Abstract
The concrete cask storage system stores spent fuel by first sealing it within canisters and then containing such canisters inside a concrete cask. This report describes the results of a full-size model test performed to examine the heat dissipation characteristics of the concrete cask and to ascertain its ability to deal with elevated temperature.
The specification to which a full-size concrete cask model was fabricated assumed an interim storage of 17×17UO2 fuel that was burned in PWR, estimating the heating value of spent fuel containing canister to be approximately 20kW apiece. The test, which actually covered canister heating values ranging from 10kW to 30kW per unit to allow for temperature variations likely to be experienced in actual operation, verified that the concrete cask member did not exceed temperature limits. Test condition anticipated highest air temperature inside the spent fuel storage facility to be 30℃ and, with reference to existing standard, set temperature limits of 65℃ or less for the main body of concrete and 90℃ or less for the local part as criteria.
Preliminary 3-D thermo hydrodynamic analysis done prior to the test indicated that the temperature of the local part of the concrete cask member would be below 90℃. It also confirmed that steel material used as the structural member of the canisters or concrete cask would remain around 200℃ even in an area where it was highest, validating that the integrity of such material would pose no problem from the analytical point of view.
Heat dissipation performance test conducted in steady state verified that the concrete cask was able to have a sufficient cooling capacity against per-canister heating values in the 10kW to 30kW range which had been chosen in anticipation of temperature variation thought to be encountered in actual service. Also, to examine the consequence of the concrete cask having lost its cooling ability, another heat dissipation test was carried out under condition simulating the closure of half of the cask’s air supply ports. The test showed that the concrete cask would increase just 10 to 15℃ in temperature throughout on the side where such closure occurred and the surface temperature of the canisters would rise to no more than 90℃, indicating that there would be no such temperature rise that affects the soundness of the members of these components.
