Development of Low-Activation Reinforced Concrete Design Methodology - I: Manufacture of Low-Activation Concrete

Screening tests using several reactors were performed to select low-activation raw materials. The number of samples was about 1500. Detailed data were obtained on the concentrations of Co and Eu in low-activation aggregates, low-activation cements, low-activation additives, and low-activation B₄C sands. After that, we manufactured various types (1/10, 1/20, 1/30, 1/50, 1/100, 1/300) of low-activation concrete. The term "1/10 low-activation" concrete denotes that the activity reduction rate to ordinary concrete is designed to be 1/10. By admixing with a boron content of [approximately]1 × 10²¹/cm³, the total residual radioactivity reduction rates of low-activation concrete to ordinary concrete, in units of D_i/C_i (Di: concentration of radionuclide i, Ci: clearance level of radionuclide i cited from IAEA-RS-G-1.7), are estimated to range from [approximately]1/300 to 1/10 000. It was concluded that most of the shielding concrete around the advanced boiling water reactor (ABWR) or the advanced pressurized water reactor (APWR) are classified below the clearance level of decommissioning by adopting some suitable types of low-activation concrete.