Streamlining of the RELAP5-3D Code

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RELAP5-3D is widely used by the nuclear community to simulate general thermal hydraulic systems and has proven to be so versatile that the spectrum of transient two-phase problems that can be analyzed has increased substantially over time. To accommodate the many new types of problems that are analyzed by RELAP5-3D, both the physics and numerical methods of the code have been continuously improved. In the area of computational methods and mathematical techniques, many upgrades and improvements have been made decrease code run time and increase solution accuracy. These include vectorization, parallelization, use of improved equation solvers for thermal hydraulics and ... continued below

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Mesina, George L; Hykes, Joshua & Guillen, Donna Post November 1, 2007.

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RELAP5-3D is widely used by the nuclear community to simulate general thermal hydraulic systems and has proven to be so versatile that the spectrum of transient two-phase problems that can be analyzed has increased substantially over time. To accommodate the many new types of problems that are analyzed by RELAP5-3D, both the physics and numerical methods of the code have been continuously improved. In the area of computational methods and mathematical techniques, many upgrades and improvements have been made decrease code run time and increase solution accuracy. These include vectorization, parallelization, use of improved equation solvers for thermal hydraulics and neutron kinetics, and incorporation of improved library utilities. In the area of applied nuclear engineering, expanded capabilities include boron and level tracking models, radiation/conduction enclosure model, feedwater heater and compressor components, fluids and corresponding correlations for modeling Generation IV reactor designs, and coupling to computational fluid dynamics solvers. Ongoing and proposed future developments include improvements to the two-phase pump model, conversion to FORTRAN 90, and coupling to more computer programs. This paper summarizes the general improvements made to RELAP5-3D, with an emphasis on streamlining the code infrastructure for improved maintenance and development. With all these past, present and planned developments, it is necessary to modify the code infrastructure to incorporate modifications in a consistent and maintainable manner. Modifying a complex code such as RELAP5-3D to incorporate new models, upgrade numerics, and optimize existing code becomes more difficult as the code grows larger. The difficulty of this as well as the chance of introducing errors is significantly reduced when the code is structured. To streamline the code into a structured program, a commercial restructuring tool, FOR_STRUCT, was applied to the RELAP5-3D source files. The methodology employed follows Dijkstra's structured programming paradigm, which is based on splitting programs into sub-sections, each with single points of entry and exit and in which control is passed downward through the structure with no unconditional branches to higher levels. GO TO commands are typically avoided, since they alter the flow and control of a program’s execution by allowing a jump from one place in the routine to another. The restructuring of RELAP5-3D subroutines is complicated by several issues. The first is use of code other than standard FORTRAN77. The second is restructuring limitations of FOR_STRUCT. The third is existence of pre-compiler directives and the complication of nested directives. Techniques were developed to overcome all these difficulties and more and these are reported. By implementing these developments, all subroutines of RELAP were restructured. Measures of code improvement relative to maintenance and development are presented.

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  • NURETH-12,Pittsburgh, PA,09/30/2007,10/04/2007

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  • Report No.: INL/CON-07-12089
  • Grant Number: DE-AC07-99ID-13727
  • Office of Scientific & Technical Information Report Number: 938454
  • Archival Resource Key: ark:/67531/metadc900213

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • November 1, 2007

Added to The UNT Digital Library

  • Sept. 27, 2016, 1:39 a.m.

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  • Dec. 8, 2016, 11:17 p.m.

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Mesina, George L; Hykes, Joshua & Guillen, Donna Post. Streamlining of the RELAP5-3D Code, article, November 1, 2007; [Idaho Falls, Idaho]. (digital.library.unt.edu/ark:/67531/metadc900213/: accessed July 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.