**RSICC
CODE PACKAGE CCC-656 **

** **

**1. NAME AND TITLE**

WIMSD-5B.12: Deterministic Code System for Reactor-Lattice Calculations.

Auxiliary Programs

UPD 2.0: Update emulator from LANL.

WILLIE: Converts the included WIMS ASCII cross section to binary.

**2. CONTRIBUTOR**S

Answers Software Service, AEA Technology, Winfrith, Dorset, United Kingdom, through the OECD Nuclear Energy Agency Data Bank, Issy-les-Moulineaux, France.

**3. CODING LANGUAGE
AND COMPUTER**

Fortran; PC or Digital Workstation (C00656/MNYCP/02). This package is distributed by the NEADB as NEA-1507/04.

**4. NATURE OF
PROBLEM SOLVED**

The Winfrith improved multigroup scheme (WIMS) is a general code for reactor lattice cell calculation on a wide range of reactor systems. In particular, the code will accept rod or plate fuel geometries in either regular arrays or in clusters and the energy group structure has been chosen primarily for thermal calculations. The basic library has been compiled with 14 fast groups, 13 resonance groups and 42 thermal groups, but the user is offered the choice of accurate solutions in many groups or rapid calculations in few groups. Temperature dependent thermal scattering matrices for a variety of scattering laws are included in the library for the principal moderators which include hydrogen, deuterium, graphite, beryllium and oxygen. WIMSD5 is a successor version of WIMS-D/4.

This package contains the WIMSD-5B.12, WILLIE and UPD codes and the WDN29 ASCII library. New WIMSD libraries based on JEFF-3.1 are available in the WLUP 3.0 package (NEA pkg IAEA-1408 and RSICC pkg DLC-231). For details on work performed within the WIMS-D Library Update Project of the International Atomic Energy Agency (2002), see http://www-nds.iaea.org/wimsd/. Updates are also posted on this website. The major modifications and extensions are:

o Upper limit extended from 69 to 200 energy groups

o Upper energy of the first fast group extended from 10 to 20 MeV

o Number of allowed resonance groups extended from 13 to 55

o Number of allowed resonant isotopes increased to 30

o Maximum number of nuclides in the library increased to 300

o Maximum number of burnable nuclides in WIMS-D input increased to 60

o Modification to handle WIMS-D libraries with an extended format that includes multiple product-nuclei reactions

**5. METHOD OF
SOLUTION**

The treatment of resonances is based on the use of equivalence theorems with a library of accurately evaluated resonance integrals for equivalent homogeneous systems at a variety of temperatures. The collision theory procedure gives accurate spectrum computations in the 69 groups of the library for the principal regions of the lattice using a simplified geometric representation of complicated lattice cells. The computed spectra are then used for the condensation of cross-sections to the number of groups selected for solution of the transport equation in detailed geometry. Solution of the transport equation is provided either by use of the Carlson DSN method or by collision probability methods. Leakage calculations including an allowance for streaming asymmetries may be made using either diffusion theory or the more elaborate B1-method. The output of the code provides eigenvalues for the cases where a simple buckling mode is applicable or cell-averaged parameters for use in overall reactor calculations. Various reaction rate edits are provided for direct comparison with experimental measurements.

** **

**6. RESTRICTIONS OR
LIMITATIONS**

Users of this code should be aware that it was developed for regular pincell lattices and clusters of the AGR/CANDU/RBMK type. Applications to other systems (LWR, HTR, research reactors, criticality assessments, etc) are at the discretion of the user. As variable dimensions are used in WIMS, there are no specific limits on such parameters as number of energy groups or mesh intervals other than an overall limit on the core storage of the computer used. The library of cross-sections has only 69 energy groups. Flexibility is provided for running problems with a smaller number of groups.

** **

**7. TYPICAL RUNNING
TIME**

Run times vary according to problem size and computer.

**8. COMPUTER
HARDWARE REQUIREMENTS**

WIMSD-5B.12 runs on Digital Unix workstations and on personal computers.

**9. COMPUTER
SOFTWARE REQUIREMENTS**

WIMSD-5B.12 was tested at NEADB on a PC running Windows XP with LF95 and on a Digital Personal Workstation running Digital Unix 4.0 with Digital F77 V5.2. It was testsed at RSICC on a Pentium PC running Microsoft® Windows XP™ with Lahey-Fujitsu LF95 Fortran versions 5.50d, v5.60, and v7.1 and on an AMD Opteron running RedHat EL4 Linux with Portland pgi-6.0-2 Fortran. A Fortran compiler is required on all systems.

**10. REFERENCES**

ANSWERS Software Service, AEA Technology, “The ‘1986’ WIMS Nuclear Data Library,”AEEW-R 2133 (September 1986), and WIMSD, A Neutronics Code for Standard Lattice Physics Analysis,” (June 1997) in file NEA 1507_3.pdf.

T. Kulikowska, “WIMSD-5B Extensions,” in file NEA_1507_4.pdf.

**11. CONTENTS OF
CODE PACKAGE**

The package is transmitted on a CD-ROM which includes the referenced documents and a GNU-compressed Unix tar file containing source files, scripts, cross sections, and test cases.

**12. DATE OF
ABSTRACT**

December 1997, revised June 1999, revised December 2007.

**KEYWORDS: **CELL CALCULATION; CROSS SECTION
PROCESSING; CROSS SECTIONS; CYLINDRICAL GEOMETRY; REACTOR PHYSICS