A common architectural limitation in a nuclear plant pertains to a deep fuel pool and a deep cask pit, but the cask crane bridge situated at a relatively low elevation above the pool deck. At such plants, placing a heavy load on the pool/cask pit liner, such as a fuel transfer cask, means the crane hook must be immersed in the pool’s contaminated water. Some Westinghouse plants deal with this limitation by making two cask pits side-by-side: the shallow pit serves as the intermediate station for the transfer cask where a rigging changeout can be made. During the cask lowering operation, the cask is staged on the shallow pit surface and a lift yoke extension of suitable length is installed so that the crane hook above water as the transfer cask is picked up from the shallow pit surface and lowered down to the deep pit. The reverse set of steps is needed to remove the transfer cask from the deep pit. Many nuclear plants, such as AEP’s D.C. Cook, FPL’s Turkey Point, Taiwan Power Company’s Maanshan, and Energy Northwest’s Columbia Generating Station have an insufficiently high bridge, and lack the two-step cask pit. At such plants, the spread of contamination by the crane block due to its wetting by the pool’s water, must be carefully watched and appropriately dealt with by the plant’s HP department. Some plants prohibit the “dunking” of the crane hook in the fuel pool’s water except under extenuating circumstances. Prophylactic measures such as wrapping the crane block in plastic are only partially effective.
Holtec’s invention, dubbed the VECASP, precludes the need to immerse the hook in the spent fuel pool’s water. It does so without adversely impacting the crane’s safety attributes (viz., NUREG-0554, NOG-1 compliance, and NUREG-0612 compliance for the lifting device). The VECASP is, in essence, a device to eliminate the root cause for potential crane contamination, which is the wetting of the crane block and its ancillary parts by the pool water.
Further, the VECASP protects the crane hook from contamination without compromising the structural integrity of the cask lifting and handling evolutions under the plant’s Design Basis Earthquake.