Appendix A COMPARISON OF COMPUTED DOSE RATE OVER THE SEA WITH CERTAIN ACTUAL MEASUREMENTS A few measurements were made on deck and on the bridge while underwater dosages were being obtained following Shot 5. Intercomparison of these data permits a rough test of the familiar elementary theory for making predictions of dose rate above the sea from measuren.ents made by submerged instruments. The behavior of the several instruments can be compared also. Figure A.1 shows the manner in which these particular measurements were made, and Table A.1 lists the measurements andalso their values after being reduced to dosage rates by application of suitable calibration curves. Column 9 is the ratio of the,intensity in air to the intensity underwater-measured by the same instrument, Mark If. Column 10 is the ratio of intensity in air measured by the ship’s radiac set (type AN/PDR-27C) to the intensity underwater, measured by the Mark I device. Column 11 is the ratio which was computed by using the simplified theory summarized in Equation D.4.3, page 435 of “The Effects of Atomic Weapons” (1950, LASL), under the assumption of monochromatic MAND RADIAC SET,H BRIDGE HYDROGRAPHER'S PLATFORM ———___" C FANTAIL ' Figure A.1 Location of instruments during Shot 5. Surveys used for comparisons discussed in Appendix A. energy of 0.7 Mev. This equation is not strictly accurate for a volume distributed source since it assumes angular distribution of unscattered radiation coming up from the water to be the same as for a plane source. However, this deficiency leads to smaller numerical error than arises from the neglect of scattered rays. It is recognized that this simple theory is deficient; there is an additional contribution due to scattering and the actual geometry including the ship cannot be treated properly. Comparison may be made between Column 11 and Columns9 and 10; the theoretical values agree with the experimental much better than might have been hoped for considering the geometric complications introduced by the presence of the ship. The ship filters rays coming from almost half the sea, but this is somewhat compensated for by the presence of local contamination on the deck and hull. 79