Determination of environmental levels of 239240Pu, 241Am, 137Cs, and 90Sr in large volume sea water samples

A method is reported for the determination of environmental levels of 239240Pu and 241Am in approximately 60-liter size samples of seawater. 137Cs and 90Sr 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. Plutonium and americium were separated from the seawater by iron hydroxide scavenging then treated with a mixture of nitric, hydrochloric, and perchloric acids. A series of anion exchange separations were used to remove interferences and purify plutonium and americium; then each was electroplated on platinum disks and measured by solid state alpha particle spectrometry. The overall chemical yields averaged 62 +- 9 and 69 +- 14 percent for 236Pu, and 243Am tracers, respectively. Following the iron hydroxide scavenge of the transuranics, cesium was removed from the acidified seawater matrix by adsorption onto ammonium phosphomolybdate. Cesium carrier and 137Cs 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 75 +- 5 percent. After cesium was removed from the seawater matrix, the samples were neutralized with sodium hydroxide and ammonium carbonate was added to precipitate 85Sr 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 85Sr tracer averaged 84 +- 16 percent. The recovery of the yttrium oxalate precipitates averaged 96 +- 3 percent