The objective of this analysis is to assess MELCOR 1.8.5-RG against SCDAP/RELAP5 MOD 3.3kz (SR5m33kz), and SCDAP/RELAP5 MOD 3.3bf (SR5m33bf). This lower head creep rupture analysis considers: (1) Three Mile Island Unit 2 (TMI-2) alternative accident sequence-1, and (2) TMI-2 alternative accident sequence-2. SCDAP/RELAP5 model of TMI-2 alternative accident sequence-1 includes the continuation of the base case of the TMI-2 accident with the reactor coolant pumps (RCP) tripped, and the High Pressure Injection System (HPIS) throttled after approximately 6000 s accident time, SCDAP/RELAP5 model of TMI-2 alternative accident sequence-2 is derived from the TMI-2 base case accident by tripping the RCP after 6000 s, and the HPIS is reactivated after 12,012 s. MELCOR model of TMI-2 alternative accident sequence-1 is based on MELCOR TMI-2 phase-2 model by tripping the RCP and throttling back the makeup flows to zero from 6000 s onward. In MELCOR model of TMI-2 alternative accident sequence-2, the RCP are tripped from 6000 s and the constant makeup flow rate of 3.75 kg/s — including pump seal flow rate, but without HPIS flow rate — is activated from 6000 s and beyond 10440 s. The simulation is run until the lower head wall ruptures. In addition, the lower head penetration failure is also calculated with MELCOR for both TMI-2 alternative accident sequences. Lower head temperature contours calculated with SCDAP/RELAP5 are visualized and animated with open source visualization freeware ‘OpenDX’. Significant findings of the analysis include: (1) the TMI-2 lower head wall fails by creep rupture with either deactivations or activations of the HPIS; (2) for the TMI-2 alternative accident sequence-1 the time to creep rupture calculated with MELCOR 1.8.5-RG, SR5m33kz, and SR5m33bf agrees reasonably; (3) the calculation with MELCOR for the TMI-2 alternative accident sequence-1 predicts that the lower head wall failure occurred earlier than penetration failure, while MELCOR predicts the opposite for the TMI-2 alternative accident sequence-2; (4) calculation with MELCOR for TMI-2 alternative accident sequence-2 shows that when the lower head wall fails the temperature calculated with MELCOR is 1810.9 K, which exceeds the melting temperature of 1789 K for carbon steel; (5) calculations with both SR5m33kz and SR5m33bf for both TMI-2 alternative accident sequences indicate that different lower head wall locations fail rapidly one after another by a delay of a few seconds, while this is not the case for MELCOR.
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12th International Conference on Nuclear Engineering
April 25–29, 2004
Arlington, Virginia, USA
Conference Sponsors:
- Nuclear Engineering Division
ISBN:
0-7918-4689-X
PROCEEDINGS PAPER
Assessment of MELCOR 1.8.5 Versus Different Versions of SCDAP/RELAP5 MOD 3.3 With Lower Head Creep Rupture Analysis of Alternative Accident Sequences of the Three Mile Island Unit 2
Sang Lung Chan
Sang Lung Chan
Swiss Federal Institute of Technology, Zurich, Switzerland
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Sang Lung Chan
Swiss Federal Institute of Technology, Zurich, Switzerland
Paper No:
ICONE12-49032, pp. 363-370; 8 pages
Published Online:
November 17, 2008
Citation
Chan, SL. "Assessment of MELCOR 1.8.5 Versus Different Versions of SCDAP/RELAP5 MOD 3.3 With Lower Head Creep Rupture Analysis of Alternative Accident Sequences of the Three Mile Island Unit 2." Proceedings of the 12th International Conference on Nuclear Engineering. 12th International Conference on Nuclear Engineering, Volume 3. Arlington, Virginia, USA. April 25–29, 2004. pp. 363-370. ASME. https://doi.org/10.1115/ICONE12-49032
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