Thermal analysis of a ventilated high-level waste repository. [Cooling]
The cooling response of a single ventilated storage room in an unventilated array of rooms is examined. Calculations show that ventilation provides a thermal sink in the heated system inducing temperature gradients in the formation different from the unventilated case. An asymptotic cool-down limit exists for the storage room temperature; this minimum temperature depends on inlet air temperature, ventilation flow rate, and convective heat transfer coefficient. For inlet air at 75/sup 0/F and 50,000 cfm and a heat transfer coefficient of 0.8 Btu h-/sup 0/F-ft/sup 2/, the limit is about 100/sup 0/F. A storage room sealed for 5 years will achieve temperatures of approximately 180/sup 0/F, and approximately 4 months would be required in order to cool the storage room floor to a temperature of 120/sup 0/F with a flow rate of 50,000 cfm at an inlet air temperature of 75/sup 0/F, assuming a convective heat transfer coefficient of 0.8 Btu/h-/sup 0/F-ft/sup 2/. Two months would be needed to cool the exhaust air to 120/sup 0/F. For large air flow rates, the cooling time is independent of the flow rate. Increasing the storage room surface area by 25% over the baseline model depresses the cool-down temperatures by only 4/sup 0/F and decreases cooling times by 20%. Modifications in canister design or width have virtually no effect on the cooling, but placing the waste deeper beneath the storage rooms and/or using longer canisters can lower the operating temperatures and cooling times. Reducing the canisters from 3.5 kW power density for 10-year-old waste (108.5 kW/acre) to 2.0 kW/canister (62 kW/acre) reduces cooling temperatures by more than 20/sup 0/F and reduces cooling times to a few weeks or less. The cooling times are nearly independent of the conductivity of the geologic formation. The temperature increase in the air brought from the surface down the supply shaft to the storage room level is about 5 to 7 F/sup 0/ per 1000 feet. Temperature increases in regionsshould not be seriously restricted 30 or more feet away.
- Research Organization:
- Science Applications, Inc., Oak Ridge, TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 7303141
- Report Number(s):
- Y/OWI/SUB-76/16527; SAI/OWI-001; TRN: 77-017171
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
RADIOACTIVE WASTE STORAGE
UNDERGROUND STORAGE
COOLING
HEAT TRANSFER
HEATING
TEMPERATURE GRADIENTS
VENTILATION
ENERGY TRANSFER
MANAGEMENT
STORAGE
WASTE MANAGEMENT
WASTE STORAGE
052002* - Nuclear Fuels- Waste Disposal & Storage