1. NAME AND TITLE OF DATA LIBRARY

PEFPYD: Aggregate Fission-Product Decay Data Based on ENDF/B-IV and -V.

2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS

PEFPYD: Obtains Analytic Fits to Aggregate Fission-Product Decay-Energy Spectra.

3. CONTRIBUTOR

Los Alamos National Laboratory, Los Alamos, New Mexico.

4. HISTORICAL BACKGROUND AND INFORMATION

PEFPYD is the results from summation calculations by the CINDER-10 and peripheral codes and fission-product decay, cross section and yield data from the ENDF/B-IV incorporated into a processed ENDF/B fission-product and energy-yield data (PEFPYD) library. The library contains aggregate beta and gamma spectra produced by neutrons of one or more energies incident upon six important nuclides.

5. APPLICATION OF THE DATA

The ENDF/B-IV fission-product files contain neutron cross sections, decay constants, decay energies, and other decay data for 824 important fission products. They also contain fission yields for these fission products produced by one or more fission-neutron energies (14 MeV, fast, and thermal fission). Also, spectral data exist for the most important decay-heat contributors among the 824 nuclides.

Because the spectra are based on fission pulses, the libraries have a general utility. The exponential fits, for example, can be folded into any power (fission) history that can be described analytically or by a histogram representation. The effects of neutron absorption are also treated and approximately accounted for in the methodology.

6. SOURCE AND SCOPE OF DATA

The summation codes and libraries were used to produce secondary aggregate libraries and pulse functions shown as "additional output" which could be used directly or incorporated into neutronics codes. The summation codes were used to produce beta- and gamma-temporal spectra in 150 groups following fission pulses for each fuel and fission neutron energy in ENDF/B-IV and the results were stored in formats similar to ENDF/B. In addition, collapsing and exponential fitting and folding codes were developed and exponential fits to a particular few-group spectra were made available.

Data based on ENDF/B-IV (designated as DLC-96A/PEFPYD):

²³²Th, ²³³U, ²³⁵U, ²³⁸U, ²³⁹Pu, ²⁴¹Pu.

Data based on ENDF/B-V (designated as DLC-96B/PEFPYD):

²³²Th, ²³³U, ²³⁵U, ²³⁸U, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu.

7. DISCUSSION OF THE DATA RETRIEVAL PROGRAM

FITPULS retrieves data from a library containing aggregate fine-group spectra (150 energy groups) from fission products, collapse the data to few groups (up to 25), and fit the resulting spectra along the cooling time axis with a linear combination of exponential functions. FITPULS runs on Cray computers under CTSS. Some modifications will be required for Fortran 77 compilers as noted in README.FIT.

8. DATA FORMAT AND COMPUTER

ASCII card images; Cray or CDC (D00096ALLCP02).

9. TYPICAL RUNNING TIME

No information is available on run time.

10. REFERENCES

R. W. Roussin, "Informal Contents of DLC-96/PEFPYD" (1982).

R. J. LaBauve and D. C. George, "PEFPYD - A Library of Aggregate Fission Product Decay Data Derived from ENDF/B-IV," LA-8365-MS (May 1980).

R. J. LaBauve, D. C. George, and T. R. England, "FITPULS - A Code for Obtaining Analytic Fits to Aggregate Fission-Product Decay-Energy Spectra," LA-8277-MS (March 1980).

11. CONTENTS OF LIBRARY

Included are the referenced documents and the FITPULS source and PEFPYD libraries on 4 DS/HD diskettes.

12. DATE OF ABSTRACT

April 1985, abstract revised November 1992, July 2001. Note that data in this package have not been changed since the initial October 1982 release by RSICC.

KEYWORDS: FISSION PRODUCT YIELDS; RADIOACTIVE DECAY SPECTRA