Feasibility study on Plutonium burning in future Monju cores

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Udo, Wehmann; 影山 武*

Udo, Wehmann; Kageyama, Takeshi*

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These studies have been planned and performed as a contribution to the demon- stration of the plutonium burning capabilities of fast reactors in future Monju cores. For an upgraded Monju core design with an increased average discharge burnup of 100 GWd/t, burner cores with diluents and with diluting pins have been investigated, the main aim of which is to increase the average plutonium enrichment of the fuel and thus the plutonium burning rate. On the other side the consequences of the suppression of the radial and/or axial blanket have been investigated. The results of these studies had been documented separately in [1] to [5], while this reports gives the compilation of these studies and a judgement about the different burner concepts. Among the burner concepts different types of diluents (containing sodium and steel or B4C) and diluting pins (Steel, moderator or B4C) have been compared with each other. The diluent concept with B4C-diluents has been found to be the preferable one, because it causes the smallest increase of the maximum linear rating and because it offers the largest design flexibility to adapt the core reactivity via a modification of the B4C content. For the case of the blanket suppression the replacement of the blanket zones by a steel reflector has been found to be the best solution, whereby the addition of some B4C in the outer reflector regions may be necessary to increase the shielding efficiency. The main consequence of the suppression of both blankets is the increase of the maximum linear rating by up to 12%. Whether this increase may lead to problems, will depend on the actual linear power level of the core and the maximum allowable value as defined by the non-melting criterion. For cores with partly reduced radial and/or axial blanket data are also provided.