aap Delayed Shutters These shutters were closed et zero time but subsequently were opened for a pre-selected time interval during the power pulse. sustained burns in this series, Four of 16 rabbits The interval of 10 to 250 msec produced a lesion in 1 of 2 animals exposed. In 2 of 2 rabbits the increment of 10 to 1000 msec produced burns essentially the seme size and severity as those observed in the ERT study. The interval of 500 to 600 msec caused a small mild burn in 1 of 2 animals. Although this animal was exposed only about one-third of his blink reflex time, the dose rate was near the maxirum for this shot. The time of the meximum is calculated at about 600 + 20 msec. No burns were produced efter the first second of the flash, Protective Flectronic Shutters No burns were sustained by the 2 rabbits exposed behind these shutters. Unfortunately the electronic recordinrs system for these devices was inoper- ative at the time of the shot. The results of this portion of the study ere inconclusive. Protective Filters Only 2 burns were produced in 27 exposures behind the fixed density optical filters. moderate severity. These lesions were both 1/Z d.d. in size end were of Unexplainatly, neither burn was produced behind the least protective filters. CONCLUSIONS The tlink reflex time for man and animals is not fastyenough to protect against the flash from an atomic detonation An air burst of this size on a clear day (90 percent transmission/rile) is sufficient to cause large chorioretinal burns in rabbits and monkeys at 7.€ statute miles and in men at 5.1 statute miles. Additional date are needed in order to estellish the limiting distance for burns\ = amee —aet 7 Me CAT, ue Ee _— - 30 - 3