Plastic Collapse Evaluation of Fuel Channel Assembly in Pressurized Heavy Water Reactor

400 fuel channel assemblies are there in a PHWR. Each assembly consist of a CT as outer tube, a PT as inner tube, and 4 GSs to prevent contact between two tubes. The fuel bundles, inserted into PT of fuel channel assembly, heat the coolant to high temperature by nuclear fission. Furthermore, the pressurizer compresses the coolant not to boil in high temperature. From this, high pressure and high temperature condition happened in the PT. So, the integrity of PTs needs to be guaranteed. Although large number of previous researches were performed, they assumed a PT as single tube and did not take into account the constrained effect. In actual behavior, PT contact with CT, GS or both. In addition, its structural shape made bending restraint effect to the PT. Since the contact force and bending restraint effect make limit in behavior of the PT, previous evaluation results are not accurate. In order to obtain more accurate result, it is needed for the PT to be modeled as fuel channel assembly including CT and GSs. For this, 3D FE model of fuel channel assembly is proposed and validated by comparing with previous creep analysis result in previous study. In this study, fracture mechanical FE analysis is conducted for the PHWR fuel channel with circumferential surface or through-wall crack at the PT. Parameters of PIP geometry and bending restraint effect which can apply to plastic collapse evaluation of the PHWR fuel channels are extracted.