Irradiated Fuel Performance Evaluation Technology Development

Performance evaluation system was established to investigate the irradiation characteristics of dual-cooled annular fuel. A new program which has a function of calculating fuel temperature and heat split of dual-cooled annular fuel is developed, and modules for calculating the distribution of thermal stress and deformation are presented. The reference code for transient performance has been analyzed in the aspects of the structure and model characteristics. The annealing tests were performed to evaluate the behaviors of the high burnup pellet and the large-grain pellet under transient conditions. A new post-irradiation annealing apparatus, which make a ultra-high temperature test possible, was established by substituting a new heating module an old heating one. Creep and embrittlement behaviors were also tested using newly established equipment in a hot cell. RIA(Reactivity Initiated Accident) and LOCA(Loss of Coolant Accident) test results were acquired and analyzed through international collaboration research with CABRI project in France and Halden reactor project in Norway. The second irradiation test is being performed with a burn-up target of 70 MWd/kgU for large-grain fuel pellets. Test fuel rods were fabricated for Fuel Test Loop and a steady state irradiation test is under way. The test rig were designed and fabricated for the irradiation of dual-cooled fuel rod, and then out-of reactor tests and safety analysis were conducted for the licensing of irradiation test. The dual-cooled fuel rods were irradiated to about 10 MWd/kgU in Hanaro reactor, and the post irradiation examination is going on. The profile of gamma scan shows that the annular pellet is stable in position during irradiation