1. **NAME AND TITLE**

EQUIVA-1.1: Generation of Few-Group Equivalent Diffusion Theory Parameters for PWR Reflector Regions.

2. **CONTRIBUTOR**

Atomic Energy Corporation of South Africa (Ltd), Pretoria, Republic of South Africa.

3. **CODING LANGUAGE AND COMPUTER/OPERATING SYSTEM**

Fortran 77, IBM 370, and IBM PC.

4. **NATURE OF PROBLEM SOLVED**

EQUIVA-1 generates few-group equivalent diffusion theory parameters for pressurized water (PWR) reflector regions from the results of simple one-dimensional (slab) multigroup transport calculations. The one-dimensional "normalized generalized equivalence theory" (NGET) method is used for this purpose. Equivalent parameters can be generated for any number of condensed energy groups and for different material regions, such as for the explicit baffle and water reflector of the radial reflector of PWR, or for the homogenized baffle/reflector.

5. **METHOD OF SOLUTION**

Equivalent group constants are computed by dividing the standard flux-volume-weighted constants by so-called "normalized" discontinuity factors which are analytically computed.

6. **RESTRICTIONS OR LIMITATIONS**

EQUIVA-1.1 is a variably dimensioned code and there is no restriction on the number of energy groups, etc. The size of the problem is restricted only by the computer core storage available.

7. **TYPICAL RUNNING TIME**

The running time for a single PWR radial reflector problem consisting of group condensation from 69 to 2 energy groups, spatial homogenization of 2 regions, and computation of the NGET parameters for the homogenized node, is of the order of a few seconds on a mainframe computer.

8. **COMPUTER HARDWARE REQUIREMENTS**

EQUIVA has run routinely on IBM mainframes and on 32-bit 80386/80486 class personal computers.

9. **COMPUTER SOFTWARE REQUIREMENTS**

The code is written in Fortran 77 and has run under MVS on IBM mainframes. The executable file for the pc included in the package was created with the Lahey F77L-EM/32 Version 5.0 compiler.

10. **REFERENCES**

E. Z. Muller, "EQUIVA-1: A Code for Generating One-Dimensional NGET Cross Sections for PWR Ex-Core Regions," PEL 301 (1991).

E. Z. Muller, "The One-Dimensional Normalized Generalized Equivalence Theory (NGET) for generating Equivalent Diffusion Theory Group Constants for PWR Ex-Core Regions," PEL 303 (1991).

E. Z. Muller, "Environment-Insensitive Equivalent Diffusion Theory Group Constants
for Pressurized Water Reactor Radial Reflector Regions," *Nucl. Sci. Eng., 103, 359-376
(1989).*

11. **CONTENTS OF CODE PACKAGE**

Included in the package are the referenced documents and 1 DS/HD disk which includes the source files, pc executable file, test case input data and output in DOS format.

12. **DATE OF ABSTRACT**

February 1993.

**KEYWORDS: ** DIFFUSION THEORY; MICROCOMPUTER; PWR