1. NAME AND TITLE

RIBD-IRT: Radioisotope Buildup and Decay Code System.

RIBD/IRT is a modified version of CCC-137/RIBD II for use in LOCA studies.

2. CONTRIBUTORS

IRT Corporation, San Diego, California.

Sandia National Laboratories, Albuquerque, New Mexico.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; UNIVAC 1100/81.

4. NATURE OF PROBLEM SOLVED.

RIBD-IRT is a radioisotope buildup and decay code system designed to analyze the fission product content of irradiated reactor fuel. Concentrations of individual elements can be tracked and modified for all time steps following reactor shutdown (useful for computing time-dependent source terms following a hypothetical loss-of-coolant accident).

5. METHOD OF SOLUTION

RIBD-IRT is a grid processor that calculates isotopic concentrations resulting from two fission sources with normal down-chain decay by beta-ray emission and isomeric transfers and inter-chain coupling resulting from n,gamma ray reactions. Calculations can be made to follow an irradiation history through an unlimited number of step changes of unrestricted duration and variability including shutdown periods, restarts at different power levels and/or any other level changes. Output information includes time-dependent inventories, activities, decay powers, and energy releases for as many as 800 fission products (requires the ENDF-B/IV fission product data library for one of the inputs). The user can track and modify the concentration of individual elements as they decay with time following reactor shutdown. Tracking individual elements enables one to estimate time-dependent source terms for a hypothetical LOCA based on known or postulated fission product release mechanisms.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

For 34 time steps, the approximate CPU time was 1 minute.

8. COMPUTER HARDWARE REQUIREMENTS

On the UNIVAC 1100/81, 64 K is required. Five mass storage files, either tapes or disks, and a printer are needed.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCES

a. Included in documentation:

D. D. Thayer and N. A. Lurie, "A User's Manual for Computer Code RIBD/IRT," IRT 6406-003, January 1982.

D. R. Marr, "A User's Manual for Computer Code RIBD-II, A Fission Product Inventory Code, HEDL-TME 75-76 (January 1975).

b. Background information:

N. A. Lurie, D. H. Houston, and J. A. Naber, "Definition of Loss-of-Coolant Accident Radiation Source: Summary and Conclusions," IRT 8167-004, SAND78-0091 (March 1978).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document (10.a) and one (1.2MB) DOS diskette which contains the source program and sample problem input.

12. DATE OF ABSTRACT

February 1982; revised September 1982, updated February 1983.