Deep Fission Targets 2027 Grid Power From First Underground Nuclear Reactor

Deep Fission is targeting commercial grid electricity by late 2027 from a 5-megawatt underground pressurized-water reactor planned for Parsons, Kansas, under the U.S. Department of Energy’s Reactor Pilot Program.

The company’s design places the reactor roughly one mile underground, using surrounding rock and a water column for containment, pressure and cooling. Deep Fission says this could reduce construction complexity and lower reactor-canister costs compared with conventional nuclear plants.

Deep Fission is conducting drilling and engineering tests in 2026, while pursuing Nuclear Regulatory Commission licensing. Its broader development pipeline includes 18.5 gigawatts of letters of intent, though spent-fuel storage and permanent disposal plans remain subject to regulatory and community approval.

Deep Fission is targeting commercial electricity generation from its first underground nuclear reactor in Parsons, Kansas, by the end of 2027, Chief Executive Officer Liz Muller said during a company presentation. Muller said the company has been accepted into the U.S. Department of Energy’s Reactor Pilot Program and has begun construction-related work.

The company plans to deploy a pressurized-water reactor in a borehole about one mile underground, using drilling, geothermal and existing nuclear technologies to reduce the cost and complexity of conventional nuclear plant construction.

Rather than building a conventional reactor above ground with a containment dome, pressurizer and extensive cooling infrastructure, Deep Fission plans to use the surrounding rock and water column in a deep borehole as part of its containment, pressure and cooling approach. Muller said a one-mile water column would create approximately 160 atmospheres of pressure, eliminating the need for a conventional pressurizer. She also said the underground configuration could reduce the need for above-ground safety-related construction and use geothermal-style systems to bring heat from the reactor to surface turbines.

“The best thing to manufacture is nothing,” Muller said, describing the company’s focus on removing components rather than relying solely on mass manufacturing to lower reactor costs. The company’s reactor canister is expected to cost in the “single-digit millions” of dollars, compared with what Muller described as roughly $1 billion each for conventional reactor vessels and pressurizers. She said the canister could be manufactured by dozens of U.S. suppliers in less than six months for a first-of-a-kind unit.

Deep Fission plans to use pressurized-water reactor technology, which Muller said represents the most common commercially operating nuclear technology in the United States. She cited 67 gigawatts of pressurized-water reactor capacity operating in the country, supplying about 12% of U.S. electricity. The company intends to use low-enriched uranium in standardized fuel assemblies that have already been approved and licensed by the Nuclear Regulatory Commission, according to Muller. She said this approach allows Deep Fission to rely on established reactor physics, fuel designs and safety measures rather than developing an entirely new reactor technology.

Deep Fission is conducting commercial borehole proof-of-concept work in 2026, including drilling tests and emplacement analysis. Muller said the company is also testing the coordination of nuclear and drilling teams before beginning operations in a nuclear environment. First reactor deployment is planned for the first half of 2027 under the DOE Reactor Pilot Program. The initial unit is expected to operate ...