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MASTER
CALCULARED TISSUE FLUX-TO-DOSE CONVERSION FACTORS FOR
NUCLEONS OF ENERGY BELOW 400 MeV *
W. E. Kinney and C. D. Zerby
To evaluate the hazard to personnel encountering radiation in space or
near nich-energy accelerators it is necessary to know the distribution of
energy deposition within the body resulting from the impinging radiations.
Important regions of the depth-cose distribution are the surface dose for es-
timating skin and eye damage and the dose at a depth of 5 cm which is the average
depth of the blood-forming organs. In addition, the average whole-body dose is
an important parameter of a depth-dose distribution to estimate over-all damage.
A series or calculations has been performed to supply tissue :lux-to-
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dose conversion iactors for incident neutrons and protons having energies in
Uits
the range from 60 to 400 MeV. A general set of factors were computed which way
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be applied to specific radiation fields to give upper and lower bounds on the
surface, 5 cm depth, average, and maximum coses.
The model chosen for study was a 30-cm-thick slad of tissue infinite in
its lateral dimensions. The calculations were performed by means of a series
of Monte Carlo Computer codes. Nucleons were effectively introduced wiformly
over one face of the slab both normally and isotropically to give doses which
should bracket those resulting from actual angular distributions. The doses
were computed by swing the energy deposited in unit cubes distributed through
the slab in a direction normal to the surface. Ten thousand source particles
were run for each angular distribution and each of the incident energies of
400, 300, 200, 100, and 60 vev. Energy deposition was broken down into
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Horarth Sponsored by the National Aeronautic Space Administration under Union
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contributicos crom primary protons, secondary protons, and heavy nuclei. In
order to yemit ireedome in choosing proton RBE as a function or onercy, the
proton rad cose was subdivided into contributions from protons having energies
above 50 keV, lying in the energy ranges 10 to 50 MeV, 5 to 10 VeV, and I to
5 Nev; and having energies below I MeV. The RBE chosen in this study for these
ezersy groups were 1, 1, 1.25, 3, and 8, respectively. Heavy nuclei were taken
to have ar. R33 0: 20.
ine calculated doses were found to be in agreement with Snalnov's mea-
surements ou dose in water and paraffin due to nearly monoenergetic 140-MeV
neutrons stripped from 280-veV deuterons on Cu and also due to rieutrons result-
inoizom the charge exchange reaction of 480-MeV protons on Be.
3
The cose due to secondary particles increases wità increasing primary
beam exercy since the secondary production increases. The average rem cose que
to secondaries resulting from normally incident protuns rises from 12.5% of
the total cose at an incident energy of 100 MeV to 53% of the total dose at
400 VeV incident energy.
The data may be conveniently expressed by the following equations for
illisi.?.: :1...6... alwa ? si cineti... "
the cose where D is the dose in rem, E is the energy in MeV, ano. logarithms are
taken to the base 10. The range on E is 60 to 400 MeV unless indicated to
the contrary.
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Doses due to normally incident protons are,
.
For average cose:
1-7.72 + 6.4 x 10°33 - 1.12 x 20°572; 60 < E < 215,
Log D = 1
1 -6.20 - 4.32 x 20 3E + 5.5 x 10*8g2; 215 < E < 400,
5-cm dose
Log D = -6.267 - 4.56 x 10°3E + 6.113 x 10°652;
80 < E < 450,
surface dose
105 D = -6.638 - 2.2.7 x 10-30 + 2.86 x 10"882,
and maxima dose
los De
-6.018 - 1.2 x 10"E, 60 < E < 215,
-6.624 - 1.12 x 10°35, 215 < E < 400.
Xornally incident neutron doses are expressable as,
for average dose
208 D = -7.4267 + 2.67 x 207*E,
5-cm dose
108 D = -7.378,
surface dose
log D = -7.59221 + 3.68 x 10245,
and maximum cose
108 D = -7.275 + 4.5 x 10E.
The doses resulting from isotropically incident protons are given by
for average dose
1-7.789 + 7.89 x 10°38 - 1.7 x 10°5E, 60 < E < 215
log D =
(-6.806 + 1.66 x 10-3E - 1.95 x 10-652, 215 < E < 400,
*
5-cm dose
103 D = -6.5657 - 5.43 x 10°E, 80 < E < 400
Tui
Tui
*
surface dose
log D = -6.770 - 3.45 x 10°32 + 5.0 x 108E2,
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20.com or cose
103 D = -6.259 - 2.92 x 10°32 + 4.1 x 10^872.
Isotropically incident neutron's give doses represented by
for average cose
103 D = -7.2586 + 5.64 x 10°*E,
5-cm cose
103 D = -7.1785 + 3.92 x 10°*E,
sürücc dose
105 D = -7.2568 + 4.47 x 10°45,
Er. maxime cose
103 D = -7.284 + 4.0 x 10°E.
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Rezerences
1. W. E. Kinney, "che Nucleon Trüngport Code, NTC," ORVL-3610 (1961).
2. M. I. Shalnov, "Tissue Doses of Fast and Ultra-Fast Neutrons," Sovicu
J. At. Eserny V, 735 (June 1958).
3. V. P. Dzhelepov et al., IZV Akad. Nauk., SSSR Ser. Fiz. 19, 573 (1955).
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LEGAL NOTICE
This report was prepared as an accourt of Government sponsored work. Neither the United
States, nor the Commission, nor any person acting on bchalſ of the Commission:
A. Makes any warranty or representation, expressed or implied, with respect to the accu-
racy, completene88, or usefulness of the information contained in this report, or that the use
of any information, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; or
B. Assumes any liabilities with respect to the use of, or for damager resulting from the
use of any information, apparatus, method, or process disclosed in tö!8 report.
As used in the above, "person acting on behalf of the Commission” includes any em-
ployee or contractor of the Commission, or employee of such contractr, to the extent that
such employee or contractor of the Commission, or employee of such contractor prepares,
disseminates, or provides access to, any information pursuant to his employment or contract
with the Commission, or his employment with such contractor.
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