DOE funding propels US towards first advanced fuel factory by 2023
Federal funding for fuel partner Centrus has bolstered X-energy's bid to build the first U.S. advanced reactor fuel factory but licensing and supply challenges remain, experts told Nuclear Energy Insider.
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Last month, the U.S. Department of Energy (DOE) awarded funding to American Centrifuge Operating (ACO), a subsidiary of Centrus Energy, to demonstrate the production of high assay low enriched uranium (HALEU).
The HALEU Demonstration Program will aim to produce ACO's AC-100M 19.75% enriched uranium, using U.S.-designed and operated advanced centrifuge technology, by October 2020.
The current fleet of commercial reactors uses uranium-235 enriched at a level of 3 to 5%. A number of advanced reactor designs are based on HALEU fuel but as yet there are no commercial U.S. facilities to produce it.
The DOE's HALEU program is a major boost for advanced reactor developer X-energy, which is developing the Xe-100 High Temperature Gas-cooled Reactor (HTGR) and plans to build the U.S.’ first commercial HALEU fuel fabrication plant.
In November, X-Energy and Centrus agreed to proceed with the preliminary design and licensing of a new fabrication facility for X-energy's uranium oxycarbide/tristructural isotropic (TRISO) HALEU-based fuel forms.
The DOE’s HALEU program will accelerate the development of a fully domestic U.S. fuel HALEU supply chain, critical for the deployment of the Xe-100 reactor and other advanced reactor designs.
X-energy is aiming to start fuel production at its planned TRISO-X Fuel Fabrication Facility by 2023-24 and this will require an "aggressive" project schedule, Pete Pappano, Vice president, Fuel Production at X-energy, told Nuclear Energy Insider.
X-energy and Centrus have yet to decide the location of the fabrication facility and preliminary design and pre-application licensing discussions are underway with the NRC, Pappano said.
“Early and frequent collaboration between the HALEU producer, fuel fabricators and advanced reactor developers will be needed,” he said.
To meet their schedule, X-Energy and Centrus will need to overcome licensing and supply chain challenges brought about by the jump to next-generation fuel technology.
Safety layer
TRISO fuel particles consists of a microsphere or kernel of enriched uranium oxide/carbide encased in multiple layers of pyrocarbon and silicon carbide to form a miniature pressure vessel to prevent the release of fission products.
The fuel can be supplied in different final forms, including pebbles as used in the Xe-100 design, or compacts.
X-Energy's TRISO-X fuel facility could support multiple reactor designs but supply chain gaps must be filled, Pappano said.
"The remaining gaps are the enrichment of a HALEU to UF6 [Uranium Hexafluoride] and deconversion of the UF6 to uranium oxide powder,” he said.
Advanced fuel technologies can improve the safety and economics of advanced reactors by providing more robust fuel performance and safety with reduced reliance on additional safety systems, John Wagner, Associate Laboratory Director at the Nuclear Science and Technology Directorate, Idaho National Laboratory (INL), told Nuclear Energy Insider.
“Innovations providing increased fuel density, for example, can yield longer operating cycles with improved operations and economics,” he said.
The use of TRISO-based fuels in pebble bed reactors such as the Xe-100 has been proven to provide a “meltdown proof/walk away safe” core, Pappano said.
Other safety features of the Xe-100 plant include no requirement for backup power and no significant off-site release, according to the developer.
Non-LWR developers engaged in NRC pre-application licensing activity
(Click image to enlarge)
Source: Nuclear Regulatory Commission, February 2019.
Cost efficiency
The Xe-100 plant design is based on modules of 75 MWe (200 MWt) and the levelized cost of energy (LCOE) is estimated at $84/MWh for a 300 MWe plant.
X-energy predicts modular construction efficiencies will reduce the construction and transport costs of the Xe-100 design and cut construction times to around 2.5 to 4 years.
Key performance advantages cited by the company include higher fuel utilisation before discharge than other types of plants, and higher coolant outlet temperatures which increases the efficiency of electricity production and opens up potential industrial heating applications.
SMR developers see huge potential in industrial and district heating applications and hydrogen production as companies and governments strive to cut carbon emissions.
Power to heat switching efficiency and storage capability will impact the competitiveness of these plants. High-temperature gas-cooled reactors may be the most economical designs for these applications, according to some experts.
Global industrial heat demand by temperature level
(Click image to enlarge)
First of a kind
Centrus' experience in fuel development and manufacturing will play a crucial role in the TRISO-X fuel fabrication project.
Centrus’ will provide detailed nuclear criticality safety analysis, infrastructure design and balance of plant support systems and perform initial work on the license application for the facility.
The project partners are faced with several significant regulatory challenges in licensing the fabrication plant.
The facility would be the first in the U.S. to produce Category II fuel material, denoting enrichment levels between 10% and 20%.
Plant security, material control and accounting requirements may have to be fleshed out with the NRC on a case by-case basis, Pappano said.
Applicants for a license to operate a fuel manufacturing facility must work with the NRC to determine “appropriate site-specific implementing details,” he said.
HALEU fuel developers will have to provide data and assurance on the performance of these fuels under different operating conditions, Wagner noted.
“We have less experience and performance data for advanced reactors and fuels,” he said.
If X-energy and Centrus can overcome these challenges, they will be well-placed to become the U.S.' first commercial producers of HALEU fuel.
“We see great promise in this market," Daniel Poneman, president and CEO of Centrus, said in a statement.
"The advanced TRISO fuel to be produced in this facility will offer an attractive and competitive solution to power advanced reactors around the world,” he said.
By Neil Ford