make significant contributions to the gross gamma fields observed; however, radiation due ‘to radioactive water remains a possible undetected addition to the free-field dose at the close-in stations. Consequently, the discussion of the gamma dose rate resulting from deposited radio- active material remaining suspended in the surface water layer is extended to include radiation from the passage or upwelling of water directly contaminated by the nuclear device even though such discussion is not properly included in this section. 3.3.1 Deposited Radioactive Material. The fact that any detector records the summation of radiation received from airborne, waterborne, and deposited material requires that at least two of these three potential sources be individually evaluated. Consequently, considerable effort was devoted to the prediction and assessment of possible deposited and waterborne radiation. In the light of the results from Wahoo and Umbrella, these efforts may appear to have been unnecessary; however, the very fact that the large deposits expected did not occur is in itself of particular significance. This fact has therefore been substantiated by all available evidence in addition to that obtained from the IC collections themselves. These measurements were not originally intended to provide such information, and thus, precision is understandably lacking. Evidence proving the deposit dose to be tactically unimportant is provided by: (1) the IC collections, (2) the standard GITR records after passage of the base surge, and (3) radiac meter surveys of the coracles upon recovery. The relative contribution of the deposited material to the gross gamma field may be estimated from the data presented in Table 3.6 in which all values are converted to std-GITR response. The GITR and meter survey readincs have been brought to a common time of 1 minute, using the ionization chamber decay curve in Reference 89 extended to early time by normalization with the decay curve in Reference 36 (Section B.2). For brevity, this combined decay curve is hereafter referred to as the Standard decay curve. The IC collections were also corrected to the common time of 1 minute by a method described later. : A pilot of the deposit dose rate estimated from meter survey data versus distance from sur- face zero (Figure D.34) shows no Significant variation with distance, a fact which suggests that the meter survey readings are not representative of the deposition phenomena. The meter survey data indicates rather that the general background on Wahoo was approximately 10 times higher than on Umbrella. This increase in background, which was detected in other data (see Figure D.35), is attributed to the fact that Eniwetok Atoll was subjected to secondary fallout just prior to Wahoo from Shot Koa fired at Bikini. If Koa is accepted as the origin, the application of the standard decay curve on the assumption that the material was deposited fram Wahoo is obviously false, and consequently the high meter survey estimates for Wahoo cannot be accepted. Even if meter survey estimates are accepted, they are less than 3 percentof the recorded peak dose rate at stations that were transited by the base surge. The std-GITR records after passage of the base surge provide a better estimation of the deposit dose (Appendix F). A background dose rate after passage of the base surge was selected from each gamma record at a time not later than 3 hours after zero time and in a region where there was no immediate evidence of sources other than material deposited on the coracle decks. This background dose rate was then corrected by means of the standard decay curve (Appendix F) to the rate of 1 minute after zero time. A plot of these deposit dose rates (Figures 3.32 and 3.33) shows some scatter, which must be expected when all positions are represented without wind corrections, but which may also result from bodies of waterborne radioactive material in the neighborhood of the coracle. Nevertheless, the plotted points show some dependence on distance from surface zero and thus are more acceptable as an indication of deposition phenomena. If only points from downwind stations are considered, a straight line may be drawn through the points from the Wahoo close-in stations. Unfortunately, due to the large number of overturned coracies, there are almost no close-in points for Umbrella; however, a straight line parallel to that drawn through the Wahoo data fits the few Umbrella points reasonably well. If these straight line plots are accepted, the deposit dose rate may be approximated by the expression: 105 Page 106 deleted. £§