The U.S. Department of Energy is building the first fast neutron reactor since the Experimental Breeder Reactor-II, to support advanced reactor development.

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Last month, the U.S. Department of Energy (DOE) launched a project to build the U.S.' first fast neutron reactor in over 20 years. The new "Versatile Test Reactor" (VTR) will "drastically” accelerate the testing, development and qualification of advanced reactor technologies, the DOE said.

Designed by the DOE’s Idaho National Laboratory (INL), the VTR will be a sodium-cooled fast reactor and will be used to conduct accelerated irradiation tests required for non-light water reactor (non-LWR) designs, such as those cooled by molten salt, liquid metal, or helium gas.

The VTR will be a modified version of existing designs and INL plans to complete the conceptual design– roughly 30% of the final design– by October 2020, Kemal Pasamehmetoglu, executive director of the VTR Program at INL, told Nuclear Energy Insider.

The facility could become fully operational in 2026-2028, assuming a 300 MW plant based on a well-characterized fuel form, Pasamehmetoglu said.

INL and other DOE teams are now working with commercial reactor and component developers to ensure the supply chain will be ready to support final design, testing and construction, he said.

Supplier openings

The VTR project was included in the 2017 Nuclear Energy Innovation Capabilities Act, enacted into law in September 2018. Fast reactor developers are seeking support to build the first commercial plants in the coming decade and the U.S. has not had a fast neutron spectrum testing facility in full operation since the Experimental Breeder Reactor-II (EBR-II) was shut down in 1994.

More than 40 U.S. companies are working on advanced nuclear energy designs and private companies have already invested more than $1 billion in this area, according to the DOE's Office of Nuclear Energy (ONE).

           Non-LWR developers in formal US NRC licensing dialogue

                                                        (Click image to enlarge)

Source: Nuclear Regulatory Commission (NRC)

As the first fast reactor developed for decades, the VTR project will need to procure new component solutions.

"Testing will be needed for things like electromagnetic pumps, custom design and fabrication," Pasamehmetoglu said.

Special steel alloy (HT9) will also be required and N-stamped manufacturing capability of HT9 will need to be re-established, he said.

The DOE also recently provided funding which will help complete the commercial supply chain for high assay low enriched uranium (HALEU). In January, the DOE awarded funding to American Centrifuge Operating (ACO), a subsidiary of Centrus Energy, to build the first U.S.-designed and operated advanced centrifuge technology by October 2020.

Advanced monitoring

The VTR will test the performance and safety of advanced reactor materials and collect valuable data for design development and licensing. New fuels, materials, instruments and sensors will be exposed to the conditions they would experience inside an advanced reactor.

Advanced monitoring and analytics technologies will be implemented at reactor-level, core-level and experiment-level, Pasamehmetoglu said.

At reactor-level, this could include in-situ ultrasonic non-destructive evaluation (NDE) for inspection and monitoring of hard-to-replace components, he said.

At reactor core level, fibre-optic sensors and ultrasonic guided wave monitors may be used to provide power information such as flow rate, temperature and neutron flux measurements, Pasamehmetoglu said. Chemistry control instrumentation will also be installed.

"A major objective of the instrumentation and sensor development activities in the R&D program is to be able to obtain as much real-time data as possible during irradiation testing of fuels and materials, instead of heavily relying on post-irradiation examination (PIE) data to reconstruct the irradiation history," he said.

The VTR facility will provide the greatest benefits for fast reactor developers, “not only for sodium-cooled but also for lead-, LBE [Lead-Bismuth Eutectic] and gas-cooled reactors as well as molten salt reactors,” Pasamehmetoglu said.

Advanced reactor developers will need to expand fuel test data to license the designs, he said.

“Data on fuel performance and life cycle in a specific reactor design environment – particularly lead, LBE and gas-cooled fast reactors – is limited or non-existent,” he noted.

Design needs

The VTR’s high neutron flux and neutron energies will allow accelerated testing of materials for thermal reactors, providing neutron damage rates 20 times greater than current water-cooled test reactors.

The following functional requirements will steer the design of the VTR:

• An ability to reach fast flux of approximately 4.E15 n/cm2-s, with prototypical spectrum.
• A load factor as large as possible to maximize annual displacements per atom to >30 dpa/year.
• The capability of running loops representative of typical fast reactors. For instance, candidate coolants include Na, Pb, LBE, gas and molten salt. This could be a single location with replaceable cartridge loops.
• An effective testing height up to 1 meter.
• The ability to perform a large number of experiments simultaneously.

Global competition

The VTR is being designed for a 40 to 60 year lifespan and will allow U.S. companies to "conduct advanced technology and fuels tests without having to go to our competitors in Russia and China,” U.S. energy secretary Rick Perry said in a statement.

Russia, China, India and Japan are currently the only countries to operate fast reactors but a large number of countries are developing these facilities, according to the World Nuclear Association (WNA).

                   Global fast neutron reactors under development

                                                         (Click image to enlarge)

Source: World Nuclear Association (WNA)

The VTR will help modernize the U.S. nuclear research infrastructure and could support the export of new technologies.

“Having this domestic capability is critical to our national security and our ability to re-establish ourselves as a global leader in advanced reactor technologies,” Ed McGinnis, ONE principal deputy assistant secretary, said.

By Neil Ford