The Behavior of fission products in irradiated mixed oxide/nitride fuel under transitional heating conditions

Sato, Isamu

In the safety research for severe accidents of atomic power plants, it's of value to evaluate kinds and amounts of radioactive species released into the environment during atomic reactor accidents, which is called "source term". Especially, there are no experimental source term data for irradiated fast reactor fuels under the temperature over the melting point of fuels. JAEA has performed some experimental researches of FP release behavior in order to recognize the source term in FR plants with mixed oxide fuels irradiated in the experimental fast reactor, "JOYO". In the tests for oxide fuels, the time-dependence of the release rate of Cs indicate that Cs release could controlled not only by diffusion in fuel but also by vaporization. The source term results for nitride fuel were partly differed from those for oxide fuel. With thermochemical consideration, we indicated that the oxygen partial pressure around oxide fuel under the test was higher than around nitride fuel.