**RSIC COMPUTER CODE PSR-073**

**1. NAME AND TITLE**

CODAC: For TIMOC 72, Monte Carlo Three-Dimensional Neutron Transport Code's Data
Generator.

CODAC 2: Cross Section Generator for TIMOC 2 (Reads ENDF/B-II and III).

**2. CONTRIBUTOR**

CCR Euratom, Ispra, Italy, through the ENEA Computer Programme Library, Ispra, Italy.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; IBM 360/370.

**4. NATURE OF PROBLEM SOLVED**

TIMOC solves the energy- and time-dependent (or stationary) homogeneous or inhomogeneous neutron transport equation in three-dimensional geometries. It can treat absorption and all commonly used scattering kernels, such as: fission, isotropic and anisotropic scattering, level excitation, the evaporation model, and the energy transfer matrix model, which includes (n,2n) reactions.

TIMOC 72 uses the flexible O5R geometry routine which is able to describe any body or body combinations with surfaces of second order. It calculates the stationary or time-, energy-, and region-dependent fluxes as well as the transmission ratios between geometrical regions and the following integral quantities or eigenvalues, the leakage rate, the slowing down density, the production to source ratio, the multiplication factor based on flux and collision estimator, the mean production time, the mean destruction time, time distribution of production and destruction, the fission rates, the energy dependent absorption rates, and the energy deposition due to elastic scattering for the different geometrical regions.

CODAC is a nuclear data processing code. It converts ENDF/B data into group averaged cross
sections in the form needed by Monte Carlo codes.

**5. METHOD OF SOLUTION**

TIMOC is a Monte Carlo program and uses several partially optional variance reducing techniques, such as: the method of expected values (weight factor), Russian roulette, the method of fractional generated neutrons, double sampling, semi-systematic sampling, and the method of expected leakage probability.

The program can be linked to the ENDF/B data file via the CODAC code. CODAC generates,
for any desired group structure, the nuclear parameters and group averaged cross sections needed by
TIMOC. Averaging is done by using a weighting spectrum to be input. Group averaged cross sections
are calculated by summing up the smooth contributions and the contributions of the resolved and
unresolved resonances.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for CODAC.

**8. COMPUTER HARDWARE REQUIREMENTS**

CODAC is operable on the IBM 360/370 computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required.

**10. REFERENCES**

R. Jaarsma and H. Rief, "TIMOC-72, General Purpose Monte Carlo Code for Stationary and Time Dependent Neutron Transport - User's Manual."

H. Kschwendt and H. Rief, "TIMOC, 1970: A General Purpose Monte Carlo Code for Stationary and Time Dependent Neutron Transport," EUR-4519.e.

H. Krainer, CODAC: "A Fortran IV Programme to Process a TIMOC Library from the ENDF/B File," EUR-4521.e (1970).

F. Beonio-Brocchieri and C. Daolio, "CODAC 2: A New Version of the CODAC Code Which
Accepts ENDF/B-Version II Data for the Production of a Few Group Library for TIMOC--Also
Accepts ENDF/B-III," EUR/C-IS/816.72.e (March 30, 1972).

**11. CONTENTS OF CODE PACKAGE**

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

**12. DATE OF ABSTRACT**

February 1984.

**KEYWORDS: ** ENDF FORMAT; MULTIGROUP CROSS SECTION PROCESSING;
NEUTRON CROSS SECTION PROCESSING