EXPOSURE TO PROMPT NEUTRON RADIATION A relatively small percentage of the 250,000 atmospheric test participants were exposed to neutrons, and it can generally be clearly determined whether or not an individual was so exposed. For those so exposed, their neutron dose can be calculated with good accuracy, and all such neutron exposures are believed to have ‘been low (less than a rem--generally much less), with the possible exception of participants in the Volunteer Observer Program (officer volunteers). Neutron exposure can occur only at the time of detonation (prompt radiation). Contact with fallout neutrons. (delayed radiation) will not cause exposure to Thus, the possibility of exposure to neutrons can be determined with relative accuracy, since individuals' locations are known with more certainty at times of detonations than at other times--and were controlled with utmost rigor. are rapidly attenuated in air. Additionally, neutrons from a detonation For example, at a distance of two miles from an atmospheric nuclear detonation in Nevada, the neutron dose to a totally unprotected individual would be less than one rem. Of course, no personnel were ever permitted in such an exposed location for close-range detonations of significant yield. Finally, neutrons are severely attenuated by earth~-for example, by a factor of six in an open trench, or by a factor of 100 behind three feet of earth. Since all personnel at the Nevada Test Site who were within several miles of a detonation were protected in trenches, any neutron exposures that did occur were not only below one rem, but generally in the low raat. wR 7