Slide 1

MELCOR 2.1 Leak Path Factor Assessment and GuidanceDavid L.Y. Louiedllouie@sandia.govSandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energys National Nuclear Security Administration under contract DE-AC04-94AL85000. Switching to MELCOR 2.1Some re-training may be required for using the block input approach for the MELCOR 1.8.6 users.Easy-to-use converter, which allows the decks developed in Version 1.8.5 without the COR package, and Version 1.8.6 to be converted into MELCOR 2.1.Symbolic Nuclear Analysis Package (SNAP) developed by Applied Programming Technology, Inc. for NRCThere is a plug-in for MELCORThe use of SNAP requires a license agreement with NRCSome users may find CVH thermodynamic input difficult to use. To help this, an alternative Input, CV_THERM, restores some of the Version 1.8.6 features.5MELCOR Results Example 3 of LA-UR-03-7945#8CaseCrack Width (mm)Wind Speed (mph)Smoke Generated by Fire (kg)HEPA Collect Efficiency (%)MELCOR LPF Results (fraction)*1.8.5 Reference**1.8.51.8.62.110.530None99.983.910-33.010-33.010-33.010-32130None99.989.310-37.510-37.510-37.410-33230None99.982.010-21.710-21.710-21.710-2451None99.985.110-24.510-24.410-24.410-250.510None99.982.810-71.210-72.310-72.310-760.520None99.981.110-47.210-57.610-57.410-570.530None99.981.010-39.610-49.610-49.310-480.5301099.982.610-52.810-32.810-32.710-390.5302599.981.110-52.510-32.510-32.410-3100.5305099.983.910-32.110-32.110-32.010-3110.530None99.953.910-33.010-33.010-33.010-3#LA-UR-99-2513 (C. Shaffer and M. Leonard)*1.8.5 values are using the official release version RL, 186 values are calculated using the official release version YV 3404, and 2.1 values are calculated using official release version RL NL 4261.**1.8.5 reported values from Table 4-2 of LA-UR-03-7945 The codes we ran show consistency and variations of the results among versions are not great. Only Case 5 in 1.8.5 shows much smaller LPF the value for comparison is 10 to -7, so we conclude that the differences among versions are acceptable. For the smoke cases, our results show that as the smoke mass increases the LPF decreases, which make senses because of the agglomeration effect, but the referenced 185 results were unexplained.4

AssessmentsThe assessment task is in progress at SNL Volume III (Demonstration Problems) of the manual is being developed.Appendix A of this manual devotes for the non-reactor applicationThis appendix addresses a finding for MELCOR with the gaps analyses conduced by DOE in 2004, which indicated inadequate sample problems for LPF specific cases.Much of the thermal hydraulics and aerosol physical models of MELCOR are assessed using experiments tailored for reactor applications.For LPF applications, we try to verify the MELCOR results from the previously reported calculations done, such as those results reported in the DOE MELCOR guideline report, and other reports, such as from LA-UR-03-7945 by Jordan and Leonard. 6The creation of Appendix A is intended to address Table 4.8-1 Criteria 8.1 for including sample problems LPF specific cases in the DOE gap analyses.In additional to these verifications, we will include test cases in comparison to the analytical results such as those discussed in LA-UR-0307945, and identify any aerosol transport experiments from the reactor applications to the LPF conditions.MELCOR LPF Results (%)* from MELCOR Guidance ReportTest ProblemReference Value from interpolated from (figures) in Guidance Report1.8.51.8.62.1Appendix C~8.1 (7-6)8.138.108.09Appendix D~0.39 (7-12)0.390.390.39Appendix E~26.3 (7-18)26.6626.6426.63Appendix F~0.43 (7-21)0.430.430.43Appendix G1000 g100g10g1g~11.58 (7-26)~12.03 (7-26)~12.09 (7-26)~12.09 (7-26)10.4210.7910.8310.8310.3910.7510.7910.7910.3810.7410.7810.787*1.8.5 is calculated using the official release version RL, 1.8.6 is calculated using the official release version YV 3404, and 2.1 is calculated using revision 1570.OMICRON now the NSA has reported some discrepancies when comparing their 186 results with the guidance report, so the discrepancies are not repeated here. As you can see, using examples from the guidance report, there are not much differences among the versions of MELCOR. Useful Features in MELCOR 2.1Physical Models:Counter-current flow model (FL_CCF card) allows coupling of two paths through momentum exchange using Epstein-Kenton correlations mainly for natural circulationsBenchmark against CFD codeCan be used to address the counter-current exchange of combustion gases through open doorway in a fire scenario Turbulent aerosol deposition model (RN1_TURB) [optional input] models the aerosol deposition in pipes or ducts -the turbulent flow regime. (cautions should be placed when applying this model for the LPF applications, because the benchmark is done for the reactor accident conditions)9Counter-current flow model Useful Features (continued)Enhance Features:Aerosol deposition deactivation flag (RN1_ADFG card) [optional input] allows to switch off deposition models, such as gravitational, thermophoresis and diffusive settlingFilter model flexible enough to permit the user to model a variety of aerosol or vapor deposition, flow and degradations in filters via control functionsSpray model Because of the generality of the spray inputs, the spray model can be used to simulate the fire sprinkler system reduce thermal condition of the accident and to scrub radionuclides/aerosols to minimize the LPF value.

10Useful Features (concluded)Utility Features:Common block feature (((name block and ending with ))) can be used to allow a single input file to simulate a number of different runs, especially good for sensitivity studies.ResultsReviewer Utility, in conjunction of the RN input (RN1_VISUAL) to provide a way to study the aerosolsExample Appendix E in the MELCOR Guidance Report Simulation for the V300 adjacent to the room with the fire and aerosol release.SNAP simulation Appendix C sample in the MELCOR Guidance Report aerosol fraction display, with evacuation door simulated.11ConclusionsMELCOR 2.x represents the latest version of MELCOR, which should be used by the safety basis community for the LPF applications.Assessments of this current code version show results that are consistent with MELCOR 1.8.5, the current DOE Toolbox code.With the enhancements to be included in this code version and beyond, the safety analyst should be benefited.12Future Development of MELCORDesired improvement:Hot gas layer modeling for simulating fire scenarios should be added.Currently MELCOR only models deflagration of hydrogen and carbon monoxide, combustion of other solid, liquid and gas (including user-defined type) should be added.MELCOR may be used in the development of a fuel reprocessing source term analytical tool for NRCEmpirical correlations for aerosol generation size/mass and wall failure phenomena from liquid explosions and liquid criticality eventsAdditional development model may be included in the effort that could be benefited for the DOE safety basis community for the LPF applications.

13Adding a hot gas layer in the atmosphere region of the control volume would enable MELCOR to model the fire scenario better.Questions?14SNAP Interface15

returnExample 3 of LA-UR-03-7945Brief DescriptionFire occurs in the labSource: 1 g PuO2Sensitivity StudiesLeakage door gap sizeWind speedSmokeFilter efficiencyNodalization: 55 CV multi-level problem16

RETURNReferenced from LA-UR-99-2513 (C. Shaffer and M. Leonard)Fire 2.7 MW 45 min long.Thermodynamic Input OptionsCV_ID VOLUME ONE RCSCV_ARE NOCF 12.5CV_THR NONEQUIL FOG ACTIVECV_PAS SEPARATE POOLANDATM SATURATED ATURATEDCV_PTD PVOL 7.0E6CV_BND ZPOL 9.5CV_VAT 2 !N CVZ CVVOL 1 0.0 0.0 ! Bottom at 0 m 2 10.0 150.0 ! 150 m3 total volumeCV_ID VOLUME ONE RCSCV_ARE NOCF 12.5CV_THR NONEQUIL FOG ACTIVECV_THERM 1 1 PVOL 7.0E6 ZPOL 9.5CV_VAT 2 !N CVZ CVVOL 1 0.0 0.0 ! Bottom at 0 m 2 10.0 150.0 ! 150 m3 total volumeCurrent Input FormatAlternative Input Format via CV_THERM17RETURNThe current input format is somewhat user-unfriendly, which requires to provide information about water state and vapor state. The CV_PAS is used to match CVnnnAk input from 1.8.6.Typical SNAP ConversionIMPORT input file (version 1.8.5 without COR or version 1.8.6)Selected version to be converted (i.e., 2.1)Export input file

18

RETURN