Trace elements with large activation cross section in concrete materials in Japan

Amounts of trace elements with large activation cross section in concrete m aterials were measured to offer the basic data for developing of low activa tion concrete. From the measurements, the quantities of the activated radio activities in biological shielding concrete were measured and evaluated for the clearance level. The average concentrations of Co-60, Eu-152 and Cs-13 4 formed in concrete were 21.9, 1.08 and 3.21 ppm, respectively. The combin ation of the concrete materials for the most lowering concentrations of Co- 60, Eu-152 and Cs-134 was the limestone as aggregate and the white Portland cement produced in specific places. The most lowering concentrations of th is limestone concrete were 0.16, 0.049 and 0.060 ppm, respectively. The lim estone concrete was excellent as biological shielding concrete, because the neutron shielding effect was excellent a little compared with ordinary con crete. If this concrete used for biological shielding concrete, concrete wa ste will be able to handle as follows. Usage of this limestone low-activate d concrete makes almost all concretes satisfy the clearance level for Co-60 after 20 yr cooling from decommissioning. In respect of Eu-152, radioactiv ation quantity in the biological shielding concrete is reduced up to a half of the average value or less. With regard to Cs-134, all concrete satisfie s the clearance level.