CHAPTER 1 - THE PORTION OF ACTIVITY DEPOSITED IN LOCAL FALLOUT 1. In recent years there has been some concern that DCPA (and other) estimates of the fallout hazard that would be associated with a nuclear war may be excessively high. The basis for this concern was that the fallout models used in calculating this hazard were thought to seriously over-predict the amount of the radioactivity deposited in local fallout. According to the discussions of Chapter 1, this concern is not justified. Specifically, the K~factor value of 2000 (R/hr)/(kt/sq mile), which has been in general usage, varies from the figure of 1930 recommended in the report by the Subcommittee by a small percentage. 2. Past procedures for accounting for reduction in the ambient radiation levels attributable to ground roughness (unevenness in terrain features) have been either: (1) in effect reducing the amount of radioactivity (and consequently R/hr at any given time) assumed to be associated with a particular weapon's fallout pattern; or (2) assuming that personnel or other objects of interest, such as crops or livestock, receive some protection because of this ground roughness. Although the net result of either method of treatment is the same, logically the latter procedure is preferable since patently ground roughness would have little if any effect on the amount of activity deposited per unit area. By accepting the recommendations of Chapter 1, i.e., that a K-factor of 1930 be used in damage assessment models, then implicity, procedure Number 2 for accounting for ground roughness effects is to be used, This means, however, that when damage assessment of nuclear radiation effects from a hypothetical attack on personnel or things in the open is performed, an allowance for ground roughness protection must be made. Unless a specific evaluation of this ground roughness for the condition of interest is available, an average PF of 4/3 should be assumed. 3. The monitoring instruments of DCPA correctly read (assuming proper calibration of course) the ambient dose rates, and no instrument correction factor (as was necessary for older instrument designs) is required. “(The test data on which the Subcommittee's recommendations were based largely came from these old instruments and have been adjusted, by using a multiplying factor of 4/3, instrument response factor.) II-5 to eliminate the