Post irradiation examination results of MA containing MOX fuel. Non-destructive examination results of the fuel pins

Japan Atomic Energy Agency (JAEA) researchers have carried out irradiation experiments of minor actinide-containing mixed oxide fuel (MA-MOX) in the Fast Experimental Reactor 'JOYO'. The MOX fuel that contained 3% or 5% americium, and the MOX fuel that contained 2% americium and 2% neptunium were used. The irradiation experiments were for 10min or 24h at the maximum high linear heat rate of about 430W/cm. After the irradiations, the post irradiation examinations were done in JAEA's Fuel Monitoring Facility. This report presents the results of the post irradiation examinations. The main results are as follows. (1) The X ray CT examination showed that the predicted density decrease in the vicinity of the center of the fuel pellet was occurred for the 10min irradiation. The formation of the central void was observed clearly at the center of the fuel pellet in the 24h irradiation. (2) The elongation of about 3mm was observed in the stack length of the fuel pin in the 24h irradiation. This was due to some of the gaps being less than 1mm. (3) Bowing of the fuel pins was 7.2mm for the Am-MOX fuel pin (24h irradiation) and 12.5mm for the Np/Am-MOX fuel pin (24h irradiation). This bowing (PFB110) is larger than bowing of the other short-term irradiation fuel pin (PFB052 and PFBF40). (4) The γ-ray intensity of Zr-95 decreased and that of Ru-103 increased at the upper region of the fuel stack in the pin irradiated for 24h. (author)