and produced a sufficiently characteristic dose rate record so that the presence of wateri radiation can be detected by inspection. At Some locations, radiation due to contaminated became important at later times (5 minutes or greater) when, in the absence of free-fieid tion, the water intensities can be determined directly from the GITR record, Although the underwater detectors were not needed as originally intended, these instrur provide attenuated traces of the free-field record which are used as a check on the standar Strument. A distinction between the attenuated free-field record and the water record as s by an anderwater detector was possible through a comparison of curve shapes, since the ty phenomena produce a characteristic record. Caiculations based on predicted venting times (Reference 24} and previous measuremen! dose rates occurring at early times (References 20 and 49 through 52) indicated that rates high as 10° to 10’ r.’hr were possible at close ranges, particularly on Umbrella. Although duration of these early peak rates would be very short, these peak dose rates could result doses of tactical significance. Since these rates were beyond the range of the NRDL gamr detectors (maximum rate 10° r/hr), and since high time reSolution would be advantageous | any analysis of early dose rates, the project borrowed a number of high-range gamma dete tors developec by the Army Signal Engineering Laboratory (ASEL) with a maximum rate of 108 r/hr and a possible time resolution of 0.1 msec. These units, called Gustave I’s (Refe ences 49 and 50), were installed on coracles closer than 6,500 feet from surface zero and| vided a record of gamma radiation intensity for the first 85 seconds after zero time. The project also requested detailed photographic coverage of cloud movement on both W and Umbrella so that the visual phenomena could be correlated with the time-based gamma tensity records obtained at all locations. By means of these visual records, meteorologic: parameters and current theories of fallout transport mechanisms, the project intended to: the gamma reccrds at the coracle locations to gamma-intensity-time contours about surfac The production of such contours obviously requires a far greater station density than that | mitted by available funds; therefore, the project had to rely heavily on photographic track: the base surge. Since the operational limitations on both photographic and meteorological age would affect the reliability of these contour plots, the project attempted to augment the tion density through the use of approximately 70 floating film packs (FFP), which were eit! anchored or so placed as to drift into preselected locations throughout the coracile array. recorded by these FFP’s were interpreted by means of similar film packs installed aboard coracle station. Redwing experience (Reference 33) had shown that a good correlation exis: between National Bureau of Standards (NBS) film pack measurements and the integrated tot gamma dose obtained from an associated time-based gamma detector; therefore, the use o these FFP’s made possible a finer grid of correlation points for the analysis of visual clou phenomena and the construction of gamma contours. The FFP’s placed for Wahoo were necessarily free-floating, which greatly increased bc operational and analytical difficulties. An analysis of current data taken by the Scripps In: tion of Oceanography (SIO) during its November-December 1956 survey of the proposed shc area (Reference 53) and additional information provided by the Office of Naval Research ‘O indicated that an average surface drift of 1 ft/sec could be assumed over the entire array. the use of suitable drogues, the project hoped to reduce drift rate to about 0.5 ft/sec, whic Speed was used for computing the distance traveled during film pack exposure. The relati: cloud dose Da ,expressed as a percentage of the total dose Da + Dy accrued from both tr cloud and deposited radicactive material suspended in the surface-water layer Dy, wasc puted by integrating the expressions derived earlier for cloud intensity I, and water inten. Iw. Selected values, together with the estimated distances traveled during exposure wer¢ then used to evaluate the feasibility of attempting this FFP operation (Table 1.3). As indic earlier in this chapter and borne out by actual experience in the field, cloud slopes (Appen F) greater than 0.1 (corresponding to a time of arrival 5 minutes or less) were expected w the range of project stations for both Wahoo and Umbrella; therefore, drift distances were expected to exceed 1,000 feet. 41