1. NAME AND TITLE

PEPIN: Methodology for Computing Concentrations, Activities, Gamma-Ray Spectra, and Residual Heat from Fission Products.

DATA LIBRARIES

Independent Yields Library: 8 independent yields for ²³⁵U, ²³⁸U, ²³⁹Pu, ²³²Th, ²³³U.

Chain Library: Precursor chain file for 635 nuclides.

Gamma-Ray Energies Library: Average beta and gamma-ray energies in increasing order.

2. CONTRIBUTOR

CEA Centre d'Etudes Nucleaires de Saclay, France.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

The concentrations, activities, gamma-ray spectra, and residual heat from fission products can be calculated as a function of time for instantaneous fission or for one or more irradiation steps.

5. METHOD OF SOLUTION

Using the basic data in the libraries, the PEPIN code solves the differential equations satisfied by the fission product concentrations.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

The sample problem ran in less than 30 seconds on the IBM 360/91 computer.

8. COMPUTER HARDWARE REQUIREMENTS

PEPIN was designed for an IBM 360 computer. It requires approximately 270 K storage.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required.

10. REFERENCES

"Description of the Pepin Library," Informal notes.

"Pepin Input Data," Informal notes.

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents and one (1.2MB) DOS diskette which contains the source codes, data libraries, overlay cards, and input and output from the sample problem.

12. DATE OF ABSTRACT

December 1983.