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SUBJECT:
OBJECTIVE:
The measurement of ncutron effects on various biological
systems.
TEST PROCEDURE: The responses of biologicsl systems have been calibrated
against knorm doses of laboretory x-rays permitting the
evaluetion of neutron cffects in terms of REM units. Mice
were exnosed to the thermal colum of the Los Alamos weter
boiler where a reasonable estimate of the physical damage,
reccived in REP units could be determined for the various
biological systems tested.
“ice end some other biological materials were exposed at
veapons tests within seven inch thick lead hemispheres
designed to protect them from blast and thermal radiation
and to eliminate gamma radiation which would otherwise
affect the same systems studied for neutron effects.
STATUS OF
KNOSLEDGE:
Lethality, atrophy of the spleen and thymus, mitotic depression of the testes, end iron uptake by the bone marrow all
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shoved an RBE of 1.5 to 2.0 between x-rays and thermal
neutrons for mice exposed in the laboratory. RBE for catarects wes greater by a factor of four or more. Two strains
of mice showing different sensitivities for x-rays demon-
strated the same RBE for thermal neutrons. Little experimentel data for fast neutron exnosures is available.
Initial calculations indiccted threat the animels exposed at
weapons tests within the hemispheres demonstrated about 90%
of the neutron effect thet they would have show had they
been exposed to the neutron radiation of the wearons in
free air.
Recent work indicetes that such shields attenuate
neutrons more severely than this, and that the correct
figure mey be no higher than 50%, denending to some extent
“upon the external neutron svxectrun.
Various biological test systems in mice characteristically
shoved different RE values at sny given station in the
weapons tests, and the time of peak death following midletnal exposures was less than that for compsrable x-ray
doses, indicating that orgen system radiosensitivities and
species mechanisms of deeth may ciffer somewhat among
different ionizing rediutions. Grertest reliability and
consistency of data was found emong lethality and spleen
and thymus ctrophy, with the letter proving most practical
for correlation with physical data.
Comperison of REM data vith physical measurements shoved
the biological response to ba ouite sensitive to neutron
spectrum. It is cleer thet these biological systems operate
Incl #5