PAHR in-pile and out-pile complementary studies

In the frame of the European, LMFBR related PAHR program, 4 in-pile experiments must be performed in the BR2 reactor. The ultimate goal of the program is to reach 3000 °C, i.e. the remelting of both stainless steel and UO₂, in a mixed debris bed initially saturated by liquid sodium. The first irradiation campaign (performed from November 10 through 19, 1986) allowed the detailed observation of the PAHR phenomena in a UO₂ debris bed till 1500°C. The paper not only describes the in-pile test device, developed by the CEN-MOL and called PIRAMID but also the out-pile test facility, developed by the Von Karman Institute and called OPERA, used for the modelling and the prediction of the PAHR phenomena. The interpretation of the experimental results of the PIRAMID 1 campaign will then be analyzed, covering heat conduction and convection, boiling, dry out, possible channeling and also the influence of disturbances induced by power ramps.