NESC0618 GAPCON-THERMAL-2

1. NAME OR DESIGNATION OF PROGRAM:  GAPCON-THERMAL-2 & GT2R2-1

3. DESCRIPTION OF PROBLEM OR FUNCTION

GAPCON-THERMAL2 Rev. 1
calculates the thermal behavior of a nuclear fuel rod during normal  steady-state operation. The program was developed as a tool for estimating fuel-cladding gap conductances and fuel-stored energy. Models used include power history, fission gas generation and release, fuel relocation and densification, and fuel-cladding gap conductance. The gas release and relocation models can be used to make either best-estimate or conservative predictions.
GT2R2, a revision of GAPCON/THERMAL, is used by the U.S. Nuclear Regulatory Commission for audit calculations of nuclear fuel thermal performance computer codes.

4. METHOD OF SOLUTION

The fuel to cladding gap conductance for each equal-length, user-designated axial region is determined by an iterative scheme. Radial temperatures are calculated using a finite  difference procedure. The solution procedure consists of iterative convergence for each axial fuel region, followed by iterative convergence on the fuel rod gas release for each time-power step. A  mixture of empirical, theoretical, and physical models is used.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

(1) GAPCON-THERMAL2:
    Maxima of -
    15 axial nodes
    35 time-steps
No mechanical plastic strain is considered. The thermal model is axisymmetric. The first time-step must be zero time and the second cannot be at zero power.
(2) GTR2:
    Maxima of
    35 time-steps
    23 sets of temperature and physical properties parameters for
       cladding
    20 pairs of time and diametral change parameters for cladding
       creepdown
    20 pairs of diameter and relative power parameters for the
       radial power profile
    10 sets of temperature and thermal conductivity parameters for
       fuel thermal conductivity

6. TYPICAL RUNNING TIME

Typical run time on the CDC CYBER74 is approximately 30 seconds per time-step; the sample problem runs in less than 20 CP seconds on a CDC7600.

NEA-DB ran the test case included in this package on a  VAX-6000 computer in 47 seconds of CPU time.

7. UNUSUAL FEATURES OF THE PROGRAM

Most models have been compared individually with experimental data; however, the code as a whole has not been adjusted to conform to any set of data.

8. RELATED AND AUXILIARY PROGRAMS

GTR2 is a revision of GAPCON- THERMAL2 Rev.1 to improve predictive abilities at high burnup and coding structure and to conform to the ANSI FORTRAN 77 language standard.
GAPCON-THERMAL2 is a modification of GAPCON-THERMAL1 to reduce the uncertainties associated with the calculation of power history and burnup. GAPCON-THERMAL3 (NESC Abstract 770) is a related program which calculates detailed fuel rod mechanical conditions.
GAPCON-THERMAL3 (NESC0770) is a related program which calculates detailed fuel rod mechanical conditions.

10. REFERENCES

- C.E. Beyer, C.R. Hann, D.D. Lanning, F.E. Panisko and L.J. Parchen   User's Guide for GAPCON-THERMAL2: A Computer Program for Calcu-
  lating the Thermal Behavior of an Oxide Fuel Rod,
  BNWL-1897, November 1975.

- M.E. Cunningham and C.E. Beyer:
  GT2R2 - An Updated Version of GAPCON-THERMAL-2
  NUREG/CR-3907, PNL-5178 (September 1984).
- C.E. Beyer et al.:
  GAPCON-THERMAL-2 - A Computer Program for Calculating the Thermal
  Behavior of an Oxide Fuel Rod
  BNWL-1898, NRC 1 and 3 (November 1975).

11. MACHINE REQUIREMENTS

GAPCON-THERMAL3 Rev.1: About 54k words of main memory is needed for compilation and execution.
GTR2: About 151 Kbytes of storage are needed for execution on a DEC  VAX11/780.

The program was implemented at NEA-DB on a DEC VAX-6000 computer.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED

VMS 3.7 (DEC VAX11/780); SCOPE 3.4 (CDC6600); NOS/BE (CDC CYBER74); SCOPE 2.1 (CDC7600).

The program was compiled and executed at the NEA-DB under VAX/VMS V5.5-2 using the VAX FORTRAN compiler V5.5-98.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

C.E. Beyer*, M.E. Cunningham*, C.R. Hann, D.D. Lanning,
F.E. Panisko, and L.J. Parchen
Pacific Nothwest Laboratories
Battelle
P.O. Box 999
Richland, Washington 99352
* Contact

File name	File description	Records
NESC0618_05.001	This information file	126
NESC0618_05.002	GT2R2-1 Fortran source	4801
NESC0618_05.003	Common Block INPUTV	16
NESC0618_05.004	Common Block AZ	4
NESC0618_05.005	Common Block AF	4
NESC0618_05.006	Common Block AD	11
NESC0618_05.007	Common Block PH	5
NESC0618_05.008	Common Block HGAP	4
NESC0618_05.009	Common Block AB	10
NESC0618_05.010	Common Block INIT	13
NESC0618_05.011	Sample problem input	82
NESC0618_05.012	Sample problem output	2484