The THETA testing campaign is focused on the key thermal-hydraulic behavior of Oklo’s fast fission reactor design. Oklo says a better understanding of key thermal-hydraulic behavior enables design optimizations while providing high-fidelity data using high-fidelity instrumentation.

“Argonne’s leadership and technical expertise have been pivotal to THETA’s success, and the completion of the second phase of testing is a huge accomplishment,” said Patrick Everett, Deputy Senior Director of Product at Oklo. “THETA has and will continue to play a major role in Oklo’s testing endeavors to support our commercialization plans for our Aurora Powerhouses”

Oklo shared costs for the work done at Argonne National Laboratory with funding from a Department of Energy Gateway for Accelerated Innovation in Nuclear voucher.

Last month, Oklo announced the signing of a lands right agreement with the non-profit Southern Ohio Diversification Initiative (SODI) for land including options for the siting of two plants. The company recently announced that the U.S. Department of Energy (DOE) reviewed and approved the Safety Design Strategy (SDS) for its Aurora Fuel Fabrication Facility at Idaho National Laboratory (INL).

The Aurora Fuel Fabrication Facility is being designed to demonstrate the reuse of recovered nuclear material to support Oklo’s planned commercial advanced fission power plant demonstration at INL.

This agreement is an extension of Oklo and SODI’s announcement in May 2023, related to the deployment of two Aurora powerhouses, and the company says it signifies progress toward siting development and implementation. SODI is a nonprofit community improvement corporation and serves as the DOE-designated community reuse organization for the former Portsmouth Gaseous Diffusion Plant (PORTS) facility near Piketon, Ohio.

Subject to the terms and conditions of the land rights agreement and in exchange for an upfront fee, which will be credited toward any purchase by Oklo under the land rights agreement, SODI has granted Oklo an option and right of first refusal to purchase land in Southern Ohio from SODI.

Oklo aims to build its second and third plants on land owned by SODI, it announced last May. The land will host two commercial 15-MWe Aurora powerhouses (30 MWe total) and over 50 MW of clean heating, with opportunities to expand.

Oklo’s Aurora powerhouse design is a fast neutron reactor that would transport heat from the reactor core to a power conversion system and is designed to run on material from used nuclear fuel known as HALEU, or “high assay, low-enriched uranium.” The reactor builds on the Experimental Breeder Reactor-II and space reactor legacy.

Oklo obtained a site use permit from the DOE for the Idaho site at Idaho National Laboratory (INL) in 2019. The company applied with the U.S. Nuclear Regulatory Commission (NRC) in March 2020 to build and operate a reactor at INL. This was the first combined license application ever accepted by the NRC for an advanced non-light water reactor.

The company recently announced that the U.S. Department of Energy (DOE) has reviewed and approved the Safety Design Strategy (SDS) for its Aurora Fuel Fabrication Facility at INL. The Aurora Fuel Fabrication Facility is being designed to demonstrate the reuse of recovered nuclear material to support Oklo’s planned commercial advanced fission power plant demonstration at INL.

Oklo was selected for access to the fuel material through a competitive process launched in 2019 by INL. The goal of the solicitation was to accelerate the deployment of commercially viable reactors by providing developers with access to the material needed to produce fuel for their reactors. The DOE is supporting INL to produce High-Assay, Low-Enriched Uranium for advanced reactors by recovering uranium through electrorefining treatment on used fuel from the now-decommissioned Experimental Breeder Reactor-II.

The SDS marks the initial stage in a comprehensive DOE approval process prior to the operation of the Aurora Fuel Fabrication Facility. Oklo and Battelle Energy Alliance, operator of INL, are currently working on the next phase, focusing on the Conceptual Safety Design Report (CSDR). The purpose of the CSDR is to summarize 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.

Oklo Power, which hopes to build and operate the company’s Aurora compact fast reactor, has submitted a licensing project plan to the U.S. Nuclear Regulatory Commission.

Oklo said the plan outlines future licensing activities and aims to support an “efficient and effective review process.”

Silicon Valley-based Oklo had applied to NRC in March 2020 to build and operate its 1.5 MW nuclear microreactor at the Idaho National Laboratory site. This was the first combined license application ever accepted by the NRC for an advanced non-light water reactor.

But the NRC rejected Oklo’s application in January 2022.

Oklo’s application contained “significant information gaps” in its description of Aurora’s potential accidents as well as its classification of safety systems and components, the NRC said. Although the gaps prevented further review, NRC said it was prepared to re-engage with Oklo if the company submitted a revised application.

An Oklo spokesperson told us at the time: “…There are many new things for all to learn from and work through to support a successful review, and it provides a foundation from which we can supply additional information and continue work with the NRC.”

The Aurora design is a fast neutron reactor that would transport heat from the reactor core to a power conversion system and is designed to run on material from used nuclear fuel known as HALEU, or “high assay, low-enriched uranium.”