Research of Corrosion Products Migration Behavior in PWR Primary Circuit Under Extended Low Power Operation Mode

Abstract

AbstractIn order to improve the flexibility of response to power grid demand, both newly built and in-service nuclear power units need to demonstrate the feasibility of ELPO (Extended Low Power Operation) and design schemes. During ELPO, the change of local thermal hydraulic conditions caused by the change of core power will have a great impact on the migration behavior of corrosion products in the primary circuit of PWR (Pressurized Water Reactor). Corrosion products deposited in the core will affect the heat transfer of fuel cladding, axial power distribution and critical heat flux. Corrosion products deposited outside the reactor, such as the main tubes, will affect the dose rate of personnel and pose challenges to radiation protection. A model for simulating the migration of corrosion products in the primary circuit of a PWR was established. The variation trends of the total amount of fuel CRUD (Chalk Rivers Unidentified Deposit), the total amount of fouling outside the reactor, the removal amount of corrosion products, the coolant source term and the main tubes deposition source term of a PWR before and after ELPO were compared. The results show that ELPO mode can inhibit the deposition of corrosion products in the core, and make more corrosion products deposit outside the core or be removed by CVCS (Chemical and Volume Control System). Because ELPO mode accelerates the migration of activated corrosion products to other regions, the coolant source term increases slightly. For the source term of main tubes sediment, ELPO model can reduce its total activity, thus reducing the personnel dose rate.