Fuel storage work completed at US Vermont Yankee NPP

17 August 2017

US Holtec International has said all major civil construction work associated with the Independent Spent Fuel Storage Installation (ISFSI) expansion project at Entergy's Vermont Yankee NPP has been completed ahead of schedule. Entergy announced in August 2013 that it would shut the 600MWe boiling water reactor (BWR) on economic grounds. The unit, which began operations in 1972, is undergoing complete defueling of its pool as a prelude to decommissioning. Holtec has already decommissioned several site structures, such as the north warehouse and auxiliary diesel generator, and reconfigured and upgraded electrical, service air, and potable water supply systems. In addition to expanding the ISFSI through the addition of a second pad, the site work included installation of a new diesel generator, and its blast protection structure that houses the generator.

Holtec said the technologies being developed at Vermont Yankee  to minimise crew dose will be valuable in decommissioning other BWRs in the future, the company said. Vice president of engineering Stefan Anton said: "Our pool-to-pad loading duration, reflecting our core emphasis on long-term canister integrity and ALARA (as-low-as-reasonably-achievable), is deliberately programmed to occur in five days." This approach has enabled the multi-purpose canister's field closure weld size to be made four times that of any peer supplier, and the canister dried to a "greater level of vacuum than any other in the industry", he added. Holtec has loaded six HI-STORM 100 casks "with steadily declining crew dose" as it deploys ALARA solutions to compensate for the elevated background radiation levels at the BWR. Holtec has not used neutron absorbers - which "trap moisture and pose the risk of in-process swelling or carbon steel in the fuel basket" - or a loading process that risks "gouging" the canister, said Anton.

Entergy last year agreed to sell Vermont Yankee and transfer its licences to NorthStar for an undisclosed price in a transaction expected to close by the end of 2018, subject to conditions and regulatory approvals. Under the agreement, NorthStar, would start decontamination and dismantling work at Vermont Yankee by 2021 and complete decommissioning and site restoration ( except for the ISFSF) by 2030. NorthStar will operate the ISFSF until the US government fulfils its statutory responsibility for the final disposal of all used fuel in the USA, after which NorthStar would decommission the ISFSF, terminate the site's licence and complete site restoration.



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