Trace Elements with Large Activation Cross Section in Concrete Materials in Japan.

Abstract

Amounts of trace elements with large activation cross section in concrete materials were measured to offer the basic data for developing of low activation concrete. From the measurements, the quantities of the activated radioactivities in biological shielding concrete were measured and evaluated for the clearance level. The average concentrations of 60Co, 152Eu and 134Cs formed in concrete were 21.9, 1.08 and 3.21 ppm, respectively. The combination of the concrete materials for the most lowering concentrations of 60Co, 152Eu and 134Cs was the limestone as aggregate and the white Portland cement produced in specific places. The most lowering concentrations of this limestone concrete were 0.16, 0.049 and 0.060 ppm, respectively. The limestone concrete was excellent as biological shielding concrete, because the neutron shielding effect was excellent a little compared with ordinary concrete. If this concrete used for biological shielding concrete, concrete waste will be able to handle as follows. Usage of this limestone low-activated concrete makes almost all concretes satisfy the clearance level for 60Co after 20 yr cooling from decommissioning. In respect of 152Eu, radioactivation quantity in the biological shielding concrete is reduced up to a half of the average value or less. With regard to 134Cs, all concrete satisfies the clearance level.