GAPCON-THERMAL-1: a computer program for calculating the gap conductance in oxide fuel pins
GAPCON-THERMAL-1, a modification of GAPCON, can be used to calculate the gap conductance and fuel temperatures in oxide fuel pins. The code in its current form was developed for the Regulatorv Staff who use the code as a tool to independently calculate gap conductances for understanding various thermal performance models supplied by fuel venders. The code is capable of calculating fuel temperatures for several coolant, cladding, and fuel material combinations. Changes in the diametral gap width are modeled. The source of these changes include differential thermal expansion of pellet and cladding, elastic and creep deformation of cladding, fission product expansion of the pellet, and fuel expansion induced by cracks and subsequent thermal ratcheting. In addition to the gap changes, the code simulates a variety of fill gas compositions and changes to the gas composition caused by the release of fission gap and volatile impurities. Comparisons of calculations and experimental data indicate iuel temperatures are predicted reasonably well for short term irradiations and small gaps. The disagreement between predictions and experimental data is roughly proportional to the gap width and the calculated values are typically higher than the experimental values. Fuel temperature calculations for extended periods of irradiation become more uneertain because of inadequacies in the code and the dearth of well characterized data. These inadequacies are related principally to the kinetics of gap closure and fission gas release. On-going work is focused on reducing the uncertainty in these two areas of the code and in other areas of somewhat lesser significance. The effects of these uncertainties on the fuel stored energy are offset somewhat by the reduction in rod powers with burnup. (auth)
- Research Organization:
- Battelle Pacific Northwest Labs., Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AT(45-1)-1830
- NSA Number:
- NSA-29-002098
- OSTI ID:
- 4428219
- Report Number(s):
- BNWL-1778
- Resource Relation:
- Other Information: Orig. Receipt Date: 30-JUN-74
- Country of Publication:
- United States
- Language:
- English
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