EXPLORING INL | REACTOR DESIGN
examination capabilities for non-fuel materials that are used primarily for components and structures in nuclear reactors.
4) National Reactor Innovation Center (NRIC) Reactor Demonstration Test Beds – Two reactor demonstration test beds (DOME and LOTUS) are under development. a. Demonstration of Microreactor Experiments (DOME) is a repurposed and redesigned containment facility, formerly Experimental Breeder Reactor-II (EBR-II), capable of housing Category B nuclear reactors that generate up to 20 megawatts of thermal energy using high-assay low-enriched uranium (HALEU) or low- enriched uranium fuels. The facility provides a location and a supporting ecosystem of systems, equipment, and personnel to shepherd industry partners through a testing program for experimental microreactors to achieve first criticality and validate their design and analytical model algorithms. The DOME is expected to support operations beginning in 2026. Current industry partners engaged in front end engineering and experiment design work in preparation for potential testing are Westinghouse, Radiant and Ultra Safe Nuclear Corporation. b. Laboratory for Operations and Testing in the US (LOTUS) is a repurposed and redesigned confinement facility, formerly the Zero Power Physics Reactor, capable of housing Category B nuclear reactors that generate up to 500 kilowatts of thermal energy using high-enriched uranium fuels. The facility provides a location and a supporting ecosystem of systems, equipment, and personnel to shepherd industry partners through a testing program for experimental reactors to achieve first criticality and validate their design, fuel characteristics and analytical model algorithms. LOTUS is expected to support operations beginning in 2027/28. A current industry partner engaged in design work in preparation for a potential test program is the Southern/TerraPower Molten Chloride Reactor Experiment (MCRE) project.
5) Collaborative Computing Center (C3) provides state-of- the-art computer systems to perform modeling and simulation of nuclear reactors and fuels to support research on reactor concepts and fuels. C3 currently contains the Sawtooth computer, widely used across the nuclear R&D community. Sawtooth supports the use of advanced simulation software based on INL’s MOOSE framework.
NEI: Describe current research underway at the ATR, both in-house and collaborative ATR supports the testing of a range of nuclear reactor fuels. 1) Accident tolerant fuels – In support of industry development of accident tolerant fuels for light water reactors, INL is performing irradiations of fuel samples from Westinghouse, General Electric and Framatome to provide fuel performance data to support regulatory approvals for the use of these fuels in commercial power reactors.
2) TRISO fuels – The irradiation program for the Department of Energy’s Advanced Gas Reactor Fuels Program has been completed and the remaining experiments are undergoing post-irradiation examination. Capabilities to support new TRISO fuel irradiations are being developed and irradiation experiments are being designed to support specific advanced reactor developers.
3) High-performance research reactor fuels – Researchers are developing and testing fuels to support the conversion of high-performance research reactors from using highly-enriched uranium to low-enriched uranium.
NEI: What experiments are currently underway at TREAT including latest advances on MARVEL? The TREAT facility is performing experiments to support a range of fuels development activities. In 2023, the first Transient Water Irradiation System for the TREAT (TWIST) calibration test demonstrated the ability to conduct experiments that simulate the first phase of a loss of coolant accident in a light water reactor to support fuel safety testing. This addresses a key gap since the Halden reactor shut down. As part of a joint project between the U.S. and Japan
to perform the first transient tests on fast reactor fuels in more than two decades, INL developed the Temperature Heatsink Overpower Response capsule. The device houses fuel experiments in TREAT that mimic conditions of fast reactors during postulated accident conditions. The MARVEL team completed an updated 90% final
design package for the microreactor that included resolving hundreds of technical comments, followed by the final design review. A contract has been signed for cask recertification to support transporting the Training, Research, Isotopes, General Atomics (TRIGA) fuel from France, and the lab procured high-assay low-enriched uranium for fuel fabrication in February 2023 and a contract has been finalized to produce the MARVEL fuel.
NEI: When do you expect DOME and LOTUS to be available to researchers and how will these new test beds be used? The NRIC DOME facility will be available in 2026 to support reactor experiments. In 2023, NRIC announced the selection of three companies for front-end engineering and experiment design (FEEED) process that will support activities before performance experiments within DOME. The outcome of the FEEED process will determine the specific timing of the microreactor experiments. The companies chosen for the FEEED process includes Radiant, Ultra Safe Nuclear Corporation and Westinghouse. The LOTUS test bed will be available in 2027 for
installation of the first reactor experiment, which is anticipated to be the Molten Chloride Reactor Experiment.
NEI: What research, in-house and collaborative, is currently underway on molten salt reactors? INL is performing a range of research and development on molten salt reactors and to support Advanced Reactor Demonstration Program projects. INL has established a capability to perform irradiation of molten salt fuels and in 2023 performed the first uranium-fueled chloride salt irradiation in history at the lab’s Neutron Radiography Reactor. Through NRIC, INL is establishing the Molten Salt Thermophysical Examination Capability to perform key property measurements on irradiated fuel salts. In partnership with Southern and TerraPower on the
Advanced Reactor Demonstration Program MCRE project, INL has made significant progress to produce fuel salts. In 2023, INL achieved a ~98% yield during a fuel salt synthesis scale- up run, exceeding project requirement of a 90% yield, and performed a full-scale fuel salt synthesis demonstration
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