Effect of core power variation on crud deposition behavior on fuel cladding surface

BackgroundFor a pressurized water reactor (PWR), under the synthesis effects of primary water chemistry, reactor operation mode, system facilities replacement, fuel design and management, the corrosion products in primary coolant will deposit on the outer surface of fuel cladding, which is commonly called fuel crud. Fuel crud formed on the cladding surface may result in crud induced localized corrosion (CILC), crud induced power shift (CIPS) and raise the primary source term. The deposition behavior of fuel crud is affected by both the corrosion products concentration and the core boiling rate.PurposeThis study aims to investigate the influences of core power variation on the corrosion products concentration and the core boiling rate, and eventually evaluate the fuel crud deposition states under different core powers.MethodsThe core crud mass and the maximum crud thickness on fuel cladding surface were estimated by the CAMPSIS, an independent crud behavior analysis software developed by China Nuclear Power Technology Research Institute Co., Ltd (CNPRI). Influence of core power variation and the combined effect of core boiling rate and corrosion product concentration were analyzed.ResultsComputational results that, within the range of 75%⁓100% full power (FP), the lower the core power is, the smaller the core crud mass will be, but the maximum crud thickness will increase. When the core power decreases to 50% FP, the maximum boiling rate is close to zero, and both of the core crud mass and the maximum crud thickness are minimum.ConclusionsThe core power reduction of a nuclear reactor may lead to the increase of local fuel crud thickness, and adversely affect the heat transfer between the fuel cladding and the coolant. It is suggested that the influence of core power reduction on fuel crud deposition should be considered if a nuclear reactor tends to operate at a lower core power.