The Research On Release And Diffusion Mechanism Of Fission Products In Advanced Pressurized Water Reactor

Many radioactive fission products will be produced in the core when the nuclear reactor runs. These radioactive fission products will release to the fuel rod gap by the mechanism of recoil, knockout and diffusion under high temperature condition. Meanwhile, the radioactive fission products in the gap will release to the primary coolant circuit if the fuel rod damage occurs. These radioactive fission products in the radioactive fission products are the main source term in the reactor.To calculate the fractional release precisely, we studied and analysed many methods of American and France. After studying American NRC ANSI/ANS-5.4 methods and French methods of calculating the fractional release of volatile fission products, we calculated the fractional release of volatile fission products of a fuel rod at different power and different burn up by these methods, after that we made some comparison and analysis of these results. We found that the fractional release of volatile fission products would increase if the power and burn up of the fuel rod increase,and compare to ANSI/ANS-5.4-2011, the French method is more conservative, but ANSI/ANS-5.4-1982 is the most conservative among these methods. ANSI/ANS-5.4-2011 can be used to calculated the fractional release precisely.