US microreactor clears initial stage of pre-testing safety review

California-based Radiant is developing the 1 MWe Kaleidos high-temperature gas-cooled portable microreactor, which will use a graphite core and TRISO (tri-structural isotropic) fuel. It was one of three microreactor developers selected in October last year to receive a share of USD3.9 million Department of Energy (DOE) funding to develop and test their designs in the new DOME test bed facility at Idaho National Laboratory (INL). Testing is scheduled to begin in 2026.

Radiant said the Safety Design Strategy (SDS) - which describes the accepted safety analysis approach for the Kaleidos reactor - marks the initial stage in a comprehensive safety review process each microreactor developer will undertake prior to a fueled test at DOME.

The company said testing in DOME will allow it to gather critical safety and performance data to support the future commercial licensing process with the US Nuclear Regulatory Commission (NRC).

Radiant is currently working with INL on the next phase of the safety review, focusing on the Conceptual Safety Design Report (CSDR). The purpose of the CSDR is to summarise the hazard analysis efforts and safety-in-design decisions incorporated into the conceptual design, along with any identified project risks associated with the selected strategies.

Following its successful completion of reactor testing in the DOME facility, Radiant expects to deliver a limited number of pre-ordered Kaleidos units as soon as 2028, after obtaining NRC licences.

"The SDS is the cornerstone of the safety roadmap we're building as we approach commercialisation of a fueled reactor in a few years' time," said Radiant CEO Doug Bernauer. "We're grateful for DOE Idaho's review and approval as we take this important step forward and for INL's continued thorough support throughout this critical process."

"The approval of the SDS is an important step towards enabling a microreactor developer to perform a test in our DOME facility," said Brad Tomer, acting director and chief operating officer of the National Reactor Innovation Center. "As the nation's nuclear energy research laboratory, we are committed to working with private companies to help further develop advanced nuclear technologies that will provide clean energy solutions for the US."

The DOME test bed will repurpose the Experimental-Breeder Reactor-II containment structure at INL. EBR-II operated from 1964 to 1994, and was originally built to demonstrate a complete sodium-cooled breeder reactor power plant. It was later modified to test other reactor designs and to test materials and fuels for fast reactors, as well as generating power and heat for the site. While the reactor and much of its supporting equipment has been dismantled, the remaining 70-foot diameter, 80-foot high containment structure is particularly suited to host reactor demonstration and other nuclear projects.