Postirradiation examination of "JOYO" MK-II B-Type uninstrumented irradiation subassembly (Fab.No.PFB000)(1)

not registered; Enokido, Yuji*; not registered

Nondestructive examination of uninstrumented irradiation subassembly(Fab.No.PFB000, average burn-up 5,100MWD/MTM) has been performed. The subassembly was the first one which introduced into Fuel Monitoring Facility (FMF) as uninstrumented irradiation subassembly series in "JOYO" MK-II irradiation project. The results of the postirradiation examination in FMF are summarized as follows: (1)Subassembly inspection : Visual observation, measurement of face to face distance of wrapper tube, and the observation of interior construction condition of the rig indicated that the subassembly has behaved normally in reactor "JOYO". (2)Compartment inspection : No detrimental dimensional changes were not observed, and the contents in the compartments have been installed as were fabricated. (3)Fuel pin inspection : A slight changes in fuel stack length in comparison with the fabricated one have been confirmed by X-ray radiography, and the fission gas pressure in the fuel pins with large plenum volume was 897 Torr, while the pressure with small plenum volume was 913 Torr. No other irradiation behaviors were obviously observed. (4)Evaluation of remote handling operation with the rig and reassembling : No serious problems in the postirradiation examination performance, disassembling and reassembling have found. But it was not possible to decontaminate the materials surfaces in hot cells for reassembling. As present conclusion it is proposed that new materials except the fuel pins should be provided for the reassembling.