Assessment of the radioactivity production in water coolant system of WCCB for CFETR

Abstract

A massive amount of radioactive isotopes, including both water activation products and activated corrosion products (ACPs), are produced in the water coolant of a fusion power plant. These are gaining increasing attention, because they determine the occupational radiation exposure during operation and maintenance, and decrease radioactive safety. The purpose of this study is to assess radioactivity production in the coolant system of a water cooled ceramic breeder (WCCB) blanket of the Chinese Fusion Engineering Test Reactor (CFETR) during its design stage. The Monte Carlo N-Particle Transport Code (MCNP) and nuclear inventory code FISPACT-2007 were used to calculate the water activation products, while the CATE 2.1 code was applied to evaluate the ACPs production in the coolant system. In this study, the CFETR was assumed to operate under a 200 MW fusion power with a duty factor of 0.5. Furthermore, the WCCB blanket was assumed to operate for five years (2.5 FPY) prior to dismantling. The specific activity of 16N at the blanket outlet reaches approximately 2.26 × 1012 Bq/kgH2O, while 17N reaches approximately 6.38 × 108 Bq/kgH2O during the operation. The dose rate contributed by water activation products in the coolant system is more than 2.07 × 103 Sv/h during the operation. At the end of the WCCB operation time, the corrosion products deposited in the pipe surface of the in-flux and out-flux regions are 7.54 and 22.25 kg, respectively, and there are 0.05 g of corrosion products dissolved in the coolant. At the end of the WCCB operation time, the activities at the pipe surface of the in-flux and out-flux regions are 1.78 × 1012 and 4.99 × 108 Bq/m2, respectively. Furthermore, the activity contributed by the dissolved ACPs in the coolant is 4.76 × 104 Bq/kgH2O during the operation.