TABLE OF CONTENTS This appendix considers one of the more extreme solutions against severe accidents (see Chapter 5) which consists of a steel-reinforced concrete cage built around a PWR vessel with the purpose of absorbing, by plastic deformation, the energy released by a steam explosion (internal or external to the vessel) and which causes its rupture and the violent projection of its pieces into the surrounding space.
A possible conceptual scheme is presented with the verification calculations. (The calculations and drawings are due to Dr Eng Giuseppe Pino.) The results of some experimental tests at a reduced scale performed several years ago on safety cages similar to the one described are presented.
This evaluation is undertaken for an AP 600 reactor.
The mass of the molten core is about 110 t (61 t of UO 2, 18.8 t of Zr, 29.2 t of stainless steel). The initial temperature of the corium ranges between 2000K and 2500K and the final temperature, after quenching in water, is about 400K.
On the basis of the specific heat and of the fusion heat, the specific thermal energy is about 1 MJ kg ?1 and therefore the total energy amounts to about 110 000 MJ.
The conversion of thermal energy into mechanical energy in this phenomenon has a low efficiency, ranging from 2 to 15 per cent with a likely value close to 4 5 per cent.
Therefore the mechanical energy produced by the...
