1. NAME AND TITLE

CARNAC: Calculation of Flux and Neutron Spectra in the Case of Criticality Accident.

2. CONTRIBUTOR

Radiological Protection Studies Section, Nuclear Safety Department, Nuclear Research Center, CEA/CEN, Saclay, France.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

CARNAC was designed to evaluate the dose received by personnel after a criticality accident, especially for neutrons, by determining the neutron radiation field at the spot. The fluence and spectrum of neutrons at a point are calculated and a maximum dose of corresponding irradiation is estimated.

5. METHOD OF SOLUTION

Two codes (CRITIC and NARCISSE) are combined into one system to perform the calculations. CRITIC, using a method based on the FERMI age theory, evaluates the number of neutrons per fission emitted from a moderated critical assembly and its energy spectrum. NARCISSE, using a method based on the albedo, studies the reflection from the walls and determines the flux and the spectrum at any point and its energy distribution.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

The calculating time varies significantly only with the fineness of division of the walls into panels, especially where the second reflection is concerned. Because the convergence of the results is quite rapid, it is generally sufficient to divide each of the three edges of the space into 100 equal parts for the first reflection and into 12 equal parts for the second reflection. CARNAC then requires less than 3 minutes on the IBM 360/91.

8. COMPUTER HARDWARE REQUIREMENTS

CARNAC is operable on the IBM 360/370 computers. On the IBM 360/91 it requires only 100 K of memory.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required.

10. REFERENCES

J. Bessis, "Rapid Method of Calculating the Flux and Neutron Spectra in the Case of a Criticality Accident (Computer Code CARNAC)," ORNL-tr-2825; CEA-N-1612 (May 1973).

J. Bessis and M. de Mareuil, "Use of CARNAC Calculation Program," ORNL-tr-2822; CEA-SESR-N-05 (March 1973).

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

August 1975; revised November 1982.