ICONE19-43954 Development of Estimation of Activity Induced in Concrete in Nuclear Power Plants

Abstract

Biological shielding wall (BSW) concrete of commercial LWR is activated by neutrons emitted from the reactor core during its operation. Most of wasted BSW, having a large volume, is classified as very low radioactive level. It has been suggested that deterministic calculation methods give inaccurate estimation of activation in nuclear facilities. By using Monte-Carlo calculation methods, induced radioactivity in concrete could be estimated more accurately.The discrepancy between the calculated and measured activation in concrete is said that it attributed to water content of concrete and reinforcing bars. Concrete samples with different water to cement weight ratio without reinforcing bars and one containing reinforcing bars were exposed to neutrons in the fast column of the research reactor "YAYOI" and induced radioactivity inside were measured with gold foils by the foil activation method. Radiation transport was simulated by DORT, MCNP-5 and compared with experimental results.The build-up of 197 Au (n,) reaction rate depth profile in the sample was not found. Regardless of the water to cement ratio, the distribution of activation in the concrete samples agreed within the margin of error. The reinforced concrete was weakened reaction rate about 40 percent. Reinforcing bars did not affect epi-thermal neutron flux significantly.