“a .4 2. CONTAMINATION The 23 nuclear tests H-bomb shot of 1954, from 1946 to 1958, and deposited radioactive Bikini Atoll, including the lagoon. in particular the Brayo fallout unevenly throughout Over the past 26 years, contamination has diminished through spontaneous decay, and in the case of the lagoon, by exchange of water with the open sea. The most important remaining nuclide is cesium-137 (half-life, 30 years). Also present but much less important is strontium-90 (half-life, 29 years). Traces of the transuranic elements are also present (plutonium-239, -240; americium-241), but contribute very little to the total dose. In the discussion that follows, the level activity) is expressed in picocuries substance as the of 1987, pCi/g signifies that emits a burst of in one radiation earliest of radioactivity (specific- per gram that (pCi/g) of soil resettlement might or other occur. gram of substance one atom disintegrates every occurring potassium-40 in soil 27 seconds. For comparison, One and naturally ranges between 0.5-0.8 pCi/g (9, p. 30); in sea water it is about .03 pCi/g. 2.1 Lagoon The nuclear shots that occurred at Bikini (Appendix C) affected the floor, water and sediment of the lagoon. 2.1.1 the lagoon. Floor. During Three shots in particular affected the floor of Operation Crossroads in 1946, 11 ships sank to the bottom, five during the Able shot and six including the carrier Saratoga during the Baker shot (Figure 2, sunken ships). These ships carried fuel, ‘loaded guns and stores of ammunition. The remnants of several observation towers also lie on the bottom, near Lomilik Island (B4, Figure 2). 50000 lb 17