reaction or from unfissioned materials that emitted alpha, beta, and gamma radiation (5). Because residual radiation decayed or diminished, the characterization of the residual environment was defined by the radiation intensity as a function of type and time. Radiological survey data were used to determine specific intensities at times of personnel exposure. Inter- polation and extrapolation were based on known decay characteristics of the individual materials that comprised the residual contamination (1; 3). In those rare cases where insufficient radiation data existed to adequately define the residual environment, source data were obtained from the appropriate weapon design laboratory and applied in standard radiation transport codes (7; 8; 9) to determine the initial radiation at specific distances from the burst. This radiation, together with material composition and charac- teristics, led to a description of the neutron-activated field for each location and time of interest. In all cases, observed data, as obtained at the time of the operation, were used to calibrate the calculations. 7.5.2 Activities of Participants. This part of the process was precisely the same as that described in section 7.2. It was important that this step be carefully accomplished in order to define unique groups for which the radiation exposure was essentially common. Possible and reasonable variations in group activities, as well as individual deviations from those of the group as a whole, with respect to both time and location, were considered in each uncertainty analysis, described in section 7.5.4. 7.5.3 Calculation of Radiation Dose. The initial radiation doses to close-in personnel (normally positioned in trenches at the time of the detonation) were calculated from the above-ground environment by simulating the radiation transport into the trenches. Various calculational approaches (7; 10), standard in health physics, were employed to relate in-trench to above-trench doses for each source of radiation. Detailed modeling of the human body in appropriate postures in the trench was performed to calculate not only the gamma dose that would have been recorded on a film badge, but also the maximum neutron dose (11). The neutron, neutron-generated gamma, and prompt gamma doses were accrued during such a short time interval :. 171