Analysis of Fast Reactor Fuel Irradiation Behavior in the MA Recycle System

A recycle system for minor actinides (MAs) is currently studied to reduce the degree of hazard and the amount of high-level radioactive wastes. In this system, MAs will be recycled by reprocessing and irradiating as mixed oxide (MOX) with plutonium (Pu) and uranium (U) in a fast reactor. It was reported that MA-containing influences up to MA content less than ∼3 wt.% of the heavy metal amount on thermal fuel properties, i.e. melting temperature and thermal conductivity, would be slight. However, MA content of MOX fuels is expected to be ∼5 wt.% in the future recycle system for MAs, and MAs might affect irradiation behavior of MA-MOX fuels. The main influences of MA-containing would be increase of fuel temperature and cladding stress, and the important irradiation behavior of MA-MOX would be fuel restructuring, redistribution, helium (He) generation and cladding corrosion. Several irradiation experiments were performed in experimental fast reactor Joyo to study MA-containing influence on fuel behavior during irradiation. In addition, CEPTAR.V2 was developed so that fuel properties and analysis models would be included to evaluate the MA-MOX fuel behavior during irradiation. In this study, the MA-containing influences were evaluated with CEPTAR.V2 by using the results of highly americium (Am) containing MOX irradiation experiment, B8-HAM, performed in Joyo, and as a consequence, the irradiation behavior of Am-MOX fuels could be precisely analyzed and revealed as the influences of Am content.