into an area that might produce an "effective biological dose" (the term given to the radiation exposure according to the above assumptions) of one roentgen. <0 This graph may be extrapolated to other readings. For example, if fallout begins three hours after detonation and the ~ dose rate at that time is 10 r per hour, about 67 r (éffective biological dose) will be accumulated provided personnel continues to live normally in the contaminated area. This is computed as follows: 10 = 67 0.15 It is frankly recognized that in any single curve, such as that shown in Figure 6, there are inherent a number of uncertainties. Criteria based on deliberate analyses of the relevant data, however, may be more valid than those determined under the duress of an emergency situation. Such a simplified graph might provide radiological monitors with a quick, even if rough, estimate of the potential hazards and thus assist in making decisions on questions such as evacuation. Using Figure 6, the idealized fallout diagram on page was constructed to ijlustrate a possible pattern from a single high yield surface burst. The two innermost isodose lines shown were selected to suggest regions where (a) a significant percentage of personnel might be expected to die (400 r) and (b) a few percent to become ill (100 r), assuming continued occupancy of these areas with no special protective measures. the encompassed areas. These percentages would, of course, rise within The 50 r effective biological isodose line has no unique significance but suggeststhe magnitude of dosewhich _ ‘ -14-