MCCOOR code was used to simulate the nuclide compositions for pressurized water reactor(PWR) fuel and boiling water reactor(BWR) fuel in the pin-cell model at different burnups for two different initial fuel enrichments and full power history,respectively.

Experiences in-core indicate that the swelling of metallic fuels is so severe that the cladding begins to fail at a low burnup,moreover the solidus temperature of uranium or uranium-plutonium fuel and eutectic temperature with stainless steel cladding materials are low and made it impractical to use metallic fuels in a commercial reactor.

The problem of how to calculate the spontaneous combustion depth,based on a study of the characteristics of temperature distribution in a rock dump,was considered and we propose to answer the question by calculating the spontaneous combustion depth from an analysis of the balance equation of heat generation and dissipation in the rock dump.