RMI Nuclear Justice Documents

average value of 1.02 with a standard deviation of 0.11. These comparisons showthat, with few exceptions, there is good agreement and apparently no bias between results obtained from GITR and film-badge dose data. 3.2 REMOTE-SOURCE GAMMA RADIATION The directionally shielded GITR Station 14 was designed to permit discrimination between remote-source radiation and high backgrounds of radiation from aeposited contaminants. How- ever, examination of the data indicated that the background of radiation from contaminants on the washed weather decks was so lowthat the differences between remote-source andtotal radiation were smaller than the probable errors in the radiation measurements. This led to the foliowing approach for estimation of the remote-source-radiation contribution to the total radiation observed on the washed weather decks. The basis for the estimation technique was examination of the decay-corrected plots of the average total dose rates on the weather decks, which are presented in Figures 3.37 through 3.40. Measured decay data were available for the period later than 6 minutes after Shot Um- prella (Section 3.4). For Shot Wahoo and for the period earlier than 6 minutes after Shot Umprelia, estimated probable limits for the unknown decay curve were based upon: (1) the calcu- lations of gamma dose-rate decay for unfractionated fission products (Reference 10); and (2) straicht-line extrapolation on the log-log plot of the measured gamma dose-rate decay shown in Figure 3.42, The following discussion requires the assumptions that some undetermined decav-corrected dose-rate curve can represent the buildup of contaminants on the ships’ weather sur:aces; and that this unknown curve always had either zero or positive slopes during the period of interest, even though the decks were continuously washed (Reference 3 indicates that the ma- jor value of washdown is the continuous suppression of contaminant buildup). assumptions and refer to Figures 3.37 through 3.40. Consider the above The minima between the two major peaks o: the Shot Umbrella curves can certainly be considered to be upper limits of the decay-corrected dose rate from fallout deposited on the weather surfaces of the ships at the indicated times, becazse even if no radiation was contributed by airborne radioactivity (which may not have been the case) the contribution from deposited fallout could not be greater than the total. For similar reasons, those portions of the curves which tend to level off after the last major peak for either shot can also be considered upper limits of decay-corrected dose rates from deposited radioacuvny, especially if there was a significant drop in the decay-corrected dose rate after the nearly horizontal portion of the curve. Therefore, if the assumption of a continuously increasing buildup of contaminants is valid, it follows that overestimates of the contribution by deposited conlaminants to the decay-corrected dose rates can be represented by the horizontal lines labeled as such in Figures 3.37 through 3.40. These decay-corrected estimates were converted to dose Tates that were integrated to obtain upper limits of the estimated dose contributed by deposited contaminants for each assumed decay curve. The estimated doses contributed by remote-source radiation to the total doses observed on tne washed weather decks of the three target ships, based upon the above-mentioned approach, are presented in Table 3.10. These values indicate that at least 95 and 98 percent of the total dose observed on the washed decks was due to remote-source radiation resulting from Shots Umbrella and Wahoo, respectively. AS a consequence, the observedtotal-radiation data can jose dis- iscussed adequately represent the remote-source radiation for the washed weather-deck areas during te first 10 minutes after shot. Unfortunately, there was no data available from which it would na\e been feasible to estimate the percent contribution of the remote-source radiation to the ‘Xai dose for unwashed weather decks. -egented and have ilm-badgé fable 3.9. i have ar 2.2 BEST AVAILABLE COPY TOTAL GAMMA RADIATION IN ADJACENT WATER The attempt to measure the radiation in the water adjacent to the target ships was not suc- *+85:1. No data was obtained for Shot Wahoo, because the starting signals were not received 29 Ci,