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Assessment of S/R5/MOD3.3 Models of Stratified Molten Pool and Debris-to-Vessel Contact Resistance by TMI-2 Lower-Head Creep Rupture Analyses

2006; Taylor & Francis; Volume: 156; Issue: 2 Linguagem: Inglês

10.13182/nt06-a3785

1943-7471

Sang Lung Chan,

Fatigue and fracture mechanics

The U.S. Nuclear Regulatory Commission (NRC) is consolidating all its severe-accident codes into one code, MELCOR, and making an effort to bring it into a state of parity with SCDAP/RELAP5/MOD3.3 (S/R5/M3.3) to model a Three Mile Island Unit 2 (TMI-2)–like accident. In this regard, this cooperative research project seeks to help the NRC to assess S/R5/M3.3 associated with case studies of the TMI-2 lower-head creep rupture. The results of the simulations clearly demonstrate that the TMI-2 lower-head failure occurs. Thus, solely using the S/R5/M3.3 models of the molten pool and debris-to-vessel contact resistance, without implementing the gap cooling model, cannot explain the conservation of the TMI-2 lower head during the accident. These studies also conclude that the results calculated with the UNIX and Microsoft PC versions of S/R5/M3.3 are comparable, and hydrogen productions as well as lower-head creep ruptures vary with different time steps for the alternative accident. Further, those results for the base case and alternative accident are alike; thus, the models cannot differentiate between the base-case and alternative accident scenarios.