The Department of Energy’s Idaho Operations Office (DOE-ID) approved Aalo’s Documented Safety Analysis for the Aalo-X on 30 April. The Documented Safety Analysis is the authoritative safety basis for a DOE nuclear facility. It demonstrates in detail that a facility can be operated safely across its full range of normal, off-normal, and accident conditions. It is one of the most rigorous regulatory gates in the DOE process. Because the Aalo-X Critical Test Reactor is an experimental facility located on DOE land, it is being authorised under the DOE framework rather than the NRC. For a commercial reactor, the closest analogue would be the Final Safety Analysis Report issued by the Nuclear Regulatory Commission (NRC).
Approval of the DSA advances Aalo into its final pre-operations phase, the Operational Readiness Review, in which the DOE verifies that the people, facility, and programmes can be cleared to operate as documented.
Aalo Atomics broke ground in August last year on land leased from DOE at the Idaho National Laboratory (INL) to start construction of its first experimental reactor, the Aalo-X. Aalo said it planned to complete construction and achieve criticality by 4 July this year, the target date set by the US Department of Energy for at least three test reactors to reach criticality under the programme to expedite the testing of advanced reactor designs it announced in June 2025. Aalo-X will be manufactured at Aalo’s pilot factory in Austin, Texas, before being transported to and installed at the INL site.
In the Aalo-X Critical Test Reactor (CTR), Aalo will test its full-scale nuclear core, with fuel equivalent to what is necessary for 10 MWe, before adding sodium coolant to the equation. The goal is to achieve criticality, a self-sustaining nuclear reaction, at low power and with reduced heat generation. The Critical Test Reactor contains nuclear fuel, moderator, control rod drive mechanisms, shielding, and instrumentation systems that are direct analogues of what will operate in the 10 MWe Aalo-X power reactor being built next door. Operating the Critical Test Reactor will validate the company’s neutronics and offer key test data that verifies its computational models.
The test reactor is the precursor to the Aalo Pod, a 50 MWe XMR (Extra Modular Reactor) power plant purpose-built for data centres – demand for which is increasing rapidly following the widespread adoption of AI. Each fully modular Aalo Pod will contain five factory-built, sodium-cooled, Aalo-1 reactors, using low-enriched uranium dioxide fuel. The company says it will be in commercial use by 2029.
“Our team’s experience with the Documented Safety Analysis brought to light many facets of compliance that we’ll carry forward to the commercial licensing process when building Aalo Pods for AI data centres,” Aalo said. “We radically improved our internal competencies on nuclear licensing, and as such, we laid the foundation for regulatory success during commercial scale-up.”
Aurora powerhouse PDC
Nuclear technology company Oklo announced that the NRC has approved the Principal Design Criteria (PDC) topical report for its Aurora powerhouse at INL.
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Oklo’s rendering of an Aurora powerhouse (Image: Oklo)
The topical report was approved on an accelerated review schedule, reflecting the NRC’s efforts to modernise licensing pathways for advanced reactors while maintaining stringent safety standards, following executive orders issued in May 2025 to streamline licensing procedures. It also follows the Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy Act, or ADVANCE Act, which calls for a more efficient path to deployment for advanced nuclear technology.
The Principal Design Criteria topical report was approved in less than half the traditional review timeline. Oklo also received notice of the report’s acceptance in just 15 days compared with the typical 30 to 60-day period following submission to the regulator.
Oklo said the approval clears the path for the report to be referenced in future applications and reduces the need to re-review established material. The company’s Principal Design Criteria topical report establishes a regulatory framework that defines the fundamental safety, reliability, and performance requirements to guide future reactor licensing and design activities.
“This milestone reflects strong work by the Oklo team and timely engagement by the regulator,” said Oklo co-founder and CEO Jacob DeWitte. “Performance-based licensing, clear criteria, and efficient reviews are important to advancing modern nuclear projects safely and responsibly.”
Last month, Oklo received DOE approval for the Nuclear Safety Design Agreement for its first Aurora powerhouse at INL. The Nuclear Safety Design Agreement is the first step under DOE’s Reactor Pilot Program authorisation licensing pathway.
Oklo held a groundbreaking ceremony at INL for the Aurora-INL sodium-cooled fast reactor in September last year.
The Aurora powerhouse is a fast neutron reactor that uses heat pipes to transport heat from the reactor core to a supercritical carbon dioxide power conversion system to generate electricity. Building on the design and operating heritage of the Experimental Breeder Reactor II (EBR-II), which ran in Idaho from 1964 to 1994, it uses metallic fuel to produce electricity and usable heat, and can operate on fuel made from fresh HALEU or used nuclear fuel.
