Holtec completes main work at Vermont Yankee

The USA's Holtec International has announced the early completion of all major civil construction work associated with the Independent Spent Fuel Storage Installation (ISFSI) expansion project at Entergy's Vermont Yankee nuclear power plant. The facility is undergoing complete defueling of its pool as a prelude to decommissioning.

Entergy announced in August 2013 that it would shut the 600 MWe boiling water reactor (BWR) as its continued operation was not financially viable. The unit, which provided almost three-quarters of Vermont's electricity, began operations in November 1972.

As part of the site construction effort, Holtec has decommissioned several existing 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 has loaded six HI-STORM 100 casks "with steadily declining crew dose" as it deploys ALARA (as-low-as-reasonably-achievable) solutions to compensate for the elevated background radiation levels inherent to an inactive BWR. The technologies being developed at Vermont Yankee  to minimize crew dose will be valuable in decommissioning other BWRs in the future, the company said.

Stefan Anton, Holtec's vice president of engineering, said: "Our pool-to-pad loading duration, reflecting our core emphasis on long-term canister integrity and ALARA, is deliberately programed 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 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, he said.

Entergy announced in November last year it had 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 - with the exception of the ISFSF - by 2030. NorthStar would continue to 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.

Researched and written
by World Nuclear News