Radiation characteristics of graphite in the commercial uranium-graphite reactors at the Mayak industrial association

The results of investigations of the radiation characteristics of graphite samples taken from the masonry in two commercial uranium–graphite reactors at the Mayak Industrial Association are presented. The specific activity of α, β, and γ emitters present in the graphite in different parts of the masonry, including cells located next to the damaged cell, is determined. The specific activity of the main product of activation 60Co is 102–104 Bq/g. The concentration of 137Cs in the graphite is higher than that of any other fission product (the specific activity in the cells located next to the damaged cell is 104–106 Bq/g). 244Cm makes the largest contribution to the total activity of transuranium elements; its activity in one sample was 2·107Bq/g. More than 90% of the activity of the masonry graphite is due to 14C. The outer and inner surfaces of the graphite bricks are most highly contaminated with radionuclides. The results obtined are the basis for the high estimated content of radionuclides in the entire graphite masonry for each reactor.