Simulation of activated corrosion product activity in Korean design system-integrated modular advanced reactor (SMART) under steady-state flow and linearly accelerated corrosion

Abstract

The activated corrosion products are the leading source of radiation in Nuclear Power Plants (NPPs). Particularly in advanced integrated systems with a reduction in piping and advanced safety features such as system-integrated modular advanced reactor (SMART), the corrosion product activity is needed to be investigated. In this work, simulation of corrosion product activity has been evaluated for the SMART reactor under normal and shutdown conditions and compared with a typical Pressurized Water Reactor (PWR). For this purpose, a computer code ACP-SMART has been developed and implemented in MATLAB, which uses OpenMC as a subroutine. The effective group cross-section has been generated by OpenMC under the core design constraints. The results for 56Mn, 59Fe, 24Na, 99Mo, 58Co, and 60Co have been found as 0.072 μCi/cm3, 0.240 μCi/cm3, 0.290 μCi/cm3, 0.360 μCi/cm3, 0.015 μCi/cm3, and 0.020 μCi/cm3, respectively. The total specific activity due to corrosion products in the core, primary coolant, and inside the steam generator is 2.790 μCi/cm3, 0.183 μCi/cm3, and 0.145 μCi/cm3, respectively, which are 89.5%, 5.8%, and 4.7% of the overall contribution. Results indicate that the primary coolant and steam generator specific activity reach their saturation values fairly rapidly. Predominant corrosion product activity during normal operation is due to 56Mn while 58Co and 59Fe dominate after reactor shutdown. 99Mo remains dominant to 24Na and 59Fe during normal operation while 59Fe leads over 99Mo and 24Na after shutdown. A linearly increasing corrosion rate has been employed, and an effect on saturation activity has been investigated. For the linearly increasing corrosion rate, the specific activity behavior has changed considerably. The time taken to reach the saturation activity strongly depends upon the corrosion rate. The saturation activity in the primary coolant and steam generator depends on the CRUD removal rate from the core scale.