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RELAP5-3D Restart and Backup Verification Testing

Description: Existing testing methodology for RELAP5-3D employs a set of test cases collected over two decades to test a variety of code features and run on a Linux or Windows platform. However, this set has numerous deficiencies in terms of code coverage, detail of comparison, running time, and testing fidelity of RELAP5-3D restart and backup capabilities. The test suite covers less than three quarters of the lines of code in the relap directory and just over half those in the environmental library. Even in terms of code features, many are not covered. Moreover, the test set runs many problems long past the point necessary to test the relevant features. It requires standard problems to run to completion. This is unnecessary for features can be tested in a short-running problem. For example, many trips and controls can be tested in the first few time steps, as can a number of fluid flow options. The testing system is also inaccurate. For the past decade, the diffem script has been the primary tool for checking that printouts from two different RELAP5-3D executables agree. This tool compares two output files to verify that all characters are the same except for those relating to date, time and a few other excluded items. The variable values printed on the output file are accurate to no more than eight decimal places. Therefore, calculations with errors in decimal places beyond those printed remain undetected. Finally, fidelity of restart is not tested except in the PVM sub-suite and backup is not specifically tested at all. When a restart is made from any midway point of the base-case transient, the restart must produce the same values. When a backup condition occurs, the code repeats advancements with the same time step. A perfect backup can be tested by forcing RELAP5 to perform ...
Date: September 1, 2013
Creator: Mesina, Dr. George L
Partner: UNT Libraries Government Documents Department

Implementation of a New DTSTEP Algorithm for use in RELAP5-3D and PVMEXEC Completion Report

Description: The PVM Coupling methodology for decomposing a complex model into domains onto which individual programs may be applied has proven effective for solving many multi-physics problems. There have been, from the outset, some detailed and/or long-running models that cause the process to fail. This project addressed the PVM coupling issues surrounding the DTSTEP subroutines on RELAP5-3D and PVMEXEC. Some 25 errors are listed in Tables 1 and 18 and in Section 11. These arise from deficiencies in the floating point calculation and testing of time steps, cumulative time, and time targets. The algorithmic replacement of floating point control of these items with integer based timestepping was developed and implemented. The result of the first phase, undertaken by the INL was that all but three of these issues were resolved. Moreover, two conceptual errors in DTSTEP that were not PVM coupling related were discovered and solved. The final, and most difficult three PVM Bettis User Problems, were solved during the Bettis phase of development and debugging. In 8 months since the conclusion of the project, no further DTSTEP related PVM Coupling errors have been reported.
Date: December 1, 2010
Creator: Mesina, Dr. George L
Partner: UNT Libraries Government Documents Department

BPLU Completion and Verification Report

Description: The Border Profile LU (BPLU) linear equation solver is the default solver for newer versions of RELAP5-3D. It can significantly reduce execution time compared to the previous default solver, MA18. Particularly for 3D cases, it can reduce run time by one to two orders of magnitude over MA18. However, because of some user reported failures, the MA18 solver currently must be used for coupled analyses. Over one dozen User Problems (UP) have been reported between 1999 and 2011 that involve the BPLU solver in RELAP5-3D. These issues can be combined into two categories of problems with the solver: (1) It fails when running multidimensional components with the nearly-implicit hydrodynamics advancement scheme. (2) It fails with some input models where the MA18 sparse solver does not fail. The sources of these UP have been found and corrected. The modified coding has been thoroughly tested with over 3000 test cases and on two different compute platforms. The updates are incorporated in RELAP5-3D, version 3.0.2.
Date: September 1, 2011
Creator: Mesina, Dr. George L
Partner: UNT Libraries Government Documents Department

Uncertainty Analysis for RELAP5-3D

Description: In its current state, RELAP5-3D is a 'best-estimate' code; it is one of our most reliable programs for modeling what occurs within reactor systems in transients from given initial conditions. This code, however, remains an estimator. A statistical analysis has been performed that begins to lay the foundation for a full uncertainty analysis. By varying the inputs over assumed probability density functions, the output parameters were shown to vary. Using such statistical tools as means, variances, and tolerance intervals, a picture of how uncertain the results are based on the uncertainty of the inputs has been obtained.
Date: August 1, 2011
Creator: Pawel, Aaron J. & Mesina, Dr. George L.
Partner: UNT Libraries Government Documents Department

Uncertainty Analysis of RELAP5-3D

Description: As world-wide energy consumption continues to increase, so does the demand for the use of alternative energy sources, such as Nuclear Energy. Nuclear Power Plants currently supply over 370 gigawatts of electricity, and more than 60 new nuclear reactors have been commissioned by 15 different countries. The primary concern for Nuclear Power Plant operation and lisencing has been safety. The safety of the operation of Nuclear Power Plants is no simple matter- it involves the training of operators, design of the reactor, as well as equipment and design upgrades throughout the lifetime of the reactor, etc. To safely design, operate, and understand nuclear power plants, industry and government alike have relied upon the use of best-estimate simulation codes, which allow for an accurate model of any given plant to be created with well-defined margins of safety. The most widely used of these best-estimate simulation codes in the Nuclear Power industry is RELAP5-3D. Our project focused on improving the modeling capabilities of RELAP5-3D by developing uncertainty estimates for its calculations. This work involved analyzing high, medium, and low ranked phenomena from an INL PIRT on a small break Loss-Of-Coolant Accident as wall as an analysis of a large break Loss-Of- Coolant Accident. Statistical analyses were performed using correlation coefficients. To perform the studies, computer programs were written that modify a template RELAP5 input deck to produce one deck for each combination of key input parameters. Python scripting enabled the running of the generated input files with RELAP5-3D on INL’s massively parallel cluster system. Data from the studies was collected and analyzed with SAS. A summary of the results of our studies are presented.
Date: July 1, 2012
Creator: Gertman, Alexandra E & Mesina, Dr. George L
Partner: UNT Libraries Government Documents Department

Java XMGR

Description: The XMGR5 graphing package [1] for drawing RELAP5 [2] plots is being re-written in Java [3]. Java is a robust programming language that is available at no cost for most computer platforms from Sun Microsystems, Inc. XMGR5 is an extension of an XY plotting tool called ACE/gr extended to plot data from several US Nuclear Regulatory Commission (NRC) applications. It is also the most popular graphing package worldwide for making RELAP5 plots. In Section 1, a short review of XMGR5 is given, followed by a brief overview of Java. In Section 2, shortcomings of both tkXMGR [4] and XMGR5 are discussed and the value of converting to Java is given. Details of the conversion to Java are given in Section 3. The progress to date, some conclusions and future work are given in Section 4. Some screen shots of the Java version are shown.
Date: August 1, 2004
Creator: Mesina, Dr. George L. & Miller, Steven P.
Partner: UNT Libraries Government Documents Department

RELAP5-3D Architectural Developments in 2004

Description: Currently, RELAP5 is undergoing a transformation that will replace much of its coding with equivalent structured Fortran 90 coding. Four efforts are underway to modernize the code architecture of RELAP5-3D. These are parallelization, vectorization, code restructuring, and conversion to Fortran 90. The first two improve code run speed via on computer platforms of certain architectures. These code modifications have little effect on normal code performance on non-vector and non-parallel computers because they are mostly done with compiler directives. The third and fourth efforts involve considerable rewriting of the source code. The third code improvement effort addresses code readability and maintainability. These are being greatly enhanced by application of a Fortran code-restructuring tool. The fourth effort is conversion to Fortran 90. The bulk of the coding is being rewritten in Fortran 90. This is a ground up reworking of the coding that begins with completely reorganizing the underlying database and continues with the source code. It will reach every part of RELAP5-3D. Each of these efforts is discussed in detail in a different section. Section 1 relates background information. Section 2 covers the parallelization effort. Section 3 covers the efforts to vectorize the code. Section 4 covers the code restructuring. Section 5 covers the Fortran 90 effort. Outline Background: longevity, maintenance & development, reliability, speed Parallelization: KAI to OpenMP, previous work & current, domain decomposition, done. Vectorization: Speed - Fed init, vectors in PCs, INL Cray SV1, R5 Phant, EXV, results. Code Restructuring: Reason to restructure, study of restruct, For Study: what it does, Fortran 90: Modernization -
Date: August 1, 2004
Creator: Mesina, Dr. George L.
Partner: UNT Libraries Government Documents Department

Architectural Advancements in RELAP5-3D

Description: As both the computer industry and field of nuclear science and engineering move forward, there is a need to improve the computing tools used in the nuclear industry to keep pace with these changes. By increasing the capability of the codes, the growing modeling needs of nuclear plant analysis will be met and advantage can be taken of more powerful computer languages and architecture. In the past eighteen months, improvements have been made to RELAP5-3D [1] for these reasons. These architectural advances include code restructuring, conversion to Fortran 90, high performance computing upgrades, and rewriting of the RELAP5 Graphical User Interface (RGUI) [2] and XMGR5 [3] in Java. These architectural changes will extend the lifetime of RELAP5-3D, reduce the costs for development and maintenance, and improve it speed and reliability.
Date: November 1, 2005
Creator: Mesina, Dr. George L.
Partner: UNT Libraries Government Documents Department

Reformulation RELAP5-3D in FORTRAN 95 and Results

Description: RELAP5-3D is a nuclear power plant code used worldwide for safety analysis, design, and operator training. In keeping with ongoing developments in the computing industry, we have re-architected the code in the FORTRAN 95 language, the current, fully-available, FORTRAN language. These changes include a complete reworking of the database and conversion of the source code to take advantage of new constructs. The improvements and impacts to the code are manifold. It is a completely machine-independent code that produces machine independent fluid property and plot files and expands to the exact size needed to accommodate the user’s input. Runtime is generally better for larger input models. Other impacts of code conversion are improved code readability, reduced maintenance and development time, increased adaptability to new computing platforms, and increased code longevity. The conversion methodology, code improvements and testing upgrades are presented in a manner that will be useful to future conversion projects for other such large codes. Comparison between the pre- and post-conversion code are made on the basis of code metrics and code performance.
Date: August 1, 2010
Creator: Mesina, Dr. George L
Partner: UNT Libraries Government Documents Department