Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Thermo-mechanical behavior of ablated reactor pressure vessel (RPV) during in-vessel melt retention is assessed. Specifically, we provide a preliminary synthesis of a benchmark exercise on a generic Pressurized Water Reactor (PWR) RPV with external water cooling. A two-layer pool configuration with a molten metal layer atop, reaching a local heat flux of 2 MW/m² on the vessel wall is assumed reflecting a focusing effect which in turn results in a thin ablated wall with remaining thickness of 16 mm. The aim is to investigate the effect of internal pressure on the structural integrity of the RPV. A total of 7 contributions from different organizations using 5 different codes are analyzed. The results are divided into low internal pressure cases where no vessel failure is expected, and high internal pressure cases where vessel failure is found based on specific failure criteria applied by the users. At 3 bar internal pressure, all the results reflecting stresses and strains indicate no vessel failure. Four contributions found vessel failures at internal pressure of 40, 45, 50, and 52 bars. The mode of failure in all calculations is the same, which is plastic instability caused by high stresses, although the failures are indicated by different criteria. Further, the results are compared against a simplified approach and reasonable agreement is found. Finally, a preliminary failure map is generated to demonstrate the applicability of a previously proposed methodology that utilizes a safety criterion based on the relation between the minimum vessel thickness and the maximum internal load.