RSIC COMPUTER CODE PSR-029

1. NAME AND TITLE

SCANS: Spectra Calculation from Activated Nuclide Sets.

2. CONTRIBUTOR

Idaho Nuclear Corporation, Idaho Falls, Idaho.

3. CODING LANGUAGE AND COMPUTER

Fortran IV and Assembler language; IBM 360/75/92

4. NATURE OF PROBLEM SOLVED

SCANS determines the fast (above 1 MeV) and thermal neutron flux levels from Co⁵⁸ and Co⁶⁰ disintegration rates, given the irradiation history (operating power level versus time) of the reactor in which the activities were produced in Ni and Co wires. It processes up to 50 pairs of disintegration rates per problem; hence, all the data from a pair of irradiated wires monitored at a number of corresponding positions can be handled.

5. METHOD OF SOLUTION

The flux energy spectrum is first divided into a number of energy groups, as in the customary multigroup formulations in reactor physics. The problem then becomes that of finding the group fluxes. The solution method used in SCANS is based on two assumptions: 1) the energy dependence of the neutron flux at the point of irradiation is independent of the power level, and 2) the irradiation of the samples produces a set of activities to be monitored.

The solution method is applied to the evaluation of the fast (above 1 MeV) and conventional thermal neutron fluxes, given the activities of Co⁵⁸ and Co⁶⁰, respectively, that arise in the irradiation of Ni⁵⁸ and Co⁵⁹ samples. In the application, Ni and Co wires are irradiated in a reactor, removed, and, after a suitable wait time, monitored at a number of positions along the wires. The pair of activities measured at each position satisfy the second assumption in that the Co⁶⁰ activity is virtually dependent only on the thermal flux while the Co₅₈ activity is a function of both group fluxes.

6. RESTRICTIONS OR LIMITATIONS

The method, in its present form, is a "fully determined" one (there must be as many given activities as there are flux groups to be determined). This may restrict its use to cases of relatively small numbers of flux groups and accordingly crude spectra.

Each group flux determined can be a function of no other fluxes than those already determined. However, this guarantees an exact solution for the set of group fluxes with one sweep through the set.

7. TYPICAL RUNNING TIME

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

8. COMPUTER HARDWARE REQUIREMENTS

SCANS is operable on the IBM 360/75/91 computer.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required. Compile using OPT=2.

10. REFERENCE

M. H. Putnam and G. E. Putnam, "SCANS: Spectra Calculation from Activated Nuclide Sets," IN-1446 (November 1970).

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

November 1983.