Fluid-dynamic loading during lower head failure Original Research Article

The containment concept of Eibl, Keβler, and Hennies for nuclear power plants equipped with large pressurised water reactors is aimed at developing passive mechanisms that are capable of safely confining core-melt consequences. Regarding this, it is important to know the ultimate loads acting on the supporting containment structures in case of core-melt accidents. In this study a large break of the reactor pressure vessel under high pressure (17 MPa) is assumed. The hydraulic load acting on the vessel supporting structure during the vessel blowdown was estimated. The results presented are based on calculations performed with the transient analysis thermal-hydraulic code RELAP5/ MOD3. The information obtained provides a force-function input for necessary structural dynamic investigations. On the assumption of a global circumferential rupture of the lower head of the pressure vessel, the computational results show a load peak of 340 MN and a continuing load of 160 MN acting on the vessel support ring.