Analysis of QUENCH-ACM Experiments using SCDAP/RELAP5

摘要

The QUENCH experimental programme at Karlsruhe Institute of Technology (formerly Forschungszentrum Karlsruhe (FZK)) investigates heat-up and reflooding of a core under severe accident conditions, but while the geometry is still mainly rod-like. The recent QUENCH-ACM series of experiments, comprising QUENCH-12 (E110), -14 (M5~?) and -15 (Zirlo?), together with QUENCH-06 (reference case, Zry4) addressed the effect of alternative cladding materials on oxidation and quenching under similar conditions. The cladding material and bundle configuration reflected different reactor core designs, namely WER, EPR, Westinghouse AP-1000 and Siemens Konvoi, respectively. Superficial inspection of the experimental results reveals only minor differences in the thermal and oxidation response, except for the much larger hydrogen release during reflood in QUENCH-12. Post-test calculations were performed using a version of SCDAP/RELAP5/MOD3.2, modified to represent the QUENCH facility and to invoke alternative oxidation correlations. The calculations agreed rather well with experiments QUENCH-06, -14 and -15 but the significant hydrogen release during reflood in QUENCH-12 was not captured. Closer examination of the experimental results reveals further differences between QUENCH-12 which may be linked to breakaway oxidation of the E110 cladding, for which there is evidence from post-test inspection. Sensitivity studies using the Sokolov correlation (for El 10) and a trial correlation for M5 indicate no improvement over the SCDAP standard correlation (Cathcart-Pawel/Urbanic-Heidrick). The analyses support the heuristic observation that there was no major difference between the influence of Zircaloy-4, M5 or Zirlo, but the E-110 exhibited a contrasting behaviour with a consequent impact on the reflooding.