Evaluation of the power-to-melt experiments POTOM

Abstract

The determination of rod powers leading to fuel melting is the object of the irradiation experiments POTOM of the German Fast Breeder Projects. In the irradiation campaign of these POwer-TO-Melt experiments three types of irradiations with fresh mixed oxide fuel pins have been carried out in the HFR Petten, The Netherlands. Three fuel pins with 15, 20, and 30% Pu highly dense mixed oxide fuel have been simultaneously irradiated up to melting during approximately 1–75 h. In the 1 h experiment melting was reached from 547 W/cm for the 30% Pu fuel up to 622 W/cm for the 15% Pu fuel. These power limits were increased by up to 70 W/cm due to fuel restructuring and relocation. Extensive post irradiation examination and thermal analysis with the fuel behaviour code SATURN-S showed good agreement. As the experiments were conducted under epithermal flux with a resulting depression of 0.5, calculations under fast flux conditions with the same fuel pin data have been carried out. Power-to-melt decreases significantly by about 100 W/cm, compared with the epithermal conditions.