Nuclear Technology / Volume 168 / Number 2 / November 2009 / Pages 564-570
Shielding Materials / Special Issue on the 11th International Conference on Radiation Shielding and the 15th Topical Meeting of the Radiation Protection and Shielding Division (Part 2) / Radiation Measurements and Instrumentation
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 Di/Ci (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.