RIH 35% Large Break LOCA without ECC for the RUFIC core

CATHENA models for a PHTS circuit and fuel channel analyses have been developed for a CANDU-6 reactor loaded with CANFLEX-RU (Recycled Uranium) fuel, and a demonstration analysis for a RIH 35% LBLOCA/LOECC has been performed. The major difference of the CATHENA circuit and slave fuel channel models for the CANFLEX-RU core from those for a standard 37-element NU core came from the different power distributions in the bundle and core resulting from the increase of the fuel fissile content, average discharge burnup, and axial power shape change due to the change in the refueling scheme. The minimum CPR is found to be M-19. However the M-04 channel, a twin channel to M-19 channel, is chosen as the hypothetical limiting channel for a Large LOCA accident analysis. As for the results of the reactor power pulse calculation, the peak reactor power and the peak power of the limiting channel are found to be 1.485 times, and 1.986 times as big as those of a standard 37-element fuel case. It is expected that the breakup criterion of the fuel, 840 J/g, is not exceeded at the hottest bundle in the limiting channel. The fuel channel blowdown analysis result shows that the portion of the pressure tube corresponding to bundles 2 to 8 is predicted to be ballooned contact during 22 to 32 sec into the accident, similar to the NU core case. As for the results of a demonstrative post-blowdown analysis for the inlet steam flow condition of 10 g/s, the center fuel temperature at bundle number 5, reaches 2057.6oC at about 331.5 sec. In general, the results of the CATHENA circuit analysis including the power pulse analysis, blowdown and post-blowdown fuel channel analyses for the CANFLEX-RU core fall within the foreseeable expectations with reasonable trends. (author)