The Spent Nuclear Fuel (SNF) storage facility at Savannah River Site (SRS) mainly consists of an array of Vertical Tube Storage (VTS) racks and a group of High Flux Irradiation Reactor (HFIR) fuel cores. The facility is integrally designed as a wet SNF storage system with a water chemistry control pool. In case of a hypothetical accident such as an earthquake, the water may be drained away, resulting in a dry SNF storage condition. The objective of the work is to estimate the maximum SNF temperature when the entire SNF storage area of the facility is completely drained away. A Computational Fluid Dynamics (CFD) modeling approach was taken for the thermal analysis of a water-drained SNF storage facility at SRS. The modeling calculations were performed by using a two-step method to achieve the objective, assuming that the storage racks are fully loaded with SNF assemblies containing decay heat source. In this situation, the SNF facility stores 14600 SNF assemblies in VTS racks and 120 HFIR cores in 60 HFIR racks. The model was benchmarked against theoretical results and literature data. Based on the benchmarked model, several sensitivity calculations with respect to the nominal operating case were performed.

The computational results of the present model yielded maximum temperatures of VTS and HFIR fuel assemblies for different fuel loading patterns of the SNF storage racks. The results showed that peak rack temperature for the uniform loading of the storage facility occurred in the center of the front VTS racks, and the maximum temperature for the conservatively differentiated loading pattern with the highest VTS decay heat of 420 watts and the highest HFIR decay heat of 871 watts was found to be about 320oC. It was also noted that when the maximum fuel bundle power of the 4x10 VTS rack increased from 420 watts to 600 watts, the peak temperature was increased by 43oC during the entire storage period.