ial bh The original computation of gamma dose from total beta activity on gummed eiim'7) was developed to meet this lack of suitable dose estimates, Unfortunately, the gamma dose calculations are subject to the same errors in evaluating multiple bursts as the Sr°~ 90 estimates. | The gamma dose computed is the air dose to infinite time from uniform fallout on an infinite smooth plane. No reduction for shielding or weather- ing has been introduced, nor has there been included any build-up factor for (14) for converting to fo bo: scattering. The usual overall reduction facttér is 10 gonad dose, It might be noted here that the thirty year dose is only slightly - less than the infinity dose. There is a second possible estimate of gamma dose. Cs 137 If we assume that is produced and deposited in a fixed ratio to sr, the dose from cs? can be computed, 7 The calculations are based on the same assumptions as the total beta activity!7), the modified formas are: Dose 6,64 x 10719 >. N in mrads where, Dose = C337 infinity y dose in millirads yn Total Cs137 gamma disintegrations to infinity per sq. ft, Accepting a half-life for cst” of 26.6 years and an initial 6 dpm ratio for cst3”/gr90 of 1.75, there would be 2.8 x 10° 63237 B disintegrations to infinity per sq. ft. for each me/mi? of Sr?0, 2.3 x 10? cst This would give ae 37 y disintegrations per sq. ft. The final formula would be: Dose = 1,5 (me/mi* Sr?) in mrads The estimate of gamma dose based on 03137 will be extremely low for fallout occurring shortly after a test and will improve with age of the debris. ‘ . a k FE r r ' , k b. Be r “y pe t. b i r bes4 - 26 -