Performance Evaluation of Typical 3-Loop PWR With Annular Fuel Assemblies Under Typical Accidents

Abstract The externally and internally cooled annular fuel is considered to have a good prospect with the shorter heat transfer path, larger heat transfer surface and higher burnup depth, which can effectively improve the safety of the reactor. This paper takes the nuclear power plant CPR1000, which is representative in China, as the reference power plant. The system analysis code NUSOL-SYS was used to estimate the thermal and hydraulic parameters of the reactors during the transient period, and the sub-channel analysis code NACAF was used to estimate the MDNBR of the core. The results showed that in the large break loss of coolant accident, since the annular fuel has less heat storage and a larger heat transfer surface during steady-state operation, the peak temperature of its cladding surface was only 861K, which was much lower than the corresponding temperature 1233K of the solid fuel. In addition, because the thickness of the annular fuel is small, the temperature of the inner and outer cladding was basically the same, but because the inner channel does not have the spacer grid and other effects, the level of the inner channel was slightly higher than the outer channel, and the inner wall surface was completely quenched slightly earlier than the outer wall surface. In the main steam line break accident and the reactor coolant pump rotor seizure accident, the annular fuel had a larger MDNBR, which caused a smaller risk of fuel damage. During the rod ejection accident, the average temperature of the annular fuel was lower than 900K, and the average enthalpy was lower than 200kJ/kg, which is far lower than the corresponding value of the solid fuel. In addition, the results of the annular fuel calculation model at 150% power showed that in the above four accidents, it was feasible to increase the power of the core loaded with annular fuel by 50%.