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Tasaki, Yudai
no journal, ,
Fuel pellets contained in a fuel rod of a light water reactor release some degree of FP gas, and it raises inner gas pressure of the fuel rod. It is important for fuel design and safety evaluation to estimate fission gas release ratio (FGR), since excessive inner gas pressure may impair fuel integrity. Therefore, JAEA develops fuel performance code FEMAXI for evaluating various fuel behaviors. However, FEMAXI has limited capability for considering FGR in case of evaluating to compare MOX fuels which have different microstructures arised from the difference of production method. Because, FGR model of FEMAXI can apply only one kind of fuel grain. From the above, it is necessary to acquire sufficient understanding of MOX fuel behavior based on experimental data, and FGR modeling has to be improved accordingly. This study modified FGR model so that two kinds of grains with respect to Pu enrichment get applicable and released fission gas values from them are applied weighted average based on volume occupancy ratio of each structures. Upon analyzing two types of MOX fuels, the different homogeneity of microstructure, with and without the modified FGR model, then comparing the experimental data provided by a testing reactor, analytical results of FGR captured tendency of experimental data qualitatively. Hence, it was revealed that modified FGR model is valid for evaluating FGR in consideration of the heterogeneous structure of MOX fuel.
Taniguchi, Yoshinori
no journal, ,
no abstracts in English
Okada, Yuji
no journal, ,
Kakiuchi, Kazuo
no journal, ,
Fission gas release from MOX fuel pellet during reactivity-initiated accident (RIA) was estimated by using SEM-EPMA data before and after the pulse irradiation experiment for high burnup MOX fuel (BZ-3, BZ-4). As a results of considering the relative change of Xe depression in Pu-spot and the crack enhancing effect in the periphery region, the amount of fission gas released form Pu-spot was estimated as roughly approximately 5% in BZ-4 and 10% in BZ-3. In comparison with the measured fission gas release by the puncture test, it is probable that fission gas releases also from the region excluding Pu-spot.