US startup in deal with data centre customer to deploy underground SMRs

Using its concept of underground small modular reactors (SMRs), California-based startup Deep Fission has reached an agreement to help power Endeavour Energy’s expanding data centre portfolio.

The companies have committed to co-developing 2GW of nuclear energy to power Endeavour’s edge data centres, with the first reactors expected to be operational in 2029.

Deep Fission is basing its reactor design on the widely deployed pressurized water reactor (PWR), operating at the same pressure and core temperature as a standard PWR.

The main difference is its unique configuration. Deep Fission’s 15MW SMRs would be placed in 30-inch boreholes, producing energy from a mile underground. The company has said ten of its reactors need only a ¼ of a square acre to yield 150MW, while less than three square acres can house 100 Deep Fission reactors to generate 1.5GW.

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The company claims its underground approach leverages natural geological advantages – robust containment and constant pressure – making the reactor inherently safe.

According to regulatory documents submitted by Deep Fission, the company says these features eliminate the need for costly concrete and steel surface containment buildings, enabling its reactor to produce electricity at a cost similar to coal power. Removing surface construction costs would also significantly reduce the deployment timeline, Deep Fission says.

“There is significant momentum for nuclear power right now, but the cost is still a challenge,” said Elizabeth Muller, co-Founder and CEO of Deep Fission. “Our technology not only ensures the highest levels of safety but also positions us to deliver zero-carbon continuous power at a cost of just 5-7 cents per kWh.”

According to the regulatory documents, the reactor core will be cooled by light water in a primary loop, with circulation driven by natural convection. Above the reactor core, but still deeply buried, a heat exchanger will boil water in a secondary loop, and the steam will be brought to the surface through a steam pipe.

The secondary loop water flow will be driven by a pump operating at the surface. As in other PWRs, the light water in the primary loop provides both cooling and neutron moderation.

The company’s regulatory engagement plan follows similar regulatory and technical approaches taken by fellow PWR and SMR industry peers, including NuScale and Holtec. Deep Fission began pre-application engagement with the US Nuclear Regulatory Commission (NRC) in February 2024.

Deep Fission intends to submit a Standard Design Approval Application (SDAA) no later than September 2026, according to documents filed with NRC. The company plans to consider the submission of a Combined License Application (COLA), according to the filings.

Originally published by Kevin Clark on power-eng.com