**
1. NAME AND TITLE**

TRIGAP: A Computer Code for TRIGA Type Reactors.

**2. CONTRIBUTOR**

Jozef Stefan Institute, Ljubljana, Yugoslavia through the International Atomic Energy Agency, Vienna and the NEA Data Bank, Gif-sur-Yvette, France

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN 77; IBM PC.

**4. NATURE OF PROBLEM SOLVED**

TRIGAP was developed for reactor physics calculations of the 250 kW TRIGA reactor. The program can be used for criticality predictions, power peaking predictions, fuel element burn-up calculations and data logging, and in-core fuel management and fuel utilization improvement.

**5. METHOD OF SOLUTION**

The program solves the one-dimensional, two-group diffusion equation using the finite- difference method.

**6. RESTRICTIONS OR LIMITATIONS**

Expected accuracy of the calculations is 1.5% absolute and 0.5% for relative criticality, 15% for power distributions and peakings and 10% for fuel element burnup.

**7. TYPICAL RUNNING TIME**

The sample problem only took about 1/2 minute on a PC/AT and a few seconds on a PC-486.

**8. COMPUTER HARDWARE REQUIREMENTS**

TRIGAP runs on the IBM PC with at least 540kb of memory.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The code was written in FORTRAN 77 and was tested using the Microsoft Version 5.0 compiler.

**10. REFERENCES**

I. Mele, S. Slavic, and M. Ravink, "Burnup Calculation of TRIGA Fuel Elements - Calculation of Radionuclide Inventories of TRIGA Fuels," IJS-DP-5883 (September 1990).

M. Ravnik, I. Mele, S. Slavic, and B. Zefran, "Development of Computer Programs for Research Reactor Calculations Using Small Computers," IJS-DP-5040 (1987).

I. Mele and M. Ravink, "TRIGAP - A Computer Programme for Research Reactor Calculations IBM.PC. Version," IJS-DP-4238 (December 1985).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and a 5.25-in. DS/HD (1.2MB) diskette which includes source codes, sample input and output.

**
12. DATE OF ABSTRACT**

April 1992.

**KEYWORDS:** BURNUP; CRITICALITY CALCULATIONS;

MICROCOMPUTER; REACTOR PHYSICS