ar ell, ar. Jutnma serve aS mnemonic devices once the reader is familar with them. All symbcls 2 key placed at the beginning of the individual record sequence ana again in Appendix F an to being defined as they appearin the text. The initi. .ed base surge is called the primary base surge, and the assumed second surge is calle. ..e secondary base surge. The terms “inner” and “outer” are used to describe surge boundaries, since the adjectives “leading” and ‘trailing’ fail when describing upwind events. In the ensuing discussion two visible surge boundaries are used: an irregular photographically determined boundary (photo-bounJary) and a smooth boundary defined by a circle best approximating the photo-boundary. Thus four visible boundaries of the primary surge are employed: the outer and inner photo-boundary (P, and P, respectively) and the outer and inner smooth boundary (By and B; respectively). The secondary base surge is photographically indistinct; therefore, the smooth boundary of the secondary surge B, is used unless otherwise noted. The final Project 1.3 (Reference 91) radii mentioned above are employed to construct another smooth boundary (labeled NOL”) using the center of the circle defining the primary Smooth boundary (the photographic surge center X). The base surge torus is also divided into upwind, crosswind, and downwind segments always with respect to the official Task Force surface wind (15 knots from 090° T for Wahoo and 20 knots from 050° T for Umbrella). Presumed areas of decreased radioactivity either between the primary and secondary base surge or at the center of the surge are called the intersurge decrement and central decrement, respectively. As suggested previously, these areas are apparently coincident with photographically clear areas within the base surge. In anydiscussion, a careful distinction must be maintained between photographically and radiologically established parameters; thus, wherever ambiguity is possible, the modifiers photo- or rad- will be prefixed to the parameter in question. Although the treatment of the two shots is similar, it cannot be identical because of the pronounced phenomenological differences. In all cases where more than one similar gamma record was obtained at a single location, only that record most closely approximating the free field is analyzed, i.e., the coracle record from the std-GITR or the shipboard record from the GITR facing surface zero or the hot line (Appendix F). In general, base surge transit is responsible for all dose received at locations more than . 1,500 feet from surface zero, as far as tactical considerations are concerned. time varies with position relative to surface zero. Surge transit For Wahoo, transit times range from ap- proximately 3 minutes at upwind and crosswind locations to approximately 20 minutes at dis- tant downwind positions; for Umbrella, these approximate times are 3 minutes and 10 minutes, respectively. Thus, the area in the imiriediate vicinity of surface zero should be safe for entry by combatant ships approximately 25 minutes after detonation. The generalization is correct as stated for larger combatant ships, but a consideration of waterborne material (discussed later) requires an exception for small boats operating in the vicinity of surface zero, The gamma dose rate record characteristic of Wahoo starts with a relatively blunt first major dose rate peak followed by a shallow valley, which in turn is followed by a series of blunt dose rate peaks slowly decreasing in magnitude over a period of about 10 to 15 minutes. A characteristic Umbrella record begins witha high, sharp peak in dose rate followed by a prolonged period of low dose rate, which finally increases to a flat-topped rise of approximately 4 minutes’ duration. These characteristic records, supported by additional photographic evidence, indicate fundamental differences in the complex structure of the base surge produced by the two detonations. Such differences are not surprising but require considerable interpretation. All peak dose rates and times of peaks are Summarized for both shots in Table 3.8 (also see discussion in second preceding paragraph). The valley occurring immediately after the first major peak in dose rate has also been included in this table, since itis often indicative of an important feature of the base surge. The fact that all weather-deck GITR’s 122 Page 123 deleted.