1. NAME AND TITLE OF DATA LIBRARY

LAFPX-E: A Multigroup Reaction Cross-Section Collapsing Code and Library of 154- Group Fission-Product Cross Sections.

2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS

No retrieval program is in the package.

3. CONTRIBUTORS

Theoretical Division, Los Alamos Scientific Laboratory, Los Alamos, New Mexico, for the Electric Power Research Institute, Palo Alto, California, and the United States Nuclear Regulatory Commission, Washington, D.C.

Electric Power Research Institute, Palo Alto, California.

4. HISTORICAL BACKGROUND AND INFORMATION

Version four of the Evaluated Nuclear Data File (ENDF/B-IV) included evaluated cross sections for many significant long-lived fission-product and actinide nuclides. The cross sections of the ENDF/B-IV fission products were processed into multigroup form and furnished with a flexible cross-section collapsing code called TOAFEW.

5. APPLICATION OF THE DATA

The code reads multigroup cross sections from a compatible data file and collapses user-selected reaction cross sections to any few-group structure using one of a variety of user neutron flux spectrum options given below:

Option Flux description

1 Built-in function including Maxwellian, fission, fusion and slowing-down regions and requiring user-specified parameters and energy-region boundaries.

2 Set of log-log flux-energy interpolation points read from input cross-section data file.

3 Set of log-log flux-energy interpolation points read from user-supplied card input.

4 - 6 Histogram flux values read from user-supplied card input in arbitrary group structure in units of flux-per unit-energy, flux-per-unit lethargy, or integral group flux.

LAFPX-E may be used to collapse any set of multigroup reaction cross sections furnished in the required format. However, the code was developed for, and is furnished with, a library of 154-group fission-product cross sections processed from ENDF/B-IV with a typical light water reactor (LWR) flux spectrum and temperature. Four-group radiative capture cross sections produced for LWR calculations are tabulated in the code documentation and are incorporated in the EPRI-CINDER data library, RSIC Code Package CCC-309.

6. SOURCE AND SCOPE OF DATA

LAFPX-E produces few-group flux weighted average cross sections by collapsing multigroup values, using either a flux weighting function provided by the user or a log-log flux weighting function read from the data file. Fine-group cross sections processed and collapsed to a few-group subset with a common flux weighting function yield few-group structure with that flux description. Few group cross sections for use in calculations with a spectrum different from that used in processing may be closely approximated by collapsing with the appropriate flux spectrum. Few-group values so produced are generally far more sensitive to the flux description used in collapsing than to that used in processing the multigroup values.

7. DISCUSSION OF THE DATA RETRIEVAL PROGRAM

Not applicable.

8. DATA FORMAT AND COMPUTER

Card images; CDC computer (D00054C0000/01, /02).

9. TYPICAL RUNNING TIME

On a CDC-6600, a four-group cross section calculation using the flux weighting function read from the data file, required ~ 8 seconds to compile the code, read the multigroup structure and log-log weighting function from the data file, and compute initial quantities. An additional ~ 61 seconds were required to read and collapse all 960 cross-section tabulations to 4 groups.

10. REFERENCES

W. B. Wilson, T. R. England, R. J. LaBauve, and R. M. Boicourt, " TOAFEW-V Multigroup Cross- Section Collapsing Code and Library of 154-Group-Processed ENDF/B/V Fission-Product and Actinide Cross Sections," NP-2345 (April 1982).

W. B. Wilson, T. R. England, and R. J. LaBauve, "Multigroup and Few-Group Cross Sections for ENDF/B-IV Fission Products; The TOAFEW Collapsing Code and Data File of 154-Group Fission-Product Cross Sections," LA-7174-MS (March 1978).

11. CONTENTS OF LIBRARY

Included are the referenced documents and one DC6150 tape cartridge in TAR format which contains, the TOAFEW_V source code, the LAFPX-V data library, and input and output from TOAFEW-V. Version 01 is also available on three and version 02 is available on two DS/HD 3.5-in. (1.44 MB) diskettes in self-extracting compressed DOS files.

12. DATE OF ABSTRACT

March 1985.