ESTIMATION OF THE CORE-MATERIAL-RELOCATION BEHAVIORS TO THE PEDESTALS IN FUKUSHIMA-DAIICHI UNITS 2 AND 3

抄録

The conditions for the Reactor Pressure Vessel (RPV) boundary failure and the behavior of the post-failure core material relocation to the pedestal in Fukushima Daiichi Nuclear Power Plant Units 2 and 3 were evaluated by integrating plant data, internal investigation results, and existing researches.

As a result, it is estimated that melting of Control Rod Drive (CRD) penetrations on the RPV wall occurred in Units 2 and 3, causing a leakage of core materials consisting mainly of molten metals. It is also suggested that local failure of the RPV side wall could have taken place at some time during this period. After this moment, cooling of remaining debris inside the RPV by injected water seems to have been established in Unit 2. In contrast to this, in Unit 3, in-vessel debris cooling is likely to have been insufficient allowing further debris/RPV heat up and resultant massive debris relocation to the pedestal.