Engineering Analysis And Design

The CSB structure is designed to house canisters containing radioactive material at the DOE Hanford Site.  The canister storage area of the building is divided into three vaults.  The first vault will house the Hanford N Reactor spent nuclear fuel contained within 400+ multi-canister overpack (MCO) canisters, while the remaining two storage vaults will be used for the future storage of glass logs resulting from the vitrification of liquid wastes.  The MCO storage vault includes 226 storage tubes capable of holding two MCO canisters each, stacked one on top of the other.  Passive cooling is provided through the ‘stack effect’ which uses a temperature differential between the ambient and the inside of the CSB to generate buoyancy forces that balance the friction and duct losses resisting the movement of air through the vault. 

As a result of  radiolytic decay, the spent nuclear fuel (SNF) to be stored within the CSB will produce heat.  As such, the safety basis analysis had to ensure that the passive cooling mechanisms and air flow levels expected could be validated. Q­-Metrics was contracted to determine the thermal performance of the Canister Storage Building under a variety of conditions ranging from startup to fully loaded conditions.  The analysis addressed the potential for exceeding the thermal limits for the concrete structure or the MCO shell walls due to localized effects and during the period when the CSB is initially being loaded and before the global through flow resulting from stack effects could be fully established.

Q-Metrics employed a computational fluid dynamics (CFD) code (i.e., FLUENTÔ) to evaluate the combined thermal and fluid flow interactions.  The evaluations showed that the hot spot within the vault would occur near the inlet vent.  This counter-intuitive result occurs due to the effects of internal circulation within the vault and the tendency the cool incoming ambient air to flow along the floor of the vault due to its density differences from the vault air.  The evaluations further established a loading pattern for the vault that ensures the passive losses within the vault will remove the radiolytic decay heat from the MCOs until global flow through the vault is established.

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Last modified: September 06, 2002