Dismantling of Vermont Yankee reactor core completed

These operations, started in early 2019 after two years of preparatory studies, are part of a contract signed in 2017 with the NorthStar group. As the site owner, NorthStar is performing the accelerated decommissioning of the facility with expected completion in 2027.

Since waste shipment options in the Vermont Yankee region were limited to rail and narrow, hilly roads, the Orano team determined that the optimal decommissioning strategy was a full segmentation of the reactor and its internals.

The reactor pressure vessel - nearly 20 metres high, more than 5 metres in diameter and weighing about 400 tonnes - is the largest metal component of a boiling water reactor (BWR). The reactor internals are all the components inside the reactor pressure vessel that control the nuclear reaction and the water/steam cycle, minus the used nuclear fuel, which was removed earlier.

To access and perform the segmentation of these highly-irradiated components in their complex configurations, the Orano team used a variety of robust technology, including underwater, with remote operators, such as large bandsaws, reciprocating saws, abrasive water jet systems, diamond wire saws, and thermal cutting. Some of the parts were first cut into large segments and then lifted by the reactor building's overhead crane to other work zones on the reactor refuelling floor or into the water-filled but empty used fuel pool for further cutting into smaller pieces.

A transport cask containing waste from Vermont Yankee (Image: Orano)

Orano also packaged and transported the waste from the dismantling operations to Waste Control Specialists' waste disposal site in Texas. In all, 630 tonnes of low-level radioactive waste were shipped from the Vermont Yankee site. The used nuclear fuel and greater-than-Class C waste remain onsite in secure dry storage.

"Completion of this complex segmentation of Vermont Yankee's reactor represents more than 280,000 hours of our Orano teams performing safely and professionally," said Orano USA President and CEO Amir Vexler. "For the waste transportation, our attention to detail and transparent, close coordination resulted in incident-free shipments and informed appreciation from a variety of stakeholders."

"The Orano hallmarks of strong customised design, planning, and field operations derived from decades of experience delivered this complex first-of-a-kind BWR segmentation project safely and successfully for our customer NorthStar and the community," said Orano Decommissioning Services President and CEO Geoff Wilde.

Vermont Yankee, a single-unit 604 MWe BWR, generated its last power in December 2014. Although safety regulators had granted a licence for the unit to operate until 2032, Entergy decided to close it early for economic reasons. Entergy in November 2016 announced the sale of the plant to NorthStar for accelerated decommissioning.

In the USA, Orano is also supporting NorthStar in the dismantling of the pressurised water reactor at unit 3 of the Crystal River nuclear power plant in Florida and management of its used fuel, while in Germany the group is dismantling the cores of six nuclear reactors.