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Title: Recent Updates to the MELCOR 1.8.2 Code for ITER Applications

Abstract

This report documents recent changes made to the MELCOR 1.8.2 computer code for application to the International Thermonuclear Experimental Reactor (ITER), as required by ITER Task Agreement ITA 81-18. There are four areas of change documented by this report. The first area is the addition to this code of a model for transporting HTO. The second area is the updating of the material oxidation correlations to match those specified in the ITER Safety Analysis Data List (SADL). The third area replaces a modification to an aerosol tranpsort subroutine that specified the nominal aerosol density internally with one that now allows the user to specify this density through user input. The fourth area corrected an error that existed in an air condensation subroutine of previous versions of this modified MELCOR code. The appendices of this report contain FORTRAN listings of the coding for these modifications.

Authors:
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - SC
OSTI Identifier:
911938
Report Number(s):
INL/EXT-07-12493
TRN: US0800228
DOE Contract Number:
DE-AC07-99ID-13727
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 - PLASMA PHYSICS AND FUSION TECHNOLOGY; AEROSOLS; AIR; COMPUTER CODES; EXPERIMENTAL REACTORS; FORTRAN; MODIFICATIONS; OXIDATION; SAFETY ANALYSIS; TRANSPORT; ITER safety, MELCOR

Citation Formats

Merrill, Brad J. Recent Updates to the MELCOR 1.8.2 Code for ITER Applications. United States: N. p., 2007. Web. doi:10.2172/911938.
Merrill, Brad J. Recent Updates to the MELCOR 1.8.2 Code for ITER Applications. United States. doi:10.2172/911938.
Merrill, Brad J. Sun . "Recent Updates to the MELCOR 1.8.2 Code for ITER Applications". United States. doi:10.2172/911938. https://www.osti.gov/servlets/purl/911938.
@article{osti_911938,
title = {Recent Updates to the MELCOR 1.8.2 Code for ITER Applications},
author = {Merrill, Brad J},
abstractNote = {This report documents recent changes made to the MELCOR 1.8.2 computer code for application to the International Thermonuclear Experimental Reactor (ITER), as required by ITER Task Agreement ITA 81-18. There are four areas of change documented by this report. The first area is the addition to this code of a model for transporting HTO. The second area is the updating of the material oxidation correlations to match those specified in the ITER Safety Analysis Data List (SADL). The third area replaces a modification to an aerosol tranpsort subroutine that specified the nominal aerosol density internally with one that now allows the user to specify this density through user input. The fourth area corrected an error that existed in an air condensation subroutine of previous versions of this modified MELCOR code. The appendices of this report contain FORTRAN listings of the coding for these modifications.},
doi = {10.2172/911938},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}

Technical Report:

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  • This report documents recent changes made to the MELCOR 1.8.2 computer code for application to the International Thermonuclear Experimental Reactor (ITER), as required by ITER Task Agreement ITA 81-18. There are four areas of change documented by this report. The first area is the addition to this code of a model for transporting HTO. The second area is the updating of the material oxidation correlations to match those specified in the ITER Safety Analysis Data List (SADL). The third area replaces a modification to an aerosol tranpsort subroutine that specified the nominal aerosol density internally with one that now allowsmore » the user to specify this density through user input. The fourth area corrected an error that existed in an air condensation subroutine of previous versions of this modified MELCOR code. The appendices of this report contain FORTRAN listings of the coding for these modifications.« less
  • A version of MELCOR 1.8.2 modified for use in ITER Preliminary Safety Report analyses was validated against recent data from the EVITA facility located in Cadarache, France. EVITA Test Series 7 was used for this study to verify MELCOR’s ability to predict the pressures, temperatures, cryoplate ice mass, and vaccum vessel (VV) condensate mass for test conditions in EVITA that include injections of steam, nitrogen, and water in to the EVITA VV after the walls had been heated to 165 ºC and the cryoplate had been cooled to -193 ºC. In general, the ability of MELCOR to predict the VVmore » pressure and wall temperatures for the steam only and water only injection tests was very good. Predicted ice layer masses where larger than reported for the EVITA cryoplate, in particular for the steam only injection tests (~40% too high), and the predicted condensate masses were less that measured in EVITA. Both of these descrpancies can be explained by ice porosity. The modified MELCOR 1.8.2 over predicts the EVITA VV pressure for the co-injection tests (e.g., steam plus nitrogen, or water plus nitrogen injections) by almost a factor of two. Based on parametric runs that where made by increasing the predicted cryoplate condensation rate, it is believed that this pressure over prediction is a result of an under predicted cryoplate condensation rate. The particulars of this study are documented in this report as well as conclusions about the impact this study has regarding the use of this verions of MELCOR for consequence analyses for ITER safety reports.« less
  • During the Engineering Design Activity of the International Thermonuclear Experimental Reactor (ITER), the MELCOR 1.8.2 code was selected as one of several codes to be used to perform ITER safety analyses [1]. MELCOR was chosen because it has the capability of predicting coolant pressure, temperature, mass flow rate, and radionuclide and aerosol transport in nuclear facilities and reactor cooling systems. MELCOR can also predict structural temperatures (e.g. first wall, blanket, divertor, and vacuum vessel) resulting from energy produced by radioactive decay heat and/or chemical reactions (oxidation). The Idaho National Laboratory (INL) Fusion Safety Program (FSP) made fusion specific modifications tomore » the MELCOR 1.8.2 code [2-6], including models for water freezing, air condensation, beryllium, carbon, and tungsten oxidation in steam and air environments, flow boiling in coolant loops, and radiation in enclosures, that allowed MELCOR to assess the thermal hydraulic response of ITER cooling systems and the transport of radionuclides as aerosols during accident conditions. Recently, the ITER International Organization (IO) used a “pedigreed” version of MELCOR 1.8.2 [7] to perform accident analyses for ITER’s “Rapport Préliminaire de Sûreté” (Report Preliminary on Safety - RPrS). The MELCOR thermal-hydraulics code [8] is currently under development at the Sandia National Laboratory (SNL) for the US Nuclear Regulatory Commission (NRC). MELCOR is used to model the progression of severe accidents in light water fission reactors. Because MELCOR has undergone many improvements between version 1.8.2 and 1.8.6, the INL FSP decided to introduce fusion modifications into MELCOR 1.8.6, and thereby produce a version of MELCOR 1.8.6 with similar capabilities to the pedigreed version of MELCOR 1.8.2 used for the ITER RPrS. We have applied this version of MELCOR 1.8.6 to the same set of problems used in the MELCOR 1.8.2 pedigree analysis [7]. Section 2 describes a non-regression analysis that involves comparing the results from the modified version of MELCOR 1.8.6 against those predicted by the original, unmodified version of MELCOR 1.8.6. The purpose of this non-regression analysis is to demonstrate that the modifications made to the MELCOR 1.8.6 code do not drastically alter the intended functions of the MELCOR base code, and if they do to explain why the departure occurs and if the change is needed. The analysis was performed using the demonstration problem that came with the MELCOR 1.8.6 source distribution. Section 3 makes a comparison between the pedigreed version of MELCOR 1.8.2 and the new modified version of MELCOR 1.8.6 on a set of accident problems used by the ITER Joint Central Team (JCT) in the Generic Site Safety Report (GSSR) [9]. Finally, in section 4, the two versions of the code are compared on a series of developmental test problems described in the change documents [2-4, 6].« less
  • This report documents the pedigree analysis of the MELCOR 1.8.2 code to be used for ITER’s Report Preliminary on Safety. To pedigree the code the process involved four steps. First, taking the modified MELCOR 1.8.2 code used by the ITER Joint Central Team (JCT) for analyses in previous ITER Safety Assessments and compared the FORTRAN code of this version line-by-line to the original 1.8.2 version of MELCOR. The second step was a non-regression analysis which involves comparing the results from the pedigreed version against those predicted by the original, unmodified version of MELCOR 1.8.2. The third step involved comparing themore » pedigreed version results to results from the MELCOR version used by the ITER JCT for the Generic Site Safety Report (GSSR) against a set of accident problems analyzed for the safety report. The fourth and final step involved a comparison between the pedigreed version of the code and the developmental test problems cited in the change documents referenced in this report. The results from the pedigree process are described in this report.« less
  • MELCOR is a fully integrated, engineering-level computer code, being developed at Sandia National Laboratories for the USNRC. This code models the entire spectrum of severe accident phenomena in a unified framework for both BWRs and PWRs. As part of an ongoing assessment program, the MELCOR computer code has been used to analyze a station blackout transient in Surry, a three-loop Westinghouse PWR. Basecase results obtained with MELCOR 1.8.2 are presented, and compared to earlier results for the same transient calculated using MELCOR 1.8.1. The effects of new models added in MELCOR 1.8.2 (in particular, hydrodynamic interfacial momentum exchange, core debrismore » radial relocation and core material eutectics, CORSOR-Booth fission product release, high-pressure melt ejection and direct containment heating) are investigated individually in sensitivity studies. The progress in reducing numeric effects in MELCOR 1.8.2, compared to MELCOR 1.8.1, is evaluated in both machine-dependency and time-step studies; some remaining sources of numeric dependencies (valve cycling, material relocation and hydrogen burn) are identified.« less