Deep Fission, NX Atomics strike partnerships to advance small reactors

A mile beneath Parsons, Kansas, Deep Fission wants to turn an underground borehole into a reactor site, and it has now handed Day & Zimmermann the above-ground job of getting the Gravity project ready for construction.

That is the kind of detail advanced reactor developers have spent years promising and far too often only sketching on slides. Here, the split is concrete: Day & Zimmermann said it will handle pre-construction planning and above-ground construction for Deep Fission’s Gravity reactor, while Sciaky said it will produce components for NX Atomics’ small modular reactor platform using its EBAM electron-beam additive manufacturing process.

The Deep Fission project is unusual even by SMR standards. The company says Gravity is a small modular pressurized-water reactor installed one mile underground, designed to use low-enriched uranium fuel and to rely on the earth itself for passive shielding and natural containment. Each unit is expected to generate 15 MWe. Deep Fission says the layout should shrink the land footprint while making the reactor safer, faster and cheaper to deploy.

The company has already broken ground at the Great Plains Industrial Park in Parsons, a site that Deep Fission says covers more than 14,000 acres in Labette County, Kansas. Deep Fission and the Great Plains Development Authority also signed a letter of intent to work together on the pilot and pursue a full-scale commercial project at the same site. Deep Fission held a ceremonial groundbreaking there on December 9, 2025.

The project also sits inside the U.S. Department of Energy’s Reactor Pilot Program, in which Deep Fission was one of 10 companies selected. The program, launched with a request for applications on June 18, 2025, is meant to expedite advanced reactor development and reach criticality for at least three concepts outside the national laboratories by July 4, 2026. For Deep Fission, that makes Parsons more than a pilot site. It becomes a test of whether an underground reactor can move from excavation to operating physics on a federal clock.

NX Atomics is solving a different bottleneck, but an equally stubborn one. Its partnership with Sciaky puts additive manufacturing directly into the reactor supply chain, where component repeatability and lead times can make or break a project. Sciaky described the deal as the first time its EBAM capability has been brought into commercial nuclear power at this scale. NX Atomics says it is developing high-temperature SMRs for clean baseload power and industrial process heat.

For a sector crowded with partnership announcements that never reach steel in the ground, these two deals stand out because they assign real work to real firms. One partnership tackles construction execution. The other tackles parts production. Together, they sketch the pieces of the SMR puzzle that still have to fit before the hardware stops being a promise and starts being a reactor.