Pyroprocessing of ZrN-based nitride fuels

Hayashi, Hirokazu ; Sato, Takumi  

Transmutation of long-lived radioactive nuclides including minor actinides (MA: Np, Am, Cm) is effective to reduce the burden of high level radioactive wastes and using repositories efficiently. Uranium-free nitride fuel has been chosen as the first candidate fuel for MA transmutation using accelerator-driven system (ADS) in Japan Atomic Energy Agency (JAEA) under the double strata fuel cycle concept. To improve the transmutation ratio of MA, reprocessing of spent MA fuel and reusing the recovered MA is necessary. Our target is to transmute 99% of MA arisen from commercial power reactor fuel cycle, with which the period until the radiotoxicity drops below that of natural uranium can be shorten from about 5000 years to about 300 years. Each reprocessing process is required to recover 99.9% of MA to meet the target. Typical composition of the solid solution type (MA,Pu,Zr)N fuel is considered as 30 wt.% of MA nitride, 20 wt.% of Pu nitride, and 50 wt.% of ZrN (dilution material to adjust the power density). Pyroprocessing has been proposed to adopt for reprocessing of the spent MA nitride fuel. This paper summarizes the status of our study on pyroprocessing of ZrN-based nitride fuels.