There is a strong radiation field in operating fuel pins, which affects the chemical state of fission products. The effect of the radiation field on the iodine partial pressure in operating fuel pins has been theoretically studied. The decomposition rate of CsI in operating fuel pins has been calculated by a Monte Carlo code and the radiation effect on iodine partial pressure in a fuel-cladding gap has been evaluated. It has been found that the iodine partial pressure calculated with consideration of the radiation effect is higher than that in the thermal equilibrium without radiation. The probability of CsI decomposition has been calculated as a function of distance from the fuel surface. The calculation results show very large decomposition probability at the near surface of the fuel, where low energy particles are dominantly emitted. When the gap is closed, the very high partial pressure of iodine is expected in a remaining small space between fuel and cladding.
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Nuclear Energy and Engineering
- Materials Science(all)