3. An approximate set and drift of the contaminated sea water east to west at 0.5 knotg . If tg is the time of sampling then: tm =ts - ta (4.6) The distance J is not the distance from surface zero to the point at which water samples were collected but rather to the geographical coordinate at which the sampled water re~ ceived the fallout. It may be determined by successive approximations in the manner shown in the illustrative calculation. Attg = 0 + 32.5 hours water samples were taken following Shot 5 at 12° 10' N 166° 06' E. Let the distance from this point to surface zero be the first approximation]. and tm, = 32.5 - 4 = 28.5 hours. 20 F | ~ 1, = 53 miles. “TT \ Tor i4 x 8 12 i} po T .- 64 T r oof LZ "4 _ : ae Tt g ap = 6 + s ‘ 4 t+; 2 3 + +—- L <q > HOTS J 2 10 u T of L 2r aw T peodet bo gy e — ze From Figure 4.3, ta, = 0+ 4 hours, The east to west drift correction is approximately 0 20 40 60 80 18 GO 100 !20 140 160 DISTANCE FROM GZ,2(N MI!) 200 220 240 260 Figure 4.3 Estimated times of arrival of fallout. 0.5tm, = 0-5 x 28.5 = 14.3 miles. Applying this correction and re-plotting position, it is found that the second approximation of the geographical point of fallout is I, = 64 miles from ground zero, andtm, =ts = ta, = 32.5-5 = 27.5 hours. The second approximation of the drift correction is 0.5tm, = 0.5 x 27.5 = 13.8 miles: which is sufficiently close to the first estimate of the drift correction that no further improvement in the value of tm is realized. The geographical pointof fallout is therefore established as 13.8 miles east of the point of sampling. Z = 62 x 10? cm, and 510 x 62 x 10? 1 A = CZ From Figure 4.2, 31.6 x 10° counts min7!em~ 2 Values for A for other points are given in Column 3, Table 4.6 and Table 4.7. 62 East to