Out-of-pile bundle experiments for the investigation of severe fuel damage (CORA-program): Test CORA-13

CORA-13 confirmed the behavior of the earlier quench test CORA-12 and is in agreement with the behavior of the BWR quench test CORA-17 and the inpile LOFT FP2 test, which was also finished by quenching. In all tests a temporary temperature increase especially in the upper part of the bundle was found with the initiation of the quench process. The temperature increase is always accompanied by a parallel development of the hydrogen production. The increase of temperature and hydrogen production is the more pronounced the higher is the temperature at the beginning of quenching. This result can be explained by a temporary increase of the Zr/steam reaction during the quench process. The unoxidized metallic Zircaloy must have been exposed to the steam in an increased manner. The formation of cracks and break away of the protecting oxide layer may be the reason for this increased access. (orig.)