CORA-W2 experiment on severe fuel damage for a Russian type PWR OECD/NEA-CSNI international standard problem ISP 36. Comparison report

An OECD/NEA-CSNI International Standard Problem (ISP) has been performed on the experimental comparison basis of the severe fuel damage experiment CORA-W2. The out-of-pile experiment CORA-W2 was executed in February 1993 at the Forschungszentrum Karlsruhe. The objective of this experiment was the investigation of the behavior of a Russian type PWR fuel element (VVER-1000) during early core degradation. The main difference between a Western type and a Russian type PWR bundle is the B_4C absorber rod instead of AgInCd. Measured quantities are boundary conditions, bundle temperature, hydrogen generation and the final bundle configurations after cooldown. Due to the large number of participants the comparisons between experimental and analytical results could be grouped by codes and examined separately. The thermal behavior up to significant oxidation has been predicted quite well by most of the participants and all codes. Larger deviations have been observed for the oxidation-induced temperature escalation, both time of onset and maximum temperature as well. The bundle behavior is greatly influenced by chemical interactions involving B_4C absorber rod material, which failed relatively early at low temperature due to eutectic interaction between B_4C and SS cladding as well as the SS guide tube. Regarding the complex material interaction larger differences can be recognized between calculated and measured results because of inappropriate models for material relocation and solidification processes and the lack of models describing the interactions of absorber rod materials with the fuel rods. (orig./HK)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman