1. NAME and TITLE

REBUS-PC 1.4: Code System for Analysis of Research Reactor Fuel Cycles.
 

AUXILIARY ROUTINES

REBUS-PC contains DIF3D 9.0/VARIANT9.0, a code system using variational nodal methods and finite difference methods to solve neutron diffusion and transport theory problems. This release is an update of CCC-649 DIF3D8.0/VARIANT8.0, which was provided by the authors of that code. REBUS-PC provides new capabilities beyond that of CCC-653, REBUS3/VARIANT8.0. REBUS-PC was developed for analysis of research reactor cores and fuel cycles, but it remains generally useful for any reactor type.
 

2. CONTRIBUTORS

RERTR Program, Technology Development Division, Argonne National Laboratory, Argonne, Illinois. The included DIF3D/VARIANT9.0 code was provided by the Reactor Analysis and Engineering Division, Argonne National Laboratory, Argonne, Illinois.
 

3. CODING LANGUAGE and COMPUTER

Fortran 77, PC under either WINDOWS or Linux (C00709/PC586/00).
 

4. NATURE of PROBLEM SOLVED

REBUS-PC Version 1.4 is a system of codes designed for the analysis of research reactor fuel cycles. It is based on an updated 9.0 version of DIF3D that is similar to RSICC Code Package CCC-653, REBUS-3/VARIANT 8.0 (which is intended for use on unix workstations). The full capabilities of the workstation version are retained and enhanced for use in a PC environment. Two basic types of analysis problems are solved: 1) the infinite-time, or equilibrium, conditions of a reactor operating under a fixed fuel management scheme, or 2) the explicit cycle-by-cycle, or non-equilibrium operation of a reactor under a specified periodic or non-periodic fuel management program. For the equilibrium type problems, the code uses specified external fuel supplies to load the reactor. Optionally, reprocessing may be included in the specification of the external fuel cycle and discharged fuel may be recycled back into the reactor. For non-equilibrium cases, the initial composition of the reactor core may be explicitly specified or the core may be loaded from external feeds and discharged fuel may be recycled back into the reactor as in equilibrium problems.

Four types of search procedures may be carried out in order to satisfy user-supplied constraints: 1) adjustment of the reactor burn cycle time to achieve a specified discharge burnup, 2) adjustment of the fresh fuel enrichment to achieve a specified multiplication constant at a specified point during the burn cycle, 3) adjustment of the control poison density to maintain a specified value of the multiplication constant throughout the reactor burn cycle, and 4) adjustment of the reactor burn cycle time to achieve a specified value of the multiplication constant at the end of the burn step.

REBUS-PC will handle both equilibrium and non-equilibrium problems using a number of different core geometries including triangular and hexagonal mesh. The neutronics solution may be obtained using finite difference or nodal diffusion-theory methods. Other features include: fully automatic restart capability, no restrictions on number of neutron energy groups, and general external cycle with no restrictions on number of external feeds, reprocessing plants, etc. Fuel management is completely general for non-equilibrium problems.

Microscopic cross sections are permitted to vary as a function of the atom density of various reference isotopes in the problem as appropriate for thermal reactor systems. The previous capability where neutron capture and fission processes were fitted to low-order polynomials as functions of burnup is retained. In addition, the user now may select cubic spline interpolation for (n,gamma), (n,fission), (n,alpha), (n,p), (n,d), and (n,t) reactions as functions of burnup. The user may specify control rod positions at each time node in the problem. Output edits have been extensively revised and better organized for use in a PC environment. A number of ASCII format datasets containing various types of summary results are available for use in tailoring reports with the aid of auxiliary PC software such as spreadsheet or word processor programs.

This is a standalone and expanded version of the modular REBUS-3 code system described in Refs. 1-7. It utilizes the 9.0 update of CCC-649/DIF3D code to obtain the neutronics solution. All but the main program "path driver" of DIF3D 9.0/VARIANT 9.0 (with finite difference and hexagonal nodal option) is included in this code package. Dataset A.ISO is extended to retain full single-precision accuracy for neutron cross sections in BCD format. REBUS-PC operation is fully compatible with the DOE Committee on Computer Code Coordination coding standards and interface data sets [Ref. 10].

Changes were made to power-related edits in the fuel cycle computational module FCC004 such that they are now consistent with those from DIF3D. The cross section homogenization module HMG4C was extended to provide the necessary information. HMG4C is now called after a neutronics solution in order to write the necessary data to file COMPXS. FCC004 is then called to create power-related edits (using COMPXS) and to predict the next burn step isotopic compositions.
 

5. METHOD of SOLUTION

The total reactor burn cycle time is divided into one or more subintervals, the number of which is specified by the user. An explicit burnup is performed in each region of the reactor over each of these subintervals using the average reaction rates over the subinterval. These average reaction rates are based on fluxes obtained from an explicit 1-, 2-, or 3-dimensional finite-difference or nodal diffusion theory solution computed at both the beginning and end of the subinterval, iterated to a prescribed convergence. The transmutation equations are solved by the matrix-exponential technique. The isotopes to be considered in the burnup equations, as well as their transmutation reactions, are specified by the user. Burnup-dependent transmutation reaction cross sections can be used.
 

6. RESTRICTIONS or LIMITATIONS

Very large problems can be solved. LF95 v6.1 is limited to 4 Gigabytes of available memory, 250 files open concurrently, and a maximum file size of 2 Gigabytes. Variable dimensioning is used throughout.
 
 
 

7. TYPICAL RUNNING TIME

Minutes to many hours depending on size and complexity of the problem, and on CPU speed and memory utilized. An equilibrium problem with 84 burnable regions, 7 neutron groups, an X-Y-Z mesh of 78x69x23, requiring 9 neutronics solutions over 4 burn steps, took 34 minutes on a 2.0GHz Pentium IV PC running under Linux. Each sample problem required over 1 GB memory and about 2 hours execution time on a P3 650mHz with 128 MB RAM running Windows 2000.
 

8. COMPUTER HARDWARE REQUIREMENTS

The PC version of the code is in production use at Argonne National Laboratory on PC's using Pentium IV processors under the Red Hat Linux 7.2 operating system, using up to 1 Gigabyte of random access memory. The code can be compiled for use on any PC from Intel 80486, Pentium, Pentium MMX, Pentium Pro, Pentium II, Pentium III, Pentium IV, and Celeron processors or their generic counterparts.

At least 32 MB of RAM are needed for compilation. 128 Mbytes of RAM are recommended for program and file buffer storage, and internal data, when running the code. More RAM is better, as wall clock time is generally reduced when all or most of the problem is contained in core memory (limiting paging). External data storage must be available for approximately 40 scratch and interface files. Fourteen of these files are random access scratch files (grouped into 6 file groups). The remainder are sequential access files with formatted or unformatted record types. The code is of modular design, but standalone form. Dynamic memory allocation uses two containers whose sizes are dictated by the needs of a given problem and by the user's choice depending upon code options and hardware limitations.
 

9. COMPUTER SOFTWARE REQUIREMENTS

The code is written entirely in Fortran 77. The program can be compiled with Lahey Fortran 95 Pro V6.1 for Linux or Lahey Fortran 95 V5.60g or V5.56 for Windows. Executables created with these Lahey compilers are included in the package for Linux and Windows. Other advanced Fortran compilers could be used but would require minor changes in dynamic memory management calls and clock timer routines, or anywhere else where the particular Fortran dialect differs from Lahey Fortran 95. The standalone source code contains approximately 1140 subroutines and 262,000 Fortran statements. The operating system can be any of Windows 95/98/NT4.0/2000 or newer, or any linux variation such as Red Hat Linux 7.2 that is compatible with the user's Fortran compiler. An interpreter or manager or executive routine is not needed. No nonstandard library routines are used. No special I/O table is required. Output file FT06 is actually created on unit 4, in order to reserve unit 6 for screen output.
 

10. REFERENCES

a Included in documentation:

A. P. Olson, "A User's Guide for the REBUS-PC Code, Version 1.4," Argonne National Laboratory, (December 21, 2001).
 

b. Background information:

1. J. Hoover, G. K. Leaf, D. A. Meneley, and P. M. Walker, "The Fuel

Cycle Analysis System, REBUS," Nucl. Sci. Eng. 45, p. 53, 1971.
 

2. A. P. Olson, J. P. Regis, D. A. Meneley, and L. J. Hoover, "A User's

Manual for the Reactor Burnup System, REBUS," FRA-TM-41, Argonne National Laboratory, September 28, 1972.

3. A. P. Olson, "A User's Manual for the Reactor Burnup System,

REBUS-2," FRA-TM-62, Argonne National Laboratory, March 1, 1974.

4. R. P. Hosteny, "The ARC System Fuel Cycle Analysis Capability, REBUS-2," ANL-7721 (October 1978) distributed in file rebus-pc/documents/rebus3_docs/ANL-7221.pdf.

5. B. J. Toppel, "A User's Guide for the REBUS-3 Fuel Cycle Analysis Capability," ANL-83-2 (1983) distributed in file rebus-pc/documents/rebus3_docs/REBUS-3_document.pdf.

6. K. L. Derstine, "DIF3D, A Code to Solve One-, Two-, and Three-

Dimensional Finite-Difference Diffusion Theory Problems," ANL-82-64 (April 1984) distributed in directory rebus-pc/documents/rebus3_docs/D3D.

7. G. Palmiotti, E. E. Lewis, and C. B. Carrico, "VARIANT: VARIational

Anistropic Nodal Transport for Multidimensional Cartesian and Hexagonal Geometry Calculation," ANL-95/40 (October 1995) distributed in file rebus-pc/documents/rebus3_docs/Var.manual.pdf.

8. J. F. Breismeister, ed., "MCNP - A General Monte Carlo N-Particle

Transport Code, Version 4B," LA-12625-M. Los Alamos National Laboratory, 1997.

9. N. A. Hanan, A. P. Olson, R. B. Pond, and J. E. Matos, "A Monte Carlo

Burnup Code Linking MCNP and REBUS," presented at the 1998 International Meeting on Reduced Enrichment for Research and Test Reactors, October 18-23, Sao Paolo, Brazil.

10. R. D. O'Dell, "Standard Interface Files and Procedures for Reactor

Physics Codes, Version IV," LA-6941-MS, UC-32, Los Alamos National Laboratory, September 1977.

11. R. D. Lawrence, "The DIF3D Nodal Neutronics Option for Two-and Three-Dimensional Diffusion Theory Calculations in Hexagonal Geometry," ANL-83-1 (March 1983) distributed in directory rebus-pc/documents/rebus3_docs/D3DN.

12. C. H. Adams, et.al., "The Utility Subroutine Package Used by Applied Physics Division Export Codes," ANL-83-3 (May 1992) distributed in file rebus-pc/documents/rebus3_docs/anl833.pdf
 

11. CONTENTS of CODE PACKAGE

Included are the reference in 10.a and the references in 10.b which indicate they are distributed in electronic files and a CD which contains a self-extracting compressed Windows file and a GNU compressed tar file. Approximately 360 MB is required for installation. Included in the distribution files are the source code, Lahey-compiled Windows and Linux executables, sample problem input and output, and code dependent BCD and binary card-image file descriptions.
 

12. DATE of ABSTRACT

June 2002.
 

KEYWORDS: BURNUP; FUEL MANAGEMENT; DIFFUSION THEORY; CRITICALITY CALCULATIONS; REACTOR PHYSICS; COMPLEX GEOMETRY; CCCC INTERFACE FORMAT