60Co content in the spent graphite masonry of commercial reactors at the siberian chemical combine

Some results of comprehensive investigations of the radioactive contamination of graphite masonry from shutdown commercial uranium-graphite reactors at the Siberian Chemical Combine are reported. The objective of the investigations was to study the distribution of radionuclides and to determine the contamination level. In the present paper information about60Co in the gaphite of the I-1 and Él-2 reactors is reported. Its content in the samples was measured by γ-spectrometry. There were about 250 graphite samples from the I-1 reactor and 200 from Él-2. According to the data obtained, the surface contamination level of the blocks can be taken as the same for the entire core within the limits of the errors presented. The average60Co contamination of the graphite in the surface of blocks from the I-1 core is 5600−500+550 Bq/g and 8400−1000+1200 Bq/g for the Él-2 core. The60Co content in the interior volume of the graphite blocks of a I-1 reactor is now 1100−160+200 Bq/g and 2000−300+1350 Bq/g in ÉI-2. The60Co activity in all blocks from the I-1 core is 1.22·1012 Bq, and for ÉI-1 the figure is 2.16·1012 Bq. 4 figures, 3 tables, 7 references.