**1. NAME AND TITLE**

FRCRL2: Calculation of Fission-Product Release in Reactor Accident Analyses.

**2. CONTRIBUTOR**

Battelle Columbus Laboratories, Columbus, Ohio.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV; CDC 6400.

**4. NATURE OF PROBLEM SOLVED**

FRCRL2 calculates the cumulative fractional release of fission products from nuclear reactor
fuel under postulated loss-of-coolant accident conditions. The mathematical model for release is
based on simple volume diffusion theory and the equivalent-sphere approximation of fuel porosity.
Both the operational pre-accident release component and the accident core thermal transient-induced release component are calculated. Detailed core temperature data are needed to make the
latter set of computations. In addition, specific core power distribution factors and fission product
diffusion parameters must be supplied.

**5. METHOD OF SOLUTION**

Analytical solutions to the conventional problem of one-dimensional diffusion from a sphere are
used. For the pre-accident release component, uniform conditions are assumed over the period of
reactor operation. Parabolic radial temperature profiles for the fuel pellets are computed and used
to define five radial temperature zones for each core segment. From this, the corresponding set of
dimensionless release parameters are calculated for insertion in the analytical solution. For the
accident release component, the change in temperature versus time is considered by incrementally
modifying the dimensionless release parameters for each of the core segments.

**6. RESTRICTIONS OR LIMITATIONS**

The calculation is limited to maxima of 12 fission product species, 10 radial core regions, and
11 axial core regions. Also, four separate sets of fission product diffusion parameter values must
be supplied for different temperature ranges or assumed atmosphere conditions.

**7. TYPICAL RUNNING TIME**

Approximately 2 seconds are required per fission product species per accident time step.

**8. COMPUTER HARDWARE REQUIREMENTS**

FRCRL2 is operable on the CDC 6400 computer.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A FORTRAN IV compiler is required.

**10. REFERENCE**

R. L. Ritzman and D. L. Morrison, "FRCRL2A Computer Code for Calculating Fission-Product Release in Reactor Accident Analyses," BMI-1913 (August, 1971).

**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.

**12. DATE OF ABSTRACT**

July 1975; revised October 1982.

**KEYWORDS: ** REACTOR ACCIDENT; FISSION PRODUCTS