Melting test of penetrating tube through BWR-RPV bottom wall

Melt behavior of a BWR in-core monitor (ICM) guide tube, which penetrates a RPV bottom wall, under a severe accident condition was tested using a corium with a mixture of UO2, ZrO2 and Zr. There are several BWR-ICMs; two of them are a short range monitor (SRM) and an intermediate range monitor (IRM), which are made of stainless steel, have the same tube dimensions and the bottom ends of the tubes open to the drywell (or, the pedestal region). In the test, the full scale SRM/IRM guide tube with the same dimension as one of Fukushima Daiichi Unit-1 but short length, was installed in the lower crucible which simulated the lower plenum and which bottom simulated the RPV bottom wall with about 200 mm thickness. The melt corium was generated in the upper crucible and it was discharged into the lower crucible. The test result showed that: