Holtec’s Davit Crane for Decommissioning Structurally-Challenged Fuel Pool Enclosure Buildings in Nuclear Plants
When it comes to decommissioning of a nuclear power plant, the cask handling crane plays one of the most crucial roles. Modern high-capacity, high-heat load casks typically require a cask handling crane with capacity in excess of 100 tons that is fully qualified as single-failure-proof load handling device in accordance with NUREG-0554 or ASME NOG-01. A crane trolley replacement to a higher capacity is insufficient if the safety pedigree and the load bearing capacity of the building structure are inadequate which the case is often. The cost for upgrading both the building structure and the crane is usually too expensive for a plant nearing its licensed life, leading the owner to adopt short term palliative measures. However, the short-term solutions are uneconomical when the business imperative is to decommission the plant expeditiously as defueling the pool is a critical path activity in deconstructing a nuclear plant.
With its crane rated at 40 tons (manufactured in 1947) and the supporting building structure built a decade later, PG&E’s Humboldt Bay plant in Northern California faced this conundrum. The solution came in the form of a new crane embodiment called the Davit Crane which exploits the load bearing capacity of the fuel pool’s walls and adjacent slab to handle the loaded cask; the buildings walls. The existing crane are completely bypassed. The photos on this page show the Humboldt Bay crane in use.
As a result, the structural margins of safety in the Davit Crane in the Humboldt Bay application were so impressively large and the crane’s single-failure-proof features so persuasive, that the NRC issued the supporting SER in mere 20 months after the licensing submittal. It should also be noted that the Davit Crane installation effort at Humboldt Bay was quite straight forward requiring only modest human labor. The initial debut of the Davit Crane was also a huge ALARA success beating the owner’s target crew dose by a large margin.
Named the Davit Crane which recalls its superficial similarity to cranes used in naval applications, this crane design was patented by Holtec International in 2005 and the first crane was fabricated for Humboldt Bay at the Company’s own manufacturing plant. Expeditious defueling of Humboldt Bay occurred enabling the spent fuel pool to be fully defueled by 2008.
A number of adaptations of the original Humboldt Bay crane design (protected by US patent laws) are available from Holtec to overcome structural (load handling limitations) in power plant decommissioning projects.