DETERMINATION OF ENVIRONMENTAL LEVELS OF Pu-23 9,240, Am-241.Cs-137 AND Sr-90 IN LARGE VOLUME SEA WATER SAMPLES

摘要

A method is reported for the determination of environmental levels of Pu-239,240 and Am-241 in ~60 liter size samples of sea water. Cesium-137 and Sr-90 were also separated and determined from the same samples. The samples were collected at the sea surface and at various depths in the oceans through the facilities of the Woods Hole Oceanographic Institution.nPlutonium and americium were separated from the sea water by iron hydroxide scavenging then treated with a mixture of nitric, hydrochloric, and perchloric acids to destroy organic material and to achieve equilibrium between added tracers and the environ¬mental transuranics. A series of anion exchange separations were used to remove interferences and purify plutonium and americium then each was electroplated on platinum discs and measured by solid state alpha particle spectrometry. The overall chemical yields averaged 62 ± 9 and 69 ± 14 percent for Pu-236, and Am-243 tracers, respectively.nFollowing the iron hydroxide scavenge of the transuranics, cesium was removed from the acidified sea water matrix by adsorp¬tion onto ammonium phosphomolybdate. Cesium carrier and Cs-137 isolation was effected by ion exchange and precipitations were made using chloroplatinic acid. The samples were weighed to determine overall chemical yield then beta counted, Cesium recoveries averaged 7 5 ± 5 percent.nAfter cesium was removed from the sea water matrix, the sample were neutralized with sodium hydroxide and ammonium carbonate was added to precipitate Sr-85 tracer and the mixed alkaline earth carbonates. Strontium was separated as the nitrate and scavenged by chromate and hydroxide precipitations. Yttrium-90 was allowed to build-up for two weeks, then milked and precipitated as the oxalate, weighed, and beta counted. The overall chemical yields of Sr-85 tracer averaged 84 ± 16 percent. The recovery of the yttrium oxalate precipitates averaged 96 ± 3 percent.