Developments in the fabrication technology of low density MOX pellets for fast breeder reactor fuel

Asakura, Koichi; Yamaguchi, Toshihiro; Otani, Tetsuo

The fabrication of low density MOX pellets was studied using some organic compounds as pore formers. The pore former, K3 showed the best performance among five organic compounds in the 7.5 kg-UOX runs, but K3 lost this in 36 kg-MOX run, possibly because plutonium decay heat affected its performance. Comparison of thermal stubilities between K3 and a newly introduced pore former, Avicel, of high softening temperature, showed that K3 lost its spherical particle shape and consequently, its pore forming ability at 70C which was below its reported melting point (84-88C) while Avicel could maintain its spherical particle shape up to 150C. The pore forming performance of Avicel was also comfirmed in the 36 kg-MOX run which is the same scale as for mass production of MOX fuel pellets.