Oklo and Argonne complete second THETA testing campaign

Thursday, 14 March 2024

THETA is a 450-litre pool-type sodium vessel installed inside Argonne National Laboratory's (ANL's) Mechanisms Engineering Test Loop (METL) facility and consists of a primary system, submerged in a liquid sodium pool, and a secondary system, located outside of the pool, that contains all the major components of a sodium-cooled fast reactor. The primary system consists of a pump, electrically heated core, intermediate heat exchanger and connected piping and thermal barriers, while the secondary system consists of a pump, sodium-to-air heat exchanger and connected piping and valves. Fibre-optic temperature sensors provide thousands of temperature measurement points across a specific flow field, allowing tests to be performed in real-time with immediate feedback.

As well as helping researchers gain insight on how coolant flows through the reactor under all operating conditions, THETA modelling will ultimately identify parameters that could enhance fundamental knowledge for more predictable safety margins, define higher operating temperatures, and provide more efficient power operation to support a wide range of advanced reactor designs, according to the US Department of Energy (DOE) Office of Nuclear Energy.

Oklo - developer of the 15 MWe Aurora fast neutron reactor - is using THETA via a voucher through the DOE's cost-shared Gateway for Accelerated Innovation in Nuclear initiative.

The THETA testing campaign is strategically focused on key thermal-hydraulic behaviour of Oklo's fast fission reactor design. A better understanding of key thermal-hydraulic behaviour enables design optimisations while providing high-fidelity data using high-fidelity instrumentation. Ultimately, the THETA testing campaign enables the opportunity to further improve the demonstrated safety and economic potential of bringing Oklo's fast fission technology to market.

"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 endeavours to support our commercialisation plans for our Aurora Powerhouses."

In May 2022, Oklo became the first developer to run tests at THETA.