SEFOR reactor vessel prepares to leave site

16 October 2018

The reactor vessel of the Southwest Experimental Fast Oxide Reactor (SEFOR) in Arkansas, which shut down over 45 years ago, has been placed in a carbon-steel container in preparation of its transport to a disposal site in Nevada.

SEFOR's reactor vessel is lowered into the container (Image: EnergySolutions)

Construction of SEFOR - near Fayetteville, Arkansas - started in 1965. It began operating in 1969 by a consortium of private energy companies, including General Electric, under contract to the US government. It was the only fast reactor to use a full core of plutonium-uranium mixed oxide (MOX) fuel, and was sodium-cooled. It completed its safety test programme in 1972, demonstrating the capability of the Doppler coefficient (related to core thermal expansion) in a MOX reactor to stabilise it and control accidents in oxide-fueled, sodium-cooled fast reactors.

The fuel and coolant were removed from SEFOR in 1974 and the facility was placed in SAFSTOR. This is one of three decommissioning strategies available to US nuclear power plant licensees. It is a deferred dismantling strategy under which a nuclear facility is maintained and monitored in a condition that allows the radioactivity to decay, usually for a period of 40-60 years, after which the plant is dismantled and the property decontaminated. Defuelling a shut-down nuclear reactor removes about 99% of its radioactivity.

The SEFOR site was given to the University of Arkansas to use for radiological instrument calibration and other research purposes, which ended in 1986. The university has since maintained the facility, while seeking federal funding to dismantle the facility.

In 2005, the federal government passed legislation to decommission and decontaminate the site. The University of Arkansas was eventually granted USD10.5 million in funding in September 2016 by the US Department of Energy (DOE) to begin dismantling SEFOR.

In 2009, nuclear commercial services company EnergySolutions was contracted by the university to carry out initial decontamination and dismantling work.

The SEFOR decommissioning project is being carried out in three phases. Phase one involved surveying the site and developing a decontamination plan and a project cost estimate. That phase was completed in 2011. During phase two, equipment and material was cleared out of the reactor building, leaving the reactor itself intact. That work was completed in September 2017.

An additional USD10 million in funding was announced by the DOE in April 2017.

EnergySolutions in May signed a USD9.45 million contract to complete the third and final phase of the decommissioning project. This involves the demolition of the reactor building and containment building.

EnergySolutions announced yesterday that the 38-tonne reactor vessel had been lifted from the reactor building and placed within a six-meter-tall, carbon steel transport/disposal container. The container will be filled with grout and sealed before being transported by truck to the Nevada National Security Site.

The SEFOR decommissioning project is expected to be completed in May 2019, with the site being returned to greenfield status.

Researched and written by World Nuclear News