The test results showed that the CRD structural material reacted with the metal debris and melted and failed at about 1050-1250°C, which was lower than the melting point of the CRD itself. It was also observed that the molten material flowed into the CRD, suggesting that the CRD structure was preferentially damaged during SA. From the cross-section observation of the sample and phase diagrams on its materials, it was found that the housing and the stub tube of the CRD melted and failed due to the Zr-Fe and Zr-Ni eutectic reactions with Zr in the molten metals, respectively. In the experiment, it took a certain amount of time from the start of the CRD reaction with the metal pool until it melted and broke, indicating that the reaction speed was also an important factor in the failure of RPV.