PLUTONIUM ISOTOPIC COMPOSITION IN SOIL FROM THE FORMER SEMIPALATINSK NUCLEAR TEST SITE

This paper reports preliminary results on plutonium isotopic compositi on in soil sampled at the Semipalatinsk Nuclear Test Site in the forme r USSR. The soil was sampled in October 1994 from two locations in the test site, the first nuclear explosion site and the bank of the crate r called ''Bolapan'' along the Shagan River Site. The Pu isotopic comp osition of these samples was determined through the measurements of Pu -240/Pu-239 (and Pu-242/Pu-239) atom ratios by high resolution ICP-MS, Pu-241 by a low background liquid scintillation counting method and P u-238 and Pu-239,Pu-240 by alpha-ray spectrometry. As a result, a high level of Pu-239,Pu-240 With weapon-grade Pu was detected in the first nuclear explosion site and Bolapan. The isotopic composition of the P u in the soil for the Ist nuclear explosion site was estimated to be P u-238 0.006%, Pu-219 96.5%, Pu-240, 3.48%, Pu-241 0.01% and Pu-242 0.0 04%, and for the Bolapan to be Pu-238 0.19%, Pu-239 93.4%, Pu-240 6.30 %, Pu-241 0.08% and Pu-242 0.03%.