Primary coolant source term of System-Integrated Modular Advanced Reactor (SMART) due to activated colloidal crud under dynamic grid load following

Abstract

The grid load following result in power modulation accelerates the corrosion and activated colloidal crud activity in the primary coolant of PWRs. This paper seeks the response of activated colloidal crud in primary coolant under grid load following resulting in dynamic power modulation. Therefore, a computer code ACCP-SMART “Activated Colloidal Crud Particle in System Integration Modular and Advanced” has been developed. The core of the SMART reactor is modeled in OpenMC to generate the group fluxes under the reactor design constraints. The dynamic grid load following has been employed under the guideline and regulations of IAEA and NEA. The primary coolant activity due to activated colloidal crud has been observed as 51Cr >56Mn >99Mo >24Na >59Fe >58Co >54Mn >60Co. The activated colloidal crud with shorter half-lives (24Na, 54Mn, and 65Mn) responded swiftly corresponding to the power modulation under grid load fluctuation. However, the activated colloidal crud with longer half-lives (51Cr, 58Co, 59Fe) gradually responds to operated power maneuvering corresponding to the grid load and takes several hours (≈200 h) to attain a new saturation value after the stabilization of reactor operating power. The specific primary coolant activity due to colloidal crud is predominated in the primary coolant. Later, the steam generator activity dominated the primary coolant activity due to the gradual deposition of crud on steam generator tubes. The primary coolant specific activity due to 56Mn, 54Mn, 24Na, and 59Fe abruptly responded to reactor power modulation in primary coolant and on the core scale. while their response is trivial on steam generator surfaces. On the other hand, the primary coolant specific activity due to activated colloidal crud containing 51Cr, 58Co, and 60Co are less vulnerable and gradually respond to the power modulation and take several hours to attain a new saturation value after power stabilization.