ABSTRACT

" MELCOR 1.8.2 Independent Assessment: MIST SBLOCA Test 3109AA "

S. B. Rodriguez, L. D. Archuleta, and R. Jenks-Johnson



We have completed a posttest calculation and analysis of the Multi-Loop Integral System Test (MIST) 3109AA using MELCOR 1.8.2 (MO). Boundary conditions and geometrical input from a TRAC MIST model developed at Los Alamos National Laboratory were used to develop the MELCOR model; however, the nodaIization for the MELCOR model was coarse compared to the finely noded TRAC model, This coarse nodalization is consistent with modeling practice for MELCOR. We found that during steady state, agreement between test data and the calculation was excellent. We also compared the MELCOR output against TRAC and RELAP5 output. No difficulties were encountered during the MELCOR analysis of the steady state.

Next, the transient phase of Test 3109AA, a small-break loss-coolant accident, was simulated. During the first 200 s of the transient (mostly single-phase thermal hydraulics), MELCOR output compared successfully with data. Throughout the transient, MELCOR reasonably calculated the majority of the important parameters, such as break flow, primary system heat-up. natural and intermittent circulation, loop stagnation, and refill. In addition, primary pressure was calculated with minimal agreement. The MIST data showed two boiler-condenser mode (BCM)) events. Although MELCOR calculated the occurrence of BCM, the code computed the wrong initiation time and magnitude of the first BCM event. Possibly. two calculated pressure spikes early in the transient were caused by too much vaporization and not enough condensation, or lack of adequate BCM cooling. Although the timing of the second computed BCM event was good, its duration was off by several hundred seconds. A hot-leg liquid level was computed with minimal agreement. The MELCOR-calculated results during the steady state and transient were compared with TRAC- and RELAP5-calculated results to provide insight into the achievable accuracies with detailed mechanistic codes.

LA-UR-93-3458 (July 1993)

Return to Rick Johnson Home Page







































KEYWORDS: nuclear engineering los alamos hanford waste tanks privatization twrs flying pilot telecommuting oregon thermal hydraulics TRAC simulation analysis code development necessary and sufficient standards telecommuting rick johnson nuclear safety transportation safety risk telecommute work option work from home radiation heat transport numerical analysis macintosh cray research review regulations telecommuting work option flexiforce safety telecommuting MELCOR TRAC simulation nuclear telecommuting analysis MELCOR severe accident analysis nuclear computer code TRAC