United States Nuclear Regulatory Commission - Protecting People and the Environment

TRAC-M/FORTRAN 90 (Version 3.0) Programmer's Manual (NUREG/CR-6725)

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Publication Information

Manuscript Completed: April 2001
Date Published: May 2001

Prepared by:
B.T. Adams, J.F. Dearing, P.T. Giguere, IRC. Johns,
S.J. Jolly-Woodruff, J.W. Spore, RLG. Steinke, LANL

J.H. Mahaffy, C. Murray, PSU

Los Alamos National Laboratory
Los Alamos, New Mexico 87545

Pennsylvania State University
University Park, PA 16802

F. Odar, NRC Project Manager

Prepared for:
Division of Systems Analysis and Regulatory Effectiveness
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code W6245

Availability Notice


The Transient Reactor Analysis Code (TRAC) was developed to provide advanced best-estimate predictions of postulated accidents in light-water reactors. The TRAC-P program has provided this capability for pressurized water reactors and for many thermal-hydraulic test facilities for approximately 20 years. However, the maintenance and portability of TRAC-P had become cumbersome because of the historical nature of the code and the inconsistent use of standardized Fortran. Thus, the Modernized TRAC (TRAC-M) was developed by recoding the TRAC-P algorithms to take advantage of the advanced features available in the Fortran 90 programming language while conserving the computational models available in the original code.

The TRAC code (i.e., both the versions P and M) features a one-, two-, or three-dimensional (1D, 2D, or 3D) treatment of the pressure VESSEL and its associated internals, a two-fluid nonequilibrium hydrodynamics model with a noncondensable-gas field and solute tracking, flow-regime dependent constitutive equation treatment, optional reflood tracking capability for bottom- and top-flood and falling-film quench fronts, and a consistent treatment of the entire set of accident sequences, including the generation of consistent initial conditions. The stability-enhancing twostep (SETS) numerical algorithm is used in the solution of the 1D, 2D, and 3D hydrodynamics and permits violation of the material Courant condition. This technique permits large timesteps, and thus, the running time for slow transients is reduced. A heat-structure (HTSTR) component is included that allows the user to model heat transfer accurately for complicated geometries. An improved reflood model that is based on mechanistic and defensible models has been added. TRAC also contains improved constitutive models and additions and refinements for several components.

This manual is one of a four-volume set of documents on TRAC-M. This manual was developed to assist a programmer and contains information on the TRAC-M code and data structure, the TRAC-M calculational sequence, memory management, and data precision. This document provides a code developer with a single source of information to allow either modification of or addition to the code. Sufficient information is provided to permit replacement or modification of physical models and correlations. Within TRAC, information is passed at two levels. The upper level of information is passed by systemwide and component-specific data modules at and above the level of component subroutines. At the lower level, information is passed through a combination of module-based data structures and argument lists. This document describes the basic mechanics involved in the flow of information within the code. This document directly incorporates significant information regarding the code models and architecture.

Page Last Reviewed/Updated Wednesday, June 12, 2013