TRAC-PF1 LOCA calculations using fine-node and coarse-node input models
TRAC-PF1 calculations of a 200% cold-leg break LOCA have been completed for a UHI (upper head injection accumulator) plant using both fine-node (with 776 mesh cells) and coarse-node (with 320 mesh cells) input models. This study was performed to determine the effect of noding on predicted results and on computer running time. It was found that the overall sequence of events and the important trends of the transient were predicted to be nearly the same with both the fine-node and coarse-node models. There were differences in the time-dependent behavior of the cold-leg accumulator injection, and the predicted PCT for the coarse-node calculation was about 75 K less than that for the fine-node calculation. The higher PCT of the fine-node calculation is attributed primarily to three-dimensional flow effects in the core. The complete (steady state plus transient) coarse-node calculation required 13.5 hours of CYBER 76 computer time compared to 68.3 hours for the fine node calculation, yielding an overall factor of five decrease in running time. Thus, we conclude that for any large break LOCA analyses in which only the overall trends are of concern, the loss of accuracy resulting from use of such a coarse-node model will normally be inconsequential compared to the savings in resources that are realized. However, if the objective of the analyses is the investigation of the effects of multi-dimensional flows on clad temperatures, then a detailed model is required.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5714815
- Report Number(s):
- NUREG/CR-4044; SAND-2305; ON: TI85013275
- Country of Publication:
- United States
- Language:
- English
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