Features of heat and deformation behavior of a VVER-600 reactor pressure vessel under conditions of inverse stratification of corium pool and worsened external vessel cooling during the severe accident. Part 1. The effect of the inverse melt stratification and in-vessel top cooling of corium pool on the thermal loads acting on VVER-600’s reactor pressure vessel during a severe accident

•Simulations to determine a thermal state in two-layer and inverse molten corium in VVER-600.•Top flooding of the corium decreases by more than 40% the heat flux peak in two-layer pool.•For inverse corium pool, top flooding decreases by more than 50% the heat flux peak in steel layer.•In inverse cor...

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