Nuclear Calculation Evaluation of CANDU Fuel Channel Deformation

As the operational time increases, pressure tubes and calandria tubes in CANDU core encounter inevitably a geometrical deformation along the tube length. A pressure tube may be sagged downward within a calandria tube by creep from irradiation. Fuel pin bundle shape may also be changed by irradiation creep. The worst case from safety point of views must be the irregular deformation of fuel bundle in sagged tube. When a pressure tube at high temperature contacts with a calandria tube wall at low temperature, hydrogen spread and blister by gradient of temperature may also be formed. Then, a crack course damage of pressure tube can occur. This event can bring about a problem that is serious in integrity of pressure tube. A measurement of deflection state of in- service pressure tube is, therefore, very important for the safety of CANDU reactor. In this study, effects of fuel channel deformation on nuclear safety parameters are to be analyzed. With results from analysis, methodology improvement for the correction for channel deformation will be studied. In this paper, comparisons of MCNP and HELIOS results for the deformation of CANDU fuel channels are provided as the primary step research