USA clears way for HALEU

22 January 2019

The US Department of Energy (DOE) has completed an environmental assessment clearing the way for the fabrication of high-assay low-enriched uranium (HALEU) fuel for advanced nuclear reactors at the Idaho National Laboratory (INL). Meanwhile, the US Department of Defense (DOD) has issued a Request for Information (RFI) for a small mobile reactor using HALEU fuel to provide electrical power in rapid response scenarios.

EBR-II, which operated until 1994, is the source of HALEU in storage at INL (Image: INL)

A final environmental assessment issued on 17 January determines that there will be no significant impact on the environment from using DOE-owned HALEU stored at INL to fabricate fuel at the laboratory's Materials and Fuels Complex (MFC), and possibly also at the Idaho Nuclear Technology and Engineering Center (INTEC), to support US companies in the development and deployment of new reactor technologies. The determination followed the publication in October 2018 of a draft environmental assessment, which remained open for public comment until 30 November.

The DOE's HALEU is from used fuel from the Experimental Breeder Reactor-II (EBR-II), which operated at the site from 1964 to 1994. Since 2000, DOE has employed an electrometallurgical treatment process at the MFC to refine and downblend the used high-enriched uranium fuel from the now-decommissioned reactor. About 10 tonnes of HALEU has been produced as a result of this process and is currently stored at INL.

Many advanced reactor designs currently under development will require HALEU fuel, enriched to between 5% and 20% in fissile uranium-235 (U235). The low-enriched uranium fuel used in today's nuclear power plants typically contains less than 5% U235. There are at present no commercial facilities in the US that are immediately capable of producing HALEU.

The decision means the federal government can fabricate HALEU fuel at INL from the lab's existing HALEU feedstock - mostly from the treatment of EBR-II fuel but also from some other small quantities of HALEU stored at the site - to support the near-term research, development and demonstration needs of private-sector developers and government agencies, including advanced reactor developers.

"This is a finite amount of HALEU with limited applications for specific advanced reactor designs but is one of several efforts undertaken by DOE to help ensure the availability of HALEU in support of the US nuclear power industry," the DOE said.

The DOE earlier this month announced plans to award a contract to a subsidiary of Centrus Energy Corp to demonstrate the production of HALEU using US-origin enrichment technology at the American Centrifuge Plant site in Piketon, Ohio.

DOD looking into mobile reactors

The US DOD on 18 January issued a Request for Information (RFI) to identify concepts for a "small mobile reactor" design that can address electrical power needs in rapid response scenarios.

"At a time when military operations are more energy-intensive than ever before, it is crucial that the [DOD] seek out game-changing technologies such as nuclear energy, which is a safe, reliable, and nearly unlimited resource," the RFI, issued by the Office of the Under Secretary of Defense for Research and Engineering, says.

Small mobile nuclear reactors can make domestic infrastructure resilient to an electrical grid attack and change the logistics of forward operating bases, both by making more energy available and by simplifying fuel logistics needed to support existing, mostly diesel-powered, generators. They would also enable a more rapid response during humanitarian assistance and disaster relief operations, the RFI notes.

"Small mobile nuclear reactors have the potential to be an across-the-board strategic game changer for the DOD by saving lives, saving money, and giving soldiers in the field a prime power source with increased flexibility and functionality," it says.

The mobile nuclear reactor is required to produce a threshold power of 1-10 MWe of generation, which it must be able to produce for at least three years without refuelling. It must weigh less than 40 tonnes and be sized for transportability by truck, ship, and C-17 aircraft. Designs must be "inherently safe", ensuring that a meltdown is "physically impossible" in various complete failure scenarios such as loss of power or cooling, and must use ambient air as their ultimate heat sink, as well as being capable of capable of passive cooling.

The reactor must be capable of being installed to the point of "adding heat" within 72 hrs and of completing a planned shutdown, cool down, disconnect and removal for transport in under seven days. They must be able to operate semi-autonomously and demonstrate minimisation of added proliferation risk. The RFI also specifies that the core design must use HALEU advance gas reactor tristructural isotropic - also known as TRISO - fuel.

The RFI will also help inform a decision on whether to issue a Request for Solutions, with which it forms the first phase of what is anticipated will be a multi-phase prototype project. Up to three different reactor design efforts may be awarded under Phase I, which will include a full-scope reactor prototype engineering design study that is anticipated to take 9-12 months. One design would then be selected for Phase II, which would include a complete build and testing of the system prototype.

Interested parties have until 8 February to respond to the RFI.

Researched and written by World Nuclear News