An experimental apparatus was constructed, consisting of an 8×8 array of electrically-heated rods held in a square array by stainless-steel spacer plates near their ends. The rod/plate assembly was enclosed within a square-cross-section helium-filled aluminum pressure vessel and the rods were oriented vertically. The apparatus simulates the region between two consecutive spacer plates of a used nuclear fuel assembly within a vertical dry storage canister. Rod, spacer plate, and enclosure wall temperatures were measured using thermocouples in a matrix of nine experiments with total rod heat generation rates of 100, 300, and 500 W, and nominal helium pressures of 1, 2, and 3 atm.

Steady-state simulations representing the experiment were performed, which include heat generation within the rods, conduction within the solid elements, as well as buoyancy-induced motion within, and natural convection and radiation heat transfer across, helium-filled regions. These were compared to the experimental results to assess the accuracy of the computational model for a range of boundary conditions.

The comparison between the simulated and measured data showed that the simulations systematically under predict the hotter rod temperatures and over predict the cooler ones. Linear regression showed that 95% of the simulated temperatures are within 4.26°C of the correlation values.

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