Effect of Ni/Fe Ratio and Ni Concentration on Crud Deposition Behavior on Heated Zircaloy-4 Surface in Simulated PWR Primary Water

摘要

Crud deposition on fuel cladding surface would become significant issue in Japanese PWRs, because the large amounts of crud deposition has led to an increase of the dose rate in the primary coolant system and become a root cause of axial offset anomalies (AOA). In order to clarify the contribution factors of the deposition, the effects of heat flux, Ni/Fe ratio and nickel concentration in the test solution on the crud deposition were investigated in a simulated Japanese PWR fuel cycle chemistry at 325°C under sub-cooled boiling and non-irradiated condition. From the test results, it was revealed that the crud layer composed of NiFe2O4 and NiO was formed on the fuel cladding. The amounts of deposited crud layer increased with increase of heat flux and Ni/Fe ratio in the test solution. Ni contents in the crud layer increased with increase ofNi concentration in the test solution.