseudovector coupling for the pion and one with a

25% admixture of pseudoscalar coupling. Differences between the predictions of these three

models provide a measure of the uncertainty in constructing Dirac optical potentials from NN

amplitudes.

Norbury, J. W., Cucinotta, F. A., Townsend, L. W., and Badavi, F. F. (1988)

Parameterized cross sections for Coulomb dissociation in heavy-ion collisions.

Nuclear Instruments and Methods in Physics Research B31: 535-537.

Coulomb dissociation, Heavy-ion collisions

Simple parameterizations of Coulomb dissociation cross sections for use in heavy-ion transport

calculations are presented and compared to available experimental dissociation data. The agreement

between calculation and experiment is satisfactory considering the simplicity of the calculations.

Norbury, J. W. (1990) Electric quadrupole excitations in relativistic nucleusnucleus collisions. Physical Review C 42: 711-714.

Electric quadruple excitations, Heavy-ion collisions

Calculations are presented for electric quadrupole excitations in relativistic nucleus-nucleus

collisions. The theoretical results are compared to an extensive data set and it is found that electric

quadrupole effects provide substantial corrections to cross sections, especially for heavier nuclei.

Townsend, L. W. and Wilson, J. W. (1988) Comment on "trends of total

reaction cross sections for heavy ion collisions in the intermediate energy range."

Physical Review C 37: 892-893.

Heavy-ion collisions, Total reaction cross sections

The energy-dependent, semiempirical, surface transparency factor of Kox, et al., is accurately

represented by a simple analytical expression. Total reaction cross sections obtained using this

parametrization agree with Kox's predictions to within four percent.

Townsend, L. W. and Wilson, J. W. (1989) Nuclear cross sections for

estimating secondary radiations produced in spacecraft. Presented at the

Conference on High Energy Radiation Background in Space (CHERBS 87),

Sanibel Island, FL, November 3-5, 1987. AIP Conference Proceedings No. 186,

Eds. A. C. Rester, Jr. and J. I. Trombka (American Institute of Physics, New

York, 1989), pp. 177-180.

Cross sections, Transport calculations, Electromagnetic dissociation

Methods for estimating nuclear absorption (reaction) and breakup (fragmentation) cross sections

for space radiation transport calculations are presented, and comparisons with experimental data are

z
made. For the fragmentation problem, the importance of electromagnetic dissociation is discussed

and calculational methods described.

Wilson, J. W., Townsend, L. W., and Badavi, F. F. (1987) A semiempirical

nuclear fragmentation model. Nuclear Instruments and Methods in Physics

Research BI8: 225-231.

AbrasionAblation, Heavy ion fragmentation

An abrasion/ablation model of heavy ion fragmentation is derived which includes a second order

correction for the surface energy term and provides a reasonable representation of the present

elemental fragmentation cross sections. The full development of the model must await the

resolution of disagreement among different experiments and an expansion of the experimental data

base to a broader set of projectile-target combinations.

Wilson, J. W. and Townsend, L. W. (1989) Nucleon interaction data bases for

background estimates. Presented at the Conference on High Energy Radiation

Background in Space (CHERBS 87), Sanibel Island, FL, November 3-5, 1987.

AIP Conference Proceedings No. 186, eds. A. C. Rester, Jr. and J. I. Trombka

(American Institute of Physics, New York, 1989), pp. 192-202.

Nucleon cross sections, Transport codes

Nucleon interaction data bases available in the open literature are examined for potential use in a

recently developed nucleon transport code. Particular attention is given to secondary particle

penetration and the multiple charged ion products. A brief description of the transport algorithm is

given.

1.2.1. THEORY

REPORTS/MEETINGS

Badavi, F. F., Norbury, J. W., Wilson, J. W., and Townsend, L. W. (1988)

Accuracy of Analytic Energy Level Formulas Applied to Hadronic Spectroscopy

of Heavy Mesons. NASA Technical Memorandum 4042.

Potential models, Mesons, Quarks, Energy levels

In this work, linear and harmonic potential models are used in the nonrelativistic Schrrdinger

equation to obtain particle mass spectra for mesons as bound states of quarks. The main emphasis

is on the linear potential where exact solutions of the S-state (l=0) eigenvalues and eigenfunctions

and the asymptotic solution for the higher order partial waves (l>0) are obtained. A study of the

accuracy of two analytical energy level formulas (Cornwall and Sheehy and Von Baeyer) as

applied to heavy mesons is also included. Cornwall's formula is found to be particularly accurate

and useful as a predictor of heavy quarkonium states. Exact solution for all partial waves of

eigenvalues and eigenfunctions for a harmonic potential is also obtained and compared with the

calculated discrete spectra of the linear potential. Detailed derivations of the eigenvalues and

eigenfunctions of the linear and harmonic potentials are presented in appendixes.

7
k

_S

_Z

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Buck, W. W., Wilson, J. W., Townsend, L. W., and Norbury, J. W. (1987)

Possible Complementary Cosmic-Ray Systems: Nuclei and Antinuclei. NASA

Technical Paper 2741.

Galactic cosmic rays, Antinuclei, Microlesions

Arguments are presented for the possible existence of antinuclei of charge IZI > 2 and, particularly,

galactic cosmic antinuclei. Theoretical antinucleus-nucleus optical model cross sections are

calculated and presented for the first time. A brief review of the nucleon-antinucleon interaction is

also presented and its connection with the antinucleus-nucleus interaction is made. The predicted

cross sections are smooth and show no structure. Finally, the findings are tied together with the

formation of microlesions in living tissue.

Cucinotta, F. A., Khandelwal, G. S., Maung, K. M., Townsend, L. W., and

Wilson, J. W. (1988) Eikonal Solutions to Optical Model-Coupled Channel

Equations. NASA Technical Paper 2830.

Eikonal optical model, Total cross sections, Reaction cross sections

Methods of solution are presented for the eikonal form of the nucleus-nucleus coupled-channel

scattering amplitudes. Analytic solutions are obtained for the second-order optical potential for

elastic scattering. A numerical comparison is made between the first- and second-order optical

model solutions for elastic and inelastic scattering of 1H and 4He on 12C. The effects of boundstate excitations on total and reaction cross sections are also estimated.

Cucinotta, F. A., Khandelwal, G. S., Townsend, L. W., and Wilson, J. W.

(1988) Correlations and density of excited states in particle scattering. Abstract

a presented at the Spring Meeting of the American Physical Society, Baltimore,

MD, April 18-21, 1988. Bulletin of the American Physical Society 33: 1101.

Correlations, Excited states, Coupled-channel equations, Total cross sections

The effects of short-range correlations and deviations of an average 4He excited state density from

the ground state density in medium energy a- nucleus scattering are estimated using semi-classical

solutions to optical model coupled-channel equations derived from Watson's form of the nucleusnucleus multiple scattering series. Calculations are compared to experimental measurements of

elastic angular distributions and total and reaction cross sections and Glauber model calculations.

Cucinotta, F. A., Khandelwal, G. S., Maung, K. M., Townsend, L. W., Wilson,

J. W., and Norbury, J. W. (1987) Eikonal solutions to optical model coupled

channel equations for 1 GeV p-12C and 1 GeV/nucleon 4He-12C scattering.

Abstract presented at the Fall 1987 Division of Nuclear Physics Meeting, New

Brunswick, N J, October 15-17, 1988. Bulletin of the American Physical Society,

32: 1567-1568.

Coupled-channel equations, Optical models, Eikonal approximation, Total cross sections

Coupled channel Schroedinger equations derived under high energy, optical model considerations

are solved in the eikonal approximation. A similarity transformation allows us to sum an infinite

series, equivalent to the infinite order multiple scattering series in the eikonal limit, for each

scattering amplitude of our channel space. We investigate corrections to the coherent

approximation for the elastic channel and obtain non-perturbative, analytic solutions for inelastic

channels. Applications are made to 1 GeV p-12C scattering and 1 GeV/A 4He-12C scattering.

8
Cucinotta, F. A., Norbury, J. W., Khandelwal, G. S., and Townsend, L. W.

(1987) Doubly Differential Cross Sections for Galactic Heavy-Ion Fragmentation.

NASA Technical Paper 2659.

Heavy ion fragmentation, Differential cross sections, Galactic cosmic rays

An abrasion-ablation T-matrix formulation is applied to the calculation of doubly differential cross

sections in projectile fragmentation of 2.1 GeV/nucleon 160 on 9Be and 86 MeV/nucleon 12C on

12C and 1°SAg. An exponential parameterization of the ablation T-matrix is used and the total

width of the intermediate states is taken as a parameter. Fitted values of the total width to

experimental results are used to predict the lifetime of the ablation stage and indicate a decay time

on the order of 10 -19 s.

Cucinotta, F. A., Norbury, J. W., and Townsend, L. W. (1988) Multiple

Nucleon Knockout by Coulomb Dissociation in Relativistic Heavy-Ion Collisions.

NASA Technical Memorandum 4070.

Coulomb dissociation, Weizsiicker-Williams method, Nucleon knockout

The Coulomb dissociation contributions to fragmentation cross sections in relativistic heavy-ion

collisions, in which more than 1 nucleon is removed, are estimated using the Weizs_cker-Williams

method of virtual quanta. Photonuclear cross sections taken from experimental results are folded

into target photon-number spectra calculated with the Weizs_icker-Williams method. Calculations

for several projectile-target combinations are reported over a wide range of charge numbers and a

wide range of incident projectile energies. These results suggest that a multiple nucleon emission

process (knockout) by the Coulomb field is of negligible importance in galactic heavy-ion studies

for projectiles lighter than 56Fe.

Cucinotta, F. A., Townsend, L. W., Wilson, J. W., and Norbury, J. W. (1990)

Coupled channel effects in high-energy alpha particle fragmentation on nuclear

targets. Abstract presented at the Fall 1990 Division of Nuclear Physics Meeting,

Urbana-Champaign, IL, October 25-27, 1990 (Bulletin of the American Physical

Society).

Coupled channel, Differential cross sections, Alpha particles

Double differential cross-sections for the two-body dissociation of alpha particles are calculated in

the high energy optical model of nuclear multiple scattering. Momentum distributions for forward

scattered fragments are often evaluated using a participant-spectator model or the DWBA. Using

the high energy optical model, we estimate the importance of coupled channel effects on

predictions of inclusive momentum distributions and their role in determining the large momentum

components of the two-body overlap functions from small angle data. For elastic fragmentation,

interference effects between participant and spectator interactions are shown to be non-negligible

for forward scattered fragments.

Khan, F., Khandelwal, G. S., Wilson, J. W., Townsend, L. W., and Norbury,

J. W. (1987) Momentum transfer in relativistic heavy ion collisions. Abstract

presented at the Annual Meeting of the Virginia Academy of Sciences, Norfolk,

VA, May 20-22, 1987. Virginia Journal of Science 38: 70.

Relativistic heavy ion, Momentum transfer

9
|

zs

Momentum (and Excitation Energy) transfer in Heavy Ion Collisions is investigated assuming an

impulsive excitation mechanism. Interaction Representation is used; in the limit of t collision << t

nucleonic motion, it is shown that momentum transfer is determined by the "Optical Potential" of the

projectile. Assuming constant velocity, momentum transfer is transverse (AP^). When "constant

velocity" assumption is relaxed, it is shown how to obtain momentum transfer (AP,) parallel to the

beam.

Khan, F., Khandelwal, G. S., Wilson, J. W., Townsend, L. W., and Norbury,

J. W. (1988) Excitation-decay contribution to fragment production compared for

the reactions [12C, 11B + P] and [l_O, lSN + P] at 1.05 A GeV and 2.1 A GeV on

12C target. Abstract presented at the Spring Meeting of the American Physical

Society, Baltimore, MD, April 18-21, 1988 Bulletin of the American Physical

Society 33: 963.

Fragment production, Inclusive cross section, Impulse approximation

An impulsive excitation formalism is utilized to show the dependence of fragment production cross

section on incident energy per nucleon for the reaction (12C, 11B + p) on a 12C target. Excitationdecay of projectile fragments was previously shown to be consistent with the inclusive cross

section at 2.1 A GeV. Similar analysis are performed for 1.05 A GeV incident energy. These

results are compared with the reaction (160, 15N + P) at 1.05 and 2.1 A GeV, respectively, and

cross sections predicted for the direct step of the reaction. These will be compared with

experimental data from the BEVALAC when they become available.

Khan, F., Khandelwal, G. S., Wilson, J. W., Townsend, L. W., and Norbury,

J. W. (1988) Momentum downshifts of projectile fragments in 12C fragmentation

at 2.1 A GeV on Be, C, AI, Cu, Ag, and Pb targets. Abstract presented at the

1988 Annual Meeting of the Southeastern Section of the American Physical

Society, Raleigh, NC, November 10-12, 1988. Bulletin of the American Physical

Society 33: 2193.

Projectile fragmentation, Momentum transfer, NUCFRAG

In the Bevalac experiments on 12C fragmentation on various targets at 2.1 A GeV, it was observed

that the longitudinal momentum distribution of the projectile fragments showed a mean momentum

downshift <P11> less than the projectile momentum. We have developed a model of momentum

transfer in an impulsive excitation picture between relativistic heavy ions. Guided by the impact

parameters from the semi-empirical code NUCFRAG, we have been able to calculate mean

momentum downshifts for C, B, Be, Li fragments produced in the collision of 12C on Be, C, AI,

Cu, Ag, Pb targets - at 2.1 A GeV. Results will be shown and possible energy dependence will be

discussed.

Hong, B. S., Maung, K. M., Wilson, J.W., and Buck, W. W. (1989) KaonNucleus Scattering. NASA Technical Paper 2920.

Kaon, Optical potential, Eikonal approximation, Total cross sections, Absorptive cross sections

m

The derivations of the Lippmann-Schwinger equation and the Watson multiple-scattering series are

given. A simple optical potential is found to be the first term of that series. The number density

distribution models of the nucleus, harmonic well and Woods-Saxon are used with our t-matrix

taken from the scattering experiments. The parameterized two-body inputs, which are kaonnucleon total cross sections, elastic slow parameters, and the ratio of the real to the imaginary part

of the forward elastic scattering amplitude, are presented. The eikonal approximation was chosen

10
asour solution method to estimate the total and absorptive cross sections for the kaon-nucleus

scattering.

Maung, K. M., Townsend, L. W., and Deutchman, P. A. (1987) Corrections to

the impulse approximation of the first-order optical potential. Abstract presented

at the Fall Meeting of the Division of Nuclear Physics, New Brunswick, N J,

April 20-23, 1987. Bulletin of the American Physical Society 32: 1566.

OpticaI potential

Corrections to the tp approximation of the first-order optical potential are discussed. Calculations

will be presented for both the Watson and KMT formalisms.

Norbury, J. W., Deutchman, P. A., Townsend, L. W., and Cucinotta, F. A.

(1988) A General Formalism for Phase Space Calculations. NASA Technical

Paper 2843.

Phase spaces, Heavy-ion collisions

General formulas for calculating the interactions of galactic cosmic rays with target nuclei are

presented. Methods for calculating the appropriate normalization volume elements and phase space

factors are presented. Particular emphasis is placed on obtaining correct phase space factors for

two- and three-body final states. Calculations for both Lorentz-invariant and noninvariant phase

spaces are presented.

Norbury, J. W. and Townsend, L. W. (1990) Calculation of Two-Neutron

Multiplicity in Photonuclear Reactions. NASA Technical Paper 2968.

Neutrons, P hotonuclear reactions, Heavy-ion collisions

The most important particle emission processes for electromagnetic excitations in nucleus-nucleus

collisions are the ejection of single neutrons and protons and also pairs of neutrons and protons.

Methods are presented for calculating two-neutron emission cross sections in photonuclear

reactions. The results are in a form suitable for application to nucleus-nucleus reactions.

Norbury, J. W., Townsend, L. W., and Badavi, F. F. (1988)

for Parameterization of Nucleus-Nucleus Electromagnetic

Sections. NASA Technical Memorandum 4038.

Computer Program

Dissociation Cross

Electromagnetic dissociation, Cross sections

A computer subroutine parameterization of electromagnetic dissociation cross sections for nucleusnucleus collisions is presented that is suitable for implementation in a heavy ion transport code.

The only inputs required are the projectile kinetic energy and the projectile and target charge and

mass numbers.

Wilson, J. W., Townsend, L.W., Buck, W. W., Chun, S. Y., Hong, B. S., and

Lamkin, S. L. (1988) Nucleon-Nucleus Interaction Data Base: Total Nuclear

and Absorption Cross Sections. NASA Technical Memorandum 4053.

Neutron total cross sections, Absorptive cross sections, Differential cross sections

11
I

i

Neutrontotalcrosssectionsarerepresentedfor Li toPutargetsatenergiesabove0.1MeV andless

than 100MeV using a modified nuclearRamsauerformalism. The formalism is derivedfor

energiesabove100MeV by fitting theoreticalcrosssections.Neutronabsorptioncrosssections

arerepresentedby analyticexpressionsof similar form, but shaperesonancephenomenaof the

Ramsauereffect arenot present.Elasticdifferential crosssectionsaregiven asa renormalized

impulseapproximation. Thesecrosssectiondata baseswill be useful for nucleon transport

applications.

1.2.2. EXPERIMENTAL

Bastid, N., Alard, J. P., Arnold, J., Augerat, J., Babinet, R., Biagi, F.,

Brochard, F., Crouau, M., Charmensat, P., Dupieux, P., Fodor, Z., Fraysse,

L., Girard, J., Gorodetzky, P., Gosset, J., Laspalles, C., Lemaire, M. C., Le

Merdy, A., L'Hote, D., Lucas, B., Marroncle, J., Montarou, G., Parizet, M. J.,

Poitou, J., Qassoud, D., Racca, C., Rahmani, A., Schimmerling, W., Terrien,

Y., and Valette, O. (1990) Exclusive measurements of light fragment production

at forward angles in Ne-Pb and Ne-NaF collisions at E/A = 400 MeV and 800

MeV. Nuclear Physics A506: 637-654.

Light fragments, Diogene, Multiplicities, Production cross sections

Emission of light fragments at small angles is studied in relativistic heavy ion collisions using the

Diogene plastic wall for both symmetrical and non-symmetrical target-projectile systems with 400

MeV per nucleon and 800 MeV per nucleon incident neon nuclei. Efficiency of multiplicity

measurements in the small angle range for the selection of central or peripheral collisions is

confirmed for asymmetric systems. Differential production cross sections of Z = 1 fragments

show evidence for the existence of two emitting sources. The apparent temperature of each source

is obtained from comparison with a thermodynamical model.

Brechtmann, C., Heinrich, W., and Benton, E.V. (1989) Fragmentation cross

sections of 28Si at 14.5 GeV/nucleon. Physical Review C 39(6): 2222-2226.

28Si, Plastic nuclear track detectors, Charge changing cross sections, Partial cross sections,

Electromagnetic dissociation, Fragmentation

We used CR39 plastic nuclear track detectors (C12HlsOT) in combination with automatic track

measurement techniques to determine total charge changing and partial cross sections for the

production of fragments of charge Ze=6 to Ze=13 in collisions of 28Si beam nuclei at 14.5

GeV/nucleon in targets H, C, CR39, (C1sH380), A1, Cu, Ag, and Pb. By application of

factorization rules, measured partial cross sections are separated into pure nuclear and

electromagnetic components. The cross sections for electromagnetic dissociation agree with

theoretical models. The results are consistent with a Z 2 dependence of virtual photon spectra.

Dudkin, V. E., Kovalev, E. E., Nefedov, N. A., Antonchik, V. A., Bogdanov,

S. D., Ostroumov, V. I., Crawford, H. J., and Benton, E. V. (1990)

Multiplicities of secondaries in interactions of 1.8 GeV/nucleon S6Fe nuclei with

photoemulsion and the cascade evaporation model. Nuclear Physics A509: 783-

799.

Multiplicities, 56Fe nuclei, Emulsion, Cascade, Evaporation model, Inelastic interactions

12

E
A nuclear photographic emulsion method was used to study the charge-state, ionization, and

angular characteristics of secondaries produced in inelastic interactions of 56Fe nuclei at 1.8

GeV/nucleon with H, CNO, and AgBr nuclei. The data obtained are compared with the results of

calculations made in terms of the Dubna version of the cascade evaporation model (DCM). The

DCM has been shown to satisfactorily describe most of the interaction characteristics for two nuclei

in the studied reactions. At the same time, quantitative differences are observed in some cases.

Dupieux, P., Alard, J. P., Augerat, J., Babinet, R., Bastid, N., Brochard, F.,

Charmensat, P., De Marco, N., Fanet, H., Fodor, Z., Fraysse, L., Girard, J.,

Gorodetzky, P., Gosset, J., Laspalles, C., Lemaire, M. C., L'Hote, D., Lucas,

B., Marroncle, J., Montarou, G., Parizet, M. J., Poitou, J., Qassoud, D.,

Racca, C., Rahmani, A., Schimmerling, W., and Valette, O. (1988) Protonproton correlations at small relative momentum in neon-nucleus collisions at E/A

= 400 and 800 MeV. Physics Letters B 200: 17-21.

Proton-proton correlations, Neon, Diogene

Proton-proton small angle correlations have been measured in neon-nucleus collisions, using the

4_ detector Diogene, at 400 and 800 MeV per nucleon incident energies. Values of the size of the

emitting region are obtained by comparison with the Koonin formula, taking into account the

biases of the apparatus. The dependence of the density on target mass and incident energy is also

analysed.

Hoffmann, A., Brechtmann, C., Heinrich, W., and Benton, E. V. (1988) Search

for projectile fragments with fractional charge in relativistic heavy ion collisions.

Physics Letters B 200(4): 583-586.

Plastic nuclear track detectors, Fractional charge, Oxygen, Projectile fragments

We measured the charge of about 35,000 projectile fragments with Z>5e produced by 14.5

GeV/nucleon and 200 GeV/nucleon 160 beams in a Pb target using CR39 plastic nuclear track

detectors. A minimum track length of 3 mm in the detector without nuclear interaction was

required. No evidence for fragments carrying a fractional charge was found.

L'Hote, D., Alard, J. P., Augerat, J., Babinet, R., Brochard, F., Fodor, Z.,

Fraysse, L., Girard, J., Gorodetzky, P., Gosset, J., Laspalles, C., Lemaire, M.

C., Lucas, B., Montarou, G., Parizet, M. J., Poitou, J., Racca, C.,

Schimmerling, W., Tamain, J. C., Terrien, Y., and Valero, J. (1987) Exclusive

measurements of mean pion multiplicities in 4He-nucleus reactions from 200 to

800 meV/nucleon. Physics Letters B 198: 139-142.

Central collisions, Diogene, Pion production

Mean multiplicities of r_+ and g- in 4He collisions with C, Cu, and Pb at 200, 600, and 800

MeV/u, and with C and Pb at 400 MeV/u have been measured using the large solid angle detector

Diogene. The dependence of pion multiplicity on projectile incident energy, target mass and proton

multiplicity is studied in comparison with intra-nuclear cascade predictions. The discrepancy

between experimental results and theory is pointed out and discussed.

13
Parizet, M. J., Alard, J. P., Rahmani, A., Montarou, G., Augerat, J., Bastid,

N., Demaison, P., Dupieux, P., Fraysse, L., Marroncle, J., Raha, S., Babinet,

R., Fodor, Z., Gosset, J., L'Hote, D., Poitou, J., Schimmerling, W., Terrien,

Y., Valette, O., Lemaire, M. C., Gorodetzky, P., and Racca, C. (1989) Proton

production in relativistic heavy ion collisions: Comparison with a

thermodynamical model. International Journal of Modern Physics A 4: 3689-

3703.

Proton production, Diogene, Alpha particles

Experimental results concerning proton production in nuclear collisions, obtained at a Saturne with

the Diogene 4-pi facility, are compared with the predictions of a thermodynamical model, using

collective velocity distributions combined with a statistical thermodynamics in local rest frames.

Experimental differential cross sections for alpha + nucleus and neon + nucleus central collisions at

incident energies between 200 and 800 MeV per nucleon are well reproduced by the model, for an

angular range 30-110 degrees in the laboratory system. Extracted values of the temperatures are

compared with those given by other authors.

Wong, M., Schimmerling, W., Phillips, M. H., Ludewigt, B. A., Landis, D. A.,

Walton, J. T., and Curtis, S. B. (1990) The multiple Coulomb scattering of very

heavy charged particles. Medical Physics 17(2): 163-171.

Multiple Coulomb scattering, Heavy ions

An experiment was performed at the Lawrence Berkeley Laboratory BEVALAC to measure the

multiple Coulomb scattering of 650-MeV/A uranium nuclei in 0.19 radiation lengths of a Cu target.

Differential distributions in the projected multiple scattering angle were measured in the vertical and

horizontal planes using silicon position-sensitive detectors to determine particle trajectories before

and after target scattering. The results were compared with the multiple Coulomb scattering

theories of Fermi and Moliere, and with a modification of the Fermi theory, using a Monte Carlo

simulation. These theories were in excellent agreement with experiment at the 20 level. The best

quantitative agreement is obtained with the Gaussian distribution predicted by the modified Fermi

theory.

1.2.2. EXPERIMENTAL

REPORTS/MEETINGS

Khan, F., Khandelwal, G. S., Townsend, L.

Resonant excitation of vibrational levels as

Presented at the 1990 International Conference

XII), Cambridge, MA, June 25-29, 1990.

W., and Wilson, J. W. (1990)

the origin of positron peaks.

on Particles and Nuclei (PANIC

Heavy-ion collisions, Positrons

Resonant excitation of vibrational levels is proposed as a possible mechanism that may explain the

observation of anomalous positron peaks from positron bombardment of thorium as well as the

famous heavy-ion collision GSI peaks. In the latter case, existence of a "nuclear quasimolecule"

formed during the collision of the high-Z nuclei near the Coulomb barrier is assumed. The

excitation function for the above process is derived from a model Hamiltonian. The peak in e+-Th

scattering is reproduced with experimental data on collective (beta, gamma) modes in Th.

Systematics of target dependence are explored in some detail. The extension of the above ideas to

L--

r

14
the GSI peaksis shownto be compatiblewith the existenceof "nuclearmolecules" at these

bombardingenergiesandtheresonantexcitationof their vibrationallevels. Probesotherthane÷

arediscussed.An interestingconsequenceof theaboveexplanationmaybethatnoteverye÷andepeakfrom high-Ztargetsis correlated.

Mitchell, J. W., Guzik, T. G., Wefel, J. P., Crawford, H. J., Engelage, J.,

Lindstrom, P. J., Schimmerling, W., and Symons, T. J. M. (1987) Projectile

fragmentation of 140 at medium energies. Abstract presented at the General

Meeting of the Division of Nuclear Physics, New Brunswick, N J, April 20-23,

1987. Bulletin of the American Physical Society 32: 1109.

Projectile fragmentation, Heavy ions, Cross sections

The production of projectile-like fragments has been investigated for 160 beams incident on -1

gm/cm 2, C, and CH2 targets with energies of 170, 255, and 360 MeV/n, using a solid-state

isotope identification telescope at the Bevalac. The longitudinal and transverse momentum

distributions of the principal fragments are measured and are compared to results obtained at other

energies and to theoretical models. Partial projectile fragmentation cross sections are determined

for both target materials and for hydrogen (by CH2 - C subtraction). These are compared to data

available at higher and lower energies and from other target materials as well as to semi-empirical

calculations.

15
1.3. SPACE RADIATION

1.3.1. COSMIC RAY AND ASTROPHYSICS

J..0__UB2tAI_

Letaw, J. R., Share, G. H., Kinzer R. L., Silberberg, R., Chupp, E. L.,

Forrest, D. J., and Rieger, E. (1989) Satellite observation of atmospheric

nuclear gamma radiation. Journal of Geophysical Research 94: 1211.1221.

Gamma radiation, Gamma NKW, Solar maximum mission, Compton scattering

We present a satellite observation of the spectrum of gamma radiation from the Earth's atmosphere

in the energy interval from 300 keV to 8.5 MeV. The data were accumulated by the gamma ray

spectrometer on the Solar Maximum Mission over 3.5 years, from 1980 to 1983. The excellent

statistical accuracy of the data allows 20 atmospheric line features to be identified. The features are

superimposed on a continuum background which is modeled using a power law with index -1.16.

Many of these features contain a blend of more than one nuclear line. All of these lines (with the

exception of the 511-keV annihilation line) are Doppler broadened. Line energies and intensities

are consistent with production by secondary neutrons interacting with atmospheric 14N and 160.

Although we find no evidence for other production mechanisms, we cannot rule out significant

contributions from direct excitation or spallation by primary cosmic ray protons. The relative

intensities of the observed line features are in fair agreement with theoretical models; however,

existing models are limited by the availability of neutron cross sections, especially at high energies.

The intensity and spectrum of photons at energies below the 511-keV line, in excess of a power

law continuum, can be explained by Compton scattering of the annihilation line photons in

traversing an average of about N21gcm -2 of atmosphere.

Silberberg, R., Leising, M. D., and Murphy, R. J. (1989) Gamma-ray lines

from nucleosynthesis and from cosmic-ray and solar-flare particle interactions.

In: Cosmic Gamma Rays, Neutrinos, and Related Astrophysics, Eds. M. M.

Shapiro and J. P. Wefel. Kluwer Academic Publishers, pp. 289-319.

Solar flare, Gamma-ray lines, Cobalt decay lines, Positrons ionization

Gamma-ray lines provide a versatile probe for sites of nuclear reactions in astrophysical objects.

Two sets of nuclear reactions can be explored: (1) build-up reactions of atomic nuclei from lighter

constituents (nucleosynthesis), and (2) break-up of heavier nuclei in nuclear spallation reactions,

including nuclear excitation reactions. Nucleosynthesis occurs in presupernova stars, in supemova

events (e.g., explosive carbon and oxygen burning and silicon burning) and in novae (explosive

hydrogen buming). Spallation reactions occur when cosmic rays interact in interstellar clouds, in

the galactic gas towards the regions of the galactic center, and with matter near their acceleration

sites. Spallation and nuclear excitation are also induced by solar-flare particles. Recent

experimental observations include solar lines of several elements observed at the time of the large

27 April 1981 flare and from several other flares, the galactic 26A1 line, the e + annihilation line

from an extended region about the galactic center, and the 56Co decay lines from Supernova 1987A

in the Large Magellanic Cloud.

m

16
1.3.2. ENVIRONMENTS AND ENVIRONMENTAL MODELS

J_0_U_RJSAJ_

Konradi, A., Hardy, A. C., and

models and the atmospheric cutoff.

285.

Atwell, W. (1987) Radiation environment

Journal of Spacecraft and Rockets 24: 284-

Electrons, Protons, Magnetic field models, AP-8, AE-8, Trapped radiation

Radiation environment models are widely used to predict radiation doses expected on a variety of

space flight missions. In these models, omnidirectional electron and proton fluxes are stored in

computer codes as functions of particle energies and the parameters B and L, where B is the local

magnetic field intensity in Gauss and L is the Mcllwain drift shell parameter. While trying to

predict radiation doses expected at the space station orbit toward the end of this century, we

discovered an artifact of the model that necessitates modifications in the standard method of their

use. The following discussion explains this artifact and makes suggestions about how it can be

avoided.

The most recent models are the AP-8 for protons and the AE-8 for electrons. Each of these models

comes in two variants that incorporate different radiation intensities observed in the atmospheric

cutoff region about the 1970 solar maximum (MAX) and about the 1964 solar minimum (MIN).

During magnetically quiet periods, magnetic field models, based on the multipole expansion of the

internal sources only, represent the Earth's field quite well up to L values of about 4. Experimental

evidence indicates that the Earth's magnetic field is changing: the strength of the dipole is

decreasing at about 0.09%/year and geomagnetic surface features are drifting westward at a rate of

0.27 deg/year. Thus, to allow a certain amount of temporal extrapolation, the models contain firstorder and sometimes second-order time derivatives.

Wilson, J. W., Townsend, L. W., and Farhat, H. (1989) Cosmic-ray neutron

albedo dose in low-Earth orbits. Health Physics 57: 665-668.

Neutron albedo, Low Earth-orbit, Quality factors

Soon after the discovery of the Van Allen radiations, diffusion of neutrons from the top of the

Earth's atmosphere was suggested as a possible source of these trapped radiations (Hess 1959;

Hess and Killeen 1961). Previously, atmospheric neutrons had been studied for nearly two

decades (Bethe et al. 1940). Their biological significance was generally discounted (ICRP 1966)

until Foelsche (1962, 1968) suggested, and it was later confirmed, that the fast neutron and the

high-energy neutron components (Foelsche et al. 1974) had been underestimated in previous

studies.

Estimates of neutron exposure in low-Earth orbit yield on the order of 0.01 Gyy -1 or about 0.1

Svy -1 using the ICRP Publication No. 6 quality factor (ICRP 1964). Recent suggestions that

neutron quality factors should be increased (ICRU 1986) raise the importance of neutrons to space

exposure estimates, and it now seems prudent to establish a neutron model environment.

Extensive studies of atmospheric neutrons by the Langley Research Center (Foelsche et al. 1974;

Korff et al. 1979) provide a basis for an Earth albedo neutron environmental model.

17
1.3.2. ENVIRONMENTS AND ENVIRONMENTAL MODELS

REPORTS/MEETINGS

Wilson, J. W., Khandelwal, G. S., Shinn, J. L., Nealy, J. E., Townsend, L.

W., and Cucinotta, F. A. (1990) A simplified model for solar cosmic ray

exposure in manned Earth orbital flights. NASA Technical Memorandum 4182.

Low Earth-orbit, Geomagnetic field model, Shuttle

A simple calculational model is derived for use in estimating solar cosmic ray exposure to critical

body organs in low Earth orbit at the center of a large spherical shield of fixed thickness. The

effects of the Earth's geomagnetic field and the astronauts' self-shielding are evaluated explicitly.

The geomagnetic field model is an approximate tilted eccentric dipole with geomagnetic storms

represented as an impressed uniform field. The storm field is related to the planetary, geomagnetic

index Kp. The Shuttle geometry is introduced into the resultant computer code using the Shuttle

mass distribution surrounding two locations on the flight deck. The Shuttle is treated as pure

aluminum and the astronaut as soft tissue. Short-term average fluence over a single orbit is

calculated as a function of the location of the lines of nodes or long-term averages over all lines of

nodes for a fixed inclination.

1.3.3. SOLAR ACTIVITY AND PREDICTION

REPORTS/MEETINGS

Nealy, J. E., Simonsen, L. C., Townsend, L. W., and Wilson, J.W. (1990)

Deep-space radiation exposure analysis for solar cycle XXI (1975-1986).

Presented at the 20th Annual Intersociety Conference on Environmental Systems

(ICES), Williamsburg, VA, July 9-12, 1990. SAE Technical Paper Series

#901347.

Radiation exposures, Shielding, Dose equivalent, Radiation dosimetry

Ionizing radiation exposures and associated dosimetric quantities are evaluated for the 11-year solar

cycle ending in 1986. Solar flare fluences for the 55 largest flares occurring during the cycle are

superimposed on the galactic cosmic ray flux. Published summaries of flare data from the

Interplanetary Monitoring Platform (IMP)-7 and IMP-8 satellites are used and include flares whose

integrated fluences are greater than 107 protons/cm 2 for energies in excess of 10 MeV. A standard

cosmic ray environment model for ion flux values at solar minimum and maximum is invoked With

an assumed sinusoidal variation between the lower and upper limits. The radiation shielding

analysis is carried out for equivalent water-shield thicknesses between 2 and 15 q/cm 2. Results are

expressed in terms of cumulative incurred dose equivalents for deep-space missions lasting

between 3 months and 3 years. Since no predominantly large proton flares occurred during this

period, this analysis should provide an approximate quantification of doses to be normally

expected in the course of a long-duration interplanetary mission. It was found that medium-tolarge flare contributions are of greatest importance for the shorter-term missions, while the galactic

component dominates for the longer-duration missions. Predicted dose equivalents are presented

for various mission durations within any portion of the solar cycle.

L

18
Townsend, L. W., Nealy, J. E., and Wilson, J. W. (1988) Preliminary Estimates

of Radiation Exposures for Manned Interplanetary Missions from Anomalously

Large Solar Flare Events. NASA Technical Memorandum 100620.

Radiation exposures, Solar flare, BRYNTRN, Depth doses, Dose equivalent, SEP, Solar energetic

particles

Preliminary estimates of radiation exposures for manned interplanetary missions resulting from

anomalously large solar flare events are presented. The calculations use integral particle fluences

for the February 1956, November 1960, and August 1972 events as inputs into the Langley

Research Center nucleon transport code BRYNTRN. This deterministic code transports primary

and secondary nucleons (protons and neutrons) through any number of layers of target material of

arbitrary thickness and composition. Contributions from target nucleus fragmentation and recoil

are also included. Estimates of 5-cm depth doses and dose equivalents in tissue are presented

behind various thicknesses of aluminum, water, and composite aluminum/water shields for each of

the three solar flare events.

1.3.4. EXPERIMENTS

REPORTS/MEETINGS

Benton, E. V. and Heinrich, W. (Eds) (1990) Ionizing radiation exposure of

LDEF (LDEF prerecovery estimates). Department of Physics, University of San

Francisco: USF-TR-77.

LDEF, Induced radioactivity, Trapped protons, LET, Neutrons, Secondaries, SpaIlation products,

Recoils

The Long Duration Exposure Facility (LDEF) was launched into orbit by the Space Shuttle

Challenger mission 41C on April 5, 1984, and was deployed on April 8. The original altitude of

the circular orbit was 258.5 nautical miles (479 km) with the orbital inclination being 28.5 °. The

21,500 lb NASA Langley Research Center satellite, having dimensions of some 30 x 14 feet, was

one of the largest payloads ever deployed by the Space Shuttle. LDEF carried 57 major

experiments and remained in orbit five years and nine months (completing 32,422 orbits). It was

retrieved by the Shuttle Columbia on January 11, 1990. The data and subsequent knowledge that

will evolve from the analysis of the LDEF experiments is expected to bear heavily on the design

and construction of Space Station Freedom and on other long-term, near-Earth orbital space

missions. This publication provides a list of the radiation experiments that flew on LDEF, and

describes preliminary results in the following areas: trapped particles and cosmic rays; predictions

of LDEF fluxes and dose due to geomagnetically trapped protons and electrons; linear energy

transfer spectra; neutrons, secondaries, spallation products and high-LET recoils; induced

radioactivity in LDEF; and LDEF radiation exposure as projected from Shuttle missions.

: 19
1.4. RADIATION TRANSPORT AND SHIELDING

REPORTS/MEETINGS

f

I

I

iZ

]

!

Cucinotta, F., Hajnal, F., and Wilson, J.W. (1990) Energy deposition at the

bone-tissue interface from nuclear fragments produced by high-energy nucleons.

Health Physics 59:819-825

Energy deposition, Bone-tissue interface, Nuclear fragments, High-energy nucleons

The transport of nuclear fragmentation recoils produced by high-energy nucleons in the region of

the bone-tissue interface is considered. Results for the differential flux and absorbed dose for

recoils produced by 1-GeV protons are presented in a bidirectional transport model. The energy

deposition in marrow cavities is seen to be enhanced by recoils produced in bone. Approximate

analytic formulae for absorbed dose near the interface region are also presented for a simplified

range-energy model.

Townsend, L. W. and Wilson, J. W. (1987) Galactic heavy ion propagation

through spacecraft. Invited lecture at the Natural Space Radiation and VLSI

Technology Conference, Houston, TX, January 20-21, 1987. NASA CP-10023,

pp. II-3-i to II-3-10.

HZE, Galactic cosmic rays, Spacecraft shielding, Single-event upsets, Material degradation,

Radiation dosimetry

As the radiations composing the HZE (high-energy heavy ion) component of galactic cosmic rays

traverse a spacecraft, they undergo energy losses, nuclear breakup (fragmentation), and nuclear

attenuation processes within the bulk matter comprising the vehicle's structure. As a result of these

alterations in energy and composition, the radiation fields within the spacecraft interior may differ

appreciably from the external environment. Currently, modem methods of HZE particle interaction

and transport are being developed to evaluate the effects of these processes in spacecraft materials.

These techniques, presented herein, have direct application to such diverse research topics as (1)

single-event phenomena in microelectronic circuitry, (2) solar cell and structural material

degradation, and (3) crew radiation dosimetry and shielding requirements. To illustrate the

methods, representative calculations of HZE particle transport through nominal spacecraft

thicknesses are presented. The results of these calculations show that, for missions beyond the

Earth's magnetosphere, shielding thicknesses greater than 10 g/cm 2 appear to offer only minimal

additional protection from galactic cosmic rays. For missions within the magnetosphere, low Z

materials appear to be the shield material of choice.

Townsend, L. W., Wilson, J. W., Schimmerling, W., and Wong, M. (1987)

Studies of HZE particle interactions and transport for space radiation purposes.

Presented at the NASA Space Life Sciences Symposium: Three Decades of Life

Science Research in Space, Washington, DC, June 21-26, 1987.

HZE , Space exploration, Radiation shielding, HZE interaction, Transport model

As the era of Space Station, lunar bases, and manned Mars missions approaches, cumulative

radiation exposures of career astronauts to biologically significant levels of the high-energy heavy

ion (HZE) component of solar and galactic cosmic rays will occur for the first time in the history of

manned space flight. Since these HZE particles include nearly all nuclear species, and possess a

very broad range of incident energies, considerable attention must be devoted to developing

accurate methods of describing their physical interactions and transport through bulk matter in

- 20
order to properly assess spacecraft shielding effectiveness, and to evaluate the self-shielding

factors of the astronauts' bodies themselves. As these extremely energetic cosmic rays traverse

bulk matter, their radiation fields change composition through interactions with any target materials

encountered. Aside from continuously losing energy through collisions with atomic orbital

electrons, the incident ions collide with target nuclei within the shield and experience nuclear

attenuation (absorption) and breakup (fragmentation) reactions. The struck target nuclei also

recoil, leaving highly ionized tracks in their wakes. These interactions remove particles from the

incident field while concomitantly producing secondary and subsequent generation reaction

products. The altered composition of the transported field then results in an internal radiation field

within some critical organ of the astronaut's body which differs appreciably from that incident

upon the external spacecraft structure. Proper evaluation of the biological damage to this critical

organ requires an adequate knowledge of the physical characterizations (energies and composition)

of the complex radiation fields incident upon that organ. Studies of the physical transport and

interactions of these space radiation fields are presently hampered by a paucity of experimental

HZE interaction and transport data. Consequently, an experimental apparatus has been built to

study the composition and spectra of heavy ion beams of different types as they pass through

various materials of variable thickness. Sufficient measurements will be made to fully specify

biologically interesting dosimetric quantities as a function of shield type and depth for each beam

type. Because of the large numbers of projectile/target combinations and their nuclear

fragmentation products, it is unreasonable to expect that experimental measurements alone will ever

provide the necessary interaction and transport data. Therefore, experimentally validated

calculational methods are needed to accurately describe them. To this end a NASA-supported

collaborative research effort involving theoreticians at Langley Research Center (LaRC) and

experimentalists at Lawrence Berkeley Laboratory (LBL) has been established to develop the

necessary radiation physics methodologies for properly evaluating future HZE particle shielding

and dosimetry requirements for manned space flight. In this presentation current and planned

research efforts for the LaRC-LBL collaboration will be described.

Townsend, L. W., Wong, M., Schimmerling, W., and Wilson, J. W. (1987)

Development of a nuclear data base for relativistic ion beams. IN: Health

Physics of Radiation Generating Machines, Proceedings of the Twentieth

Midyear Topical Symposium of the Health Physics Society, Reno, NV, February

8-12, pp. 451-458 (CONF-8602106).

Heavy ion reactions, Model development

The primary limitation on the development of heavy ion beam transport methods is the lack of an

accurate nuclear data base. Because of the large number of ion/target combinations, the complexity

of the reaction products, and the broad range of energies required, it is unlikely that the data base

will ever be compiled from experiments alone. For the last 15 years, relativistic heavy-ion

accelerators have been available, but the experimental data base remains inadequate. However,

theoretical models of heavy-ion reactions are being derived to provide cross section data for beam

transport problems. A concurrent experimental program to provide sufficient experimental data to

validate the model is also in progress. Model development and experimental results for model

validation will be discussed. The need for additional nuclear fragmentation data is identified.

21
i

!

F

!3 ;

i

i1.4.1. THEORY AND MODEL DEVELOPMENT

Wilson, J. W., and Badavi, F. F. (1986)

transport. Radiation Research 108: 231-237.

Methods of galactic heavy ion

Methods, Monte Carlo methods, Heavy ion transport, Boltzmann equation

Two methods of calculating the transition of galactic heavy ions in the Earth's atmosphere are

compared with respect to accuracy, generality, and computer efficiency. The most general method

is shown to have the highest accuracy and is a simple numerical procedure.

Wilson, J. W., Chun, S. Y., Buck, W. W., and Townsend, L. W. (1988) High

energy nucleon data bases. Health Physics 55: 817-819.

Data bases, Protons, Monte Carlo, lntranuclear cascade

It is welt established that 30% to 50% of the energy absorbed during human exposure to highenergy protons (>400 MeV) is due to secondary radiations produced in nuclear reactions. There

are several transport codes for making exposure estimates and two primary data bases which are

readily found in the open literature. The first such data base is an intranuclear cascade Monte Carlo

derived data set (sometimes the intranuclear cascade code resides within the transport code itself),

and the second is an empirical fit to experimental or theoretical cross sections. This note examines

the relative differences in results attributable to these data bases.

Wilson, J. W. and Townsend, L.W. (1988) A benchmark for galactic cosmic-ray

transport codes. Radiation Research 114: 201-206.

Benchmark solution, Galactic cosmic rays, Transport codes, Uncertainties

A nontrivial analytic benchmark solution for galactic cosmic-ray transport is presented for use in

transport code validation. Computational accuracy for a previously developed cosmic-ray transport

code is established to about 1% by comparison with this exact benchmark. Hence solution

accuracy for the transport problem is limited mainly by inaccuracies in the input spectra, input

interaction data bases, and the use of a straight-ahead/velocity-conserving approximation.

Wilson, J. W. and Townsend, L. W. (1988) Radiation safety in commercial air

traffic: A need for further study. Health Physics 55:1001-1003.

ICRU, Exposure, Quality factors

Previous work at Langley Research Center on atmospheric radiation used quality factors, as

defined by the International Commission for Radiological Protection (ICRP 1964), which are

currently undergoing considerable revision. With the recent recommendation of a new quality

factor by the International Commission for Radiological Measure and Units (ICRU 1986), it seems

prudent to estimate the resulting changes in the radiation exposure rates in the Earth's atmosphere.

As a result of the change in quality factor, it is found that worst case estimates of radiation

exposure are now well above the exposure limits of the general population, and a reassessment of

radiation impact on commercial aviation is needed if these proposed quality factors are adopted.

.

o

-L_

22
Wilson, J. W., Townsend, L. W., and Badavi, F. F. (1987) Galactic HZE

propagation through the Earth's atmosphere. Radiation Research 109: 173-183.

Earth's atmosphere, HZE, Heavy ion

A comprehensive physical model for galactic heavy ion propagation is presented. The nuclear

fragmentation model, is a simplified physical model, but contains the major processes of

importance to galactic ions. Comparison is made to measurements of atmospheric ion fluence and

the limitations of these comparisons are discussed.

Wilson, J. W., Townsend, L. W., Ganapol, B., Chun, S. Y., and Buck, W. W.

(1988) Charged-particle transport in one dimension. Nuclear Science and

Engineering 99: 285-287.

Transport codes, Boltzmann equation, Numerical solutions

A numerical solution to high-energy charged-particle transport is found by evaluation of the

integral equations obtained by inverting the Boltzmann differential operator. An algorithm has

been written for either continuous or discrete spectra at the boundary, which allows efficient and

accurate evaluation of this rather complicated problem. Present results are compared with analytic

solutions based on the perturbation theory.

Wilson, J. W., Townsend, L. W., and Khan, F. (1989)

ionizing components in high-energy nucleon radiation fields.

717-724.

Evaluation of highly

Health Physics 57:

Fragment recoil, HZE

The data and models for nuclear fragment recoil distributions produced by high-energy nuclear

events in tissue are reviewed. Results for linear energy transfer distributions in soft tissue are

derived, and a simple model is developed for use in radiation studies and risk estimates.

Wilson, J. W., Townsend, L. W., Lamkin, S. L., and Ganapol, B. D. (1990) A

closed form solution to HZE propagation. Radiation Research 122: 223-228.

Analytical solution, Transport codes

An analytical solution for high-energy heavy ion transport assuming straight-ahead and velocityconserving interactions with constant nuclear cross-reactions is given in terms of a Green's

function. The series solution for the Green's function is rapidly convergent for most practical

applications. The Green's function technique can be applied with equal success to laboratory

beams as well as to galactic cosmic rays allowing laboratory validation of the resultant space

shielding code.

23
1.4.1. THEORY AND MODEL DEVELOPMENT

REPORTS/MEETINGS

Atwell, W., Beever, E. R., Hardy, A. C., and Cash, B. L. (1989) A radiation

shielding model of the Space Shuttle for space radiation exposure estimations.

Presented at Advances in Nuclear Engineering Computation and Radiation

Shielding, American Nuclear Society, Santa Fe, NM, April 9-13, 1989.

Shuttle shielding model Shuttle, Computerized anatomical man model Dose equivalent

An analytical shielding model of the Space Shuttle has been developed for use in determining the

expected space radiation dose exposures to astronauts and radiation-sensitive payloads and

experiments for various Shuttle missions. The shielding model consists of approximately 2000

volume elements (geometrical shapes) that was constructed using engineering drawings,

specification sheets, materials lists, and other available data. The Shuttle model is used as an input

data file to the Elemental Volume Dose Program (EVDP) to compute the shield distribution about

any location (dose point) in the spacecraft. Models of the naturally occurring space radiation and a

computerized anatomical man model are used to compute the absorbed dose and/or dose equivalent

for any mission scenario. The models and computational techniques are reviewed and discussed.

A comparison of the Shuttle mission space radiation exposure calculations with measurements

obtained from onboard active and passive dosimeters is discussed.

Ganapol, B. D., Townsend, L. W., and Wilson, J.W. (1989)

Solutions For the Galactic Heavy Ion Transport Equations: Energy

Dependent Problems. NASA Technical Paper 2878.

Benchmark

and Spatially

Transport codes, Benchmark solution, Analytical methods, Monoenergetic beams

Nontrivial benchmark solutions are developed for the galactic ion transport (G1T) equations in the

straight-ahead approximation. These equations are used to predict potential radiation hazards in the

upper atmosphere and in space. Two levels of difficulty are considered: (1) energy independent

and (2) spatially independent. The analysis emphasizes analytical methods never before applied to

the GIT equations. Most of the representations derived have been numerically implemented and

compared with more approximate calculations. Accurate ion fluxes (to 3 to 5 digits) are obtained

for nontrivial sources. For monoenergetic beams, both accurate doses and fluxes are found. The

benchmarks presented herein are useful in assessing the accuracy of transport algorithms designed

to accommodate more complex radiation protection problems. In addition, these solutions can

provide fast and accurate assessments of relatively simple shield configurations.

Ganapol, B. D., Wilson, J. W., and Townsend, L. W. (1988) Benchmark

solutions for the galactic ion transport equations. Invited lecture presented at the

Annual Meeting of the American Nuclear Society, San Diego, CA, June 12-16,

1988. Transactions of the American Nuclear Society 56: 276-277.

Galactic cosmic rays transport, Model verification, Benchmark solution

In the upper atmosphere and in space, high-energy heavy ions called galactic cosmic rays

originating in deep space or in our sun are the major ionizing particles. Not only is the unscattered

radiation of concern, but also the secondary particles generated from direct nuclear or Coulombic

fragmentation are responsible for a significant fraction of the absorbed dose. Thus, to ensure the

proper shielding of space bases and interplanetary vehicles, reliable dose and flux computational

models must be found. For this reason, the National Aeronautics and Space Administration has

24
initiatedaneffort to developmultidimensionaldeterministicmethodsto analyzeproposedshield

configurations.This paperdiscussesthepartialverificationof proposedion transportalgorithms

obtainedby comparisonsto standardsolutions-- benchmarks-- of the governinggalactic ion

transport(G1T)equations.

Nealy, J. E., Wilson, J. W., and Townsend, L. W. (1988) Solar-Flare

Shielding with Regolith at a Lunar-Base Site. NASA Technical Paper 2869.

Solar flare shielding, Regolith, BRYNTRN, Lunar colony

The Langley Baryon Transport computer code BRYNTRN has been used to predict time-integrated

radiation-dose levels at the lunar surface caused by high proton flux from solar flares. This study

addresses the shielding requirements for candidate lunar habitat configurations necessary to protect

crew members from large and unpredictable radiation fluxes. Three solar proton events have been

analyzed, and variations in radiation intensity in a shield medium due to the various primary

particle energy distributions are predicted. Radiation-dose predictions are made for various slab

thicknesses of a lunar soil model. Results are also presented in the form of dose patterns within

specific habitat configurations shielded with lunar material.

Nealy, J. E., Wilson, J. W., and Townsend, L. W. (1989) Preliminary analyses

of space radiation protection for lunar base surface systems. Presented at the

19th lntersociety Conference on Environmental Systems (ICES), San Diego, CA,

July 24-26, 1989. SAE Technical Paper Series #891487.

Galactic cosmic rays, HZE particles, Transport codes, Dose equivalent

Radiation shielding analyses are performed for candidate lunar base habitation modules. The study

primarily addresses potential hazards due to contributions from the galactic cosmic rays (heavy

ions). The NASA Langley Research Center's high energy nucleon and heavy ion transport codes

are used to compute propagation of radiation through conventional and regolith shield materials.

Computed values of linear energy transfer are converted to biological dose-equivalent using quality

factors established by the International Commission on Radiological Protection. Spectral fluxes of

heavy charged particles and corresponding dosimetric quantities are computed for a series of

thicknesses in various shield media and are used as an input data base for algorithms pertaining to

specific shielded geometries. Dosimetfic results are presented as isodose contour maps of shielded

configuration interiors. The dose predictions indicate that shielding requirements are substantial,

and an abbreviated uncertainty analysis shows that better definition of the space radiation

environment as well as improvement in nuclear interaction cross-section data can greatly increase

the accuracy of shield requirement predictions.

Shinn, J. L., Wilson, J. W., and Nealy, J. E., and Cucinotta, F. A. (1990)

Comparison of Dose Estimates Using the Buildup-Factor Method and a Baryon

Transport Code (BRYNTRN) with Monte Carlo Results. NASA Technical Paper

3021.

Monte Carlo, BRYNTRN, Transport codes, Shielding

Results of continuing efforts toward validating the buildup-factor method and the baryon transport

code (BRYNTRN), which use the deterministic approach to solving radiation transport problems

and are the candidate engineering tools in space radiation shielding analyses, are presented. A

simplified theory of proton-buildup factors assuming no neutron coupling has been derived to

verify a previously chosen form for parameterizing the dose-conversion factor that includes the

secondary-particle buildup effect. Estimates of dose in tissue made by the two deterministic

approaches and the Monte Carlo method are compared for cases with various thicknesses of

25
shieldsandvarioustypesof protonspectra.Theresultsarein reasonableagreement,butthereis

someoverestimationby thebuildup-factormethodwhentheeffect of neutronproductionin the

shieldis significant.Futureimprovement,includingneutroncouplingin thebuildup-factortheory,

is suggestedto alleviatethis shortcoming. Impressiveagreementfor individual componentsof

doses,such as thosefrom the secondariesand heavy-particlerecoils, is obtained between

BRYNTRN andMonteCarloresults.

Silberberg, R., Tsao, C. H., and Letaw, J. R. (1988) Transport of cosmic ray

nuclei in various materials. Transactions of the American Nuclear Society 56:

275.

ICU, Single event evaluation, HZE, GCR, Shielding

Cosmic-ray heavy ions have become a concern in space radiation effects analyses. Heavy ions

rapidly deposit energy and create dense ionization trails as they. traverse materials. Collection of

the free charge disrupts the operation of microelectronic circmts. This effect, called the singleevent upset, can cause a loss of digital data. Passage of high linear energy transfer particles

through the eyes has been observed by Apollo astronauts. These heavy ions have great

radiobiological effectiveness and are the primary risk factor for leukemia induction on a manned

Mars mission.

Models of the transport of heavy cosmic-ray nuclei through materials depend heavily on our

understanding of the cosmic-ray environment, nuclear spallation cross sections, and computer

transport codes. Our group has initiated and pursued the development of a full capability for

modeling these transport processes. A recent review of this ongoing effort is presented in Letaw,

Silberberg and Tsao (1988). In this paper, we discuss transport methods and present new results

comparing the attenuation of cosmic-rays in various materials.

Simonsen, L. C., Nealy, J. E., Townsend, L. W., and Wilson, J. W. (1990)

Space radiation shielding for Martian habitats. Presented at the 20th Annual

Intersociety Conference on Environmental Systems (ICES), Williamsburg, VA,

July 9-12, 1990. SAE Technical Paper Series #901346.

Shielding, Mars, Transport codes, Regolith

Radiation shielding analyses are performed for a candidate Mars base habitat. The Langley cosmic

ray transport code and the Langley nucleon transport code are used to quantify the transport and

attenuation of galactic cosmic rays and solar flare .protons through both the Martian atmosphere and

regolith shielding. Doses at the surface and at various altitudes were calculated in a previous study

using both a high-density and a low-density Mars atmosphere model. This study extends the

previous low-density results to include the further transport of the ionizing radiation that reaches

the surface through additional shielding provided by Martian regolith. A four-compound regolith

model, which includes SiO2, Fe203, MgO, and CaO, was selected based on the chemistry of the

Viking I Lander site. The spectral fluxes of heavy charged particles and the correspond!ng

dosimetric quantities are computed for a series of thicknesses in the shield media after traversing

the atmosphere. These data are then used as input to algorithms for a specific shield geometry.

The results are presented as the maximum dose received in the center of the habitat versus various

shield thicknesses for a base at an altitude of 0 km and 8 km.

26
Townsend, L. W., Ganapol, B. D., and Wilson, J. W. (1989) Benchmark

solutions for heavy ion transport code validation. Abstract presented at the 37th

Annual Meeting of the Radiation Research Society, Seattle, WA, March 18-23,

1989.

Benchmark, Boltzmann equation, Transport codes

Nontrivial analytic benchmark solutions for heavy ion transport are presented for use in validating

deterministic computer code solution algorithms used to predict dosimetric quantities in laboratory

beam and space radiation shielding applications. Benchmark solutions to the one-dimensional

Boltzmann transport equation are presented for three forms of the equation: (1) spatially

independent; (2) energy independent; and (3) coupled spatial and energy dependent. To illustrate

the application of these benchmarks to actual radiation transport problems, representative

comparisons between the benchmarks and numerical solutions obtained from transport codes

developed by the authors for use in galactic cosmic ray shielding studies are made.

Townsend, L. W. and Wilson, J. W. (1988) Nuclear cross sections for hadronic

transport. Invited lecture presented at the Annual Meeting of the American

Nuclear Society, San Diego, CA, June 12-16, 1988. Transactions of the

American Nuclear Society 56: 277-279.

Cross sections, Hadronic transport

The need to develop suitable methods for describing the interactions and transport of high-energy

hadrons through extended matter is important for a variety of applications, including cosmic ray

studies, exposure to space radiation, spacecraft shielding, radiobiological studies, accelerator

shield design, and clinical uses in cancer therapy. For most of these applications, the transport

equation can neglect target fragmentation and use the straight-ahead approximation. Accurate

values for the cross sections are essential to solving transport equations. Unfortunately,

experimental data for these cross sections are sparse. Hence, theoretical methods, validated by

comparison to experiment, must be used to provide the cross sections.

Townsend, L. W. and Wilson, J. W. (1990) Interaction of space radiation with

matter. Presented at the 41st Annual Congress of the International Astronautical

Federation, Dresden, Germany, October 6-12, 1990.

Radiation transport, Galactic cosmic rays, Transport codes, Sensitivity-analysis

The physical interactions of high-energy space radiations with bulk matter are described, with

particular emphasis on the nuclear and electromagnetic interactions of solar and galactic cosmic

rays. Methods of incorporating these interactions into radiation transport models that accurately

describe the propagation of the incident cosmic rays and their subsequent-generation reaction

products are also explained. Representative results for solar and galactic cosmic ray doses and

dose equivalents are presented for various aluminum and water absorber depths. For the first time,

the main contributions to human exposure in space from galactic cosmic rays will be presented on a

component by component basis, including a breakdown of the dose-equivalent contributions into

primary ions, heavy fragments, alpha particles, neutrons, and protons. For the galactic cosmic ray

environment outside of the Earth's magnetosphere, over 70 percent of the total dose equivalent

results from only seven nuclear species (hydrogen, helium, carbon, oxygen, silicon, magnesium,

and iron ions). Of these, the largest single contributor is cosmic ray iron and its secondaries,

which account for nearly one-fourth of the unshielded total dose equivalent during solar minimum.

27
Townsend, L. W., Wilson, J. W., and Nealy, J. E. (1988) Preliminary Estimates

of Galactic Cosmic Ray Shielding Requirements for Manned Interplanetary

Missions. NASA Technical Memorandum 101516.

Galactic cosmic rays, Shielding, Transport codes, Doses, Dose equivalent, Aluminum, Water,

Uncertainties

Estimates of radiation risk to the blood-forming organs from galactic cosmic rays are presented for

manned interplanetary missions. The calculations use the Naval Research Laboratory cosmic ray

spectrum model as input into the Langley Research Center galactic cosmic ray transport code. This

transport code, which transports both heavy ions and nucleons, can be used with any number of

layers of target material consisting of up to five different constituents per layer. Calculated galactic

cosmic ray doses and dose equivalents behind various thicknesses of aluminum and water

shielding are presented for solar maximum and solar minimum periods. Estimates of risk to the

blood-forming organs are made using 5-cm depth dose/dose equivalent values for water. These

results indicate that at least 5 g/cm 2 (5 cm) of water or 6.5 g/cm 2 (2.4 cm) of aluminum shielding is

required to reduce the annual exposure below the currently recommended limit of 50 rem. Because

of the large uncertainties in fragmentation parameters and the input cosmic ray spectrum, these

exposure estimates may be uncertain by as much as 70 percent. Therefore, more detailed analyses

with improved inputs could indicate the need for additional shielding.

Townsend, L. W., Wilson, J. W., Shinn, J. L., Nealy, J. E., and Simonsen, L.

C. (1990) Radiation protection effectiveness of a proposed magnetic shielding

concept for manned Mars missions. Presented at the 20th Annual Intersociety

Conference on Environmental Systems (ICES), Williamsburg, VA, July 9-12,

1990. SAE Technical Paper Series #901343.

Magnetic shielding

The effectiveness of a proposed concept for shielding a manned Mars vehicle using a confined

magnetic field configuration is evaluated by computing estimated crew radiation exposures

resulting from galactic cosmic rays and a large solar event. In this study, the incident radiation

spectra are transported through the spacecraft structure/magnetic shield using the deterministic

space radiation transport computer codes developed at Langley Research Center. The calculated

exposures unequivocally demonstrate that magnetic shielding could provide an effective barrier

against solar flare protons, but is virtually transparent to the more energetic galactic cosmic rays. It

is then demonstrated that through proper selection of materials and shield configuration, adequate

and reliable bulk material shielding can be provided for the same total mass as needed to generate

and support the more risky magnetic field configuration.

Wilson, J. W., Lamkin, S. L., Farhat, H., Ganapol, II. D., and

W. (1989) A Hierarchy of Transport Approximations for High

(HZE) Ions. NASA Technical Memorandum 4118.

Townsend, L.

Energy Heavy

Transport codes, Cross sections, Analytical solution

The transport of high-energy heavy (HZE) ions through bulk materials is studied with energy

dependence of the nuclear cross sections being neglected. A three-term perturbation expansion

appears to be adequate for most practical applications for which penetration depths are less than 30

g/cm 2 of material. The differentia/energy flux is found for monoenergetic beams and for realistic

ion beam spectral distributions. An approximate formalism is given to estimate high-order terms.

m

28
Wilson, J. W., Nealy, J. E., Atwell, W., Cucinotta, F. A.,

Townsend, L. W. (1990) Improved model for solar cosmic

manned Earth orbital flights. NASA Technical Paper 2987.

Shinn, J. L., and

ray exposure in

Shielding, Shuttle

A calculational model is derived for use in estimating solar cosmic ray exposure to a critical body

organs in low Earth orbit at the center of a large spherical shield of fixed thickness. The effects of

the Earth's geomagnetic field and the astronauts' self-shielding are evaluated explic!tly. The

geomagnetic field model is an approximate tilted eccentric dipole with geomagneuc storms

represented as an impressed uniform field. The storm field is related to the planetary geomagnetic

index Kp. The code is applied to the Shuttle geometry using the Shuttle mass distribution

surrounding two locations on the flight deck. The Shuttle is treated as pure aluminum and the

astronaut as soft tissue. Short-term average fluence over a single orbit is calculated as a function of

the location of the lines of nodes or long-term averages over all lines of nodes for a fixed

inclination.

Wilson, J. W., Townsend, L. W., and Atwell, W. (1987) Preliminary Estimates

of Galactic Cosmic Ray Exposures for Manned Interplanetary Missions. NASA

Technical Memorandum 100519.

Heavy ion, Aluminum, Solar periods, HZE

Preliminary estimates of radiation exposures resulting from galactic cosmic rays are presented for

interplanetary missions. The calculations use the Naval Research Laboratory cosmic ray spectrum

model as input into the Langley Research Center galactic cosmic ray transport code. The heavy ion

portion of the transport code can be used with any number of layers of target material, consisting

of up to five different constituents per layer. The nucleonic portion of the transport code can be

used with any number of layers of target material of arbitrary composition except hydro.gen.

Calculated galactic cosmic ray particle fluxes, doses, and dose equivalents behind various

thicknesses of aluminum shielding are presented for solar maximum and solar minimum periods.

Wilson, J. W., Townsend, L. W., Chun, S. Y., Buck, W. W., Khan, F., and

Cucinotta, F. (1988) BRYNTRN: A Baryon Transport Computer Code

Computation Procedures and Data Base. NASA Technical Memorandum 4037.

BRYNTRN, Transport codes, Data bases

The present report describes the development of an interactive data base and a numerical solution to

the transport of baryons through an arbitrary shield material based on a straight ahead

approximation of the Boltzmann equation. The code is most accurate for continuous energy

boundary values, but gives reasonable results for discrete spectra at the boundary with even a

relatively coarse energy grid (30 points) and large spatial increments (1 cm in H20).

Wilson, J. W., Townsend, J. W., Ganapol, B. D., and Lamkin, S. L. (1988)

Methods for high energy hadronic beam transport. Invited lecture presented at

the Annual Meeting of the American Nuclear Society, San Diego, CA, June 12-

16, 1988. Transactions of the American Nuclear Society 56: 271-272.

Transport codes

The equations of transport in one dimension have found numerous applications and reasonably

represent many of the properties of hadron transport. This paper discusses several such equations,

some of which are used as the basis for new transport codes for baryons of mass number greater

29
thanor equalto one. Thesecodesarenow beingextendedto couplewith themesonfield andto

thenegativebaryonnumberfields.

Wilson, J. W., Townsend, L. W., Nealy, J. E., Chun, S. Y., Hong, B. S.,

Buck, W. W., Lamkin, S. L., Ganapol, B. D., Khan, F., and Cucinotta, F.

(1989) BRYNTRN: A Baryon Transport Model. NASA Technical Paper 2887.

BRYNTRN, Boltzmann equation, Transport codes, Shielding

This report describes the develoment of an interaction data base and a numerical solution to the

transport of baryons through an arbitrary shield material based on a straight ahead approximation

of the Boltzmann equation. The code is most accurate for continuous-energy boundary values but

gives reasonable results for discrete spectra at the boundary using even a relatively coarse energy

grid (30 points) and large spatial increments (1 cm in H20). The resulting computer code is selfcontained, efficient, and easy to use. The code requires only a very small fraction of the computer

resources required for Monte Carlo codes.

1.4.2. EXPERIMENTAL STUDIES

Schimmerling, W., Miller, J.,

G., and Jarret, B. V. (1989)

function of depth in water: 1.

Wong, M., Rapkin, M., Howard, J., Spieler, H.

The fragmentation of 670A MeV Neon-20 as a

Experiment. Radiation Research 120: 36-71.

Neon, Neon transport, Fluence spectra, Water

We present the final analysis of an experiment to study the interaction of a beam of 670A MeV

neon ions incident on a water column set to different thicknesses. The atomic number Z (and, in

some cases, the isotopic mass A) of primary beam particles and of the products of nuclear

interactions emerging from the water column close to the central axis of the beam was obtained for

nuclei between Be (Z=4) and Ne (Z=10) using a time-of-flight telescope to measure the velocity

and a set of silicon detectors to measure the energy loss of each particle. The fluence of particles of

a given charge was obtained and normalized to the incident beam intensity. Corrections were made

for accidental coincidences between multiple particles triggering the TOF telescope and for

interactions in the detector. The background due to beam particles interacting in beam line elements

upstream of the detector was calculated. Sources of experimental artifacts and background in each

particle identification experiments designed to characterize heavy ion beams for radiobiological

research are summarized, and some of the difficulties inherent in this work are discussed.

Complete tables of absolutely normalized fluence spectra as a function of LET** are included for

reference purposes.

Townsend, L. W. and Wilson, J. W. (1988) An evaluation of energyindependent heavy ion transport coefficient approximations. Health Physics 54:

409-412.

Transport theory, Depth doses, Neon, Bragg curve

Using a one-dimensional transport theory for laboratory heavy ion propagation, evaluations of

typical energy-independent transport coefficient approximations are made by comparing theoretical

depth-dose predictions to published experimental values for incident 670 MeV/nucleon 2°Ne beams

30
in water. Resultsarepresentedfor caseswherethe input nuclearabsorptioncrosssections,or

inputfragmentationparameters,or both,arefixed.

1.4.2. EXPERIMENTAL STUDIES

REPORTS/MEETINGS

Miller, J., Schimmerling, W., Wong, M., Shavers, M. R., and Rapkin, M.

(1989) The transport of a 670 MeV accelerated neon beam in water: I.

Experimental. Abstract presented at the 37th Annual Meeting of the Radiation

Research Society, Seattle, WA, March 18-23, 1989.

Transport, Neon, Fluence spectra

We present the final analysis of an experiment to study the interaction of a beam of 670 MeV/A

neon ions incident on a water column set to different thicknesses. The electrical charge Z (and in

some cases the isotopic mass A) of primary beam particles and of the products of nuclear

interactions emerging from the water column close to the central axis of the beam was obtained for

nuclei between Be (Z=4) and Ne (Z=10) using a time-of-flight telescope to measure the velocity

and a set of silicon detectors to measure the energy loss of each particle. The fluence of particles of

a given charge was obtained and normalized to the incident beam intensity. Corrections were made

for accidental coincidences between multiple particles triggering the TOF telescope, and for

interactions in the detector. The background due to beam particles interacting in beam line elements

upstream of the detector was calculated. Sources of experimental artifacts and background in

particle identification experiments designed to characterize heavy ion beams for radiobiological

research are summarized and some of the difficulties inherent in this work are discussed.

Schimmerling, W. (1988) Physical considerations relevant to HZE-particle

transport in matter. Invited paper presented at the 1988 Annual Meeting of the

American Nuclear Society, San Diego, CA. Transactions of the American Nuclear

Society 56: 272-273.

HZE, Accelerator beams, Validations, Dosimetry

Heavy-ion accelerators are being seriously considered for driving inertial confinement fusion

reactors, and high-energy heavy nuclei in the cosmic radiation are likely to place significant

constraints on satellite power system deployment and space-based power generation. The use of

beams of heavy nuclei in an increasing number of current applications, as well as their importance

for the development of the state of the art of the future, makes it necessary to develop at the same

time a good understanding of their transport through matter.

Recently, transport methods have been developed to determine the radiation field produced by

relativistic heavy nuclei incident on layers of absorbers of different composition. These HZE

transport methods need to be validated by comparison with experimental data; accordingly, a

research program to develop heavy-ion transport predictions for space radiation shielding and

dosimetry was established at the Lawrence Berkeley Laboratory several years ago. The properties

of HZE particles that are relevant for transport calculations are discussed in this paper and

illustrated with results from this program, as well as from the broader spectrum of relativistic

heavy,ion research.

31
Schimmerling, W., Wong, M., Ludewigt, B., Phillips, M., Alpen, E. L.,

Powers-Risius, P., and DeGuzman, R. J. (1989) Biophysical aspects of heavy

ion interactions in matter. Presented at the Conference on High Energy Radiation

Background in Space (CHERBS 87), Sanibel Island, FL, November 3-5, 1987.

AIP Conference Proceedings No. 186, Eds. A. C. Rester, Jr. and J. I. Trombka

(American Institute of Physics, New York, 1989), pp. 369-380.

HZE particles, Fragmentation experiments, Neon, Multiple Coulomb scattering, GCR, Transport

methods, Water

The biological effects of high energy, high charge nuclei (HZE particles) occupy a central role in

the management of space radiation hazards due to galactic cosmic rays. For the energy range of

interest, the mean free path for nuclear interactions of these heavy, ions is comparable to the

thickness of the material traversed, and a significant fraction of stopping particles will undergo a

nuclear reaction with the nuclei of the stopping material. Transport methods for HZE particles are

dependent on models of the interaction of man-made systems with the space environment to an

even greater extent than methods used for other types of radiation. Hence, there is a major need to

validate these transport codes by comparison with experimental data. The basic physical properties

of HZE particles will be reviewed and illustrated with the results of nuclear fragmentation

experiments performed with the 670-MeV neon ions incident on a water absorber and with

measurements of multiple Coulomb scattering of uranium beams in copper. Finally, the extent to

which physical measurements yield radiobiological predictions is illustrated for the example of

neon.

Shavers, M. R., Schimmerling, W., Curtis, S. B., Miller, M., Wong, M.,

Wilson, J. W., and Townsend, L. W. (1989) The transport of a 670 MeV

accelerated neon beam in water: II. Transport codes and comparison with

Experiment I. Abstract presented at the 37th Annual Meeting of the Radiation

Research Society, Seattle, WA, March 18-23, 1989.

Transport codes, NKW transport, Fluence spectra, Validations

Detailed model calculations of the transport of 670 MeV neon ions incident on a water absorber

have been made and compared with experimental data using the HZESEC code developed at LBL

and the LBLBEAM code developed at NASA-Langley. For every thickness of water a model

calculation was made of the measured differential fluence spectrum (number of particles of charge

Z per cm 2 per LET interval). Theoretical differential fluence spectra were corrected for the fraction

of the fluence actually detected, calculated using the PROPAGATE code developed at LBL, and

folded with the experimental energy resolution for comparison with experimental spectra. The

shape of the model spectra conform quite closely to the shape of the ex .perimental spectra over most

of the absorber depth. Near the Bragg peak, small differences xn stopping power lead to

significant differences between theoretical and experimental spectra. The differential spectra

provide a sensitive test of model fragmentation cross sections, stopping power and attenuation

lengths.

Wilson, J. W., Schimmerling, W., Wong, M., and Townsend, L. W. (1987)

Heavy ion beams in extended materials: Computational methods and experiment.

In: Health Physics of Radiation generating Machines, Proceedings of the

Twentieth Midyear Topical Symposium of the Health Physics Society, Reno, NV,

February 8-12, pp. 442-450 (CONF-8602106).

Heavy ion transport, Shielding, Radiation quality

r

32
Thetransportof heavyion beamsin extendedmaterialsis aproblemof interestin acceleratorand

spaceshielding,radiation therapy,and astrophysicalandradiobiological studies. The beam

particleschangetheir energyanddirectionof motion throughatomic/molecularcollisions and

undergooccasionalradicaltransformationin nuclearcollision. In healthphysicsapplications,a

heavyion beamof initially welldefinedradiationqualityis transformedinto acomplexmixtureof

diverse quality components after passing through a modest amount of material. This

transformationof radiation quality must be understoodto adequatelyexplain the biological

responseof tissueto heavyion radiation. A theoretical/experimentalprogramto define anion

beamanditsproductsin extendedmatterisdescribed.

33
1.5. INSTRUMENTATION

Brackenbush, L. W., Braby, L. A., and Anderson, G. A. (1989) Characterising

the energy deposition events produced by trapped protons in low Earth orbit.

Radiation Protection Dosimetry 29: 119-121. :

Trapped protons, Low-LET, Tissue-equivalent proportional counter

Humans and equipment in space vehicles in low Earth orbit are exposed to a wide variety of

radiations, but the majority of the dose is due to trapped protons, which have energies of the order

of 100 MeV and are low LET particles. These high energy particles produce nuclear fragmentation

with high LET secondaries that may be responsible for a significant fraction of dose equivalent. In

order to understand better the biological effectiveness of this radiation environment, a portable

tissue equivalent proportional counter spectrometer has been developed that automatically records

the distribution of energy in a small tissue-like site as a function of time. This instrument weighs

about 700 g and will be flown on a number of future Space Shuttle flights.

Fanton, J. W., Cordts, R. E., Harris, R. K., Romo, D., and Wood, D. H.

(1988) Radioisotope imaging of brain tumors in two rhesus monkeys.

Laboratory Animal Science 38(2): 214.217.

Radioisotope imaging, Brain tumors, Rhesus monkeys, PET

Nuclear imaging involves the systemic administration of a radionuclide (radioisotope) to a patient

after which a picture or image is generated by recording relative quantities of radiation emitted from

regions of interest in the patient. The picture is formed from the digital radioactive counts acquired

during the procedure. This information can be recorded by a computer so that images and digital

information can be recreated for later analysis. By integrating the intensity of regions of the screen

images, objective measurement of differences in radioactivity level can be made.

Nuclear brain scans are a sensitive technique for screening brain tumors in both animals and

humans and have been described as the most practical of nuclear scan procedures for use in

veterinary medicine. In this study, nuclear scans of two rhesus monkeys provided accurate images

of intracranial neoplasia.

Ngo, D. M., Wilson, J. W., Buck, W. W., and Fogarty, T. N. (1989) NuclearFragmentation Studies for Microelectronic Applications. NASA Technical

Memorandum 4143.

Microelectronic applications, lntranuclear cascade, Single-event upsets

A formalism for target fragment transport is presented with application to energy-loss spectra in

thin silicon devices. Predicted results are compared with experiments using the surface-barrier

detectors developed by J. P. McNulty. The intranuclear-cascade, nuclear-reaction model does not

predict the McNulty experimental data for the highest energy events. A semiempirical nuclear

cross section gives an adequate explanation of McNulty's experiments. Application of the

formalism to specific electronic devices is discussed.

34
2. BIOLOGY
• 2.1. MOLECULAR BIOLOGY

J..Q.UII XaJ 

Lett, J. T. (1989) Double strand breakage in DNA and cellular radiation

sensitivity: linear energy transfer and the oxygen effect. In: Oxygen Radicals in

Biology and Medicine, Eds. M. G. Simic, J. F. Ward and K. S. Taylor. New

York: Plenum Press, pp. 419-428.

Double strand breaks, Oxygen effect, Direct and indirect action

Despite more than three decades of extensive research, identification of the chemical changes

responsible for the lethal effects of ionizing radiation has yet to be achieved. Indeed, although the

general consensus of opinion associates lethal radiation events with damage, and especially doublestrand breaks, in DNA, there is still lively debate even about the relative contributions of the direct

and indirect effects of sparsely ionizing radiations at the cellular level. Causes for the protraction in

this eludication process usually can be traced to the difficulty in determining chemical change in

mammalian cells after radiation doses of radiobiological significance, to the inflexibility of classical

positions, and to an increase in the reluctance of governmental agencies to underwrite experiments

with other than predictable outcomes. Some recent signs are more encouraging, however, because

definitive scientific advances now seem possible, but they are more likely to come from

laboratories in Europe where the expression of originality has not been blunted by dogma and

warranty. Areas where modern ideas must provoke much-needed advances in the understanding

of the chemistry of strand breakage induced in cellular DNA by ionizing radiations are discussed

here.

In the early 1960's, perceptive experiments with dilute solutions of deoxyribonucleoproteins

demonstrated that the constituent proteins provided the DNA with extensive protection against free

radicals formed in the surrounding water by radiation. Limitations to the role played by such

radicals in the DNA chemistry underlying cellular radiosensitivity, i.e., some of the effects

attributed more usually to the indirect action of ionizing radiation, were implied by such behavior.

Concurrent and subsequent findings about the efficiencies of strand breakage in DNA, DNA gels

of limited water contents, mammalian cells and so forth, also were consistent with that

interpretation. Yet during the last 20 years, the preponderance of chemical studies on radiationinduced change in DNA have been predicated upon the contrary opinion. Justification for that

experimental approach often is related to conclusions, which are based upon reaction rates in liquid

water, that "OH radicals diffuse 20-30 A in cells. Nowadays, challenge to the notion of the preeminence of such indirect action in determining cellular radiosensitivity is strengthening as

understanding broadens about the role played by the structure and hydration (solvation) of

deoxyribonucleoprotein in radiation chemical processes involving cellular DNA.

Lett, J. T., Bergtold, D. S., and Keng, P. C. (1986) Effects of LEToo on the fate

of DNA damage induced in rabbit sensory cells in situ: Fundamental aspects. In:

Mechanisms of DNA Damage and Repair, eds. M. C. Simic, L. Grossman, and

Upton, A. C. New York: Plenum Publishing Co., pp. 139-150.

Cellular radiosensitivity, RBE, Murine lymphoblast, Repair

For half a century, radiobiological theory was dominated by the notion that cellular radiosensitivity

to ionizing radiations could be explained solely on the basis of the physics of energy deposition.

The process was extended even to explanations for the variation in relative biological effectiveness

(RBE) with increased linear energy transfer (LEToo) associated with densely-ionizing, particulate

radiations. In more recent years, examination of the radiation responses of the repair-deficient S/S

m

36
variantof theL5178Ymurineleukemiclymphoblasthasdemonstratedthatradiobiologicaltheories

whichdonotincorporatemetabolicmodificationofradiochemicaldamageareuntenable.

Todd, P., Hymer, S. S., Delcourt, S. G., and Kunze, M. E. (1989) Overview

of techniques of analysis of cell damage. In: Multilevel Health Effects Research:

From Molecules to Man, Eds. J. F. Park and R. A. Pelroy. Proceedings of the

Twenty-Seventh Hanford Life Sciences Symposium on Health and the

Environment. Columbus, OH: Battelle Press, pp. 109-117.

Cell damage, Chromosome aberrations, DNA damage, Flow cytometry, Affinity labelling,

Recombinant DNA

Most physical and chemical methods for analyzing cell damage have been developed for cells

damaged in vitro. In many cases, these methods can be transferred, with minor modifications, to

the analysis of cell damage in vivo. Molecular end points for cell damage include: chemical

modifications of DNA, chromosome aberrations, point mutations, gene deletions/translocations,

malignant tranformation, and reproductive death.

For each of these end points, in vivo methods of analysis have been developed, including

centrifugation and electrophoresis of unlabeled DNA, use of probes to detect DNA damage,

characterization of severe chromosome damage by flow cytometry, somatic mutant cell

identification by image analysis and flow cytometry, electrophoresis of cellular proteins, and flow

cytometry, image analysis, and electrophoresis for detecting cell population shifts. In most cases,

problems of sensitivity, specificity, and analysis of large celt populations had to be solved to apply

these methods in vivo. Affinity labelling and recombinant DNA technology have played an

important role in nearly all cases.

Many of these methods are also useful in cell bioprocessing and biotechnology. Newer

techniques, developed mainly for biotechnology applications but with potential for analysis of cell

damage, include selective cell retrieval by laser scanning microscopy, single cell manipulation by

optical gapping, and cell electroporation and electrofusion.

37
7

2.2. CELLULAR RADIATION BIOLOGY

Lett, J. T. (1987) Cellular radiation

British Journal of Cancer 55: 145-152.

biology in consolidation and transition.

Mouse lymphoblasts, Cellular repair, Synchronous cell cultures, RBE, Heavy ions HZE particles

Cellular radiation biology currently is undergoing changes common to all science in which the

understanding in one area is becoming solidified while in another area conclusion of the classical

phase is being engendered by the needs of modern thought. Aspects of these changing

circumstances are discussed here from the standpoint of the roles played by direct and indirect

action in cell death and the position that promulgation of the correct explanations of the

radiosensitivities of mammalian cells can be facilitated if use of such classical operational

definitions as sublethal and potentially lethal damage is discontinued. The latter consideration will

be supported by a summary of the responses of synchronous populations of the L5178Y S/S

murine leukaemic lymphoblast to 2°Ne, 28Si, 4°Ar, 56Fe and 93Nb ions of energies broadly in the

region of 500 MeV/u.

Lett, J. T. (1986) Opportunities for electron microscopy in space radiation

biology. Scanning Electron Microscopy 1: 229-236.

Tissue damage, Electron microscopy, New Zealand white rabbits, Stem celt populations, Cell

culture

Densely ionizing, particulate radiations in outer space are likely to cause to mammalian tissues

biological damage that is particularly amenable to examination by the techniques of electron

microscopy. This situation arises from the fact that once the density of ionization along the particle

track exceeds a certain value, small discrete lesions involving many adjacent cells may be caused in

organized tissues. Tissue damage produced by ionization densities below the critical value also

affords opportunities for electron microscopic evaluation, as is shown by the damage produced in

optic and proximate tissues of the New Zealand white rabbit in terrestrial experiments. Late

radiation sequelae in nondividing, or terminally differentiating, tissues, and in stem cell

populations, are of special importance in these regards.

It is probable that evaluations of the hazards posed to astronauts by galactic particulate radiations

during prolonged missions in outer space will not be complete without adequate electron

microscopic evaluation of the damage those radiations cause to organized tissues.

Lett, J. T., Cox, A. B., and Bergtold, D. S. (1986) Cellular and tissue

responses to heavy ions: Basic considerations. Radiation and Environmental

Biophysics 25:1-12.

Photoreceptors, Heavy ions, Radiosensitivity, New Zealand white rabbits, Mouse cells, HZE

Responses of the S/S variant of the L5178Y murine leukemic lymphobiast, the photoreceptor cell

of the rabbit retina and the lenticular epithelium of the rabbit to heavy ions (2°Ne, 28Si, 4°Ar and

56Fe) are described and discussed primarily from the standpoint of the need for a comprehensive

theory of cellular radiosensitivity from which a general theory of tissue radiosensitivity can be

constructed.

38
Theradiationresponsesof theveryradiosensitive,repair-deficientS/SvariantduringtheG1-and

earlySphasesof thecell cyclewerefound to beunlike thoseof normally radioresistantcellsin

culture:therelativebiologicaleffectiveness(RBE)did notincreasewith thelinearenergytransfer

(LET_) of theincidentradiation.Suchbehaviorcouldbeanticipatedfor acell whichis lackingthe

repairsystemthatoperatesin other(normal)cellswhentheyareexposedto ionizingradiationsin

theG1phaseof thecell cycle. TheS/Svariantdoesexhibitapeakofradi0resistancetoX-photons

mid-G1+ 8 h into the cell cycle,however,andastheLET,, was increased,therepair capacity

responsiblefor thatradioresistancewasreducedprogressively.

Sensorycells (photoreceptors)in the retina of the New Zealandwhite (NZW) rabbit arevery

radioresistanto ionizingradiations,andseveralyearselapsedafterlocalizedexposure(e.g.,5-10

Gy) to heavyions (20Ne,4°Ar)beforephotoreceptorcellswerelostfrom theretina. During the

first few weeksaftersuchirradiations,damageto DNA in thephotoreceptorcellswasrepairedto a

point whereit could not bedemonstratedby reorientinggradientsedimentationunderalkaline

conditions, a technique that can detectDNA damageproducedby <0.1 Gy of X-photons.

Restitutionof DNA structurewasnot permanent,however,andmonthsor yearslater,but before

loss of photoreceptor cells from the retina could be detected, progressive deterioration of the DNA

structure began.

2.2.1. TRANSFORMATION, MUTATION

Mei, M.-T., Craise, L. M., and Yang, T. C. H. (1986) Induction of proline

prototrophs in CHO-K1 cells by heavy ions. International Journal of Radiation

Biology 50: 213-224.

Chinese hamster ovary cells, CHO-K1, X-rays, Iron ions, Neon ions, Silicon ions, Ethyl-methane

sulphonate, 5-azacytidine, RBE, Proline phototroph

Using an established mammalian cell line, Chinese hamster ovary cells (CHO-K1), we have

observed the induction of prototrophs by various heavy ions. This cell line requires proline for

normal growth in medium with low serum concentration. X-rays, three types of heavy particles

(600 MeV/u iron, 670 MeV/u neon, and 320 MeV/u silicon ions), ethyl-methane sulphonate and 5-

azacytidine were used to induce revertants which were proline independent. Log-phase cells

treated with 5-azacytidine showed a very high reversion frequency. The induction frequency per

viable cell appears to be dose dependent for these four types of radiation, and the dose-response

curves are approximately linear. Our results also indicate that the effectiveness of high-LET

particles in inducing proline prototrophs is much greater than that of low-LET radiation. The RBE

value for the induction of prototrophs was calculated for neon, silicon, and iron particles and found

to be about 1.3, 1.7 and 4.5, respectively. At equal survival level, the reversion frequency for Xrays and EMS was about the same.

Nelson, G. A., Schubert, W. W., Marshall, T. M., Benton, E. R., and Benton,

E. V. (1989) Radiation effects in Caenorhabditis elegans: Mutagenesis by high

and low LET ionizing radiation. Mutation Research 212: 181-192.

C. elegans, Mutations, RBE, Heavy ions

The nematode C. elegans was used to measure the effectiveness of high-energy ionized particles in

the induction of 3 types of genetic lesions. Recessive lethal mutations in a 40-map unit autosomal

region, sterility, and X-chromosome nondisjunction or damage were investigated. Induction rates

39
weremeasuredasa function of linear energy transfer, LET_, for 9 ions of atomic number 1-57

accelerated at the BEVALAC accelerator. Linear kinetics were observed for all 3 types of lesions

within the dose/fluence ranges tested and varied strongly as a function of particle LET,,,,. Relative

Biological Effectiveness (RBE) values of up to 4.2 were measured and action cross sections were

calculated and compared to mutagenic responses in other systems.

Todd, P. (1986) The evolving microlesion concept. Advances in Space

Research 6: 187-189.

Microlesions, Carcinogenesis, HZE, Harderian gland, Particle tracks

The "microlesion concept," introduced by D. Grahn in the 1970's, was further explored using

published quantitative carcinogenesis data. Laboratory experiments performed by T. C. H. Yang

and co-workers and by R. J. M. Fry and co-workers using the Fe ion beam of the Lawrence

Berkeley Laboratory Bevalac have resulted in quantitative data on in vitro and in vivo (respectively)

carcinogenesis in mouse systems. These data sets were interpreted on the basis of track

calculations, and it was found that the action cross section for tumor induction in cultured cells is

approximately 0.032 mm 2 and that it is about 1/1000th as great in mouse Harderian gland cells.

This great difference in carcinogenic sensitivity is a reflection of the biological differences between

these two highly promoted systems, neither of which may be quantitatively applicable to humans in

space.

Yang, T. C., Craise, L. M., Mei, M-T., and Tobias, C. A. (1986) Dose

protraction studies with low- and high-LET radiations on neoplastic cell

transformations in vitro. Advances in Space Research 6(11): 137-147.

Heavy ions, Low rate effect, C3H10T1/2, Low dose-rate effect, Low-LET, High-LET, Neoplastic

cell transformation, Sparing, Argon, Iron,

A major objective of our heavy-ion research is to understand the potential carcinogenic effects of

cosmic rays and the mechanisms of radiation-induced cell transformation. During the past several

years we have studied the relative biological effectiveness of heavy ions with various atomic

numbers and linear energy transfer on neoplastic cell transformation and the repair of

transformation lesions induced by heavy ions in mammalian cells. All of these studies, however,

were done with a high dose rate. For risk assessment, it is extremely important to have data on the

low-dose-rate effect of heavy ions. Recently, with confluent cultures of the C3H10T1/2 cell line,

we have initiated some studies on the low-dose-rate effect of low- and high-LET radiation on cell

transformation. For low-LET photons, there was a decrease in cell killing and cell transformation

frequency when cells were irradiated with fractionated doses and at low dose rate. Cultured

mammalian cells can repair both subtransformation and potential transformation lesions induced by

X rays. The kinetics of potential transformation damage repair is a slow one. No sparing effect,

however, was found for high-LET radiation. There was an enhancement of cell transformation for

low-dose-rate argon (400 MeV/u; 120 keVAtm) and iron particles (600 MeV/u; 200 keVAtm). The

molecular mechanism for the enhancement effect are unknown at present.

Yang, T. C., Craise, L. M., and Rhim, J. S. (1990) Neoplastic transformation

of human epidermal keratinocytes by low- and high-LET radiations. Poster

presented at the 38th Annual Meeting of the Radiation Research Society, New

Orleans, LA. April 7-12, 1990.

Human epithelial cells, SV40, RBE

For assessing radiation risk, it is important and necessary to understand the responses of human

cells, especially the epithelial cells, to various radiation modalities. Recent advances in culturing

40
humanepithelialcellsandin establishingimmortalcell linesprovideuniqueopportunitiesto study

the carcinogeniceffectsof radiation in humanepithelial cells. In our laboratories,we have

developedtechniquesandmethodsthat allow quantitativestudyof neoplastictransformationof

humanepithelialcells. Humanepidermalkeratinocytes(HEK-271),immortalizedby SV40adeno12hybridvirus,arenonproducer,nontumorigenic,andmaintaindensityinhibitionproperty. After

growing in culture for 6 weeks, transformed foci, showing extensive piling-up of cells, were

found in irradiated cells, while control cells formed only monolayers. These transformed cells

were able to grow in soft agar media, suggesting anchorage-dependent growth, an important

property of tumorigenic cells. Our studies with X rays and 470 MeV/u argon ions showed an RBE

about 2.3 at 10% survival level. Dose-response curves for neoplastic cell transformation gave

RBE about 3.7 and 7.0 at high and low doses correspondingly for 470 MeV/u argon ions.

Yang, T. C., Craise, L. M., and Rhim, J. S. (1990) Quantitative studies on

radiogenic transformation of human epithelial cells in vitro. Abstract presented at

the 81st Annual Scientific Meeting of the American Association for Cancer

Research, Washington, DC, May 23-26, 1990.

Human epithelial cells, Nude mouse, Cell transformation, High-LET

Quantitative data are important for risk assessment and for model development. Biophysical

models are valuable for understanding the basic processes of carcinogenesis. In our laboratories,

we have developed a cell system and methods for a quantitative determination of neoplastic

transformation of human epithelial cells. Human epidermal keratinocytes (RHEK-271),

immortalized by SV40 adeno-12 hybrid virus, are nonproducer, nontumorigenic, and maintain

density inhibition property. Confluent RHEK-271 cells were irradiated and then plated into dishes

at proper density. After a 6-week incubation with weekly changes of media, transformed foci,

showing extensive piling-up of cells, were formed in the irradiated cells. These transformed foci

can be identified and scored easily under a dissecting stereo microscope. Anchorage independent

growth test of these transformed cells gave positive results, and the tumorigenic test in athymic

nude mouse is underway. We have obtained the dose-response curves for X-rays and heavy ion

radiation and found that the transformation frequency per survivor increased curvilinearly with Xray doses and was higher for a given dose for high-LET radiation. Our experimental results

demonstrated that this cell system is very useful for quantitative measurement as well as for

mechanistic studies of radiation carcinogenesis.

Yang, T. C., Craise, L. M., and Tobias, C. A. (1988) Initial primary lesion

important for radiogenic cell transformation. Abstract presented at the 36th

Annual Meeting of the Radiation Research Society, Philadelphia, PA, April 16-

21, 1988.

Cultured mammalian cells, Cell transformation, C3 HI OT1/2, DNA strand breaks

For studying radiation carcinogenesis at the cellular and molecular level, cultured mammalian cells

have been found to be useful model systems. Various investigators have shown that ionizing

radiation can cause neoplastic cell transformation directly and that the nuclear DNA is the primary

target. In general, radiation-induced cell transformation involves multistep processes including

initiation, fixation, promotion, and progression into the malignant state. We have collected and

analyzed cell transformation data obtained with heavy ions for gaining some understanding of the

molecular nature of the initial primary lesion important for the initiation of cell transformation by

radiation. Our simple analysis indicates that two specific primary ionizations within 80A may be

sufficient to form a transformation lesion in C3H10T1/2 cells. For verifying this finding, we have

carried out further studies with restriction endonucleases, and preliminary results suggest that DNA

strand breaks more than two bases apart can induce cell transformation.

41
Yang, T. C., Craise, L. M., and Tobias, C. A. (1989) Molecular lesions

important for neoplastic cell transformation by ionizing radiation. In: Cell

Transformation and Radiation-lnduced Cancer, Eds. K. H. Chadwick, C.

Seymour, and B. Barnhart. New York: Adam Hilger Co., pp. 301-308.

Neoplasia, Ceil transformation, C3HIOT1/2, Double strand breaks, Human mammary epithelial

cells, Human keratinocytes .

Radiation cell transformation is a multistep process. At present we know very little about the

molecular nature of lesions important for radiogenic cell transformation and evolution of initial

damages into final malignant growth. A simple analysis of our heavy ion data of C3H10T1/2 cells

indicated that DNA double-strand breaks may be important for cell tranformation. Further studies

with restriction endonucleases showed support for this finding. Recently we have succeeded in

inducing morphological transformation of human keratinocytes and growth variants of human

mammary epithelial cells with X-rays and heavy ions.

Yang, T. C., Craise, L. M., and Tobias, C. A. (1989) Effects of fractionated

doses on mutation and neoplastic cell transformation by heavy ion radiation.

Abstract presented at the 37th Annual Radiation Research Society, Seattle, WA,

March 18-23, 1989.

Heavy ions, Iron, C3HIOT1/2, Transformation, HGPRT mutation, Fractionated doses

i

t

i

i

z

LL

:':L

i

2_2_

_5

In our laboratory we have observed that high-LET heavy ions, e.g., 600 MeV/u iron particles, at a

low dose rate can be more effective than those at a high dose rate in inducing neoplastic cell

transformation, and that this low-dose-rate enhancement effect is LET-dependent. Recently we

have extended these studies to determine whether fractionated doses can give similar enhancement

effects for somatic mutation and cell transformation. Confluent C3H10T1/2 cells were irradiated

by single or fractionated doses of heavy ions, and the transformation frequency was determined.

Experimental results showed no significant difference between cells irradiated by single and

multifractions of 600 MeV/u iron particles for survival and cell transformation. For mutation

studies, we used confluent Rat-2 cells to determine the induction of 6-TG 1 mutants by heavy ions.

Our results indicated that single and fractionated doses of 400 MeV/u argon ions were equally

effective in killing cells and inducing HGPRT mutation. So far we have not found any

enhancement effects of fractionated doses for mutation and cell transformation.

2.2.2 LETHALITY, SURVIVAL

J._Q.U.RISAJ 

Lett, J. T. (1990) Damage to DNA and chromatin structure from ionizing

radiations, and the radiation sensitivities of mammalian cells. Progress in

Nucleic Acid Research and Molecular Biology 39: 305-352.

Cellular lethality, Direct action, Indirect action, Energy transfer, Single cell, Chemical protection

This review of the basis of cellular lethality caused by ionizing radiations opens with a discussion

of transitions in the field of cellular radiation biology. The author contends that progress has

stagnated, in part due to three unusual circumstances: First, theories of cellular radiation sensitivity

that preclude post-irradiation modification of radiation damage by cellular metabolic processes

continue to be taught, despite their being demonstrably unsound. Second, the lack of utility of one

42

m
of two phenomenological (operational) interpretations of cellular radiosensitivity first introduced

more than 20 years ago has been stultifying for the reasons such abstractions often are, even on the

grandest scale. The third circumstance concerns the notion of indirect action, that is, that most of

the DNA damage responsible for cell death is caused indirectly by diffusing radicals, usually "OH

resulting from the irradiation of bulk water, that are deposited neither in the macromolecule itself

nor in adjacent molecules with which it is directly associated (bound). The author takes the view

that energy deposited in DNA chromatin -- that is, direct action -- causes most of the biologically

significant radiation damage, and presents it in this article, while remaining cognizant of the fact

that, under special conditions, radiation damage not involving DNA could be of crucial importance.

The case is made mainly in light of recent developments in the radiation chemistry of DNA

(chromatin) and the probable role of such chemistry in a general theory of cellular radiosensitivity

that overcomes the fundamental deficiencies outlined above. This review covers areas including

single-cell survival curves, mechanisms of energy transfer, chemical protection and radical

scavengers, and strand breaks in DNA, and offers general conclusions.

Lett, J. T., Cox, A. B., and Story, M. D. (1989) The role of repair in the

survival of mammalian cells from heavy ion irradiation: Approximation to the

ideal case of target theory. Advances in Space Research 9(10): 99-104.

Neon, Silicon, Argon, Iron, Niobium, Cell cycle dependence, Mouse Iymphoblasts

Theories of cellular radiation sensitivity that preclude a significant role for cellular repair processes

in the final biological expression of cellular damage induced by ionizing radiation are unsound.

Experiments are discussed here in which the cell-cycle dependency of the repair deficiency of the

S/S variant of the L5178Y murine leukemic lymphoblast was examined by treatment with the

heavy ion, 2°Ne, 28Si, 4°Ar, 56Fe and 93Nb. Evidence from those studies, which will be

described in detail elsewhere, provide support for the notion that as the linear energy transfer

(LEToo) of the incident radiation increases the ability of the S/S cell to repair radiation damage

decreases until effectively it is eliminated around 500 keVAtm. In the region of the latter LEToo

value, the behavior of the S/S cell approximates the ideal case of target theory where postirradiation metabolism (repair) does not influence cell survival. The expression of this

phenomenon among different cell types and tissues will depend upon the actual repair systems

involved and other considerations.

Lett, J. T., Cox, A. B., Story, M. D., Ehmann, U. K., and Blakely, E. A.

(1989) Responses of synchronous L5178Y S/S cells to heavy ions and their

significance for radiobiological theory. Proc. Royal Soc. London B237: 27-42.

Neon, Silicon, Argon, Iron, Niobium, RBE, Ceil cycle dependence

Synchronous suspensions of the radiosensitive S/S variant of the L5178Y murine leukaemic

lymphoblast at different positions in the cell cycle were exposed aerobically to segments of heavyion beams (20Ne 28Si, 40Ar, 56Fe and 93Nb) in the Bragg plateau regions of energy deposition.

The incident energies of the ion beams were in the range of 460 + 95 MeV u -1, and the calculated

values of linear energy transfer (LET_) for the primary nuclei in the irradiated samples were 33 +

3, 60 + 3, 95 + 5, 213 + 21 and 478 + 36 KeV um -1, respectively; 280 kVp X-rays were used as

the baseline radiation. Generally, the maxima or inflections in relations between relative biological

effectiveness (RBE) and LEToo were dependent upon the cycle position at which the cells were

irradiated. Certain of those relations were influenced by post-irradiation hypothermia.

Irradiation in the cell cycle at mid-G 1 to mid-G 1 + 3 h, henceforth called G 1 to G 1 + 3 h, resulted

in survival curves that were close approximations to simple exponential functions. As the LEToo

was increased, the RBE did not exceed 1.0, and by 478 keV um -1 it had fallen to 0.39. Although

43
similar behaviourhasbeenreportedfor inactivationof proteinsandcertain virusesby ionizing

radiations,sofar theresponseof theS/Svariantis uniquefor mammaliancells. The slopeof the

survival curve for X-photons (DO: 0.27Gy) is reducedin G1to G1+ 3 h by post-irradiation

incubationat hypothermictemperaturesandreachesaminimum(DO:0.51Gy) at 25°C. As the

LEToowasincreased,however,theextentof hypothermicrecoverywasreducedprogressivelyand

essentiallywaseliminatedat478keVum-1.

At thecyclepositionwherethepeakof radioresistancetoX-photonsoccursfor S/Scells. G1+ 8

h, increasesin LETooelicitedonly smallincreasesin RBE(at 10%survival),until amaximumwas

reachedaround200keV um-1.At 478keV uma, what little remained of the variation in response

through the cell cycle could be attributed to secondary radiations (2 rays) and smaller nuclei

produced by fragmentation of the primary ions.

Schimmerling, W., Alpen, E. L., Powers-Risius, P., Wong, M., DeGuzman, R.

J., and Rapkin, M. (1987) The relative biological effectiveness of 670 MeV/A

neon as a function of depth in water for a tissue model. Radiation Research 112:

436-448.

Spermatogonial cell killing, RBEs, Heavy ions, HZE, RBE, Mouse testes

Linear energy transfer (LEToo) spectra of identified charged fragments and primaries, produced by

nuclear interactions of 670 MeV/A neon in water, were measured along the unmodulated Bragg

curve of the neon beam. The relative biological effectiveness (RBE) values for spermatogonial cell

killing, as reported on the basis of weight loss assay of mouse testes irradiated with beams of

approximately constant single LEToo, were summed over the particle LEToo spectra to obtain an

effective RBE for each charged-particle species, as a function of water absorber thickness. The

resultant values of effective RBE were combined to obtain an effective RBE for the mixed radiation

field. The RBE calculated in this way was compared with experimental RBEs obtained for

spermatogonial cell killing in the mixed radiation field produced by neon ions traversing a thick

water absorber. Discrepancies of 10-40% were observed between the calculated RBE and the R"B'E

measured in the mixed radiation field. Part of this discrepancy can be attributed to undetected lowZ fragments, whose contribution is not included in the calculation, leading to an overestimated

value for the calculated RBE. On the other hand, calculated values 10% greater than the measured

RBE are explained as tract structure effects due to the higher radial ionization density near neon

tracks relative to the ionization density near the silicon tracts used to fit the RBE vs LE%o data.

Yang, T. C., Gruenert, D. C., Holley, W. R., and Curtis, S.

Response of cultured human airway epithelial cells to X-rays and

particles. International Journal of Radiation Biology 58: 509-518.

Alpha particles, Human epithelial cells, X-rays, RBE, Cell inactivation

B. (1990)

energetic oc

Radon and its progeny, which emit _ particles during decay, may play an important role in

inducing human lung cancer. To gain a better understanding of the biological effects of o-particles

in human lung we studied the response of cultured human airway epithelial cells to X-rays and

monoenergetic helium ions. Our experimental results indicated that the radiation response of

primary cultures was similar to that for airway epithelial cells that were transformed with a plasmid

containing an origin-defective SV40 virus. The RBE for cell inactivation determined by the ratio of

Do for X-rays to that for 8 MeV helium ions was 18-22. The cross-section for helium ions,

44
calculatedfrom the Do value, was about 24 i.tm 2 for cells of the primary culture. This crosssection is significantly smaller than the average geometric nuclear area (-180 l.tm2), suggesting that

an average of 75 a-particles (8 MeV helium ions) per cell nucleus are needed to induce a lethal

lesion.

Yang, T. C., Stampfer, M. R., and Tobias, C. A. (1989) Radiation studies on

sensitivity and repair of human mammary epithelial cells. International Journal of

Radiation Biology 56: 605-609.

Human mammary epithelial cells, Heavy ions, Repair, Radiosensitivity

For radiation risk assessment and cancer radiotherapy it is important to know how human cells,

especially epithelial cells, respond to ionizing radiation. In our laboratory we have a large

collection of normal and tumor cells of human mammary tissue and have developed techniques to

grow these cells in culture (Stampfer and Bartley 1986). In the past several years we have studied

the radiosensitivity and repair of human mammary epithelial cells from normal and tumor tissue

following low- and high-LET irradiation. For a better understanding of radiation responses of

premalignant cells to radiation, our studies also include epithelial cells immortalized in vitro and

from tissue peripheral to the tumor.

2.2.2 LETHALITY, SURVIVAL

REPORTS/MEETINGS

Lett, J. T. (1990) The end of a hiatus in cell survival theory and its significance

for radiation therapy. Journal of Cancer Research and Clinical Oncology 116

(Suppl): 844 (abstract).

Cell survival, Target theory, L5178Y S/S

For 50 years sustained efforts have been made to explain cellular radiosensitivity with general

target theory. Although its two major progenitors, Lea and Zimmer, warned that the theory was

inapplicable if radiation damage was altered by subsequent metabolic activity, efforts to use it for

mammalian cells have continued long after the discovery of cellular and molecular repair

mechanisms, and in spite of Zimmer's efforts to reverse the trend until his recent death.

Experiments that examined the responses of the cell-cycle dependent, repair-deficient, L5178Y S/S

variant x-photons and heavy ions have shown that any theory of cellular radiosensitivity that

neglects post-irradiation repair mechanisms is unsound. Target theory is applicable only if repair

systems are absent or rendered ineffective. Thus Zimmer was correct, his efforts were not in vain,

and an unusual period in the history of modem science has now ended. Certain notions derived

conceptually from target theory such as "sublethal damage" also are untenable. There is no

scientific definition of sublethal damage in the literature; and the concept of the repair of sublethal

damage likewise neglects basic scientific principles. The radiation damage that leads to cell death is

all "potentially lethal" damage. Problems arising from prolonged use of unscientific abstractions

are eliminated by rigorous use of extant scientific terminology and cell survival curves are

explicable in terms of damage to cellular deoxyribonucleoprotein and its repair. This advance is

important for the future development of radiation therapy, as will be discussed.

45
Story, M. D., Sanchez, F. J., Cox, A. B., and Lett, J. T. (1989) Factors

influencing recovery and cellular survival of the L5178Y S/S cell from

irradiation. Abstract presented at the 37th Annual Meeting of the Radiation

Research Society, Seattle, WA, March 18-23, 1989.

L5178Y S/S, Hypothermia, HZE particles, X-rays, Nutrient effect

The very radiosensitive L5178Y S/S cell has been used to examine factors influencing cellular

recovery and ultimately cellular survival via hyper(hypo)thermia, exposure to HZE particles, and

changes in the protein components of growth media after X-irradiation. Exposure to HZE particles

of LET up to 500 keV/u progressively altered the radiation substrate, making it unrecognizable to,

or unmanageable by, the relevant repair systems. When cells were incubated at 23°C for various

times after heavy-ion irradiation, cellular recovery was diminished and eliminated at 478 keV/u.

After X-irradiation, increases in hyperthermic temperature for which cell killing was less than 50%

systematically reduced the Do (0.27 Gy) of G1 cells to 0.135 Gy by 41.5°C, and at G1+8 hrs, the

shoulder was progressively eliminated. For 25 years, the cell has been grown in media containing

particular pro.tein fractions, because it had been shown that variations in sera components, and

hence the nutritional status of the cell, could change the survival curve. Recently, the advent of

more highly purified protein components has caused another increase in radioresistance at G1+8

hrs without changing karyotype. Over time, the changes in the purity of these fractions have

resulted in defined alterations in Do from 0.38, via 0.50, to 0.65 Gy, thus substantiating the very

early observation in 1963.

2.2.3. DNA DAMAGE AND REPAIR

JOURNALS

Lett, J. T., Keng, P. C., Bergtold, D. S., and Howard, J. (1987) Effects of

heavy ions on rabbit tissues: Induction of DNA strand breaks in retinal

photoreceptor cells by high doses of radiation. Radiation and Environmental

Biophysics 26: 23-36.

New Zealand white rabbits, Alkaline sucrose gradients, Strand breakage, Heavy ions, HZE, RBE,

Neon ions, Argon ions

Excised retinas from New Zealand white (NZW) rabbits were irradiated at 0°C with 9-260 Gy

(depending on the type of radiation) of 300 kVp X-rays, or the first 5 cm (range: -14 cm in water)

of 365 MeV/u Ne ions or 530 MeV/u Ar ions (LEToo's: -1, 35+3 and 90+5 keV/I.tm,

respectively). Other positions (LEToo's) in the Ne-ion beam (Bragg curve) were employed in more

limited experiments. The retinas were frozen and stored in liquid nitrogen until analysis.

Total strand breakage in the DNA of retinal photoreceptor (sensory) cells was determined from

sedimentation profiles obtained by velocity sedimentation through reoriented alkaline sucrose

gradients under conditions free from anomalies related to rotor speed. For the radiation doses

employed: the reciprocal of the number average molecular weight, Mn, was related linearly to dose

for each radiation quality and extrapolation to zero dose in each case gave positive intercepts for

which the mean unirradiated molecular weight, Mo, was 6.1+1.0 x 108 daltons; the efficiencies of

total strand breakage for the different radiations were 50!-_3, 110-&_2and 240-&-_6eV/strand break,

respectively. For the heavy ions, accurate analogous calculations for other positions in the Bragg

curves were precluded by beam degeneration due to fragmentation of the primary particles, etc.

46
Overall,theexperimentalresultssupporttheconceptthationizingradiationsdamagecellularDNA

by two generalprocesses.Oneprocesscauseslocalizeddamage,which underour experimental

conditionsisrevealedasstrandbreaksand/oralkali-labilebondsin regionsbetweenmoleculesof

sizecirca 109 daltons (subunits); the other causes essentially random damage. Base damage

caused by either process would not have been delineated in our experiments.

Peak, M. J., Peak, J. G., and Blazek, E.

Radiation-induced DNA damage and repair.

Biology 54: 513-519.

R. (1988) Symposium report:

International Journal of Radiation

Argonne National Laboratory, Symposium, Radioprotectants

The Argonne National Laboratory Symposium brought together 109 scientists from five countries

to discuss the molecular effects of radiation on DNA and the responses of cells to radiation

exposure. Six speakers covered three general areas: (1) DNA damages caused by radiations; (2)

repair of these damages in prokaryotes and eukaryotes; and (3) aminothiols as radioprotectors. In

addition, a roundtable discussion chaired by J. W. Ward dealt with alkaline and neutral elution

methodology.

Yamamoto, O., Fuji, I., Yoshida, T., Cox, A. B., and Lett, J. T. (1988) Age

dependency of base modification in rabbit liver DNA. Journal of Gerontology:

Biological Sciences 43: B132-136.

Liver, DNA, New Zealand white rabbits, Age dependence

Age-related modifications of DNA bases have been observed in the liver of the New Zealand white

(NZW) rabbit (Oryctolagus cuniculus), a lagomorph with a median life-span in captivity of 5-7

years. The ages of the animals studied ranged from 6 weeks to 9 years. After the DNA had been

extracted from the liver cell nuclei and hydrolyzed with acid, the bases were analyzed by column

chromatography with Cellulofine gels (GC-15-m). Two peaks in the chromatogram, which eluted

before the four DNA bases, contained modified bases. Those materials, which were obtained in

relatively large amounts from old animals, were highly fluorescent, and were shown to be

crosslinked base products by mass spectrometry. The yield of crosslinked products versus rabbit

age (>0.5 yr) can be fitted by an exponential function (correlation coefficient: 0.76 + 0.09).

Yang, T. C., Craise, L. M., Mei, M-T., and Tobias, C. A. (1989) Neoplastic

cell transformation by high-LET radiation: Molecular mechanisms. Advances in

Space Research 9(10): 131-140.

Neoplasia, Mouse embryo cells, C3H10T1/2, DNA strand breaks, RBE, HZE, Ceil

transformation

Experimental data on molecular mechanisms are essential for understanding the bioeffects of

radiation and for developing biophysical models, which can help in determining the shape of doseresponse curves at very low doses, e.g., doses less than 1 cGy. Although it has been shown that

ionizing radiation can cause neoplastic cell transformation directly, that high-LET heavy ions in

general can be more effective than photons in transforming cells, and that the radiogenic cell

transformation is a multi-step processes, we know very little about the molecular nature of lesions

important for cell transformation, the relationship between lethal and transformational damages,

and the evolution of initial damages into final chromosomal aberrations which alter the growth

control of cells. Using cultured mouse embryo cells (C3H10T1/2) as a model system, we have

collected quantitative data on dose-response curves for heavy ions with various charges and

energies. An analysis of these quantitative data suggested that two DNA breaks formed within

47
80A maycausecell transformationandthattwo DNA breaksformedwithin 20A maybelethal.

Throughstudieswith restrictionenzymesthatproduceDNA damagesat specific sites,wehave

foundthatDNA doublestrandbreaks,includingbothblunt-andcohesive-endedbreaks,cancause

cell transformationin vitro. These results indicate that DNA double strand breaks can be important

primary lesions for radiogenic cell transformation and that blunt-ended double strand breaks can

form lethal as well as transformational damages due to misrepair or incomplete repair in the cell.

The RBE-LET relationship is similar for HGPRT gene mutation, chromosomal deletion, and cell

transformation, suggesting common lesions may be involved in these radiation effects. The high

RBE of high-LET radiation for cell killing and neoplastic cell transformation is most likely related

to its effectiveness in producing DNA double strand breaks in mammalian cells. At present the role

of oncogenes in radiation cell transformation is unclear.

2.2.3. DNA DAMAGE AND REPAIR

REPORTS/MEETINGS

Atwell, W. and Hardy, A. C. (1989) The solar proton event radiation hazard to

high-inclination Space Shuttle missions. Abstract presented at the 6th Scientific

Assembly of the International Association of Geomagnetism and Aeronomy

(IAGA), Exeter University, United Kingdom, July 24-Aug. 4, 1989.

Shuttle, Protons, Computerized anatomical man model

The solar proton events that have occurred during the last three solar cycles are reviewed. The

free-space spectra for the large events were computed and geomagnetically attenuated to orbital

inclinations of 57 and 90 (polar) degrees. Using a shielding model of the Space Shuttle and a

computerized anatomical man model, biological dose data are presented for the skin, eye, and

blood-forming organs and are compared with the current NASA astronaut dose limits.

48

r
2.3. TISSUE, ORGANS AND ORGANISMS

Ainsworth, E.J. (1986) Early and late mammalian responses to heavy charged

particles. Advances in Space Research 6(11): 153-165.

Mouse lethality, CFU-S, Testes weight loss, Life-span shortening, Heavy ions, Neutrons, RBE

This overview summarizes murine results on acute lethality responses, inactivation of marrow

CFU-S and intestinal microcolonies, testes weight loss, life-span shortening, and posterior lens

opacification in mice irradiated with heavy charged particles. RBE-LET relationships for these

mammalian responses are compared with results from in vitro studies. The trend is that the

maximum RBE for in vivo responses tends to be lower and occurs at a lower LET than for

inactivation of V79 and T-1 cells in culture. Based on inactivation cross sections, the response of

CFU-S in vivo conforms to expectations from earlier studies with prokaryotic systems and

mammalian ceils in culture. Effects of heavy ions are compared with fission spectrum neutrons,

and the results are consistent with the interpretation that RBEs are lower than for fission neutrons

at about the same LET, probably due to differences in track structure. Issues discussed focus on

challenges associated with assessments of early and late effects of charged particles based on dose,

RBE and LET, and with the concordance or discordance of results obtained with in vivo and in

vitro model systems. Models for radiation damage/repair and misrepair should consider effects

observed with in vivo as well as in vitro model systems.

Butler, T. M. (1990) Program review: The lifetime effects of space radiation in

rhesus monkeys. USAFSAM-TR-90-3.

Program review, Rhesus monkeys

This report summarizes findings from a select panel of scientists charged with reviewing the

quality and productivity of the USAFSAM 24-year in-house study of the lifetime effects of space

radiation in the rhesus monkey. The panel also had the responsibility of assessing the value of the

study in both military and civilian scientific applications and making recommendations for

maximizing the yield of relevant data as the animals near the end of their life- span. The panelists

reviewed results presented by project scientists during a 2-day conference in San Antonio, TX

(March 9-10,1989). They were unanimous in their endorsement of the study as a uniquely

important resource of information on the late effects of space radiation and the interaction of late

effects with the normal aging processes. In asserting that the study should be continued for at least

another 5 years, the panel made specific recommendations for additional work to be carried out in

collaboration with scientists at other laboratories who could provide the breadth of technical

expertise required to fully exploit the potential of this project. The scientific proceedings of the

conference will be published as separate journal articles.

49
2.3. TISSUE, ORGANS AND ORGANISMS

REPORTS/MEETINGS

Ainsworth, E. J., Afzal, S. M. J., Crouse, D. A., Hanson, W. R., and Fry, R.

J.M. (1989) Tissue responses to low protracted doses of high LET radiations or

photons: early and late damage relevant to radio-protective countermeasures.

Advances in Space Research 9(10): 299-313.

Tissue response, Low doses, Heavy charged particles, Gamma rays

Early and late murine tissue responses to single or fractionated low doses of heavy charged

particles, fission-spectrum neutrons or gamma rays are considered. Damage to the hematopoietic

system is emphasized, but results on acute lethality, host response to challenge with transplanted

leukemia cells and life-shortening are presented. Low dose rates per fraction were used in some

neutron experiments. Split-dose lethality studies (LD 50/30) with fission neutrons indicated

greater accumulation of injury during a 9 fraction course (over 17 days) than was the case for gradiation. When total doses of 96 or 247 cGy of neutrons or g rays were given as a single dose or

in 9 fractions, a significant sparing effect on femur CFU-S depression was observeed for both

radiation qualities during the first 11 days, but there was not an earlier return to normal with dose

fractionation. During the 9 fraction sequence, a significant sparing effect of low dose rate on

CFU-S depression was observed in both neutron and g-irradiated mice. CFU-S content at the end

of the fractionation sequence did not correlate with measured LD 50/30. Sustained depression of

femur and spleen CFU-S and a significant thrombocytopenia were observed when a total neutron

dose of 240 cGy was given in 72 fractions over 24 weeks at low dose rates. The temporal aspects

of CFU-S repopulation were different after a single versus fractionated neutron doses. The

sustained reduction in the size of the CFU-S population was accompanied by an increase in the

fraction in DNA synthesis. The proliferation characteristics and effects of age were different for

radial CFU-S population closely associated with bone, compared with the axial population that can

be readily aspirated from the femur. In aged irradiated animals, the CFU-S

proliferation/redistribution response to typhoid vaccine showed both an age and radiation effect.

After high single doses of neutrons or g-rays, a significant age- and radiation-related deficiency in

host defense mechanisms was detected by a shorter mean survival time following challenge with

transplantable leukemia cells. Comparison of dose-response curves for life shortening after

irradiation with fission-spectrum neutrons or high energy silicon particles indicated high initial

slopes for both radiation qualities at low doses, but for higher doses of silicon, the effect per Gy

decreased to a value similar to that for g-rays. The two component life-shortening curve for silicon

particles has implications for the potential efficacy of radioprotectants. Recent studies on

protection against early and late effects by aminothiols, prostaglandins, and other compounds are

discussed.

2.3.1. IN VIVO/IN VITRO SYSTEMS

Geard, C. R. and Worgul, B. V. (1987) The lens and cataract: Clastogenic

responses in epithelial cells of the organ-cultured rat lens. Environmental

Mutagenesis 9: 111-122.

Cataracts, Rat lens cultures, Chromosome aberrations, Gamma rays, Mutagen-carcinogens, SCE,

Lenses

S

50
Theepithelialcellsof thevertebratelenshaveanuniquecharacterandaprobableinvolvementin

cataractformation,whichcouldbeinitiatedbyexogenoustimuli.

Individualratlenseswereorgan-cultured, and the effects of mitomycin C and gamma rays on sister

chromatid exchanges (SCE), chromosomal aberrations, and cellular kinetics assessed in cells from

the epithelial monolayer. SCE showed about a 5.5-fold increase over the mitomycin C dose range

(0, 17, 83, 170 nM), while chromosomal aberrations increased 38-fold. In cells from untreated

lenses, SCE were 1,600 times more frequent than aberrations and at a level consistent with in vivo

assessments in other cell types. Gamma rays (up to 4 Gy) had a greater inhibiting effect on cellular

progression, while 17 nM mitomycin C and 1 Gy induced similar clastogenic responses.

This first demonstration of such changes in lens epithelial cells expands on the cell types available

for monitoring potential mutagen-carcinogens. Additionally chromosomal changes resulting from

lens cellular challenge could be the basis of later cytopathological changes in the lens, of which

cataract is the primary concern to humans. Potential cataractogens warrant monitoring, and the

study outlined may aid in this endeavor, as well as contributing to an understanding of cataract

etiology.

2.3.1. IN VIVO/IN VITRO SYSTEMS

REPORTS/MEETING S

Wigle, J. C. (1989) Aberrant PLD repair as a late radiation effect. Abstract

presented at the 37th Annual Meeting of the Radiation Research Society, Seattle,

WA, March 18-23, 1989.

Rhesus monkeys, Skin cell cultures, PLD repair, Trait effects

The Chronic Radiation Colony at the USAF School of Aerospace Medicine is a lifetime study of

late effects in rhesus monkeys exposed to simulated space radiation. Radiobiological studies of

primary skin cell cultures from these aged monkeys indicate that cells from 55 MeV proton

irradiated monkeys are more sensitive to in vitro cell killing by cobalt-60 gamma rays and 55 MeV

protons than cells from age-matched controls. Preliminary data suggest these differences in

radiosensitivity could be related to differences in repair kinetics after irradiation. For initial

surviving fractions greater than 1%, cells from control monkeys irradiated in vitro with 55 MeV

protons accomplish little or no PLD repair (measured by colony formation) during the first 6 hrs

after irradiation, followed by a gradual increase in survival over the next 18 hrs. At initial

surviving fractions between 0.1% and 1%, survival increases gradually during the first 6 hrs after

irradiation. 55 MeV proton irradiated CHO cells, on the other hand, show "classical" biphasic

PLD repair kinetics within the first 6 hrs after irradiation and a slower phase occurring during the

next 18 hrs. These repair kinetics correlate with observed RBE measurements.

51
[

i

2.3.2. CARCINOGENESIS AND LIFE SHORTENING

J..032J12iAl 

Wood, D. H., Hardy, K. A., Cox, A. B., Salmon, Y. L., Yochmowitz, M. G.,

and Cordts, R. E. (1989) Delayed effects of proton irradiation in Macaca mulatta

(22-year summary). Presented at the Conference on High Energy Radiation

Background in Space (CHERBS 87), Sanibel Island, FL, November 3-5, 1987.

American Institute of Physics Conference Proceedings No. 186, eds. A. C.

Rester, Jr. and J. I. Trombka. New York: American Institute of Physics, pp.

381-392.

Rhesus monkeys, Protons, Life shortening, Cataracts, Glucose tolerance

Lifetime observations on a group of rhesus monkeys indicate that life expectancy loss from

exposure to protons in the energy range encountered in the Van Allen belts and solar proton events

can be correlated with the dose and energy of radiation. The primary cause of life shortening is

nonleukemic cancers. Radiation also increased the risk of endometriosis (an abnormal

proliferation of the lining of the uterus in females). Other effects associated with radiation

exposures are lowered glucose tolerance and increased incidence of cataracts. Calculations of the

relative risk of fatal cancers in the irradiated subjects reveal that the total body surface dose required

to double the risk of death from cancer over a 20-year post-exposure period varies with the linear

energy transfer (LET) of the radiation. The ability to determine the integrated dose and LET

spectrum in space radiation exposures of humans is, therefore, critical to the assessment of lifetime

cancer risk.

Wood, D. H., Yochmowitz, M. G., Hardy, K. A., and Salmon, Y. L. (1986)

Animal studies of life shortening and cancer risk from space radiation. Advances

in Space Research 6(11): 275-283.

Life shortening, Cancer risk, Total-body exposures, Rhesus monkeys, Cancer, Endometriosis

The U.S. Air Force study of the delayed effects of single, total-body exposures to simulated space

radiation in Rhesus monkeys is now in its 21st year. Observations of 301 irradiated and 57 agematched control animals indicate that life expectancy loss from exposure to protons in the energy

range encountered in the Van Allen belts and solar proton events can be expressed as a logarithmic

function of the dose. The primary causes of life shortening are cancer and endometriosis (an

abnormal proliferation of the lining of the uterus in females). Life shortening estimates permit

comparison of the risk associated with space radiation exposures to be compared with that of other

occupational and environmental hazards, thereby facilitating risk/benefit decisions in the planning

and operational phases of manned space missions. Calculations of the relative risk of fatal cancers

in the irradiated subjects reveal that the total body surface dose required to double the risk of death

from cancer over a 20-year post-exposure period varies with the linear energy transfer (LET) of the

radiation. The ability to determine the integrated dose and LET spectrum in space radiation

exposures of humans is, therefore, critical to the assessment of lifetime cancer risk.

52
2.3.3. CATARACTOGENESIS

Holsclaw, D. S., Merriam, G. R., Jr., Medvedovsky, C., Rothstein, H., and

Worgul, B. V. (1989) Stationary radiation cataracts: An animal model.

Experimental Eye Research 48: 385-398.

Radiation cataracts, Bullfrogs, X-rays, Restitution, Transparency

The restitution of normal fibergenesis that occurs in stationary radiation cataracts provides a unique

opportunity to study the cytopathomechanism of radiocataractogenesis. Previous attempts at

investigating this phenomenon have been limited by the lack of an appropriate animal model. This

report describes the induction of stationary radiation cataracts in postmetamorphic bullfrogs

following ocular irradiation with a l0 Gy (1 Gy = 100 rads) dose of X-rays. The eyes of nonirradiated animals and animals irradiated with 25 Gy (an established dose known to induce

progressive cataracts in frogs) served as controls. Animals were followed biomicroscopically and

histopathologically over 79 weeks. As previously described, the cataracts developed in a dosedependent manner. The 25 Gy irradiated lenses rapidly progressed to complete opacification (4+)

by 26 weeks, while lenses exposed to 10 Gy advanced to the 2.5+ stage by 35 weeks and

progressed no further. In the lower dose lenses, transparent cortex began to appear anteriorly and

posteriorly between the capsule and opaque fibers at 45 weeks. As the clear fibers accumulated,

the disrupted region came to occupy increasingly deeper cortex. Histologically, opacities in both

groups were preceded by disorganization of the bow cytoarchitecture, meridional row

disorganization, and the appearance in the lens epithelium of nuclear polymorphism, fragmented

nuclei, micronuclei, clusters of nuclei, and abnormal mitotic figures. In the lenses exposed to the

25 Gy dose, this damage continued to worsen, so that the 4+ stage was characterized by extensive

epithelial cell death, absense of the lens bow, degenerated fiber masses, and liquefied substrata. In

contrast, prior to the appearance of transparent cortex in the 10 Gy group, the lens epithelial

aberrations arc of the bow, and meridional row disorganization were all observed to improve.

Further, by 69 weeks, the lens epithelium appeared as a largely homogenous population and the

meridional rows and the arc of the bow had become reestablished. The details of these

observations and their possible relationship to the cytopathomechanism of radiation cataract

formation are discussed.

Lett, J. T., Cox, A. B., and Lee, A. C. (1986) Cataractogenic potential of

ionizing radiations in animal models that simulate man. Advances in Space

Research 6(11): 295-303.

New Zealand white rabbits, Rhesus monkeys, Beagle dog, Animal models, Heavy ions, HZE

Aspects of experiments on radiation-induced lenticular opacification during the life-spans of two

animal models, the New Zealand White rabbit and the Rhesus monkey, are compared and

contrasted with published results from a life span study of another animal model, the beagle dog,

and the most recent data from the ongoing study of the survivors from radiation exposure at

Hiroshima and Nagasaki. An important connection among the three animal studies is that all the

measurements of cataract indices were made by one of the authors (A.C.L.), so variation from

personal subjectivity was reduced to a minimum.

The primary objective of the rabbit experiments (radiations involved: 56Fe, 4°Ar and 2°Ne ions,

and 60 Co g photons) is an evaluation of hazards to astronauts from galactic particulate radiations.

An analogous evaluation of hazards from solar flares during space flight is being made with

monkeys exposed to 32, 55, 138 and 400 MeV protons.

53
i

Conclusions are drawn about the proper use of animal models to simulate radiation responses in

man and the levels of radiation-induced lenticular opacification that pose risks to man in space.

Odrich, S., Medvedovsky, C., Merriam, G. R., and Worgul, B. V. (1988)

Micronucleation in the lens epithelium following in vivo exposure to physical and

chemical mutagens. Lens Research 5(384): 203-216.

Rat lens, Lens epithelium, Micronuclei, Cataracts, Mutagenicity

Rats were exposed to cataractogenic doses of known physical and chemical genotoxic agents in

order to study the efficacy of using micronuclei to momtor mutagenicity in the lens epithelium.

The total numbers of micronuclei were counted in lens epithelia from rats exposed to graded doses

of either 250kVp X-rays or the antileukemic drug, 1,4 dimethanesulfonoxybutane (Myleran®).

The results indicate a dose-dependent incidence of micronucleation in the lens epithelium following

exposure. The findings are consistent with the hypothesis that the cataractogenicity of certain

agents may be related to their effect on the genome of lens epithelial cells.

Worgul, B. V. (1988) Accelerated heavy particles and the lens: V. Theoretical

basis of cataract enhancement by dose fractionation. Opthalmic Research 20:

143-148.

Fractionation, Track structure, Lens epithelium, Inverse dose-rate effect, Cataracts

That accelerated heavy ions are highly cataractogenic is indisputable. The basis of heavy particle

effectiveness and the augmentation by fractionation, as recently demonstrated, remains less clear.

There is no question, however, that these are tied to the "track structure" and densely ionizing

nature of the radiation. The unique energy deposition characteristics relating to charge and "track

structure" are now being explored to begin to dissect the cellular response of the lens epithelium to

radiation exposure. The elucidation of the basis of the cataractogenic effect of accelerated heavy

ions is important not only to risk assessment, but also in the consideration of theories of radiation

action and the mechanism of cortical opacification arising from a myriad of cataractotoxic agents.

Worgul, B. V., Merriam, G. R., Jr., Medvedovsky, C., and Brenner, D. J.

(1989) Accelerated heavy particles and the lens. III. Cataract enhancement by

dose fractionation. Radiation Research 118: 93-110.

Cataractogenesis, Fractionation, Rats, Ar ions, X-rays, Inverse dose-rate effect, Lens

For a number of biological end points it has been shown that, in contrast to low linear energy

transfer (LET) radiation, dose fractionation of high-LET radiation does not result in a reduction in

overall effectiveness. Studies were conducted to determine the effect of fractionating the exposures

to heavy ion doses on the development of cataracts. Rat eyes were exposed to single doses of 1,

5, and 25 cGy of 570 MeV/amu 4°Ar ions and to 2, 4, and 10 Gy or 250 kVp X rays. These were

compared to unirradiated controls and eyes that were exposed to the same total dose delivered in

four fractions over 12 hours. While in all cases fractionation of the exposure to X rays produced

significant reduction in cataractogenic potential, fractionating doses of 4°Ar ions caused a doseand stage-dependent enhancement in the development of cataracts.

54
2.3.3. CATARACTOGENESIS

REPORTS/MEETINGS

Calvin, H. I., Medvedovsky, C., Hess, J. L., David, J., and Worgul, B. V.

(1988) Rapid cataractogenesis in glutathione-depleted preweanling mice.

Investigative Ophthalmology and Visual Science 29:29 (abstract).

Mice cataractogenesis, Glutathione, Age dependence

The inhibitor of glutathione biosynthesis, L-buthionine sulfoximine (L-BSO), induces agedependent dense corticonuclear cataracts in mice. Further studies have shown that consistent

induction of lenticular pathology occurs after 6 injections of the drug (4 mmol/kg) over a 2-day

period at 8-10 days of age. The earliest abnormalities, evident by 48 h after the initiation of

treatment, include swollen fibers in the superficial anterior and posterior cortex, nucleated fibers in

the deep cortex, fragmented nuclei, and disorganization of the bow. In some lenses, disappearance

of fiber boundaries and granular degeneration are seen. Concomitantly, glutathione is depleted to

less than 5% of control values. Betwen 48 and 72 h, lens wet weight increases, dry weight

diminishes, glutathione becomes essentially undetectable, and Ca attains very high levels.

Meanwhile, fiber swelling, rupture and degeneration have become more pronounced and extend

into the deep cortex and lens nucleus. The densest opacities are seen at 16-21 days of age. Further

pathological changes include: disorganization of the epithelium (gaps and stratification), large

vacuoles in the anterior and posterior cortex, and scattered aggregates of fragmented nuclei.

Pathology is least severe in the bow. During subsequent weeks, partial recovery takes place, as

the degenerated tissue is replaced by new fibers and displaced into the deep cortex and lens

nucleus. In summary, depletion of lens glutathione in preweanling mice leads to profound agedependent damage to lens fiber cell membranes and widespread disruption of lens cytoarchitecture.

Cox, A. B., Lett, J. T., and Lee, A. C. (1990) Late cataractogenesis in primates

exposed to protons. Abstract presented at the 38th Annual Meeting of the

Radiation Research Society, New Orleans, LA, April 7-12, 1990.

Rhesus monkeys, Protons, Dose threshold

Rhesus monkeys (Macaca mulatta) irradiated in the 1960s with low acute doses of protons ranging

in energy from 10-2300 MeV are demonstrating late progressive radiation cataractogenesis 20 to 25

years following exposure. Comparable late ocular changes in humans would represent significant

radiation sequelae for astronauts exposed to showers of protons associated with periods of intense

solar activity. At the current stage of the investigation, it appears that the dose threshold for excess

cataracts attributable to radiation will be less than 2 Gy in rhesus monkeys surviving to ages in the

region of the median life-span of the species.

Holsclaw, D., Worgul, B. V., Rothstein, H., and Medvedovsky, C. (1988)

Modification of clinical and cytopathological changes in irradiation induced

cataracts: effects of hypophysectomy and hormone replacement therapy.

Investigative Ophthalmology and Visual Science 29:428 (abstract).

Hypophysectomy, Hormones, Replacement therapy, Lens epithelium, Cataractogenesis, Slit-lamp

microscopy, Radiation cataracts

Lens epithelial mitosis has long been implicated in the cytopathomechanism of radiation-induced

cataractogenesis. It has been proposed that radio-cataractogenesis depends upon the mitosis-driven

formation of aberrant fibers from epithelial cells damaged by ionizing radiation. We investigated

55
theroleof lenticularmitosisin thecytopathogenesisof radiocataractsdirectlyby manipulatingthe

cell cycleof thelensepitheliumin frogsby hypophysectomy(knownto haltmitotic activity) and

pituitary hormoneadministration(known to stimulatemitosis and reversehypophysectomyinducedmitotic suppression).An additional objective was to establish an animal model within

which aspects of radiocataractogenesis could be modulated.

Postmetamorphic bullfrogs were hypophysectomized, irradiated and given pituitary hormone

replacement. Irradiated animals, irradiated animals + hormone replacement, and irradiated

hypophysectomized animals served as controls. Cataract development was evaluated clinically by

slit-lamp biomicroscopy (Merriam/Focht method) and histologically by lens epithelial whole

mounts.

While irradiated hypophysectomized animals failed to develop opacities, as previously

demonstrated, irradiated hypophysectomized animals with hormonal replacement (mitosis

reinstated) developed cataracts; furthermore, the incidence and severity of the radiation-induced

lens changes exceeded the levels of controls. These findings support a central role for lenticular

mitosis in the cytopathomechanism of radiocataracts. Further, the ability to successfully modulate

cataractogenesis by manipulating lenticular mitosis offers a biological system that greatly facilitates

the mechanistic study of radiocataractogenesis. Applications of this system, including titrating

cataractogenesis and characterizing the behavior and consequences of DNA repair in radiationinduced injury, will also be discussed.

Kung, J. S., Worgul, B. V., David, J., and Rini, F. (1987)

exogenous genotoxic agents on the amphibian lens. Investigative

and Visual Science 28:86 (abstract).

The effects of

Ophthalmology

Mutagens, Benzo-a-pyrene, Ethyl-methane sulphonate, Rana pipiens, Lens epithelium, Cell cycle,

Cataracts

It has been postulated that agents which are genotoxic to the lens epithelium should also be

cataractogenic. A question which arises is whether incidental exposure to mutagens in the

environment can affect the lens. Therefore, the genotoxic effects of the well known environmental

mutagens Benzo-a-pyrene (BP) and Ethyl-methanesulphonate (EMS) on the lens epithelia of Rana

pipiens were assessed. Four groups of frogs were immersed in 2.5, 5.0, 10.0, and 20.0

micrograms/ml of BP for one week. Four additional groups of frogs were placed into 25, 50,

100, and 200 micrograms/ml of EMS for the same period. Following sacrifice of the animals, lens

epithelial whole-mounts were prepared. The epithelia were stained by the Feulgen technique to

permit visualization and quantitative analysis of nuclear DNA content. The lens epithelia of frogs

exposed to EMS showed evidence of genotoxicity as manifested by the appearance of

micronucleated cells. More striking, however, was a marked increase in the pre-mitotic, G2,

population in the lens epithelium. A concomitant decrease in mitoses suggests an arrest in the cell

cycle. In contrast, micronuclei were not present in the epithelia of frogs immersed in BP and the

cell cycle appeared unaffected. It is unclear whether this reflects an insensitivity of lens cells to the

mutagen or that the BP and its genotoxic metabolites failed to cross the blood aqueous barrier. In

any case, the experience with EMS strongly suggests that exposure to certain environmental

mutagens can adversely affect the lens.

Medvedovsky, C., Merriam, G. R., Jr., David, J., Rosskothen, H., and Worgul,

B. V. (1989) An integrative scoring system for experimental cataract assessment.

Investigative Ophthalmology and Visual Science (Suppl.) 30:144 (abstract).

Scoring system, Scheimpflug-based, Experimental cataracts

56
Until theadventof Scheimpflug-basedslitlampcamerasystems(SLCs),experimentalcataract

assessmenthasbeenhamperedby its subjectivity,lackof linearity, andunstandardizedscoring

criteria. While previousstudiesin this laboratoryhaveshownthatSLCanalysisis notsuitablefor

determiningcataractonset,it doesprovideforlinearquantificationof thelossof transparencyonce

opacification hasbegun. We thereforehavedevelopeda methodologywherebyconventional

slitlampbiomicroscopyis employedto monitortheearliestlenschanges.Whenfirst noted,the

cataractsareconsideredto haveavalueof one. Thereafter,progressionis followed usingaZeiss

SLC modified for experimentaluse. As opacificationproceeds,it is scoredby the following

formula:

Cataractstage= 1.0+ (It -Ii) / Ii

where Ii = Intensity 0 Time, and It = Intensity Exptl. The scores accumulate until readings become

unreliable due to very severe anterior changes preventing light from reaching the cortex. At that

point the conventional slitlamp is again used to monitor for complete opacification -- Stage 4

cataracts. The intensities (I) are the pooled average measurements from four 45 ° meridians. The

methodology and possible refinements for accurate inter- and intra-experimental comparisons will

be presented.

Medvedovsky, C., Merriam, G. R., Jr., and Worgul, B. V. (1988)

Nonsubjective assessment of radiation cataract development by Scheimpflug

image analysis. Abstract presented at the 36th Annual Meeting of the Radiation

Research Society, Philadelphia, PA, April 16-21, 1988, p. 128.

Scheimpflug image analysis, X-rays, Cataract scoring, Lens opacities, Cataracts

Historically the major impediment to radiation cataract studies, both clinical and experimental, has

been the necessarily subjective nature of assessing the transparency of the lens. This has spurred

the development of instruments which produce photographic or video images amenable to digital

analysis.

Our laboratory has incorporated the video-based Zeiss Scheimpflug Slit-Lamp System (SLS) into

our ongoing studies of radiation cataractogenesis. In order to evaluate the utility of the instrument

we employed the SLS in X-ray cataract studies in rats. As a benchmark and an indicator for future

comparisons we used the Merriam/Focht (M/F) method of scoring opacification by classical slitlamp analysis. It was found that conventional slit-lamp biomicroscopic surveys by skilled

observers are without question the most sensitive and reproducible means to detect and score the

initial appearance of radiation cataracts (M/F scale _<1+). Once cortical involvement becomes more

extensive, however (M/F scale > 1+ and < 4+), the SLS allows for a much greater resolution

reflected in a continuously incremental record. The usefulness of the assay diminishes as the

anterior cortex becomes more severely compromised. These findings as well as the potential of

using the SLS for interpreting radiation effects on the lens, will be presented.

Medvedovsky, C. P., Seidenberg, K., David, J. Broglio, T., and Worgul, B. V.

(1990) The histopathologicai basis of focal radiation damage to the lens

epithelium. Abstract presented at the 38th Annual Meeting of the Radiation

Research Society, New Orleans, LA, April 7-12, 1990 (p. 111).

Lens epithelium, Serial section, Reconstructions, Cataracts, Heavy ions, Focal damage

Recent observations of discrete focal damage to the lens epithelial population following accelerated

heavy ion exposure raised the possibility of a biological effect unique to particle radiation.

Extensive analysis of epithelia exposed to a variety of both low and high LET radiations has shown

57
this notto bethecase.Thedevelopmentof foci in thelensepitheliumappearsto bea ubiquitous,

albeitextremelylate,responseto ionizingradiation.In epithelialfiat-mountpreparations,thefoci

appearasareasof stratification,eachsurroundingacentrallow-densityregioncontainingoneto

severalargecells. Theirnumber,size,andonsettimearedependentondoseandradiationquality.

Serialsectionreconstructionsrevealthattheorganizationof thecortexsubjacento individualfoci

is alwaysatypical. Histochemicalstudiesfound that the largecentral cells producebasement

membranewithoutregardto orientation. It is believedthatthe lensfibers thatdifferentiateafter

radiationfail to provideproperscaffoldingfortheoverlyingepithelialcellsto maintaintheirnormal

spatialrelationships.

Seidenberg, K., Medvedovsky, C., David, J., Broglio, T., and Worgul, B. V.

(1990) Lens epithelial focal damage due to ionizing radiation. Investigative

Ophthalmology and Visual Science 31:204 (abstract).

Focal damage, Cataracts, Lens epithelium, Heavy ions

Recently a unique radiation pathology was described in the lens epithelia of animals exposed to

accelerated heavy ions. It was typified by discrete focal areas of stratified spindle-shaped cells

surrounding a low-density zone containing one to several large cells covering the normal

monolayered cuboidal lens epithelium. Because the damage had not been described previously, it

was thought that the foci were pathognomonic lesions specific to heavy ion exposure. Extensive

analysis has shown this not to be the case. The appearance of foci in the lens epithelium appears to

be a common late response to radiation. Serial sectioning and histochemical studies help further

define the architecture and demonstrated the intimate involvement of degenerated cortex and new

capsular material in the foci.

It is suspected that radiation injury induces a nonspecific process, which may be initiated by other

cataractogefiic causes that result in foci-like pathology. Anterior subcapsular cataracts caused by

mechanical trauma or noxious injury to the lenses have striking similarities to the foci. Thus

anterior changes in cataracta complicata (a group that includes radiation cataracts) often involve

clusters of spindle-shaped cells that produce capsular material in locations not normally found to

contain it. In the case of radiation-caused loci, the problem is probably due to the abnormal

deposition of cortical fibers after exposure, resulting in the areas of lost architectural integrity, in

turn allowing epithelial cells to invade the cortical space. While a common pathogenesis cannot be

ascribed unequivocally to the other agents that produce similar focal disorgamzation, it is not

unlikely that they all are tied to primary alterations in the substrata, i.e., the cortex.

Worgul, B. V. (1988) The theoretical basis of cataract enhancement by dose

fractionation of accelerated heavy ions. Investigative Ophthalmology and Visual

Science 29:317 (abstract).

Dose fractionation, Cataractogenesis, Heavy ions, Inverse dose-rate effect, Cell cycle, Lens

Augmentation caused by fractionation or protraction of heavy particle doses has been reported for a

number of systems, including cell transformation, cell killing, mu!agenesis, life shortening and,

most recently, cataractogenesis. Its mechanism, however, remains unknown. Currently one

popular hypothesis is that the fractionation regimen has a synchronizing effect on the cell

populations, e.g., the early fractions may place hit cells in a more vulnerable position in the cell

cycle. There is very compelling evidence that the potentiation effect of split doses of heavy ions, at

least for cell killing in vitro, is characterized by 2 distinct steps - sensitization and synchronization.

Data from our laboratory indicate that for endpoints which require a surviving population, such as

cataractogenesis (and perhaps tumorigenesis), synchronization and desensitization are critical. In

other words, by delivering a heavy particle dose in fractions, the cells may find themselves in a

less vulnerable portion of the cell cycle.

E

58
It is hypothesizedthatthesynchronizationis producedbythelow linear-energytransfercomponent

of the particle track. Studiesdissectingthe cellular responseof the lens epithelium reveal a

dependenceonchargeandtrack structureof theions. Theserelationshipsandtheirrelevanceto

cataractenhancementwill bediscussed.

Worgul, B. V. (1990) Quantifying genotoxicity in the lens. lnternat. Soc. Ocul.

Tox. 2:30 (abstract).

Genotoxicity, Cataracts, Micronuclei, Cellular differentiation

The association of aberrant differentiation of the lens epithelium and a number of cortical cataracts

suggests a causal relationship. If so, then any agent capable of disrupting normal morphogenesis

and differentiation should by definition be cataractogenic. Inasmuch as it is generally recognized

that differentiation is a function of a cascade of gene expression, one can predict that an agent

capable of disrupting the genome by definition must also be cataractogenic. In our effort to

examine this possibility, we have applied a variety of techniques to assay and quantify genomic

instability in the lens. A variety of factors singular to the lens have proved problematic, not least of

which is the limited population of epithelial cells available for study.

Of the many cytogenic techniques that we have tested, micronuclear frequency assay is the method

of choice to assess mutagenesis in this population. The micronucleus is a readily discemable

expression of the failure of the chromosome or chromosomal fragment to be included in the

daughter cell's nuclei following cell division. The technique, its limitations, and the results of our

experimental studies will be discussed. We will also present preliminary results of the application

of the methodology to the human population.

Worgul, B. V., Medvedovsky, C., Powers-Risius, P., and Alpen, E. L. (1987)

Cataractogenesis and cytopathological changes in mouse lenses exposed to 600

MeV/amu iron ions. Investigative Ophthalmology and Visual Science 28:282

(abstract).

Mice, Fe ions, Cataracts, RBE, MicronucIeation, Lens epithelium

The lenses of mice exposed to 600 MeV/amu iron ions were evaluated by slit-lamp biomicroscopy

and cytopathological analyses. The doses ranged from 0.05 to 1.6 Gy and the lenses were

assessed at 5, 10, and 16 months post-irradiation.

Cataracts which developed in a dose and time dependent manner were significantly more advanced

in all of the exposed mice when compared to the unirradiated controls. The great difference

between the severity of the cataracts caused by 0.05 Gy and those present in the control animals

indicates that the lowest dose used in the study far exceeds the threshold dose for the production of

cataracts by accelerated iron ions. These data, when considered in light of previous low LET

radiation cataract studies on the mouse lens, suggest that at very low doses the Relative Biological

Effectiveness (RBE) for iron will prove comparable to those seen for argon in the rat lens. In the

rat studies RBEs in excess of 40 were observed.

The cytopathological studies demonstrated a similar dose dependence for a number of endpoints,

including micronucleation, interphase death, and meridional row (MR) disorganization. X-ray

cataracts and MR disorganization have been shown to correlate quantitatively. A similar correlation

was seen in the present study. The microscopic changes, taken together, once again support the

view that the mechanism of heavy ion-induced cataractogensis is the same as that for cataracts

caused by low LET radiation.

59
Worgul, B. V., Medvedovsky, C., Powers-Risius, P., and Alpen, E. L. (1988)

Changes in the mouse lens caused by 600 MeV/amu accelerated iron ions.

Abstract presented at the 36th Annual Meeting of the Radiation Research Society,

Philadelphia, PA, April 16-21, 1988, p. 109.

Mouse lens, Iron, RBE, Cataracts, Cellular pathology

The lenses of mice were evaluated by slit-lamp biomicroscopy and cytopathological analysis

following doses of 600 MeV/amu iron ions ranging from 0.05 to 1.6 Gy. The examinations were

conducted at 5, 10 and 16 months post-irradiation. Cataracts were present in all irradiated animals

although the severities were dose- and time-dependent. The degree of opacification observed the

the .05 Gy dose group indicated that the threshold dose for cataractogenesis must be significantly

lower. Furthermore, when compared to results from previous low-LET radiation studies in the

mouse lens, a relatively high RBE is suggested for iron ions.

In addition to the overt loss of transparency, histopathological and analyses revealed a strong dose

dependence for a number of endpoints. These included micronucleation, interphase death, and

meridional row disorganization, previous studies have show that X-ray cataracts and meridonal

row disorganization correlate quantitatively. Taken together, the microscopic changes support the

view that the mechanism of heavy ion induced cataractogenesis is the same as that for cataracts

caused by low-LET radiation. The damage incurred in the lens by heavy particles while

quantitatively dissimilar, is qualitatively indistinguishable from that caused by X-rays.

Worgul, B. V., Medvedovsky, C., Powers-Risius, P., and Alpen, E. L. (1989)

Accelerated Heavy Ions and the lens. IV. Biomicroscopic and cytopathological

analyses of the lenses of mice irradiated with 600 MeV/amu S_Fe ions. Radiation

Research 120: 280-293.

Fe ions, Mice, Slit-lamp, Cataracts, Cytopathology, Lens epithelium

The lenses of mice exposed to 600 MeV/amu iron ions were evaluated by slit-lamp biomicroscopy

and cytopathological analyses. The doses ranged from 0.05 to 1.6 Gy, and the lenses were

assessed at several intervals post-irradiation.

Cataract, the development of which is dependent on both time and dose, is significantly more

advanced in all of the exposed mice when compared to the unirradiated controls. The great

difference between the severity of the cataracts caused by 0.05 Gy (the lowest dose used) and

those that developed spontaneously in the control animals is an indication that 0.05 Gy may far

exceed the threshold dose for the production of cataracts by accelerated iron ions.

Cytopathologically, a similar dose dependence was observed for a number of end points including

micronucleation, interphase death, and meridional row disorganization. In addition, the exposure

to the 56Fe ions produced a long-term effect on the mitotic population and a pronounced "focal"

loss of epithelial cytoarchitecture. The microscopic changes support the view that the mechanism

of heavy-ion-induced cataractogenesis is the same as that for cataracts caused by low-LET

radiation.

60

r
2.3.4. OTHER EFFECTS

Cox, A. B. and Lett, J. T. (1989) The quantification of wound healing as a

method to assess late radiation damage in primate skin exposed to high-energy

protons. Advances in Space Research 9(10): 125-130.

Late radiation damage, Protons, Rhesus monkeys, Wound healing

In an experiment examining the effects of space radiations on primates, different groups of rhesus

monkeys (Macaca mulatta) were exposed to single whole-body doses of 32- or 55-MeV protons.

Survivors of those exposures, together with age-matched controls, have been monitored

continuously since 1964 and 1965. Late effects of nominal proton doses ranging from 2-6 Gray

have been measured in vitro using skin fibroblasts from the animals. A logical extension of that

study is reported here, and it involves observations of wound healing after 3-mm diameter dermal

punches were removed from the ears (pinnae) of control and irradiated monkeys. Tendencies in

the reduction of competence to repair cutaneous wounds have been revealed by the initial

examinations of animals that received doses greater than 2 Gy more than 2 decades earlier. These

trends indicate that this method of assessing radiation damage to skin exposed to high-energy

radiations warrants further study.

Krebs, W., Krebs, I., Merriam, G. R., Jr., and Worgul, B. V. (1988) The effect

of accelerated argon ions on the retina. Radiation Research 115: 192-201.

Argon ions, Retina, Microlesions, Electron microscopy

It has been postulated that high energy heavy ions cause a unique form of damage in living tissue,

which results from the high linear energy transfer of accelerated single particles. We have searched

for these single-particle effects, so-called "microlesions," in composite electron micrographs of

retinas of rats which had been irradiated with a dose of 1 Gy of 570 MeV/amu argon ions. The

calculated rate of energy deposition of the radiation in the retina was about 100 keV/I.tm and the

fluence was four particles per 100 _m 2. Different areas of the irradiated retinas which combined

would have been expected to be traversed by approximately 2400 particles were examined. We

were unable to detect ultrastructural changes in the irradiated retinas distinct from those of controls.

The spatial cellular densities of pigment epithelial and photoreceptor cells remained within the

normal range when examined at 24 hours and at 6 months after irradiation. These findings suggest

that the retina is relatively resistant to heavy-ion irradiation and that under the experimental

conditions the passage of high energy argon ions does not cause retinal microlesions that can be

detected by ultrastructural analysis.

Krebs, W., Krebs, I., and Worgul, B. V. (1990) Effect of accelerated iron ions

on the retina. Radiation Research 123: 213-219.

Rats, Fe ions, Photoreceptors, Retina, Choroid, Microlesions

The eyes of rats were exposed to doses of 0.1 and 2.5 Gy of 450-MeV/amu 56Fe particles (LET N

195 keV/I.tm). The beam axes were oriented perpendicular to the central retina of the animals.

Retinas were harvested immediately (<10 min), 24 h, 15 days, 136 days, and 186 days after the

experiment. The retinas of animals of equivalent ages were sampled at the same intervals. By Day

15, the spatial densities of the pigment epithelial, photoreceptor, and bipolar cells in retinas

irradiated with 2.5 Gy were 15 to 20% lower than those of the controls. The cellular density of the

pigment epithelium returned to the control level by Day 186 while photoreceptor and bipolar cell

61
numbersremaineddepressed.Oneandfifteendaysafterirradiation,thechoroidalvesselsshowed

signsof radiationdamage.Exposureto 0.1Gy did notaffectthecellulardensitywithin theretina

at theintervalspecified(186days). Noneof theretinasshowedevidenceof track-specificinjury

thatcouldbeinterpretedasmicroiesionsortunnellesions.

Todd, P. (1989) Stochastics of HZE-induced microlesions. Advances in Space

Research 9: 31-34.

HZE, Microlesions, Single-particle effects

Fundamental biological experiments with bacteria, yeast, and mammalian cells irradiated with ions

heavier than helium indicate that maximal probability of single-hitinactivation does not occur when

the ion has LET below about 100-200 keV/I.tm. Theoretical treatments of cell inactivation data and

the radiation chemistry in particle tracks are consistent with this finding. If a "microlesion" is

defined as a linear array, within a tissue, of cells inactivated with maximum probability,

surrounded by non-lethally damaged cells, then, by this definition, there must be an LET below

which "microlesion" damage cannot be expected. In a retrospective survey of experimental

literature in which single-particle effects in tissues were sought, it was found that little or no

evidence has been reported supporting single-particle effects in tissues when LET was below 200

keV/I.tm, while some experimenters who irradiated tissues with particles having LET greater than z

200 keV/l.tm reported effects that could be attributed to single particle tracks.

2.3.4. OTHER EFFECTS

REPORTS/MEETINGS

Cox, A. B. (1989)

presented at the 37th

WA, 1989.

Cutaneous tissue repair in irradiated primates. Abstract

Annual Meeting of the Radiation Research Society, Seattle,

Protons, Rhesus monkeys, Wound healing

Protons will be a major radiation hazard to humans on lengthy missions in space. Even if radiation

exposures are not lethal, some doses will compound effects of normal aging in individuals at risk.

For this reason, late radiation effects are being studied in a group of primates known as the

Chronic Radiation Colony. Following single whole-body doses of 32 or 55 MeV protons in 1964

and 1965, rhesus monkeys have been maintained as part of a long-term study. The removal of

small skin biopsies for cellular studies has not compromised the health of the animals, but primates

that received proton doses greater than 2.5 Gy more than 20 years ago exhibit diminished ability to

heal 3-mm diameter holes in their pinnae when they are compared with age-matched controls.

Trends in the results of the in vivo wound-healing studies parallel those seen when skin fibroblasts

have been grown to senescence in vitro. In the latter studies, proton doses greater than 2.5 Gy

tended to reduce the numbers of generations produced by skin fibroblasts in culture. Data from in

vivo and in vitro experiments now indicate that late radiation effects following low or intermediate

radiation doses can manifest themselves in primate skin more than 20 years after exposure when a

challenge (e.g., a minor surgical treatment) is experienced.

r

D

62
Krebs, I., Krebs, W., Merriam, G. R., Jr., and Worgul, B. V. (1987)

Irradiation of the retina with high-LET (100 KeV/I.tm) argon ions does not cause

overt ultrastructural damage. Investigative Ophthalmology and Visual Science 28:

264 (abstract).

High-LET, Ar ions, Microlesions, Electron microscopy, Eye

The high linear energy transfer (LET) and charge of accelerated heavy ions has caused some to

postulate that the passage of such particles through tissues may produce a unique form of damage,

so-called "microlesions". Studies using scanning electron microscopy have suggested that tunnels

or holes seen in the tissue after irradiation were in fact manifestations of such injuries. Since these

studies remain largely unconfirmed and because of the importance of the microlesion concept in

attempts at the assessment of risk to exposure to heavy particle irradiation, we examined the retinas

of rat eyes exposed to 1 Gy of 570 MeV/amu argon ions. The ions were delivered in the plateau

region of the Bragg curve. Thus, the average energy deposition of the particles throughout the

retina was approximately 100 KeV/I.tm 2 and the dose delivered was equivalent to an everage

fluence of 1 particle traverse/251.tm 2. The analysis was conducted using composite electron

micrographs of en face sections of the retina from animals killed 24 hours or 6 months after

irradiation, each of which covered an area of approximately 100 x 100 I.tm at the level of the

pigment epithelium, the rod outer segments, and the inner nuclear layer. In none of these were we

able to detect ultrastructural changes distinct from those of the controls. We therefore could not

confirm the existence of holes or tunnels produced by argon particles of this energy. Our studies

are consistent with observations following X-irradiation of the eye which concluded that the neural

elements of the retina are far less radiation-sensitive than are other ocular tissues such as the lens.

Krebs, W., Krebs, I. P., and Worgul, B. V. (1989) Ultrastructural changes in

the retina and choroid due to irradiation with high energy iron ions. Investigative

Ophthalmology and Visual Science (Suppl.) 30:351 (abstract).

Heavy ions, HZE, Cosmic rays, Rats, Choroid, Retina, Iron

The heavy ion component (HZE) of cosmic radiation remains problematic to the assessment of risk

in manned space flight. The biological effectiveness of such radiation has yet to be established,

particularly in regard to nervous tissue. This has been complicated by the suggestion that a heavy

particle with a charge number (Z) of 20 or more, and with a linear energy transfer (LET) of

approximately 200 keV/l.tm or greater, causes a unique injury - the microlesion. We have analyzed

retinas of rats irradiated with 450 keV/amu of iron ions (56Fe, Z=26, LET= 195 keV/lam) at doses

ranging from 0.1 to 2.5 Gy. Electron micrographs of tangential sections of choroid and retina of

irradiated (2.5 Gy) and control animals revealed early vascular damage in the choroid and retina.

Twenty-four hours after irradiation, the densities of photoreceptor and pigment epithelial cells were

decreased by about 15%, after 2 weeks by 23%, and after 19 weeks by 38%. No further reduction

of cell number was seen 26 weeks after the experiment. There was no morphological evidence for

microlesion damage. These findings suggest that -- as with low LET radiation -- the primary

damage had been to the vascular system of choroid and retina. The resultant reduced blood flow

secondarily caused the destruction of retinal cells.

Worgul, B. V. (1988)

36th Annual Meeting

12-16, 1988, p. 149.

Radiation damage to the eye. Abstract presented at the

of the Radiation Research Society, Philadelphia, PA, April

Lyrical biology, Lens, Cornea, Retina, Eye

63
Streaming through the stratum corneum

a wondrous wetted window to within;

and traversing the lens called crystallin

that isolated singular sibling of skin;

to finally come upon retina oculi,

a brazenly brandished bit of brain,

course the photons with which we see,

as well those too tempestuous to tame.

And while the calmer are image bound

the latter loose a legacy lethal;

leaving we with tissue sound

to conjure constructs cosmically causal.

For though global study at first sight

provides possibilities too puny to pry;

it takes only comprehension slight

to learn far more than meets the eye.

Worgul, B. V., Krebs, W., and Krebs, I. (1989) Ultrastructural damage in the

retina and choroid of rat eyes exposed to iron ions. Abstract presented at the

37th meeting of the Radiation Research Society, Seattle, WA, March 18-23,

1989.

HZE particles, Microlesions, Rats, Fe, Retina, Choroid, Eye

The heavy ion component of cosmic radiation remains problematic to the assessment of risk in

manned space flight. The biological effectiveness of HZE particles has yet to be established,

particularly with regard to nervous tissue. This has been complicated by the suggestion that a

heavy ion with a charge of 20 or more, and with an LET approximately 200 keV/um or greater,

causes a unique injury -- the microlesion. We have analyzed retinas of rats irradiated with 450

MeV iron ions (Z=26; LET=195 keV/um) at doses ranging from 0.1 to 2.5 Gy. Electron

microscopy of tangential sections of the choroid and retina of 2.5 Gy irradiated rat eyes revealed

relatively early vascular damage in both tissues. Twenty-four hours after exposure, the densities

of the photoreceptor and pigment epithelial cells were reduced by 15% when compared to controls.

At 19 weeks after irradiation, the cell numbers were about 3/4 that of controls and remained

unchanged at 26 weeks. The time course and nature of the damage to these cell populations was

consonant with a primary injury to the vascular systems of the choroid and retina. Such is the case

following low-LET radiation -- the destruction of retinal cells resulting secondarily from ischemia.

m

Z

64
2.4. RADIOPROTECTANTS

REPORTS/MEETINGS

Frank, P., Medvedovsky, C., Haik, B., Rini, F., and Worgul, B. V. (1987)

Radioprotection of ocular tissues by WR-2721. Abstract presented at the 35th

Annual Meeting of the Radiation Research Society, p. 121.

Ocular tissues, WR-2721, X-rays, Rats

The compound WR-2721 is a derivative of mercaptoethylamine, which is currently undergoing

clinical trials as a radioprotective agent. Because of the apparent inability of WR-2721 to cross the

blood-aqueous-retina barrier, it is felt to minimize the possibility that the drug might interfere with

the tumoricidal effect of radiation of intraocular tumors. Studies were conducted on the rat to

determine if the WR-2721 might be useful in ameliorating the damage to superficial tissues

following radiotherapy for intraocular and orbital tumors.

A WR-2721 (20 mg/ml) solution in normal saline was administered topically prior to irradiating rat

eyes with 20 Gy of 250 kVp X-rays. The full range of controls consisted of eyes which received

the saline alone, saline with radiation, radiation alone and drug given post-irradiation. The

administration of WR-2721 prior to radiation significantly reduced the onset and severity of

blepharoconjunctivitis. The onset of the acute stage of radiokeratitis was delayed but late corneal

effects and permanent keratopathy were almost completely eliminated.

65
2.5. PLANTS

J.D_.U.RbtAI 

Anikeeva, I. D., Akatov, Y. A., Vaulina, E. N., Kostina, L. N., Marenny, A.

M., Portman, A. I., Rusin, S. V., and Benton, E. V. (1990) Radiobiological

experiments with plant seeds aboard the biosatellite KOSMOS 1887. Nucl Tracks

Radiat Meas 17(2): 93-97 (Int J Radiat Appl lnstrum, Part D).

COSMOS 1887, Arabidopsis thaliana, Crepis capillaris, Shielding, Biological dosimeter, Mutation

effects, Fertility

The effects of space-flight factors on the seeds ofArabidopsis thaliana and Crepis capillaris were

studied provided with various protective measures: The seeds were located inside the satellite and

in open space, protected with aluminum foil and also exposed without the foil, cover. When the

seeds were in open space without any protection, their viability was found to be suppressed; the

survival rate and fertility of plants grown from these seeds were also diminished. An increase in

the frequency of chromosome aberrations (CA) and in the number of multiple injuries was

registered in this case. Experiments with the aluminum foil shielding showed a decrease in the

suppression of the seeds' viability, but mutational changes were found to be even more increased,

while the survival rate and fertility of the plants decreased. An increase in the thickness of

shielding resulted in a decrease in the effects up to the level of the control, except for the effects

connected with CA and fertility of the plants. Analysis of the results shows that these impairments

can be ascribed to the action of single heavy charged particles (HCP). The seeds can be thus

regarded as an integral biological "dosimeter" that allows estimation of the total effects of radiation,

ecological, and biological factors.

66
3. RISK ASSESSMENT
3.1. RADIATION HEALTH AND EPIDEMIOLOGY

Sinclair, W. K. (1988)

Council on Radiation

149-157.

Trends in radiation protection -- a view from the National

Protection and Measurements (NCRP). Health Physics 55:

Chernobyl, Neutrons, Radon, Quality factors, Age dependence, Occupational exposure, Risk

systems

The present status of ionizing radiation protection in our society, with the exception of

extraordinary events such as the Chernobyl accident, can be considered reasonably satisfactory.

Occupationally, average exposures have risks no greater than accident rates in "safe" industries and

show a downward trend in concert with results of safety practices in other occupations; higher

exposures are being addressed specifically, and a new NCRP guideline may prove useful. An

important concern relating to the quality factor for neutrons is at least partially accounted for by

recent International Commission on Radiological Protection (ICRP) and NCRP recommendations.

Among public exposures, the most important by far is exposure to indoor Rn. However, this

problem is being addressed on all fronts, and its magnitude and the means to deal with it will soon

be better known.

For the near future, we should see a stabilizing of risk estimates, albeit at levels very probably

higher than formerly. There may also be an increasing tendency to use incidence rather than

mortality for calculating these estimates. These changes may require some adjustment in our

perspective on limits. As the difference in risk between the sexes becomes more definite, we may

wish to adopt a policy of equal risk rather than one of equal dose. Age data also emphasize, more

and more, the decline of risk with age; consequently, using older workers when feasible in

radiation-exposure circumstances becomes more desirable.

For the longer-term future, various developments can be expected, including, possibly, a more

suitable climate for a risk system, a more appropriate way to express differences in radiation

quality, further knowledge of the role probabilities of causation may play in radiation control, the

effect of mitigating and enhancing factors, and progress in fundamental oncology. All of these are

exciting possibilities which may provide a variety of options for the most effective radiation

protection in the future.

Wood, D. H., Pickering, J.

Y.L. (1988) Radiation

Medicine 153(6): 298-303.

E., Yochmowitz, M. G., Hardy, K. A., and Salmon,

risk assessment for military space crews. Military

Cancer risk, Occupational exposure, Radiation exposure

Space crews on Department of Defense missions may be required to accept greater radiation risks

than their civilian counterparts. Data accumulated over a 20-year period on nonhuman primates

exposed to simulated space radiation now make it possible to estimate life expectancy loss and

cancer risk for space radiation events. The numeric risk estimated facilitate risk versus gain

decisions and support more conservative radiation protection standards for non-emergency

operations, especially for females.

Worgul, B. V., Krebs, W., and Koniarek, J. P. (1989) Microlesions: Theory

and reality. Advances in Space Research 9(10): 315-323.

r

68
Microlesions, HZE particles, Fe ions, Galactic cosmic rays, Quality factors, Rats

Efforts to assess radiation risk in space have been complicated by the considerable unknowns

regarding the biological effects of the heavy ion component (HZE particles) of the cosmic rays.

The attention has focused primarily on the assignation of a quality factor (Q) which would take into

account the greater effectiveness of heavy ions vis-a-vis other forms of ionizing radiation. If,

however, as the so-called "Microlesion Theory" allows, the passage of HZE particles through

living tissue produces unique biological damage, the traditional use of Q becomes meaningless.

Therefore, it is critical to determine if microlesions, in fact, do exist.

While the concept does not necessarily require detectable morphological damage, "tunnel-lesions"

or holes in ocular tissues have been cited as evidence of microlesions. These data, however, are

open to reinterpretation. On-going light, scanning, and transmission electron microscopic studies

of the corneas, lenses, and retinas of rat eyes exposed to 450 MeV/amu 56Fe ions thus far have not

revealed tunnel-lesion damage. The morphological effects of the heavy ions have been found to be

qualitatively similar to the changes following other kinds of ionizing radiation.

Worgul, B. V., Merriam, G. R., Jr., and Medvedovsky, C. (1989) Cortical

cataract development - an expression of primary damage to the lens epithelium.

Lens and Eye Toxicity Research 6(4): 559-571.

Cortical cataract, Cataractotoxic load, Cell differentiation, Lens epithelium

Inasmuch as cortical opacities constitute the majority of senile cataracts their pathogenesis has been

a matter of investigative concern for over a century. Evidence has been accumulating indicating a

primary role for the lens epithelium in the loss of transparency of the cortex. Data from

experimental work and clinical experience are consistent with a primary damage to the genome of

the lens epithelial cell. The damage is mediated by the aberrant differentiation of the lens fiber cells

which collectively express as a cataract. The present paper reviews some of that evidence and

offers preliminary analysis of the contributing aspects of cellular parameters associated with the

pathology. Also, the concept of the "cataractotoxic load" and its applicability to the development of

human senile cortical cataracts is discussed.

3.1. RADIATION HEALTH AND EPIDEMIOLOGY

REpORTS/MEETINGS

Lett, J. T., Atwell, W., and Golightly, M. J. (1990) Radiation hazards to

humans in deep space: a summary with special reference to large solar particle

events. Presented at the National Oceanic and Atmospheric Administration

(NOAA) Space Environment Services Center Users Conference, Boulder, CO,

May 15-17, 1990.

Solar particle events, Radiation hazards

For didactic purposes, an adumbration is given here of the health risks faced by astronauts from

radiation hazards during extended missions in deep space. Special emphasis is given, by way of

the examples provided by very recent solar activity, to biological consequences of large solar

proton events and the need for accurate prediction of such events. The circumstances pertaining to

missions within the protection of the magnetosphere of the Earth are relatively well understood and

recently they have been documented in detail.

69
Nachtwey, D. S. (1989) Radiological health risks. Presented at the 19th

Intersociety Conference on Environmental Systems (ICES), San Diego, CA, July

24-26, 1989. SAE Technical Paper Series #891432.

HZE, Heavy ions, Doses, Dose equivalent, Quality factors, Galactic cosmic rays

The crew of a manned Mars mission will be unavoidably exposed to galactic cosmic ray (GCR)

flux. If one employs conventional radiological health practices involving absorbed dose (D), doseequivalents (H), and LET-dependent quality factors (Q), the Mars mission crew shielded by 2

g/cm 2 A1 could receive about 0.7 Sv in a 460-day mission at solar minimum. However, threefourths of this dose-equivalent in free space is contributed by high LET heavy ions (Z>3) and

target fragments with average Q of 10.3 and 20, respectively. Such high quality factors for these

particles may be inappropriate. Moreover, in a 460-day mission, less than half of the nuclei in the

body of an astronaut will have been traversed by a single heavy particle. The entire concept of

D/Q/H as applied to GCR must be reconsidered.

Silberberg, R., Tsao, C. H., Adams, J. H., Jr., and Letaw, J. R. (1987)

Radiation hazards in space. Aerospace America, October 1987, p. 38.

Radiation dose, Shielding, Space exploration

In order to understand the radiation hazards associated with space flight, one must consider the

shielding necessary to protect space travellers who venture outside of the Earth's magnetic field.

This article describes the three types of radiation of concern, explains radiation dose units and

recommended limits by the National Council on Radiation Protection, and reviews mathematical

models for calculating risk associated with different types of shielding.

Sinclair, W. K. (1990) Risk estimates for human exposure to galactic radiation.

Presented at the 20th Annual Intersociety Conference on Environmental Systems

(ICES), Williamsburg, VA, July 9-12, 1990. SAE Technical Paper Series

#901344.

Low doses, NCRP, ICRP, Galactic cosmic rays

The probability of cancer induction is the main concern in the exposure of individuals to low doses

of ionizing radiation. Estimates of the risk of cancer induction formerly (1977-1980) about 1 x 10-

2 Sv-1 have recently been increased to 3-5 x 10 .2 Sv -1 for low doses. These increased estimates are

mainly the result of changes in the assessment of the Japanese survivors of the A-bombs in 1945.

They result from the accumulation of 11 years or more of data on solid tumors, changes in the

statistical projection methods, and revisions in the dosimetry of those exposed. The dosimetry

revisions are the result of a very comprehensive U.S.-Japan study that defines the doses more

precisely than before. The high dose, high dose rate exposures in Japan result in risks higher than

those due to low doses and dose rate. Thus these risks must be reduced by a dose rate

effectiveness factor, which is derived mainly from laboratory information.

These changes in cancer risk estimates will affect NCRP and ICRP recommendations on protection

limits for low-LET radiation. For high-LET radiations such as those encountered in space, the

risks are known relative to low-LET radiation effects; therefore a quality factor must be applied that

introduces additional uncertainty.

70
Sinclair, W. K. Recent estimates of cancer risk from low-LET ionizing radiation

and radiation protection limits. Adv. Space Research, 1990

ICRP, NCRP, Low-LET, Low doses

Estimates of the risk of cancer induction, formerly about l%/Sv, formed the basis of ICRP

radiation protection limits in 1977. They have now increased to about 4-5%/Sv for low doses.

These increases are based mainly on new data for the Japanese survivors of the A-bombs of 1945.

They result from the accumulation of 11 years more of data on solid tumors, the revisions in the

dosimetry of those exposed, and improvement in statistical methods and projections. The

application of a dose rate effectiveness factor between effects at high dose rate and those at low

dose and dose rate is also an important consideration. Not only has the total risk changed, but also

the distribution of risk among organs. Thus the effective dose equivalent may require

modification. These changes are modifying ICRP and NCRP thinking about recommendations on

protection limits, especially for radiation workers.

Worgui, B. V., David, J., Odrich, S., Merriam, J., Merriam, G. R., Jr., and

Geard, C. (1990) An evaluation of in situ mutagenic damage in the lens epithelia

of cataract patients. Investigative Ophthalmology and Visual Science 31:435

(abstract).

Lens epithelium, Cataracts, MicronucIei, Cataract patients, Mutagens

Utilizing fragments (tags) of lens epithelium recovered during the extracapsular cataract extraction

procedure, we have been able to assess cytogenic changes in the epithelial population that reflect

genomic instability. Epithelial tags comprising 30,000 to 90,000 cells were obtained from patients

without prior regard to the type of cataract or the age of individuals. Thirty of such tags were

prepared as fiat mounts and stained by the Feulgen method or with chromomycin A3. Both stain

DNA stoikiometrically and therefore allow quantitative determination of a variety of nuclear

parameters including size, distribution, and relative number, as well as DNA content.

A high percentage of the tags contain a population of micronucleated cells. A micronucleus (MN)

is typically the consequence of a deletion of the centromere region preventing spindle attachment to

the chromosome or chromosomal fragment during mitosis. MN frequency has been shown to be a

correlative measure of genomic instability in a number of tissues. Experimentally, studies on the

lens have established a dose-response relationship between MN frequency and exposure to

genotoxins.

The presence of micronuclei in the epithelia of cataract patients appears to be independent of age.

The data is less clear for the type of cataract or past exposure to mutagens due to the anecdotal

nature of the assessment. However, the number of MNs in the epithelial cells of some individuals

strongly suggest a history of compromised genomic integrity.

71
3.2. SPACE FLIGHT RADIATION HEALTH PHYSICS

Akatov, Y. A., Dudkin, V. E., Kovalev, E. E., Benton, E. V., Frank, A. L.,

Watts, J. W. Jr., and Parnell, T. A. (1990) Depth distribution of absorbed dose

on the external surface of COSMOS 1887 biosatellite. Nuclear Tracks Radiation

Measures 17(2): 105-107 (lnt J Radiat Appl Instrum, Part D).

COSMOS 1887, Thermoluminescent detectors, Depth distribution, Absorbed dose, Shielding

thickness, Vette model

Significant absorbed dose levels exceeding 1.0 Gy per day have been measured on the external

surface of the Cosmos 1887 biosatellite as functions of depths in stacks of thin thermoluminescent

detectors (TLDs) of USSR and USA manufacture. The dose was found to decrease rapidly with

increasing absorber thickness, thereby indicating the presence of intensive fluxes of low-energy

particles. Comparison between the USSR and US results and calculations based on the Vette

model environment are in satisfactory agreement. The major contribution to the dose under thin

shielding thickness is shown to be from electrons. The fraction of the dose due to protons and

heavier charged particles increases with shielding thickness.

Akopova, A. B., Magradze, N. V., Dudkin, V. E., Kovalev, E. E., Potapov, Y.

V., Benton, E. V., Frank, A. L., Benton, E. R., Parnell, T. A., and Watts, J.

W. Jr. (1990) Linear energy transfer (LET) spectra of cosmic radiation in low

Earth orbit. Nucl Tracks Radiat Meas 17(2): 93-97 (Int J Radiat Appl Instrum,

Part D).

Integral LET spectra, Low Earth-orbit, U.S.S.R.-U.S., COSMOS biosatellite, PNTD,

Thermoluminescent detectors, Fission foils, Nuclear emulsions

Integral linear energy transfer (LET) spectra of cosmic radiation (CR) particles were measured on

five Cosmos series spacecraft in low Earth orbit (LEO). Particular emphasis is placed on results of

the Cosmos 1887 biosatellite, which carried a set of joint USSR-USA radiation experiments

involving passive detectors that included thermoluminescent detectors (TLDs), plastic nuclear track

detectors (PNTDs), fission foils, nuclear photoemulsions, etc., which were located both inside and

outside the spacecraft. Measured LET spectra are compared with those theoretically calculated.

Results show that there is some dependence of LET spectra on orbital parameters. The results are

used to estimate the CR quality factor (QF) for the Cosmos 1887 mission.

Atwell, W., Beever, E. R., and Hardy, A. C. (1989) A parametric study of space

radiation exposures to critical body organs for low Earth orbit missions.

Advances in Space Research 9(10): 243-245.

Shuttle, Anatomical man models, Low Earth-orbit

The geomagnetically-trapped and galactic cosmic radiation environments are two of the major

sources of naturally-occurring space radiation exposure to astronauts in low Earth orbit. The

exposure is dependent primarily on altitude, spacecraft shielding, crew stay-times, and solar cycle

effects for a 28.5 ° orbital inclination. Based on Space Shuttle experience, the calculated results of

a parametric study are presented for several mission scenarios using a computerized anatomical

man model and are compared with the NASA crew exposure limits for several critical body organs.

m

72
Atwell, W., Beever, E. R., Hardy, A. C., Richmond, R. G., and Cash, B. L.

(1989) Space radiation shielding analysis and dosimetry for the Space Shuttle

Program. Presented at the Conference on High Energy Radiation Background in

Space (CHERBS 87), Sanibel Island, FL, November 3-5, 1987. American

Institute of Physics Conference Proceedings No. 186, Eds. A. C. Rester, Jr. and

J. I. Trombka. New York: American Institute of Physics, pp. 289-296.

Active dosimeters, Passive dosimeters, Shuttle, Anatomical man models, Missions, Radiation dose

Active and passive radiation dosimeters have been flown on every Space Shuttle mission to

measure the naturally occurring, background Van Allen and galactic cosmic radiation doses that

astronauts and radiation-sensitive experiments and payloads receive. A review of the various

models utilized at the NASA/Johnson Space Center, Radiation Analysis and Dosimetry is

presented. An analytical shielding model of the Shuttle was developed as an engineering tool to aid

in making pre-mission radiation dose calculations and is discussed in detail. The anatomical man

models are also discussed. A comparison between the onboard dosimeter measurements for the 24

Shuttle missions to date and the dose calculations using the radiation environment and shielding

models is presented.

Benton, E. V. (1986) Summary of radiation dosimetry results on U. S. and

Soviet manned spacecraft. Advances in Space Research 6(11): 315-328.

Passive radiation detectors, Active radiation detectors, U.S. spacecraft, Soviet spacecraft, Low

Earth-orbit, Spacelabs

Measurements of the radiation environment aboard U.S. and Soviet manned spacecraft are

reviewed and summarized. Data obtained mostly from passive and some active radiation detectors

now exist for the case of low Earth-orbit missions. Major uncertainties still exist for space

exposure in high altitude, high inclination, geostationary orbits, in connection with solar effects

and that of shielding. Data from active detectors flown in Spacelabs 1 and 2 suggest that a variety

of phenomena must be understood before the effects of long-term exposure at the space-station

type of orbit and shielding can be properly assessed.

Benton, E. V. and Parnell, T. A. (1988) Space radiation dosimetry on U. S. and

Soviet manned missions. In: Terrestrial Space Radiation and Its Biological

Effects, Proceedings of the NATO Advanced Study Institute, Vol. 154, eds. P.

D. McCormack, C. E. Swenberg, and H. Buecker. New York: Plenum Press,

pp. 729-794.

U.S. spacecraft, Soviet spacecraft, Low Earth-orbit, Plastic nuclear track detectors,

Thermoluminescent dosimeters, CR-39, Polycarbonate, Cellulose-nitrate sheets, Shuttle,

Spacelab, Shielding

Radiation measurements obtained on board U.S. and Soviet spacecraft are presented and

discussed. A considerable amount of data has now been collected and analyzed from

measurements with a variety of detector types in low Earth orbit. The objectives of these

measurements have been to investigate the dose and LET spectra within the complex shielding of

large spacecraft. The shielding modifies the external radiation (trapped protons, electrons, cosmic

ray nuclei) which, in turn, is quite dependent on orbital parameters (altitude, inclination). For

manned flights, these measurements provide a crew exposure record and a data base for future

spacecraft design and flight planning. For the scientific community, they provide useful

information for planning and analyzing data from experiments with high sensitivity to radiation. In

this paper, results of measurements by both passive and active detectors are described. High-LET

spectra measurements were obtained by means of plastic nuclear track detectors (PNTDs) while

= 73
thermoluminescentdosimeters(TLDs)measuredthedose.A few flights cardedactivedetectors--

tissueequivalention chambers(TEICs),particle spectrometers(generailyto measurethe LET

distribution),andparticleratecounters.On someflights, thermalandepithermalneutronswere

measuredwith the useof fission foils, andmetalsamplesanalyzedby gammaray spectroscopy

measuredlow levelsof severalactivationlines. PNTDsconsistingof different combinationsof

CR-39, polycarbonate,and cellulose-nitratesheetshaveproved to be an effective meansof

measuringthehigh-LET spectra.To date,they havebeenusedon all the SpaceShuttleflights,

including Spacelabs1 and2, andtheearliermissionsof theGemini,Apollo, andSkylabseries.

The assemblyof varioustypesof detectors,especiallythe largenumbersdeployedin thecrew

compartments,modules,accesstunnels,andpalletsof Spacelabs1and2, haveprovidedthemost

comprehensivemappingyet availableof theradiationenvironmentof a large spacecraftin low

Earthorbit. Theydemonstratetheefficiencyandadvantagesof coordinatedmeasurementswith

passiveand active detectors. The dosimetricresultsaccumulatedfor over twenty-five years

indicatethedifficulty of accuratelypredictingthetotalpictureof radiationphenomenaasit will be

encounteredby spacestationcrews and other future missions. Understandingthe effectsof

differenttypesandconfigurationsof shieldingis alsoof particularimportance.Detailedresultsof

themeasurementsandcomparisonwithcalculatedvaluesaredescribed.

Curtis, S. B., Atwell, W., Beever, R., and Hardy, A. (1986) Radiation

environments and absorbed dose estimations on manned space missions.

Advances in Space Research 6(11): 269-274.

Radiation risk, Radiation environment, Space mission scenarios, Space Station, Geosynchronous

orbit, Lunar mission, Low Earth-orbit

In order to make an assessment of radiation risk during manned missions in space, it is necessary

first to have as accurate an estimation as possible of the radiation environment within the spacecraft

to which the astronauts will be exposed. Then, with this knowledge and the inclusion of body

self-shielding, estimations can be made of absorbed doses for various body organs (skin, eye,

blood-forming organs, etc.). A review is presented of our present knowledge of the radiation

environments and absorbed doses expected for several space mission scenarios selected for our

development of the new radiation protection guidelines. The scenarios selected are a 90-day

mission at an altitude (450 km) and orbital inclinations (28.5 °, 57" and 90`') appropriate for

NASA's Space Station, a 15-day sortie to geosynchronous orbit, and a 90-day lunar mission. All

scenarios chosen yielded dose equivalents between five and ten rem to the blood-forming organs if

no large solar particle event were encountered. Such particle events could add considerable

exposure particularly to the skin and eye for all scenarios except the one at 28.5 ° orbital inclination.

Dudkin, V. E., Potapov, Y. V., Akopova, A. B., Melkumyan, L. V., Benton, E.

V., and Frank, A. L. (1990) Differential neutron energy spectra measured on

spacecraft in low Earth orbit. Nucl Tracks Radiat Meas 17(2): 87-91 (Int J

Radiat Appl Instrum, Part D).

Neutrons, Plastic nuclear track detectors, Photographic emulsions, Radiation dose, Fission foils

Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were

used. In the first method, alpha-particles emitted from the 6Li(n, alpha)T reaction are detected with

the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons.

Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are

recorded by nuclear photographic emulsions (NPE). The results of measurements on board

various satellites are presented. The neutron flux density does not appear to correlate clearly with

orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while

74
thefluxes insidethe satellitesare15-20%higherthanthoseontheoutside.Estimatesshowthat

theneutroncontributionto thetotalequivalentradiationdosereaches20-30%.

Letaw, J. R., Silberberg, R., and Tsao, C. H. (1987) Radiation hazards on

space missions. Nature 330:709-710 (commentary).

Shielding, Space exploration

On the ambitious forays into space currently being contemplated, astronauts would encounter

unfamiliar radiation environments. The risk of undue exposure would be diminished by spacecraft

shielding.

Letaw, J. R., Silberberg, R., and Tsao, C. H. (1988) Galactic cosmic radiation

doses to astronauts outside the magnetosphere. In: Terrestrial Space Radiation

and Its Biological Effects, Proceedings of the NATO Advanced Study Institute,

Vol. 154, Eds. P. D. McCormack, C. E. Swenberg, and H. Bucker. New York:

Plenum Press, pp. 663-673.

GCR, Dose equivalent, Shielding, Space Station, HZE, Radiation dosimeter

The dose and dose equivalent from galactic cosmic radiation outside the magnetosphere have been

computed. Each of the principal radiation components were considered. These include primary

cosmic rays, spallation fragments of the heavy ions, and secondary products (protons, neutrons,

alphas, and recoil nuclei) from interactions in tissue. Conventional quality factors were used in

converting from dose to dose equivalent.

Three mission environments have been considered: free space, the lunar surface, and the Martian

surface. The annual dose equivalents to the blood-forming organs in these environments are

approximately 500 mSv, 250 mSv, and 120 mSv, respectively (1 mSv - 0.1 rem). The dose on

the lunar surface is one-half of free space because there is only a single hemisphere of exposure.

The dose on the Martian surface is half again the dose on the moon because of the shielding

provided by a thin carbon dioxide atmosphere.

Dose versus aluminum shielding thickness functions have been computed for the free space

exposure. Galactic cosmic radiation is energetic and highly penetrating. 30 cm of aluminum

shielding reduces the dose equivalent 25% to 40% (depending on the phase of the solar cycle).

Aiming for conformity with the draft NCRP annual dose limit for Space Station crew members,

which is 500 mSv yr -1, we recommend 7.5 cm of aluminum shielding in all habitable areas of

spacecraft designed for long-duration missions outside Earth's magnetosphere. This shielding

thickness reduces the galactic cosmic ray dose and diminishes the risk to astronauts from energetic

particl e events.

Letaw, J. R., Silberberg, R., and Tsao, C. H. (1989) Radiation hazards on space

missions outside the magnetosphere. Advances in Space Research 9(10): 285-

291.

Dose equivalent, Shielding materials, Doses, Solar energetic particles

Future space missions outside the magnetosphere will subject astronauts to a hostile and unfamiliar

radiation environment. An annual dose equivalent to the blood-forming organs (BFOs) of -0.5

Sv is expected, mostly from heavy ions in the galactic cosmic radiation. On long-duration

missions, an anomalously large solar energetic particle event may occur. Such an event can expose

astronauts to up to -25 Gy (skin dose) and up to -2 Sv (BFO dose) with no shielding. The

75
anticipatedradiationexposuremaynecessitatespacecraftdesignconcessionsandsomerestriction

of missionactivities. In thispaperwediscussourmodelcalculationsof radiationdosesin several

exo-magnetosphericenvironments.Specificradiationshieldingstrategiesarediscussed.A new

calculationof aluminumequivalentsof potentialspacecraftshieldingmaterialsdemonstratesthe

importanceof low-atomic-masspeciesfor protectionfromgalacticcosmicradiation.

Letaw, J. R., Silberberg, R., Tsao, C. H., and Benton, E. V. (1989) Model

analysis of Space Shuttle dosimetry data. Advances in Space Research 9(10):

257-260.

Plastic track detector, Shuttle, STS-51F, STS-51J, STS-61C, Radiation dosimeter

An extensive model analysis of plastic track detector measurements of high-LET particles on the

Space Shuttle has been performed. Three shuttle flights, STS-51F (low-altitude, high-inclination),

STS-51J (high-altitude, low-inclination), and STS-61C (low-altitude, low-inclination), are

considered. The model includes contributions from trapped protons and galactic cosmic radiation

as well as target secondary particles. Target secondaries, expected to be of importance in thickly

shielded space environments, are found to be a significant component of the measured LET (linear

energy transfer) spectra.

Parnell, T. A., Watts, J. W., Jr., Fishman, G. J., Benton, E. V., Frank, A. L.,

and Gregory, J. C. (1986) The measured radiation environment within Spacelabs

1 and 2 and comparison with predictions. Advances in Space Research 6(12):

125-134.

Spacelab, Passive radiation detectors, Active radiation detectors, Thermoluminescent dosimeters,

Ion chambers, South Atlantic Anomaly, Proportional counters

To measure the radiation environment in the Spacelab (SL) module and on the pallet, a set of

passive and active radiation detectors was flown as part of the Verification Flight Instrumentation

(VFI). SL1 carded 4 passive and 2 active detector packages which, with the data from the 26

passive detectors of Experiment INS006, provided a comprehensive survey of the radiation

environment within the spacecraft. SL2 carried 2 passive VFI units on the pallet.

Thermoluminescent dosimeters (TLDs) measured the low linear energy transfer (LET) dose

component; the HZE fluence and LET spectra were mapped with CR-39 track detectors; thermal

and epithermal neutrons were measured with the use of fission foils; metal samples analyzed by

gamma ray spectroscopy measured low levels of several activation lines. The TLDs registered

from 97 to 143 mrad in the SL1 module. Dose equivalents of 330-__70 mrem in the SL1 module

and 537+37 mrem on the SL2 pallet were measured. The active units in the SL1 module each

contained an integrating tissue-equivalent ion chamber and two differently-shielded xenon-filled

proportional counters. The ion chambers accumulated 125 and 128 mrads for the mission with 17

and 12 mrads accumulated during passages through the South Atlantic Anomaly (SAA). The

proportional counter rates (-1 cps at sea level) were -100 cps in the middle of the SAA (mostly

protons), -35 cps at large geomagnetic latitudes (cosmic rays), and -100 cps in the South Horn of

the electron belts (mostly bremsstrahlung). Detailed results of the measurements and comparison

with calculated values are described.

Richmond, R. G., Badhwar, G. D., Cash, B., and Atwell, W. (1987)

Measurement of differential proton spectra onboard the Space Shuttle using a

thermoluminescent dosimetry system. Nuclear Instruments and Methods in

Physics Research A256: 393-397.

Shuttle, Thermoluminescent dosimeters, Low-inclination orbits, Low Earth-orbit

76
An experimentaltechniquethatpermitstheextractionof orbit-averaged, differential energy spectra

of trapped radiation belt protons using simple passive detectors is described. An inversion

technique is used for the data analysis. The basic principle of the described system is the

measurement of the energy deposited in six thermoluminescent (TLD) detector assemblies behind

various spherical absorbers. The technique has been applied to a detector assembly flown on four

Shuttle flights. Although severe restraints were placed on the flight package, the differential

energy spectra derived from these measurements are in good agreement with analytical results

using a modified trapped proton environment model. The technique shows good promise for

measuring the spectra in low inclination orbits where the flux of high energy galactic cosmic ray

protons is small. Modifications to the detector assembly to improve the accuracy and to extend the

range of the system to higher energies are suggested.

Simonsen, L. C., Nealy, J. E., Townsend, L. W., and Wilson J. W. (1990)

Space radiation dose estimates on the surface of Mars. Journal of Spacecraft and

Rockets 27: 353-354.

Radiation dose, Mars, Galactic cosmic rays, Solar energetic particles

A future goal of the U.S. space program is a commitment to the manned exploration and habitation

of Mars. An important consideration of such missions is the exposure of crewmembers to the

damaging effects of ionizing radiation from high-energy galactic cosmic ray fluxes and solar proton

flares. The crew will encounter the most harmful radiation environment in transit to Mars from

which they must be adequately protected. However, once on the planet's surface, the Martian

environment should provide a significant amount of protection from free-space radiation fluxes.

In the current Mars scenario descriptions, the crew flight time to Mars is estimated to be anywhere

from 7 months to over a year each way, with stay times on the surface ranging from 20 days to 2

years. To maintain dose levels below established astronaut limits, dose estimates need to be

determined for the entire mission length. With extended crew durations on the surface anticipated,

the characterization of the Mars radiation environment is important in assessing all radiation

protection requirements. This synopsis focuses on the probable doses incurred by surface

inhabitants from the transport of galactic cosmic rays and solar protons through the Mars

atmosphere.

Townsend, L. W., Nealy, J. E., Wilson, J. W., and Atwell, W. (1989) Large

solar flare radiation shielding requirements for manned interplanetary missions.

Journal of Spacecraft and Rockets 26: 126-128.

Solar flare, Radiation shielding, Transport codes, Dose equivalent, Organic polymers

As the 21 st century approaches, there is an ever-increasing interest in launching manned missions

to Mars. A major concern to mission planners is exposure of the flight crews to highly penetrating

and damaging space radiations. Beyond the protective covering of the Earth's magnetosphere, the

two main sources of these radiations are galactic cosmic rays and solar particle events. Preliminary

analyses of potential exposures from galactic cosmic rays (GCRs) were presented elsewhere. In

this Note, estimates of shielding thicknesses required to protect astronauts on interplanetary

missions from the effects of large solar flare events are presented. The calculations use integral

proton fluences for the February 1956, November 1960, and August 1972 solar particle events as

inputs into the NASA Langley Research Center nucleon transport code BRYNTRN. This

deterministic computer code transports primary protons and secondary protons and neutrons

through any number of layers of target material of arbitrary thickness and composition.

Contributions from target nucleus breakup (fragmentation) and recoil are also included. The

results for each flare are presented as estimates of dose equivalent [in units of roentgen equivalent

77
man (rem)] to the skin, eye, and blood-forming organs(BFO) behind various thicknessesof

aluminumshielding.TheseresultsindicatethattheFebruary1956eventwasthemostpenetrating;

however,the August 1972event,the largesteverrecorded,could havebeenmission-or lifethreateningfor thinly shielded(<5 g/cm2) spacecraft. Also presentedare estimatesof the

thicknessesof water shielding required to reduce the BFO dose equivalent to currently

recommendedastronautexposurelimits. Theselatterresultssuggesthatorganicpolymers,similar

to water,appearto bea muchmoredesirableshieldingmaterialthanaluminum.

Townsend, L. W., Wilson, J. W., and Cucinotta, F. A. (1987) A

parameterization for quality factor as a function of linear energy transfer.

Physics 5: 531-532.

simple

Health

Quality factors

In a recent report of a Joint Task Group of the International Commission on Radiological

Protection (ICRP) and the International Commission on Radiation Units and Measurements

(ICRU) to these same organizations (ICRU86), the problem of radiation quality and its quantitative

treatment in protection studies was addressed. The conclusions of the report, although intended as

input to these two commissions and not as recommendations from them, have nevertheless been

endorsed in principle by the ICRU and subsequently published. The ICRP is currently reviewing

its general recommendations about Q, the radiation quality factor, but has not yet altered them

(ICR486).

Wilson, J. W., Shinn, J. L., and Townsend, L. W. (1990) Nuclear reaction

effects in conventional risk assessment for energetic ion exposure. Health

Physics 58: 749-752.

Quality factors, Nuclear reaction effects

Biological risks are related to the local energy deposited by the passage of energetic ions. The

ionization energy loss is of the order of 0.2 Z 2 keVAt for a passing high-energy ion of charge Z.

Some of the ions produce nuclear reactions in which 10 to 100 MeV are released (per event) locally

as secondary nuclear fragments. The average energy transfer rate is 0.05 A 2/3 keV/l.t, where A is

the ions' atomic weight. Since the quality factor of the fragments is usually taken as 20, the risk

associated with direct atomic ionization is on the order of risk associated with the nuclear events for

incident low-charge ions (Z<5), while the risk is dominated by the direct ionization for high charge

(Z>>5). At a sufficiently low energy, the direct ionization always dominates the biological risk

independent of the ion charge and mass. In the present note, we quantify these various

contributions to biological risk using quality factors presently in force (ICRP 1977) and evaluate

the effects of newly proposed quality factors (ICRU 1986).

3.2. SPACE FLIGHT RADIATION HEALTH PHYSICS

REPORTS/MEETINGS

Atwell, W. (1989) Space radiation exposures to critical body organs for low

Earth orbit missions. Invited paper presented at the 60th Annual Meeting of the

Aerospace Medical Association, Washington DC, May 7-11, 1989.

Anatomical man models, Organ dose equivalent

m

78

==7
--4

The geomagnetically trapped, galactic cosmic, and solar particle event radiation environments are

the three major sources of naturally occurring space radiation exposure to astronauts in low Earth

orbit. The degree of radiation exposure is dependent on mission altitude, inclination and duration,

spacecraft and spacesuit shielding, and solar cycle effects. Using a computerized anatomical man

model, critical body organ dose equivalent data are presented for several mission scenarios. These

results are compared with the current NASA crew exposure limits.

Atwell, W. (1990) Astronaut exposure to space radiation: Space Shuttle

experience. Invited paper presented at the 20th Intersociety Conference on

Environmental Systems (ICES), Williamsburg, VA, July 9-12, 1990. SAE

Technical Paper Series #901342.

Shuttle, Exposure estimates, Radiation dosimeter

Space Shuttle astronauts are exposed to both the "trapped" and the galactic cosmic radiation

environments. In addition, the sun periodically emits high-energy particles that could pose a

serious threat to flight crews. NASA adheres to federal regulations and recommended exposure

limits for radiation protection and has established a radiological health and risk assessment

program. Using models of the space radiation environment, a Shuttle shielding model, and an

antomical human model, crew exposure estimates are made for each Shuttle flight. The various

models are reviewed. Dosimeters are worn by each astronaut and are flown at several fixed

locations to obtain in-flight measurements. The dosimetry complement is discussed in detail. A

comparison between the pre-mission calculations and measurements is presented. Extrapolation of

Shuttle experience to long-duration exposure is explored.

Atwell, W., Beever, E. R., and Hardy, A. C. (1987) Radiation shielding

analysis for the Space Shuttle Program: An overview. Proceedings, Theory and

Practices in Radiation Protection and Shielding, American Nuclear Society,

Knoxville, TN, April 22-24, 1987, pp. 271.280 (ISBN: 0-89448-132-0).

Dose calculations, Shielding models, Shuttle dosimeter

An overview of the capabilities and methodologies utilized at the National Aeronautics and Space

Administration (NASA)/Johnson Space Center (JSC) to perform pre-mission and real-time space

radiation dose calculations for the Space Shuttle program is presented. The three sources of

naturally occurring space radiation, a) geomagnetically trapped (Van Allen belts) protons and

electrons, b) galactic cosmic radiation (GCR), and c) solar flare particles (predominantly protons),

are discussed. Analytical tools, such as environment models, spacecraft shielding models and

radiation dose computer programs, are also discussed. Pre-mission radiation dose calculations are

compared with onboard Space Shuttle dosimeter measurements.

Atwell, W., Hardy, A. C., Beever, E. R., Richmond, R. G., and Cash, B. L.

(1987) A comparison of space radiation dose calculations with onboard dosimeter

measurements for Space Shuttle missions. Presented at the NASA Workshop,

High Energy Accelerator and Space Radiation, Berkeley, CA, February 17-19,

1987.

Shielding model, Passive dosimeters, Active dosimeters, Thermoluminescent dosimeters,

Shielding measurements

Utilizing an analytical shielding model of the Space Shuttle and the natural space radiation

environment models, pre-mission dose calculations are made prior to each Shuttle mission.

Passive dosimeters are flown at six fixed locations in the Shuttle, and active dosimeters are

onboard to support extra-vehicular activity and contingency situations for every flight. In addition,

79
eachcrewmanwearsapassivethermoluminescentdosimeter.Thedosimetersarereadout shortly

afterlanding. Thecomparisonof pre-missioncalculationswith themeasurementsis discussedin

detail. Resultsindicateagoodagreementbetweenthecalculationsandmeasurementsandprovide

confidencein theshieldingandenvironmentmodels.

Golightly, M. J., Atwell, W., Hardy, A. C., Hardy, K., Quam, W., and Riehl,

K. (1990) Time-resolved dose and dose equivalent measurements during high

inclination shuttle missions made with the U.S. Air Force radiation monitoring

equipment (RME)-III. Abstract presented at the 61st Annual Meeting of the

Aerospace Medical Association, New Orleans, LA, May 13-17, 1990.

Radiation dosimetry, RME-III, Shuttle

INTRODUCTION. Routine ionizing radiation dosimetry aboard the U.S. Space Shuttle is done

with simple passive and active dosimeters. A significant improvement is achieved by using a

tissue-equivalent instrument that provides time-correlated radiation quality, integral dose and

instantaneous dose rate information. METHODS. The RME-III is a portable active dosimeter

developed by EG&G for the U.S. Air Force. It features a 3-channel tissue-equivalent proportional

counter that measures particle fluence and dose and computes dose equivalent at operator-selected

time intervals. The data and time of each reading are stored in memory modules for future

analysis. The RME-III was flown in a middeck locker aboard Shuttle missions STS-27 and STS28; these missions featured 57 ° inclination orbits at altitudes of 242 nm and 160 nm, respectively.

Time-resolved measurements were correlated with spacecraft position. RESULTS. 102 hours and

116 hours of data, measured at 10-second intervals, were collected during STS-27 and STS-28,

respectively. Total dose and dose equivalent measured were 1580 gtGy and 2473 gtSv (STS-27)

and 636 gtGy and 1094 I.tSv (STS-28). The dose was separated into trapped proton, Galactic

Cosmic Radiation (GCR), and solar particle event (SPE) proton components. The dose/dose

equivalent measured during STS-27 was dominated by trapped protons, while measurements from

STS-28 were dominated by GCR. Additionally, the dose inside the crew module from the SPE

that occurred during STS-28 was determined. CONCLUSIONS. The RME represents a

significant improvement in manned space flight radiation dosimetry; time-resolved data permits

separation of the dose into major sources of exposure. A similar measurement of source terms is

not possible with current Shuttle dosimetry.

Hardy, K. A., Atwell, W., Golightly, M. J., Hardy, A. C., Quam, W. (1990)

Real-time and time-resolved dose measurements on Space Shuttle missions with

the radiation monitoring equipment (RME)-HI. Presented at the 35th Annual

Meeting of the Health Physics Society, Anaheim, CA, June 24-28, 1990 (Paper

No. TAM-B9).

Active dosimeters, Shuttle, Tissue equivalent proportional counter, Doses, Dose equivalent

The RME-III is a self-contained portable active dosimeter system developed by EG&G for the US

Air Force and modified for use on the Space Shuttle. It features a three-channel tissue equivalent

proportional counter that measures particle fluence and computes dose and dose equivalent at

operator-selected time intervals. The total accumulated dose and dose equivalent are displayed real

time on a liquid crystal display while the data and time of the interval dose readings are stored in

memory modules for future analysis. Analysis of the time-resolved data permits correlation of the

radiation exposure with Shuttle position and altitude.

The RME-III was flown in a middeck locker aboard STS-27, STS-28, and STS-33. STS-27 and

STS-28 featured 57 ° inclination circular orbits at 448 km (242 NM) and 296 km (160 NM),

respectively, while STS-33 flew at a 28.5 ° inclination elliptical orbit (perigee: 231 km [125 NM];

apogee: 563 km [304 NM]). Total dose and dose equivalent measured were 1580 i.tGy/2473 I.tSv

80

r
on STS-27, 636 I.tGy/1094 I.tSv on STS-28, and 3706 t.tGy/4827 I.tSv on STS-33. Analysis of

the time-resolved data indicated that doses on STS-27 and STS-33 were dominated by the trapped

Van Allen Belt protons, while the dose on STS-28 was primarily due to galactic cosmic rays. A

solar proton event also occurred on STS-28 that was measured with the RME-IH. Time-resolved

data from each mission are presented.

Keith, J. E. and Richmond, R. G. (1987) Neutrons in space: Measurements

aboard the Space Shuttle. Proceedings, theory and practices in radiation

protection and shielding, American Nuclear Society, Knoxville, TN, April 22-24,

1987, pp. 281-286 (ISBN 0-89448-132-0).

Neutron flux, Space Shuttle, Shielding measurements

One of the most complex and challenging problems of measuring radiation levels in manned

spacecraft has been the characterization of the neutron flux within the vehicle. Recently it has been

suggested that the quality factor for neutrons should be raised, resulting in larger dose-equivalents.

A simple, initial experiment to measure the time-averaged neutron fluxes within the Space Shuttle

has been completed. This paper describes the technique, reports the results, evaluates the

necessary assumptions, and discusses the implications.

Konradi, A., Richmond, R. G., Hardy, A. C., and Atwell, W. (1986) Space

Shuttle dosimeters as indicators of long-term inner belt stability. Abstract

presented at the Fall Meeting of the American Geophysical Union, San Francisco,

CA, December 1986. Eos 67: 1154.

Thermoluminescent dosimeter, Shuttle, Radiation dosimeter

Between 1983 and 1986 thermoluminescent dosimeters were carded on 20 shuttle flights at a

variety of orbital altitudes corresponding to the region of the atmospheric cutoff of the South

Atlantic Anomaly. Shielded by the Space Shuttle structure, these dosimeters respond to any

penetrating inner belt protons and galactic cosmic rays. The measured orbit averaged dose was

compared to dose calculations based on radiation belt models for solar maximum and solar

minimum derived from data centered around 1970 and 1964, respectively. The results show that

after two solar cycles the observations agree with the predictions of the solar minimum model to

better than a factor of two. This difference falls within the accuracy of the model.

Richmond, R. G., Badhwar, G. D., Cash, B. L., and Atwell, W. (1987)

Measurement of orbit-averaged, differential energy spectra of trapped protons

using thermoluminescent dosimeter techniques. Proceedings, Theory and

Practices in Radiation Protection and Shielding, American Nuclear Society,

Knoxville, TN, April 22-24, 1987, pp. 264-270 (ISBN: 0-89448-132-0).

Thermoluminescent dosimeters, Shuttle, Low-inclination orbits, Low Earth-orbit

A unique detector assembly consisting of six thermoluminescent detector (TLD) stacks under

different thicknesses of spherical absorbers, has been flown on four Shuttle flights. The TLD

detectors provide a measure of the total energy deposited by the charged particles (protons) that

penetrate the absorbers. An inversion technique has been developed to extract the orbit-averaged,

differential energy spectra of the trapped radiation belt protons from these measurements. For lowinclination orbits, the extracted spectra are in good agreement with the spectra calculated using

trapped radiation models. The technique offers good promise for estimating differential proton

spectra on a routine basis inside the Shuttle for low-inclination missions. The system/technique is

not recommended for higher (greater than 30 degrees) inclination missions for spacecraft altitudes

less than 300 nm. The reasons are discussed.

81
Shinn, J. L., Wilson, J. W., and Nealy, J. E. (1990) Reliability of the

Equivalent Sphere Model in Blood-Forming Organ Dose Estimation. NASA

Technical Memorandum 4178.

Dose equivalent, Sphere model, Mars

The radiation dose equivalents to blood-forming organs (BFOs) of astronauts on the Martian

surface due to major solar flare events are calculated using the detailed body geometry of Langley

and Billings. The solar flare spectra of February 1956, November 1960, and August 1972 events

are employed instead of the idealized Webber form. The detailed geometry results are compared

with those based on the 5-cm sphere model, which has been used often in the past to approximate

BFO dose and dose equivalent. Larger discrepancies are found for the later two events, possibly

due to the lower numbers of highly penetrating protons. It is concluded that the 5-cm sphere

model is not suitable for quantitative use in connection with future NASA deep-space, longduration mission shield design studies.

Silberberg, R., Tsao, C. H., Adams, J. H., Jr., and Letaw, J. R. (1989) Highenergy radiation environment during manned space flights. Presented at the

Conference on High Energy Radiation Background in Space (CHERBS 87),

Sanibel Island, FL, November 3-5, 1987. AIP Conference Proceedings No. 186,

eds. A. C. Rester, Jr. and J. I. Trombka (American Institute of Physics, New

York, 1989), pp. 146-158.

Galatic cosmic rays, Long-duration space missions, Shielding

Radiation doses from cosmic rays on long-duration space missions, at solar minimum, with 4

g/cm 2 A1 shielding and 5 g/cm 2 tissue self-shielding exceed by a factor of about 60 the allowable

dose of 0.5 rem/year to the general public and by a factor of about 6 the dose of 5 rem/year

allowable to radiation workers. The annual dose of 30 rem nearly equals the allowable dose to a

few volunteer astronauts which is 40 rem/year. Rare solar flare particle events would deliver doses

of about 200 to 300 rem, in a period of about one day (like the 1956 and 1972 flares) for the above

conditions of shielding. These doses are lethal to about 20 percent and 40 percent of the recipients,

respectively.

We shall present here detailed flux and dose calculations wilh shielding, using the fluxes and

energy spectra of all the nuclei from hydrogen to iron, nuclear spallation cross sections, and our

NRL propagation code for cosmic ray nuclei, and the HETC and MCNP codes developed at Oak

Ridge for protons, mesons and neutrons. Radiation quality factors, appropriate to the rate of

ionization of various cosmic-ray and secondary nuclei and of nuclear recoils, will be included in

the dose calculations.

Our calculations show that both the cosmic-ray and solar particle doses can be brought down to

acceptable levels. For thin shielding, the contribution of heavy nuclei to the dose dominates since

the rate of ionization is proportional to Z 2, and for heavy ions, the quality factor Q=20. For thick

shielding, the dose from neutron-generated nuclear recoils dominates.

Simonsen, L. C., Nealy, J. E., Townsend, L. W., and Wilson, J. W. (1990)

Radiation exposure for manned Mars surface missions. NASA Technical Paper

2979.

Mars, BRYNTRN, Galactic cosmic rays, Solar energetic particles, Transport codes

i :

82
TheLangleycosmic ray transport code and the Langley nucleon transport code (BRYNTRN) are

used to quantify the transport and attenuation of galactic cosmic rays (GCR) and solar proton flares

through the Martian atmosphere. Surface doses are estimated using both a low-density and a highdensity carbon dioxide model of the atmosphere which, in the vertical direction, provide a total of

16 g/cm 2 and 22 g/cm 2 of protection, respectively. At the Martian surface during the solar

minimum cycle, a blood-forming organ (BFO) dose equivalent of 10.5 to 12 rem/yr due to galactic

cosmic ray transport and attenuation is calculated. Estimates of the BFO dose equivalents that

would have been incurred from the three large solar flare events of August 1972, November 1960,

and February 1956 are also calculated at the surface. Results indicate surface BFO dose

equivalents of approximately 2-5, 5-7, and 8-10 rem per event, respectively. Doses are also

estimated at altitudes up to 12 km above the surface where the atmosphere will provide less total

protection.

Townsend, L. W., Nealy, J. E., Wilson, J. W., and Simonsen, L. C. (1990)

Estimates of galactic cosmic ray shielding requirements during solar minimum.

NASA Technical Memorandum 4167.

Galactic cosmic rays, Transport codes, Shielding, Doses, Dose equivalent

Estimates of radiation risk from galactic cosmic rays are presented for manned interplanetary

missions. The calculations use the Naval Research Laboratory cosmic ray spectrum model as input

into the Langley Research Center galactic cosmic ray transport code. This code, which transports

both heavy ions and nucleons, can be used with any number of layers of target material, consisting

of up to five arbitrary constituents per layer. Calculated galactic cosmic ray fluxes, doses, and

dose equivalents behind various thicknesses of aluminum, water, and liquid hydrogen shielding

are presented for the solar minimum period. Estimates of risk to the skin and blood-forming

organs (BFO) are made using 0-cm and 5-cm-depth dose and dose equivalent values, respectively,

for water. These results indicate that at least 3.5 g/cm 2 (3.5 cm) of water, or 6.5 g/cm 2 (2.4 cm)

of aluminum, or 1.0 g/cm 2 (14 cm) of liquid hydrogen shielding is required to reduce the annual

exposure below the currently recommended BFO limit of 0.5 Sv. Because of large uncertainties in

fragmentation parameters and the input cosmic ray spectrum, these exposure estimates may be

uncertain by as much as a factor of 2 or more. The effects of these potential exposure uncertainties

or shield thickness requirements are analyzed.

Townsend, L. W., Wilson, J. W., and Nealy, J. E. (1989) Space radiation

shielding strategies and requirements for deep space missions. Paper presented at

the 19th Intersociety Conference on Environmental Systems (ICES), San Diego,

CA, July 24-26, 1989. SAE Technical Paper Series #891433.

Space radiation, Shielding strategies, Dose equivalent

The ultimate limitation to manned exploration of the solar system will likely be cumulative

exposure of the crews to penetrating space radiations. The two major sources of these radiations

during deep-space missions are solar particle events (flares) and galactic cosmic rays. Methods to

estimate crew exposures and to evaluate concomitant shield requirements for these radiation

sources are currently under development. Consisting of deterministic space radiation transport

computer codes and accurate models of their nuclear interaction inputs, these calculational tools are

employed to estimate the composition and thicknesses of candidate shield materials required for

spacecraft equipment and crew protection. In this paper, the current status of model and code

development is summarized, preliminary estimates of deep-space shield requirements are

presented, and an assessment of radiation protection as a potential "showstopper" for manned

deep-space missions will be made.

83
3.3. INTER- AND INTRASPECIES EXTRAPOLATION

J..OA2RIS I 

Dalrymple, G. V., Nagle, W. A., Moss, A. J., Cavin, L. A., Broadwater, J. R.,

McGuire, E. L., Eason, C. S., Mitchell, J. C., Hardy, K. A., Wood, D. H.,

Salmon, Y. A., and Yochmowitz, M. G. (1989) The protons of space and brain

tumors: 1. Clinical and dosimetric considerations. In: High Energy Radiation

Background in Space, Eds. A. C. Rester, Jr. and J. I. Trombka. New York:

American Institute of Physics, pp. 407-411.

Rhesus monkeys, Protons, RBE, Glioblastoma, Brain tumors, Radiation therapy

Almost 25 years ago a large group of rhesus monkeys were irradiated with protons (32-2300

MeV). The experiments were designed: (1) to estimate the RBE of protons per se, and (2) to

provide some estimate of the hazards of the radiation environment of space. The initial results

showed the RBE to be about 1.0 for acute radiation effects (mortality, hematologic changes, etc.).

The colony has been maintained at Brooks AFB, TX, since irradiation. The survivors of 55 MeV

proton irradiation have developed a very high incidence of Glioblastoma multiforme, a highly

malignant primary brain tumor. These tumors appeared 1-20 years after surface doses of 400-800

rads. Reconstruction of the dosimetry suggests that some areas within the brain may have received

doses of 1500-2500 rads. More than 30 radiation-induced Glioblastomas have been reported in

human patients who had received therapeutic head irradiation. The radiation doses required to

induce Glioblastoma were of the same order of magnitude as required to induce Glioblastoma in

the Rhesus monkey.

Cox, A. B., Lee, A. C., and Lett, J. T. (1988) Delayed effects of proton

irradiation in the lens and integument: a primate model. In: Terrestrial Space

Radiation and Its Biological Effects, Proceedings of the NATO Advanced Study

Institute, Vol. 154, eds. P. D. McCormack, C. E. Swenberg, and H. Bucker.

New York: Plenum Press, pp. 415-422.

Rhesus monkeys, Chronic Radiation Colony, Protons, Glioblastoma, Endometriosis

In 1964, the NASA Manned Spacecraft Center Biomedical Research Office and the USAF School

of Aerospace Medicine inaugurated an experiment in Space Radiation Biology which now is

approaching completion. Rhesus monkeys were irradiated "whole body" with X-rays (2 MeV),

individual animals that received low and intermediate doses have been monitored for over 20 years,

and those animals, together with age-matched controls, are known as the Chronic Radiation

Colony (CRC). The CRC has provided exceptional information on late radiation effects of protons

on primates. Highlights of the data from the colony include documentation of a high incidence of

brain tumors (glioblastomas) in monkeys exposed to nominal surface doses of 55 MeV protons,

ranging from 4.00 to 8.00 Gray (e.g., Wood et al. 1986 a and b). Also of interest is a high

frequency of endometriosis in irradiated female (monkeys e.g., Wood et al., 1983). As the CRC

population decreases in size, complete physical examinations of all animals will continue to be

scheduled semiannually. In addition, however, we are looking for signs of more subtle (less

devastating) late radiation damage which might provide insight into the realistic limits of exposure

to be defined for humans participating in future space missions.

84
Lett, J. T., Cox, A. B., and Lee, A. C. (1988) Selected examples of

degenerative late effects caused by particulate radiations in normal tissues. In:

Terrestrial Space Radiation and Its Biological Effects, Proceedings of the NATO

Advanced Study Institute, Vol. 154, Eds. P. D. McCormack, C. E. Swenberg,

and H. Bucker. New York: Plenum Press, pp. 393-413.

Late effects, HZE, Minilesions, Neon, Argon, Iron, Cataractogenesis, Neoplasia

When astronauts undertake lengthy missions in outer space, they will receive extended (chronic)

exposure to a spectrum of cosmic radiations that contains a substantial component of highly

energetic particles, including heavy ions. That aspect of space flight was illustrated by the flickerflash phenomenon observed by "dark-adapted" members of the crews of the lunar (Apollo)

missions. Many of the heavy ions (HZE particles) are so penetrating that attempting to shield

against them through space vehicle design is impractical at the present time. Fluxes of protons can

become a major hazard if astronauts are caught during extravehicular activity (EVA) by the

radiations associated with a major solar flare. To ensure the safety of astronauts and space

workers, a scientific determination is needed of the health risks arising from anticipated exposures

to space radiations during future space missions of long duration. From that information, an

adequate risk/benefit analysis can be formulated. The best risk analysis available currently to

NATO, which arose from the deliberations of subcommittee #75 of the National Council on

Radiation and Protection, is but a step in the process.

Galactic heavy ions will destroy most of the cells traversed directly by their track cores, but in

organized tissues adjacent cells will be exposed to the more sparsely ionizing radiations in the

energy penumbrae surrounding the track cores, and minilesions could occur. Such penumbral

effects could enhance the long-term expression of tissue damage caused by the track cores of heavy

ions since, in general terms, late tissue damage from sparsely ionizing radiations develops more

slowly than that caused by densely ionizing radiations. For example, the volumes of incipient

minilesions could increase over extended periods of time. Significant formation of minilesions

was not anticipated, however, in the ground-based experiments discussed here because they

involved the heavy ions 2°Ne, 4°Ar, 56Fe at relativistic energies, protons of different energies, and

g(X)-photons. The heavy ion 56Fe was included in the studies not simply because it represented a

useful way of providing a level of linear energy transfer (LEToo) near 200 keV/p.m, which is the

anticipated borderline LET,,. for minilesion formation (Todd, 1983), but rather because it is

potentially the most dangerous component of the spectrum of galactic heavy ions in terms of flux

and relative biological effectiveness (RBE) (Silberberg et al., 1984).

Late sequelae resulting from chronic exposure to ionizing radiations long have been a subject of

concern for human health, and poignant illustrations of them are occurring now in the survivors

from the atomic explosions at Hiroshima and Nagasaki. Although neoplastic sequelae currently

represent the most dangerous risks to human health from chronic radiation exposure, late

degenerative, nonmalignant sequelae also present their problems. The responses of normal tissues

in a previously irradiated individual also may influence the outcome of therapies for subsequent

malignancies or other late sequelae. A 20% loss of hair follicles expressed as partial baldness

(alopecia) could be a risk worth taking under certain circumstances, but analogous damage to other

parts of the skin could be more serious if it reduced the efficacy of post-irradiation therapy

(surgery). Furthermore, even success of that treatment could still leave the need for other therapies

to stem further late progressive degeneration in the normal tissues. For whom is there an

acceptable benefit for the risk of a potentially inoperable cataract causing loss of vision late in life?

Significant losses of post-mitotic cells (neurons) from the central nervous system (CNS) surely

would cause an impairment of nervous function that is unacceptable under all but the most extreme

circumstances.

=== 85
i

i

The most plausible experimental method for evaluating radiation risks to humans is to obtain

results from animate or inanimate model systems and "extrapolate them to man"; but then the

question is: how valid are the extrapolations? This simple question is of such overriding

importance that it must be examined in depth here in conjunction with an assessment of late

degenerative effects caused by heavy ions and protons in the normal tissues of model animal

systems. The latter assessment is achieved by the use of selected examples and should be

considered as complementary to treatments of radiation carcinogenesis given elsewhere in this

publication; but the major emphasis will be upon cataractogenesis, because important comparisons

among the cataractogenic responses of higher mammals now are becoming possible.

Lett, J. T., Lee, A. C., Cox, A. B., and Wood, D. H. (1989) Late

cataractogenesis caused by particulate radiations and photons in long-lived

mammalian species. Advances in Space Research 9(10): 325-331.

Late cataractogenesis, New Zealand white rabbits, Beagle dog, Rhesus monkeys, Life-span

Radiation cataractogenesis induced by small acute doses of particulate radiations and photons in the

New Zealand white (NZW) rabbit (Oryctolagus cuniculus), the beagle dog (Canisfamiliaris), and

the Rhesus monkey (Macaca mulatta) is discussed in the context of the use of animal models to

assess the radiation hazards faced by humans during lengthy sojourns in deep space. Attention is

paid to: 1) the importance of life-span studies with long-lived species the above animals have

median lifespans in captivity of 5-7, 13-14, and -25 years, respectively; 2 the magnitudes of

possible dose thresholds for cataractogenesis from sparsely ionizing radiations and the

modifications of those thresholds of the late degenerative phase of the phenomenon.

Nagle, W. A., Moss, A. J., Jr., Dalrymple, G. V., Cox, A. B., Wigle, J. F.,

and Mitchell, J. C. (1989) The protons of space and brain tumors: II. Cellular

and molecular considerations. Presented at the Conference on High Energy

Radiation Background in Space (C_HERBS 87), Sanibel Island, FL, November 3-

5, 1987. American Institute of Physics Conference Proceedings No. 186, eds. A.

C. Rester, Jr. and J. I. Trombka. New York: American Institute of Physics.

Gliomas, Rhesus monkeys, Radiation therapy, Genetic abnormalities, Patient -"

An increased incidence of highly malignant gliomas, termed glioblastoma multiforme, has been

observed in Rhesus monkeys irradiated with 55 MeV protons and in humans treated with

therapeutic irradiation to the head. The results suggest a radiation etiology for these tumors. In

this paper, we review briefly some characteristics of glioma tumors and summarize the genetic

changes associated with malignant gliomas in experimental animals and in humans. The genetic

abnormalities include cytogenetic alterations and changes in the structure and expression of specific

oncogenes. We discuss the potential for these genetic changes to contribute to several putative =

mechanisms leading to aberrant growth stimulation and, ultimately, to tumorigenesis. In addition,

we review briefly some recent data concerning the molecular nature of radiation-induced somatic

cell mutation and oncogene activation and discuss the significance of these results for the radiation

etiology of malignant gliomas. Finally, some implications of these results are discussed in relation

to human radiation exposure in space.

86
3.3. INTER- AND INTRASPECIES EXTRAPOLATION

REPORTS/MEETING S

Cox, A. B. and Lett, J. T. (1987) Quantitation of late radiation damage in the

skin of the Rhesus monkey (abstract). In: Radiation Research, Proceedings of

the 8th International Congress of Radiation Research, Edinburgh, July 19-24,

1987. Eds. E. M. Fielden, J. F. Fowler, J. H. Hendry, and D. Scott. New

York: Taylor & Francis, Volume 1, p. 279.

Late radiation damage, Rhesus monkeys, Stem cell survival, Protons

Estimates of the survival of stem cells in the skin of the rabbit can be obtained by propagating

primary cultures of skin fibroblasts to terminal senescence by use of the Hayflick technique. The

procedure has been extended successfully to monkeys exposed some 20 years ago to protons of

different energies (32-400 MeV) and hence of different penetrations (from approximately 1 cm to

whole body). Examples of stem cell survival from animals irradiated in the range 2-4 Gy will be

presented together with results of experiments designed to simplify the technique and to explore the

effects of different modes of transportation of biopsies between the sampling site and the

laboratory. Results from biopsies selected from different sites on the primate body also will be

discussed. In initial studies, biopsies taken either from the ear or from the thorax of the rhesus

monkey gave similar results. Not only are these studies of importance for evaluating the radiation

risks of space flight, but also the potential of this analytical system for assessing late damage in the

skins of radiotherapy patients is obvious.

Dalrymple, G. V., Nagle, W. A., Moss, A. J. Jr., Wood, D. H., Wigle, J. C.,

Cox, A. B., Salmon, Y. L., Yochmowitz, M. G., and Hardy, K. A. (1988)

Brain tumors induced by protons and x-rays. Abstract presented at the 36th

Annual Meeting of the Radiation Research Society, Philadelphia, PA, April 16-

21, 1988.

Brain tumors, Protons, X-rays, Electrons, RBE, Central nervous system, Leukemia

Twenty-five years ago (1963-1969), some 2000 rhesus monkeys were irradiated with X-rays,

electrons, and protons as part of a study designed to establish the RBE of the radiations of space.

The survivors of the acute effects of 55-MeV protons developed significant numbers of malignant

gliomas. Tumors of this type have not been seen in any other surviving irradiated or control

monkeys. Other types of central nervous system (CNS) tumors (extra-axial meningioma, pituitary

tumor, etc.) have appeared in the higher-energy proton groups.

Review of the reports of radiation therapy-induced brain tumors in patients (1953-1987) indicates

that partial- and whole-head irradiation has the potential to induce a spectrum of CNS tumors

ranging from highly malignant gliomas and sarcomas to benign meningiomas. Whole-head

exposure (as used for acute leukemia) reduced the dose required and shortened the time between

irradiation and tumor appearance, as compared with localized irradiation for lesions such as

pituitary tumor and craniopharyngioma.

We will contrast the tumor induction by protons in monkeys with the human patient experience.

Also, the status of the USAF/VA Collaborative Medical Research Project will be presented; this

effort is concerned with the mechanisms of induction of brain tumors by protons and X-rays.

87
3.4. RADIATION LIMITS AND STANDARDS

JOURNALS

Fry, R. J. M. and Lett, J.T. (1988)

perspective. Nature 335:305-306 [letter].

Radiation hazards in space put in

Galactic cosmic rays, Career risk, Late effects, GCR, Dose equivalent

In this response to the Commentary by Letaw et al. concerning the radiation hazards of space

travel, the authors challenge Letaw's estimates of comparative deposition of energy for galactic

cosmic rays, and estimates of dose equivalents for large solar particle events. NCRP

recommendations on career risk and the differences between acute and stochastic late effects in

developing quality factors are also discussed.

Sinclair, W. K. (1987) Risk, research, and radiation protection. Radiation

Research 112, 191-216

Radiation protection, Late effects, NCRP

Radiation protection concerns the risk of stochastic late effects, especially cancer, and limits on

radiation exposure both occupationally and for the public tend to be based on these risks. The

risks are determined, mainly by expert committees, from the steadily growing information on

exposed human populations, especially the survivors of the atomic bombs dropped in Japan in

1945. Risks of cancer estimated up to the early 1980s were in the range of 1 to 5xl0-2/Sv, but

recent revisions in the dosimetry of the Japanese survivors and additional cycles of epidemiological

information suggest values now probably at the high end of this range. These are likely to require

an increase in the values used for radiation protection. A major problem with risk estimation is mat

data are available only for substantial doses and must be extrapolated down to the low-dose region

of interest in radiation protection. Thus the shape of the dose-response curve is important, and

here we must turn to laboratory research. Of importance are studies involving (1) dose rate, which

affects the response to low-LET radiation and often to high-LET radiation as well; (2) radiation

quality, since the shapes of the dose-response curves for high- and low-LET radiation differ and

thus the RBE, the ratio between them, varies, reaching a maximum value RBEM at low doses; and

(3) modifiers of the carcinogenic response, which either enhance or reduce the effect of a g.iven

dose. Radiation protection depends both on risk information, and especially also on comparisons

with other occupational and public risks, and on research, not only for extrapolations of risk to low

doses but also in areas where human information is lacking such as in effects of radiation quality

and in modifications of response.

Sinclair, W. K. (1990) Quality factor, concepts and issues. Radiation

Protection Dosimetry 31(1/4):355-359.

Quality factors, NCRP, ICRU, Radiation weighting factors, Effective quality factors

Three issues in quality factor assignment arise from Report 40 of the ICRU. These include the

validity of the observation of the high RBE values for high-LET radiation at low doses, the

question of reference radiation, X or g rays, and the 'effective' quality factor in the body compared

with the nominal value of Q. On the first item, high values of RBE at low doses are becoming

generally accepted, see a recent report from the NCRP. On the second, a survey of past

recommendations of both ICRP and NCRP indicate that both organizations have, for protection

purposes, always set all low-LET radiations equal to 1 and accepted the differences (of 2-3 times)

between them. However, for radiobiological purposes high energy g rays are to be preferred as

m

88
thereferenceradiation. Third, the'effective quality factor' or radiation weighting factor WR, for a

variety of whole body exposure circumstances can be estimated from HE = WR S WTDT where the

effective dose equivalent is the summation of tissue weighing factors wT, times the absorbed dose

DT for the organ, multiplied by an average 'radiation weighing factor' WR. WR values can be

calculated for a variety of exposure circumstances and are always less than Q. Maximum values,

for fission neutrons, for example, are not greatly less however. These issues are under further

consideration by the ICRP.

3.4. RADIATION LIMITS AND STANDARDS

REPORTS/MEETINGS

Sinclair, W. K. (1989) Radiation protection policy: implications for the future.

In: Radiation Protection Today: The NCRP at Sixty Years. Proceedings of the

25th Annual Meeting of the National Council on Radiation Protection and

Measurements, Washington, DC, April 5-6, 1989, pp. 343-355.

Radiation standards, Radiation limits, Radiation protection, NCRP

This audience has been treated in the last day and a half to a remarkable survey of progress in

radiation protection, from its early beginnings soon after the discovery of radiation in 1895, to the

present time. A few glimpses of the future have also been provided in the earlier papers in these

Proceedings. In this paper, some of the subjects that have been discussed in this meeting will be

recapped briefly, with special regard to the most recent results, because where we have been and

what we have learned has much to do with where we can go in the future. Furthermore, in the

process of this recap, some of the problems that the NCRP (and others) must address in the future

will be indicated.

Wilson, J. W., Townsend, L. W., and Cucinotta, F. A. (1987) On the Potential

Impact of the Newly Proposed Quality Factors on Space Radiation Protection.

NASA Technical Memorandum 89055.

Quality factors, Near-Earth environment, Low Earth-orbit

The recently proposed changes in the defined quality factor hold great potential for easing some of

the protection requirements in protection from the electron and proton environments of the near

Earth environment. At the same time, the high Linear Energy Transfer (LET) components play an

even more important role, which must be further evaluated. Several recommendations are made

that need to be addressed before these new quality factors can be implemented into space radiation

protection practice.

89
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4. MICROGRAVITY

I

0____JlIWW_dD Kfllll PRE'CF_DiNG PAGE BLArWK NOT FIL&'_ED
4.1. MICROGRAVITY

J_0..U£dSAJ_

Cassanto, J. M., Holemans, W., Moiler, T., Todd, P., Stewart, R. M., and

Korszun, Z. R. (1990) Low-cost low-volume carrier (Minilab) for

biotechnology and fluids experiments in low gravity. Space Commercialization:

Platforms and Processing, Progress in Astronautics and Aeronautics 127: 199-

213.

Flight hardware, Fluid experiment, Low gravity, Biotechnology

Research opportunities in biotechnology and fluid technology under conditions of microgravity can

be made available to research workers from developing countries through relevant research projects

and low-cost access to microgravity environments. Examples of such projects include polymeric

film formation, purification methodology, liquid-liquid diffusion, and growth of organic and

protein crystals. An example of a low-cost research device is the Materials Dispersion Apparatus

(MDA) which can be used to conduct important low-volume experiments in an automated fashion

wherever pairs, or groups of pairs, of liquids must interact. Pairs of samples of 1.0 ml or less can

be brought together surface to surface, separated by membrane, or as vapors. Studies of

miscibility, cell motility, film formation, and crystal growth are possible; and multiple samples,

more than 100 per MDA unit, can be used. The MDA is designed to be compatible with several

carriers: shuttle middeck lockers, Get-Away Special canisters, Hitchhiker, LifeSat, recoverable reentry vehicles, low-gravity aircraft flights, and sounding rockets. The MDA consists of a pair of

sliding blocks, in which wells in one block move into contact with wells in the other block under

electronic command. Requirements for power, including temperature control, are minimal.

Experiments related to biotechnology have been designed for a single flight of the MDA in which

the carder will be a sounding rocket that provides approximately 6 min of low gravity. Examples

of experiments to be conducted include the nucleation of organic crystals in aqueous solution,

behavior of immiscible aqueous solutions, solid-liquid surface phenomena at high surface-tension

gradients, and the formation of thin polymeric membranes.

Cassanto, J. M., Ziserman, H. I., Chapman, D. K., Korszun, Z. R., and Todd,

P. (1988) Simulation of launch and reentry acceleration profiles for testing of

shuttle and unmanned microgravity research payloads. Advances in Space

Research 8(12): 141-146.

Low-cost payloads, Re-entry acceleration, Protein crystals, Unmanned flight, Low gravity,

Microgravity

Microgravity experiments designed for execution in Get-Away Special canisters, Hitchhiker

modules, and Reusable Re-entry Satellites will be subjected to launch and re-entry accelerations.

Crew-dependent provisions for preventing acceleration damage to equipment or products will not

be available for these payloads during flight; therefore, the effects of launch and re-entry

accelerations on all aspects of such payloads must be evaluated prior to flight. A procedure was

developed for conveniently simulating the launch and re-entry acceleration profiles of the Space

Shuttle (3.3 and 1.7 x g maximum, respectively) and of two versions of NASA's proposed Reusable Re-entry Satellite _RS) (8 x g maximum in one case and 4 x g in the other). By using the

7 m centrifuge of the Gravitational Plant Physiology Laboratory in Philadelphia, it was possible to

simulate the time dependence of 5 different acceleration episodes for payload masses up to 59 kg.

A commercial low-cost payload device, the "Materials Dispersion Apparatus" (MDA) was tested

for (1) integrity of mechanical function, (2) retention of fluid in its compartments, and (3) integrity

of products. In particular, the sharp rise from 0 g to maximum g-loading that occurs during re92
entry in variousunmannedvehicleswassuccessfullysimulated,conditionswereestablishedfor

reliablefunctioningof theMDA, andcrystalsof 5proteinssuspendedin compartmentsfilled with

motherliquorweresubjectedto theseaccelerationloads.

Hymer, W. C., Barlow, G. H., Blaisdell, S. J., Cleveland, C., Farrington, M.,

Feldmeier, M., Grindeland, R., Hatfieid, J. M, Lanham, J. W., Lewis, M. L.,

Morrison, D. R., Olack, N., Richman, D. W., Rose, J., Scharp, D. W., Snyder,

R. S., Swanson, C. A., Todd, P., and Wilfinger, W. (1987) Continuous flow

electrophoretic separation of proteins and cells from mammalian tissues. Cell

Biophysics 10: 61-85.

Continuous flow electrophoretic separation, Electrophoresis, Polystyrene microspheres, Cultured

human embryonic cells, Canine cells, Rat cells, Microgravity, Low gravity

A new continuous flow electrophoretic separator for cells and macromolecules was built and tested

in laboratory experiments and in the microgravity environment of space flight. Buffer flows

upward in a 120-cm long flow chamber, which is 6 cm wide x 1.5 mm thick in the laboratory

version and 16 cm wide x 3.0 mm thick in the microgravity version. Electrophoretic

subpopulations are collected in 197 fractions spanning 16 cm at the upper end of the chamber. The

electrode buffer is recirculated through front and back cooling chambers, which are also electrode

chambers. Ovalbumin and rat serum albumin were used as test proteins in resolution and

throughput tests; resolution of these two proteins at 25% total w/v concentration in microgravity

was the same as that found at 0.2% w/v concentration in the laboratory. Band spreading caused by

Poiseuille flow and conductance gaps was evaluated using poly.styrene microspheres in

microgravity, and these phenomena were quantitatively the same m microgravity as in the

laboratory. Rat anterior pituitary cells were separated into subpopulations enriched with cells that

secrete specific hormones; growth-hormone-secreting cells were found to have high electrophoretic

mobility, whereas prolactin-secreting cells were found to have low electrophoretic mobility.

Cultured human embryonic kidney cells were separated into several electrophoretic subfractions

that produced different plasminogen activators; a medium-high-mobility subpopulation and a

medium-low-mobility subpopulation each produced a different molecular form of urokinase,

whereas a high- and an intermediate-mobility subpopulation produced tissue plasminogen

activator. Canine pancreatic islets of Langerhans ceils were separated into subpopulations, which,

after reaggregation into pseudoislets, were found to be enriched with cells that secrete specific

hormones; insulin-secreting beta cells were found in lowest mobility fractions, whereas glucagonsecreting alpha cells were found in the highest mobility fractions.

Results of particle electrophoresis experiments were comparable in microgravity and in the

laboratory, since cell densities that overloaded the carder buffer (resulting in zone sedimentation)

were avoided, and a 500-fold increase in protein throughput was achieved without compromising

resolution in microgravity.

Todd, P. (1989) Gravity-dependent phenomena at the scale of the single cell.

American Society for Gravitational and Space Biology Bulletin 2: 95-113.

Gravitational cell biology, Single cell functions, Low gravity, Hydrostatic pressure,

Sedimentation, Microgravity

Progress in gravitational cell biology research will depend on the continuing evaluation of a wide

variety of physical phenomena affected by gr.avity and their roles in extracellular, intercellular, and

intracellular processes. This paper examines those responses of organisms to gravity which

depend on functions at the single cell level. Single cell functions are affected by perturbations in

their internal and external environment by a variety of factors, one of which is the effect of gravity.

Physical phenomena that could influence cell function include sedimentation, buoyancy-driven

93
convection,streamingpotential,hydrostaticpressure,andinteractionsamongphysicaltransport

processes.Thermalmotionandfluid viscosityplay a significantrole in all transportprocessesat

thecellularlevel. The sedimentationof intracellularorganellestendsto becounteractedby the

cytoskeleton. Intracellular convective transportmay be possible in large plant cells. In a

microgravity environment extracellular solutes must be transportedby diffusion or active

circulatoryprocessesin theabsenceof densitygradient-drivenconvection,andflocculation and

coalescencearereducedby thelackof motionof aggregates.

Todd, P., Hymer, W. C., Morrison, D. R., Goolsby, C. L., Hatfield, J. M.,

Kunze, M. E., and Motter, K. (1988) Cell bioprocessing in space: applications

of analytical cytology. The Physiologist 31 (Suppl): 552-555.

Cell bioprocessing, Electrophoresis, Analytical cytology, Microgravity, Low gravity, Cells

Cell bioprocessing in space consists of the preparation, cultivation, purification, and investigation

of cells and their products in the microgravity environment of orbital space flight. Inertial

acceleration is used as an independent variable to explore the limits of specific bioprocessing

functions, such as cell growth and secretion, gravity-dependent phenomena in cell bioreactors, cell

fusion, the influence of thermal convection on processes at cellular dimensions, the electrophoretic

separation of cell subpopulations and subcellular particles, and two-phase partitioning of cells,

bioparticles, and macromolecules. Analytical cytology techniques are under development for onorbit application to future cell growth and separation experiments, such as those anticipated in the

Space Station era.

4.1. MICROGRAVITY

REPORTS/MEETINGS

Hymer, W. C., Grindeland, R., Hayes, C., Lanham, J. W., Cleveland, C.,

Todd, P., and Morrison, D. (1988) Heterogeneity in the growth hormone

pituitary gland "system" of rats and humans: Implications to microgravity based

research. In: Microgravity Science and Applications FHght Programs: Selected

Papers, NASA Technical Memorandum 4069, Voi. 1, 47-88.

Growth hormone, Bioassays, Muscle and bone metabolism, Cell function, Microgravity, Low

gravity

Since its discovery over 50 years ago, growth hormone (GH) has attracted the attention of both

clinical and basic research. The hormone accounts for 20% of the total protein contained in the

anterior pituitary gland. Further, some 35-50% of the six different hormone producing cell types

are committed specifically to the synthesis of GH. Milligram quantities of GH are present in the

human pituitary gland, whereas only microgram quantities of the five other peptide hormones are

contained in this 500 mg, bean-shaped structure. Why should there be such a disproportionate

amount of GH?

As the techniques to study cells and hormone molecules became more sensitive, it also became

clear that heterogeneity was a landmark of pituitary GH: Several variant forms of the hormone

molecule exist within the gland as well as in the bloodstream. Further, these variant forms possess

unique biological activities. Finally, there is evidence to suggest that GH-producing cells are also

functionally heterogeneous. Our NASA-sponsored research deals directly with these issues in

both the human and rat pituitary gland. We believe that the large percentages of cells committed to

GH production, taken together with the sizeable numbers of variant forms of GH, offer great

94
flexibility to the"GH system."It is temptingto speculatethatthisflexibility helpsthebodymeet

thevariedmetabolicdemandsplacedonit. Textbooksdescribehow GH increasesmusclemass,

increasesbreakdownof fat, decreasesuptake of carbohydrateinto cells, and increasescell

division. In light of thesenumerousactivities,therecentclaim that synthetichumanGH "will

soonbe usedto makeshortchildren taller and,possibly,help dieterslosefat and makeaging

peoplelook young"isthereforenotsurprising.

Spaceflight providesauniqueenvironmentwhichimpactstheGH systemon severalevels. First,

GH controlsmuscleandbonemetabolism,two tissuesknownto benegativelyaffectedin flight.

Second,cellular"life" aswe know it hasobviouslyevolvedundertheconstantforceof gravity.

Evidenceis beginningto accumulatethatcell function,in theabsenceof gravity,is altered.Third,

spacebioprocessingtakesadvantageof thelackof convectiveforcesin productionof materialsof

medicalrelevance.OurNASA-sponsoredresearchesonGH touchonall threeof theselevels.

The underlyingthemeof thework describedin this papercentersaroundthedifferencebetween

bioassayableandimmunoassayableGH first recognizedover10yearsago. While thecellular and

molecularbasisfor this dichotomy remainunresolved,our efforts showthat it unquestionably

exists.

Morrison, D. R., Hymer, W. D., Todd, P., and Grindeland, R. E. (1987)

Mammalian cell culture methods in microgravity. Abstract presented at the

Annual Meeting of the American Society for Gravitational and Space Biology,

Logan, UT, October 18-21, 1987.

Mammalian cell culture, STS-8, BSTA, Biorack, Bioprocessing, Microgravity, Low gravity,

RISM

Microgravity experiments on cultured cells pose unique design considerations for flight hardware.

With the exception of growth studies on WI-38 lung fibroblasts in the Biological Specimen Test

Apparatus on Skylab and the Cell Attachment Test on STS-8, cell culture experiments performed in

space have been confined to small (5-10 ml) growth or holding chambers in basic incubators.

Anchorage dependent cells were grown to confluence prior to flight and maintained on orbit.

Experiments were necessarily simple permitting only basic observations and sample fixation on

orbit for postflight analysis back on Earth. Since 1978 several conferences have identified many

areas where cell culture experiments in microgravity may provide unique insight into basic cell

biology mechanisms and potential advantages in process technology for growth and maintenance

of fragile mammalian cells. A summary of the various mammalian cell culture systems which have

been flown in space is presented. The requirements and approach for several new cell culture

flight experiments are reviewed along with adaptations of the BSTA, the Biorack culture chambers,

the Carry-on Incubator chambers, and the Refrigerator/Incubator Storage Module. Advantages and

disadvantages are discussed for various conventional systems which could be modified and for

new systems being developed for bioprocessing or basic cell biology studies in micro-g.

Todd, P. (1989) Physical phenomena and the microgravity response. Cells in

Space, Eds. J. D. Sibonga, R. C. Mains, T. N. Fast, P. X. Callahan and C. M.

Winget, NASA Conference Publication 10034: 103-116.

Microgravity, Low gravity, Statolith, Cytoskeleton

The living biological cell is not a sack of Newtonian fluid containing systems of chemical reactions

at equilibrium. It is a kinetically-driven system, not a thermodynamically-driven system. While

the cell as a whole might be considered isothermal, at the scale of individual macromolecular events

there is heat generated, and presumably sharp thermal gradients exist at the submicron level. Basic

physical phenomena to be considered when exploring the cell's response to inertial acceleration

95
i ii

[

include particle sedimentation, solutal convection, thermal convection, electrokinetics, motility,

cytoskeletal work and hydrostatic pressure. Protein crystal growth experiments, for example,

illustrate the profound effects of convection currents on macromolecular assembly. Reaction

kinetics in the cell vary all the way from diffusion-limited (very fast) to life-time limited (very

slow). Transport processes vary from free diffusion, to facilitated and active transmembrane

transport, to contractile-protein-driven motility, to crystalline immobilization. At least four

physical states of matter (phases) exist in the cell: Aqueous, non-aqueous, solid, and immiscibleaqueous. Levels of order vary from crystalline to free solution. The relative volumes of these

states profoundly influence the cell's response to inertial acceleration. Such subcellular phenomena

as stretch-receptor activation, microtubule re-assembly, synaptic junction formation, chemotactic

receptor activation, and statolith sedimentation have been studied recently with respect to both their

basic mechanisms and their responsiveness to inertial acceleration. From such studies a

widespread role of cytoskeletal organization is becoming apparent.

Todd, P., Morrison, D. R., Barlow, G. H., Lewis, M. L., Lanham, J. W.,

Cleveland, C., Williams, K., Kunze, M. E., and Goolsby, C. L. (1988)

Kidney cell electrophoresis in space flight: Rationale, methods, results and flow

cytometry applications. In: Microgravity Science and Applications Flight

Programs: Selected Papers, NASA Technical Memorandum 4069, Vol. I, 89-118.

Human kidney, Human embryonic ceil, Cell electrophoresis, ApolIo-Soyuz, STS-3, Cytology,

CFES, STS-8, Microgravity, Low gravity

The human kidney performs an incredible number of different functions. Individual cells are

responsible for the production of renin, erythropoietin, enzymes of vitamin D metabolism,

plasminogen activators of at least 3 types, granulocyte conditioning factor, the maintenance of

electrolyte balance, and the clearance of soluble wastes from the blood, to mention a few. The

sharing of these functions among cells will take decades to fully characterize, and many of these

functions, if they could be isolated, are also of commercial importance to biotechnology. For

example, the kidney is perhaps the second most prolific tissue with respect to plasminogen

activator production, which is one of today's "hottest" biotechnology future market items.

The purpose of the research project described here was to develop a means of purifying

subpopulations of cultured human embryonic kidney (HEK) cells to produce living subpopulations

for study. Urokinase, a plasminogen activator found in urine, was the original product goal.

Since primary cultures of differentiating epithelioid cells are not immortal, adequate numbers of

cells could not be purified by cloning or cell so_ng. Historically, Barlow and Kolin showed some

three major subpopulations by "continuous belt' electrophoresis in a magnetic field. This finding

was not pursued at the time of its discovery, but it was confirmed as an early goal in this project,

and the original premise that electrophoretic subfractions would separate according to function was

also confirmed.

A series of ground-based electrophoretic and enzymologic studies led to an experiment on the

Apollo-Soyuz mission in which evidence for urokinase-rich cell subpopulations was found. The

first objective of the present project was to reproduce this result with adequate statistical data and

superior technique using the same apparatus. The "EEVT" experiment on STS-3 ir/cluded two

columns of fixed erythrocytes, which were photographed in flight. The remaining 6 tubes were

dedicated to living kidney cells that were frozen for several weeks before and immediately after

electrophoresis in space. Unfortunately, liquid nitrogen loss in a ground refrigeration unit

destroyed all samples from this flight, and only photographic data from the fixed erythrocytes were

usable. NASA then made time available on the Continuous Flow Electrophoresis System (CFES)

aboard the Space Shuttle orbiters. Without the necessity of freezing cells, and without the

influence of particle sedimentation or zone convection, it was then possible to separate cells by

CFES in microgravity, as suggested by the discovery of a gravity-dependent component of

96
pituitary cell separationin free fluid electrophoresismethods.Thus far, it hasbeenpossibleto

separateonly two samplesof kidney ceils, both on STS-8. Analytical results continueto be

completedandpublished. In this paper,wedescribethe resultsof kidney cell electrophoresis

apparatusandits testing;reviewresultsof kidneycell electrophoresis;andpresentresultsin the

applicationof flow cytometryto kidney-cellelectrophoresisin low gravity.

97

KEYWORD INDEX

PRE'CED|NG PAGE BLANK NOT FILMED
KEYWORD INDEX

28Si 12

5-azacytidine 39

56Fe nuclei 12

Abrasion/Ablation 7

Absorbed dose 72

Absorptive cross sections 10, 11

Accelerator beams 3I

Active dosimeters 73, 79, 80

Active radiation detectors 73, 76

Adiabatic approximation 4

AE-8 17

Affinity labelling 37

Age dependence 47, 55, 68

Alkaline sucrose gradients 46

Alloy 4

Alpha particles 9, 14, 44

Alpha-alpha correlation 5

Aluminum 28, 29

Analytical cytology 94

Analytical methods 24

Analytical solution 23, 28

Anatomical man models 72, 73, 78

Animal models 53

Antinuclei 8

AP-8 17

Apollo-Soyuz 96

Ar ions 54, 63

Arabidopsis thaliana 66

Argon 40, 43, 85

Argon ions 46, 61

Argonne National Laboratory 47

Beagle dog 53, 86

Benchmark 2 7

Benchmark solution 22, 24

Benzo-a-pyrene 56

Bioassays 94

Biological dosimeter 66

Bioprocessing 95

Biorack 95

Biotechnology 92

Boltzmann equation 22, 23, 27, 30

Bone-tissue interface 20

Bragg curve 30

Brain tumors 34, 84, 87

BRYNTRN 19, 25, 29, 30, 82

BSTA 95

Bullfrogs 53

C. elegans 39

C3H10T1/2 40, 41, 42, 47

Cancer 52

Cancer risk 52, 68

Canine cells 93

Carcinogenesis 40

Career risk 88

Cascade 12

Cataract patients 71

Cataract scoring 57

Cataractogenesis 54, 55, 58, 85

Cataractotoxic load 69

Cataracts 50, 52, 54, 56, 57, 58, 59, 60, 71

Cell bioprocessing 94

Cell culture 38

Cell cycle 56, 58

Cell cycle dependence 43

Cell damage 37

Cell differentiation 69

Cell electrophoresis 96

Cell function 94

Cell inactivation 44

Cell survival 45

Cell transformation 41, 42, 47

Cells 94

Cellular differentiation 59

Cellular lethality 42

Cellular pathology 60

Cellular radiosensitivity 36

Cellular repair 38

Cellulose-nitrate sheets 73

Central collisions 13

Central nervous system 87

CFES 96

CFU-S 49

Charge changing cross sections I2

Charge exchange 4

Chemical protection 42

Chernobyl 68

Chinese hamster ovary cells 39

CHO-K1 39

Choroid 61, 63, 64

Chromosome aberrations 37, 50

Chronic Radiation Colony 84

Cobalt decay lines 16

Compton scattering 16

Computerized anatomical man model 24, 48

Continuous flow electrophoretic separation

93

Cornea 63

Correlations 8

Cortical cataract 69

Cosmic rays 63

COSMOS 1887 66, 72

COSMOS biosatellite 72

Coulomb dissociation 6, 9

Coulomb scattering 3

100
KEYWORD INDEX

Coupled channel 9

Coupled-channel equations 5, 8

CR-39 73

Crepis capillaris 66

Cross sections 5, 6, 11, 15, 27, 28

Cultured human embryonic cells 93

Cultured mammalian cells 41

Cytology 96

Cytopathology 60

Cytoskeleton 95

Data bases 22, 29

Depth distribution 72

Depth doses 19, 30

Differential cross sections 9, 11

Diogene 12, 13, 14

Dipole polarizabilities 2

Direct action 42

Direct and indirect action 36

DNA 47

DNA damage 37

DNA strand breaks 41, 47

Dose calculations 79

Dose equivalent 18, 19, 24, 25, 28, 70, 75,

77, 80, 82, 83, 88

Dose fractionation 58

Dose threshold 55

Doses 28, 70, 75, 80, 83

Dosimetry 31

Double strand breaks 36, 42

Earth's atmosphere 23

Effective charge 2, 4

Effective quality factors 88

Eikonal approximation 8, 10

Eikonal optical model 8

Elastic scattering 6

Electric quadruple excitations 6

Electromagnetic dissociation 6, 11, 12

Electron microscopy 38, 61, 63

Electronic devices 4

Electronic excitation 3

Electronic transitions 3

Electrons 3, 17, 87

Electrophoresis 93, 94

Emulsion 12

Endometriosis 52, 84

Energy deposition 20

Energy levels 7

Energy transfer 42

Ethyl-methane sulphonate 39, 56

Evaporation model 12

Excitations 3

Excited states 8

Experimental cataracts 56

Exposure 22

Exposure estimates 79

Eye 63, 64

Fe 64

Fe ions 59, 60, 61, 69

Fertility 66

Fission foils 72, 74

Flight hardware 92

Flow cytometry 37

Fluence spectra 30, 31, 32

Fluid experiment 92

Focal damage 57, 58

Fractional charge 13

Fractionated doses 42

Fractionation 54

Fragment production 10

Fragment recoil 23

Fragmentation 12

Fragmentation experiments 32

Fragmentation model 5

Galactic cosmic rays 8, 9, 20, 22, 25, 27,

28, 69, 70, 77, 82, 83, 88

Galactic cosmic rays transport 24

Gamma NKW 16

Gamma radiation 16

Gamma rays 50

Gamma-ray lines 16

Gas 4

GCR 26, 32, 75, 88

Genetic abnormalities 86

Genotoxicity 59

Geomagnetic field model 18

Geosynchronous orbit 74

Glioblastoma 84

Gliomas 86

Glucose tolerance 52

Glutathione 55

Gravitational cell biology 93

Growth hormone 94

Hadronic wansport 2 7

Harderian gland 40

Heavy charged particles 50

Heavy ion fragmentation 5, 7, 9

Heavy ion reactions 21

Heavy ion transport 22, 32

Heavy ions 14, 15, 23, 29, 38, 39, 40, 42,

44, 45, 46, 49, 53, 57, 58, 63, 70

Heavy-ion collisions 6, 11, 14

Helium 2

HGPRT mutation 42

101
KEYWORD INDEX

High-energy nucleons 20

High-LET 40, 41, 63

Hormones 55

Human embryonic cell 96

Human epithelial cells 40, 41, 44

Human keratinocytes 42

Human kidney 96

Human mammary epithelial cells 42, 45

Hydrogen 4

Hydrogen transitions 3

Hydrogenic 3

Hydrostatic pressure 93

Hypophysectomy 55

Hypothermia 46

HZE 20, 23, 26, 29, 31, 38, 40, 44, 46, 47,

.53, 62, 63, 70, 75, 85

HZE interaction 20

HZE particles 25, 32, 38, 46, 64, 69

ICRP 70, 71

ICRU 22, 88

ICU 26

Impulse approximation 10

Inclusive cross section 10

Indirect action 42

Induced radioactivity 19

Inelastic interactions 12

Integral LET spectra 72

Intranuclear cascade 22, 34

Inverse dose-rate effect 54, 58

Ion chambers 76

Ionization 3

Iron 40, 42, 43, 60, 63, 85

Iron ions 39

K-shell electrons 4

Kaon 10

L5178Y S/S 45, 46

Late cataractogenesis 86

Late effects 85, 88

Late radiation damage 61, 87

LDEF 19

Lens 54, 58, 63

Lens epithelium 54, 55, 56, 57, 58, 59, 60,

69, 71

Lens opacities 57

Lenses 50

LET 19

Leukemia 87

Life shortening 52

Life-span 86

Life-span shortening 49

Light fragments 12

Liver 47

Long-duration space missions 82

Low dose-rate effect 40

Low doses 50, 70, 71

Low Earth-orbit 17, 18, 72, 73, 74, 76, 81,

89

Low gravity 92, 93, 94, 95, 96

Low rate effect 40

Low-cost payloads 92

Low-inclination orbits 76, 81

Low-LET 34, 40, 71

Lunar colony 25

Lunar mission 74

Lyrical biology 63

Magnetic field models 17

Magnetic shielding 28

Mammalian cell culture 95

Mars 26, 77, 82

Material degradation 20

Mesons 7

Methods 22

Mice 59, 60

Mice cataractogenesis 55

Microelectronic applications 34

Microgravity 92, 93, 94, 95, 96

Microlesions 8, 40, 61, 62, 63, 64, 69

Micronucleation 59

Micronuclei 54, 59, 71

Minilesions 85

Missions 73

Model development 21

Model verification 24

Momentum transfer 4, 9, 10

Monoenergetic beams 24

Monte Carlo 22, 25

Monte Carlo methods 22

Mouse cells 38

Mouse embryo cells 47

Mouse lens 60

Mouse lethality 49

Mouse lymphoblasts 38, 43

Mouse testes 44

Multiple Coulomb scattering 14, 32

Multiplicities 12

Multipole polarizability 2

Murine lymphoblast 36

Muscle and bone metabolism 94

Mutagen-carcinogens 50

Mutagenicity 54

Mutagens 56, 71

Mutation effects 66

Mutations 39

102
KEYWORD INDEX

NCRP 70, 71, 88, 89

Near-Earth environment 89

Neon 13, 30, 31, 32, 43, 85

Neon ions 39, 46

Neon transport 30

Neoplasia 42, 47, 85

Neoplastic cell transformation 40

Neutron albedo 17

Neutron flux 81

Neutron total cross sections 11

Neutrons 11, 19, 49, 68, 74

New Zealand white rabbits 38, 46, 47, 53,

86

Niobium 43

NKW transport 32

NUCFRAG 10

Nuclear emulsions 72

Nuclear fragments 20

Nuclear reaction effects 78

Nucleon cross sections 7

Nucleon knockout 9

Nude mouse 41

Numerical solutions 23

Nutrient effect 46

Occupational exposure 68

Ocular tissues 65

Optical models 5, 8

Optical potential 10, I1

Organ dose equivalent 78

Organic polymers 77

Oscillator strengths 2, 3, 4

Oxygen 13

Oxygen effect 36

Partial cross sections 12

Particle tracks 40

Passive dosimeters 73, 79

Passive radiation detectors 73, 76

Patient 86

PET 34

Phase spaces I 1

Photographic emulsions 74

Photonuclear reactions 11

Photoreceptors 38, 61

Pion production 13

Plastic nuclear track detectors 12, 13, 73, 74

Plastic track detector 76

PLD repair 51

PNTD 72

Polycarbonate 73

Polymers 3

Polystyrene microspheres 93

Positrons 14

Positrons ionization 16

Potential models 7

Production cross sections 12

Program review 49

Projectile fragmentation 10, 15

Projectile fragments 13

Proline phototroph 39

Proportional counters 76

Protein crystals 92

Proton production 14

Proton-proton correlations 13

Protons 3, 4, 6, 17, 22, 48, 52, 55, 61, 62,

84, 87

Quality factors 17, 22, 68, 69, 70, 78, 88,

89

Quarks 7

Radial integrals 2, 3

Radiation cataracts 53, 55

Radiation dose 70, 73, 74, 77

Radiation dosimeter 75, 76, 79, 81

Radiation dosimetry 18, 20, 80

Radiation environment 74

Radiation exposures 18, 19, 68

Radiation hazards 69

Radiation limits 89

Radiation protection 88, 89

Radiation quality 32

Radiation risk 74

Radiation shielding 20, 77

Radiation standards 89

Radiation therapy 84, 86

Radiation transport 27

Radiation weighting factors 88

Radioisotope imaging 34

Radioprotectants 47

Radiosensitivity 38, 45

Radon 68

Rana pipiens 56

Rat cells 93

Rat lens 54

Rat lens cultures 50

Rats 54, 61, 63, 64, 65, 69

RBE 36, 38, 39, 40, 43, 44, 46, 47, 49, 59,

6O, 84, 87

Re-entry acceleration 92

Reaction cross sections 8

Recoils 19

Recombinant DNA 37

Reconstructions 57

Regolith 25, 26

Relativistic heavy ion 9

Relativity 5

103
KEYWORDINDEX

Repair 36, 45

Replacement therapy 55

Restitution 53

Retina 61, 63, 64

Rhesus monkeys 34, 49, 51, 52, 53, 55, 61,

62, 84, 86, 87

Risk systems 68

RISM 95

RME-IH 80

SCE 50

Scheimpflug image analysis 57

Scheimpflug-based 56

Scoring system 56

Secondaries 19

Sedimentation 93

Sensitivity-analysis 27

SEP 19

Serial section 57

Shielding 18, 25, 26, 28, 29, 30, 32, 66, 70,

73, 75, 82, 83

Shielding materials 75

Shielding measurements 79, 81

Shielding models 79

Shielding strategies 83

Shielding thickness 72

Shuttle 18, 24, 29, 48, 72, 73, 76, 79, 80,

81

Shuttle dosimeter 79

Shuttle shielding model 24

Silicon 43

Silicon ions 39

Single cell 42

Single cell functions 93

Single event evaluation 26

Single-event upsets 20, 34

Single-particle effects 62

Skin cell cultures 51

Slit-lamp 60

Slit-lamp microscopy 55

Solar energetic particles 19, 75, 77, 82

Solar flare 16, 19, 77

Solar flare shielding 25

Solar maximum mission 16

Solar particle events 69

Solar periods 29

Soviet spacecraft 73

Space exploration 20, 70, 75

Space mission scenarios 74

Space radiation 83

Space Shuttle 81

Space Station 74, 75

Spacecraft shielding 20

Spacelab 73, 76

Spallation products 19

Sparing 40

Spermatogonial cell killing 44

Sphere model 82

Stark effect 2

Statolith 95

Stem cell populations 38

Stem cell survival 87

Strand breakage 46

STS-3 96

STS-51F 76

STS-51J 76

STS-61C 76

STS-8 95, 96

SV40 40

Symposium 47

Synchronous cell cultures 38

Target theory 45

Testes weight loss 49

Thermoluminescent detectors 72

Thermoluminescent dosimeters 73, 76, 79,

81

Tissue damage 38

Tissue response 50

Tissue-equivalent proportional counter 34, 80

Total cross sections 8, 10

Total reaction cross sections 6

Total-body exposures 52

Track structure 54

Trait effects 51

Transformation 42

Transparency 53

Transport 31

Transport calculations 6

Transport codes 7, 22, 23, 24, 25, 26, 27,

28, 29, 30, 32, 77, 82, 83

Transport methods 32

Transport model 20

Transport theory 30

Trapped protons 19, 34

Trapped radiation 17

Two-body relativistic equation 6

U.S. spacecraft 73

U.S.S.R.-U.S. 72

Uncertainties 22, 28

Unmanned flight 92

Validations 31, 32

Vette model 72

Water 28, 30, 32

Weizs_cker-Williams method 9

104
KEYWORD INDEX

Wound healing 61, 62

WR-2721 65

X-ray production 4

X-rays 39, 44, 46, 53, 54, 57, 65, 87

105
=
AUTHOR INDEX

PRE'CEDIP_I PAGE BLANK NOT FILMED
AUTHOR INDEX

Adams, J. H., Jr. 70, 82

Afzal, S. M. J. 50

Ainsworth, E. J. 49, 50

Akatov, Y. A. 66, 72

Akopova, A. B. 72, 74

Alard, J. P. 12, 13, 14

Alpen, E. L. 32, 44, 59, 60

Anderson, G. A. 34

Anikeeva, I. D. 66

Antonchik, V. A. 12

Arnold, J. 12

Atwell, W. 17, 24, 29, 48, 69, 72, 73, 74,

76, 77, 78, 79, 80, 81

Augerat, J. 12, 13, 14

Babinet, R. 12, 13, 14

Badavi, F. F. 5, 6, 7, 11, 22, 23

Badhwar, G. D. 76, 81

Barlow, G. H. 93, 96

Bastid, N. 12, 13, 14

Beever, E. R. 24, 72, 73, 74, 79

Benton, E. R. 39, 72

Benton, E. V. 12, 13, 19, 39, 66, 72, 73,

74,76

Bergtold, D. S. 36, 38, 46

Biagi, F. 12

Blaisdell, S. J. 93

Blakely, E. A. 43

Blazek, E. R. 47

Bogdanov, S. D. 12

Braby, L. A. 34

Brackenbush, L. W. 34

Brechtmann, C. 12, 13

Brenner, D. J. 54

Broadwater, J. R. 84

Brochard, F. 12, 13

Broglio, T. 57, 58

Buck, W. W. 8, 10, 11, 22, 23, 29, 30, 34

Butler, T. M. 49

Calvin, H. I. 55

Cash, B. L. 24, 73, 76, 79, 81

Cassanto, J. M. 92

Cavin, L. A. 84

Chapman, D. K. 92

Charmensat, P. 12, 13

Chun, S. Y. 11, 22, 23, 29, 30

Chupp, E. L. 16

Cleveland, C. 93, 94, 96

Cordts, R. E. 34, 52

Cox, A. B. 38, 43, 46, 47, 52, 53, 55, 61,

62, 84, 85, 86, 8 7

Craise, L. M. 39, 40, 41, 42, 47

Crawford, H. J. 12, 15

Crouau, M. 12

Crouse, D. A. 50

Cucinotta, F. A. 5, 6, 8, 9, 11, 18, 20, 25,

29, 30, 78, 89

Curtis, S. B. 14, 32, 74

Dalrymple, G. V. 84, 86, 87

David, J. 55, 56, 57, 58, 71

De Marco, N. 13

DeGuzman, R. J. 32, 44

Delcourt, S. G. 37

Demaison, P. 14

Deutchman, P. A. 11

Dudldn, V. E. 12, 72, 74

Dupieux, P. 12, 13, 14

Eason, C. S. 84

Ehmann, U. K. 43

Engelage, J. 15

Fanet, H. 13

Fanton, J. W. 34

Farhat, H. 17, 28

Farrington, M. 93

Feldmeier, M. 93

Fishman, G. J. 76

Fodor, Z. 12, 13, 14

Fogarty, T. N. 4, 34

Forrest, D. J. 16

Frank, A. L. 72, 74, 76

Frank, P. 65

Fraysse, L. 12, 13, 14

Fry, R. J. M. 50, 88

Fuji, I. 47

Ganapol, B. D. 23, 24, 27, 28, 29, 30

Geard, C. R. 50, 71

Girard, J. 12, 13

Golightly, M. J. 69, 80

Goolsby, C. L. 94, 96

Gorodetzky, P. 12, 13, 14

Gosset, J. 12, 13, 14

Gregory, J. C. 76

Grindeland, R. E. 93, 94, 95

Gross, F. 6

Grubb, G. 3

Gruenert, D. C. 44

Guzik, T. G. 15

Haik, B. 65

Hajnal, F. 20

Hanson, W. R. 50

Hardy, A. C. 17, 24, 48, 72, 73, 74, 79, 80,

81

108
AUTHOR INDEX

Hardy, K. A. 52, 68, 80, 84, 87

Harris, R. K. 34

Hatfield, J. M. 93, 94

Hayes, C. 94

Heinrich, W. 12, 13, 19

Hess, J. L. 55

Hoffmann, A. 13

Holemans, W. 92

Holley, W. R. 44

Holsclaw, D. S. 53, 55

Hong, B. S. 10, 11, 30

Howard, J. 30, 46

Hymer, S. S. 37

Hymer, W. C. 93, 94, 95

Jarret, B. V. 30

Keith, J. E. 81

Keng, P. C. 36, 46

Khan, F. 2, 3, 4, 9, 10, 14, 23, 29, 30

Khandelwal, G. S. 2, 3, 4, 5, 8, 9, 10, 14,

18

Kinzer R. L. 16

Koniarek, J. P. 68

Konradi, A. 17, 81

Korszun, Z. R. 92

Kostina, L. N. 66

Kovalev, E. E. 12, 72

Krebs, I. 61, 63, 64

Krebs, W. 61, 63, 64, 68

Kung, J. S. 56

Kunze, M. E. 37, 94, 96

L'Hote, D. 12, 13, 14

Lamkin, S. L. 11, 23, 28, 29, 30

Landis, D. A. 14

Lanham, J. W. 93, 94, 96

Laspalles, C. 12, 13

Le Merdy, A. 12

Lee, A. C. 53, 55, 84, 85, 86

Leising, M. D. 16

Lemaire, M. C. 12, 13, 14

Letaw, J. R. 16, 26, 70, 75, 76, 82

Lett, J. T. 36, 38, 42, 43, 45, 46, 4 7, 53,

55, 61, 69, 84, 85, 86, 87, 88

Lewis, M. L. 93, 96

Lindstrom, P. J. 15

Long, S. A. T. 3

Lucas, B. 12, 13

Ludewigt, B. A. 14, 32

Magradze, N. V. 72

Marenny, A. M. 66

Marroncle, J. 12, 13, 14

Marshall, T. M. 39

Maung, K. M. 6, 8, I0, 11

McGuire, E. L. 84

Meador, W. E. 5

Medvedovsky, C. 53, 54, 55, 56, 57, 58,

59, 60, 65, 69

Mei, M.-T. 39, 40, 47

Melkumyan, L. V. 74

Merriam, G. R., Jr. 53, 54, 56, 57, 61, 63,

69, 71

Merriam, J. 71

Miller, J. 30, 31

Miller, M. 32

Mitchell, J. C. 84, 86

Mitchell, J. W. 15

Moiler, T. 92

Montarou, G. 12, 13, 14

Morrison, D. R. 93, 94, 95, 96

Moss, A. J., Jr. 84, 86, 87

Motter, K. 94

Murphy, R. J. 16

Nachtwey, D. S. 70

Nagle, W. A. 84, 86, 8 7

Nealy, J. E. 18, 19, 25, 26, 28, 29, 30, 77,

82, 83

Nefedov, N. A. 12

Nelson, G. A. 39

Ngo, D. M. 34

Norbury, J. W. 5, 6, 7, 8, 9, 10, 11

Odrich, S. 54, 71

Olack, N. 93

Olsgaard, D. A. 3

Ostroumov, V. I. 12

Pandey, L. N. 3

Parizet, M. J. 12, 13, 14

Parnell, T. A. 72, 73, 76

Peak, J. G. 47

Peak, M. J. 47

Phillips, M. H. 14, 32

Pickering, J. E. 68

Poitou, J. 12, 13, 14

Portman, A. I. 66

Potapov, Y. V. 72, 74

Powers-Risius, P. 32, 44, 59, 60

Pfitchard, W. M. 3

Qassoud, D. 12, 13

Quam, W. 80

Racca, C. 12, 13, 14

Raha, S. 14

109
AUTHOR INDEX

Rahmani, A. 12, 13, 14

Rapkin, M. 30, 31, 44

Rhim, J. S. 40, 41

Richman, D. W. 93

Richmond, R. G. 73, 76, 79, 81

Rieger, E. 16

Riehl, K. 80

Rini, F. 56, 65

Romo, D. 34

Rose, J. 93

Rosskothen, H. 56

Rothstein, H. 53, 55

Rusin, S. V. 66

Rustgi, M. L. 3

Salmon, Y. A. 84

Salmon, Y. L. 52, 68, 87

Sanchez, F. J. 46

Scharp, D. W. 93

Schimmerling, W. 12, 13, 14, 15, 20, 21,

30, 31, 32, 44

Schubert, W. W. 39

Seidenberg, K. 57, 58

Share, G. H. 16

Shavers, M. R. 31, 32

Shinn, J. L. 18, 25, 28, 29, 78, 82

Silberberg, R. 16, 26, 70, 75, 76, 82

Simonsen, L. C. 18, 26, 28, 77, 82, 83

Sinclair, W. K. 68, 70, 71, 88, 89

Snyder, R. S. 93

Spieler, H. G. 30

Stampfer, M. R. 45

Stewart, R. M. 92

Story, M. D. 43, 46

Swanson, C. A. 93

Symons, T. J. M. 15

Tamain, J. C. 13

Terrien, Y. 12, 13, 14

Tion, J. A. 6

Tobias, C. A. 40, 41, 42, 45, 47

Todd, P. 3 7, 40, 62, 92, 93, 94, 95, 96

Townsend, L. W. 5, 6, 7, 8, 9, 10, 11, 14,

17, 18, 19, 20, 21, 22, 23, 24, 25, 26,

27, 28, 29, 30, 32, 77, 78, 82, 83, 89

Tsao, C. H. 26, 70, 75, 76, 82

Valero, J. 13

Valette, O. 12, 13, 14

Vaulina, E. N. 66

Wallace, S. J. 6

Walton, J. T. 14

Watts, J. W., Jr. 72, 76

Wefel, J. P. 15

Wigle, J. C. 51, 87

Wigle, J. F. 86

Wilfinger, W. 93

Williams, K. 96

Wilson, J. W. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,

14, 17, 18, 19, 20, 21, 22, 23, 24, 25,

26, 27, 28, 29, 30, 32, 34, 77, 78, 82,

83, 89

Wong, M. 14, 20, 21, 30, 31, 32, 44

Wood, D. H. 34, 52, 68, 84, 86, 87

Worgul, B. V. 50, 53, 54, 55, 56, 57, 58,

59, 60, 61, 63, 64, 65, 68, 69, 71

Xu, Y. J. 4

Yamamoto, O. 47

Yang, T. C. 39, 40, 41, 42, 44, 45, 47

Yochmowitz, M. G. 52, 68, 84, 87

Yoshida, T. 47

Zhu, G. 3

Ziserman, H. I. 92

110
Natonal Ae_r,,aulc S a_,d

Space Ac_nnslralol

Report Documentation Page

1. Report No. 2. GovernmentAccessionNo.

NASA TM-4270

4. TitleandSubtitle

Radiation Health Research, 1986-1990

7. Author(s)

Radiation Health Program, Life Sciences Division

9. Performing Organization NameandAddress

NASA OSSA

Washington, DC

12. Spon_ring AgencyNameandAddress

National Aeronautics and Space Administration

3. Recipient's Catalog No.

5. Report Date

April 1991

6. Performing Organization Code

8. Performing Organization Report No.

10. Work Unit No.

11. Contract or Grant No.

NASW 4292

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

SBM

15. Supplementary Notes

16. Abstract

This report consists of a collection of 225 abstracts of radiation research

sponsored by NASA during the period 1986-1990. Each abstract has been categorized

within one of four discipline areas: Physics, Biology, Risk Assessment and

Microgravity. Topic areas within each discipline have been assigned as follows:

Physics - Atomic Physics, Nuclear Science, Space Radiation, Radiation Transport

and Shielding and Instrumentation: Biology - Molecular Biology, Cellular Radiation

Biology, Tissue, Organs and Organisms, Radioprotectants and Plants: Risk

Assessment - Radiation Health and Epidemiology, Space Flight Radiation Health

Physics, Inter- and Intraspecies Extrapolation and Radiation Limits and Standards;

and Microgravity. When applicable subareas have been assigned for selected topic

areas. Keywords and author indices are provided.

17. Key Words(SuggestedbyAuthor(s))

I) Radiation Health 6)

2) Space Radiation 7)

3) Human Exploration 8)

4) Research Programs

5) Risk Assessment

19. SecuriW Cla_if.(ofthisreport)

Unclassified

Radiation Biology

Radiation Physics

LifeSat

18. Distribution Statement

Unclassified - Unlimited

Subject Category 52

120. SecurityClassif.(ofthispage)

Unclassified

21. No. of pages

120

22. Price

A06

NASA FORM 1626 OCT 86 NASA-La,ngley,1991