Macaca mulatta monkeys and Sprague-Dawley rats were unilaterally exposed to whole-body doses of gamma-neutron radiations from a TRIGA reactor. Doses of 2075, 4150, and 12,450 rads were used in the monkey studies. Doses to the rats ranged from 9400 to 66,000 rads. The animals were exposed in two ways. The steady-state animals were irradiated at a dose rate of approximately 1000 rads/minute. The other animals were exposed to a single pulse of radiations. The pulse was about 15 msecond wide at half-amplitude. The average dose rate under the pulse was of the order of <tex-math>$10^{6}\ \text{rads}/\text{second}$</tex-math>. At doses sufficient to cause death within 2 days, the ordering of deaths was significantly different between pulsed and steady-state irradiated monkeys with the pulsed animals preceding. The mean survival time of pulsed animals was significantly shorter than their steady-state counterparts for both species of animals.

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