Accelerated decommissioning of the boiling water reactor (BWR) at the Vermont Yankee Nuclear Power Plant is continuing, with dismantling and packaging of the reactor pressure vessel (RPV) and internal components now complete. The Orano Group, part of the NorthStar decommissioning team, who acquired the plant from Entergy in 2019, said segmentation of the irradiated reactor core was carried out remotely underwater to ensure the highest level of safety.

As well as Orano USA, the decommissioning team includes Waste Control Specialists and Burns & McDonnell. Orano is responsible for RPV segmentation, and providing support used fuel management. Waste Control Specialists provides waste management, packaging, transport and disposal, and Burns & McDonnell provides engineering and regulatory support.

Orano said it used remote-controlled tools designed specifically for dismantling and which have proven their effectiveness in previous projects, particularly in Germany. The RPV, which was some 20 metres high and weighed several hundred tons, is the largest metal component of a BWR. Orano also packaged and transported the waste from the dismantling operations to a dedicated storage site, located in the West Texas region.

Vermont Yankee stopped operating in December 2014 after 42 years of operation. In November 2016, Entergy announced the sale of the plant to NorthStar for accelerated decommissioning. In October 2018, the US Nuclear Regulatory Commission approved the transfer of Vermont Yankee's operating licences to NorthStar and the Vermont Public Utility Commission issued an order authorising the sale in December.

In the meantime, Entergy had signed a contract with US-based Holtec International to expeditiously defuel the Vermont Yankee used fuel pool. The overall project scope included construction of a second Independent Spent Fuel Storage Installation (ISFSI) pad, security expansion, engineering, licensing, manufacturing, delivery and loading of 45 HI-STORM cask systems, all on a turnkey basis.

The work was completed in August 2018, ahead of schedule.

NorthStar said it would start decontamination and dismantling work by 2021 and complete decommissioning and site restoration by 2030 (excluding the ISFSI). Under Entergy's original decommissioning plan the target completion date had been 2075. Orano is also supporting NorthStar in the dismantling of the pressurised water reactor at unit 3 of the Crystal River NPP in Florida and management of its used fuel. The group is also dismantling the cores of six nuclear reactors in Germany.

Image: Segmented pieces of Vermont Yankee's reactor vessel are loaded into custom transport and disposal boxes (courtesy of Orano)