**1. NAME AND TITLE**

REST: Fission Product Inventory Code System with Fission Product Escape Model.

**AUXILIARY ROUTINES**

REST 1: Fission Product Activity and Decay Rate CalculationFission/Without Escape.

REST 2: Fission Product Activity and Decay Rate CalculationFission and Fission Product n-gamma Activation/Without Escape.

REST 3: Fission Product Activity and Decay Rate CalculationFission Product Escape
Model.

**2. CONTRIBUTOR**

Karlsruhe Nuclear Research Center (GFK), Karlsruhe, Federal Republic of Germany.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV; IBM 360/370.

**4. NATURE OF PROBLEM SOLVED**

The REST series was designed for the calculation of the fission product decay heat source
within a nuclear reactor. A BWR is used as a model for the calculations.

**5. METHOD OF SOLUTION**

Numerical techniques are used throughout a series of calculational steps: the time intervals for
the desired steps of equal reactor power; the fission rate integrated over each time step corresponding to the thermal reactor power input; equation coefficients are determined (REST 2 uses a
matrixREST 3 calculates along the isobars) and used for the activity and decay energy calculations, etc., until the inventory is complete.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

The following running times were noted while testing REST on the IBM 360/91:

REST 1 4.27 seconds

REST 2 10.02 seconds

REST 3 7.65 seconds

**8. COMPUTER HARDWARE REQUIREMENTS**

REST is operable on the IBM 360/370 computers. Maximum core used on the IBM 360/91,
462 K.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A FORTRAN H compiler is required. Plotting options require provision of routines which are
not in the current package.

**10. REFERENCE**

E. Waibel, "REST: Program for Calculating the Fission Product Activity and Decay Rate after
Variable Reactor History in Two Coupled Systems, Taking into Account Fission Product Escape,"
KFK 1579, ORNL-tr-271 (April 1972).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code and sample problem input and output.

**12. DATE OF ABSTRACT**

October 1975.

**KEYWORDS: ** FISSION PRODUCT INVENTORY