**1. NAME AND TITLE**

RASPA: A Code for the Calculation of Buildup and Decay of Fission Products and Actinides.

**2. CONTRIBUTOR**

INTERATOM, Bensberg, Federal Republic of Germany, through the OECD NEA Data Bank, Gif-sur-Yvette, France.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; CDC-7600.

**4. NATURE OF PROBLEM SOLVED**

RASPA calculates the buildup, decay, and burnup of fissionable isotopes and their fission products.
It calculates--for variable time steps--the concentrations, the decay heat, the total burnup, and the
gamma-ray spectrum in any energy groups and the power density of the isotopes.

**5. METHOD OF SOLUTION**

The time-dependent variations of the concentrations are described by a system of linear ordinary differential equations of first order with constant coefficients (if the flux is held constant). This system is especially easily solved in the case of a triangular matrix of the coefficients. Such a triangular form is attainable by:

(1) Restriction to reactions of the following kind:

(a) fission

(b) (n,gamma) reaction (capture)

(c) beta-ray decay

(d) gamma-ray decay of the excited states of the nuclei

(2) Arrangement of the isotopes in a special order.

This means neglecting reactions of the kind (n,alpha), (n,2n), emission of neutrons (formation of
delayed neutrons) and similar processes which are, in general, of less importance.

**6. RESTRICTIONS OR LIMITATIONS**

The code is zero-dimensional. The data of a reactor core or a zone of it must be represented by adequate average values. In addition, (1) only reactions as indicated in Method of Solution are taken into account, (2) the number of fissionable isotopes must be less than or equal to 15, (3) the number of fission products and fissionable isotopes must be less than or equal to 600, (4) the number of gamma-ray energy groups must be less than or equal to 20.

RASPA includes some auxiliary routines which are used only at INTERATOM. These can be
replaced by dummy or corresponding routines chosen by the user.

**7. TYPICAL RUNNING TIME**

Running time depends mainly on the number of power steps. For a typical case with 10 power
steps, the time will be 5 minutes.

**8. COMPUTER HARDWARE REQUIREMENTS**

RASPA is operable on the CDC-7600 computer.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required. The program is executed under a Scope 3.4 monitor.

**10. REFERENCE**

G. Gronefeld, "The Decay Heat Production by Fission Products and Actinides of the SNR 300,"
OLS-79-241 (January 1976).

**11. CONTENTS OF CODE PACKAGE**

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

**12. DATE OF ABSTRACT**

January 1982.

**KEYWORDS: ** ISOTOPE INVENTORY; FISSION PRODUCT INVENTORY; MONTE
CARLO; ACTINIDES; GAMMA-RAY SOURCE