US-based start-up Deep Fission, which plans to place small modular pressurised water reactors in boreholes one mile underground has signed an agreement to purchase low-enriched uranium (LEU) from Urenco USA. The fuel will support testing and demonstration activities as part of Deep Fission’s participation in the Department of Energy’s (DOE’s) Reactor Pilot Program as well as early commercial operations.
Urenco will supply Deep Fission with LEU for demonstration and testing of their initial Gravity Reactor. The fuel will be sourced from Urenco USA’s New Mexico enrichment plant and meets all regulatory requirements for use in the US. “Securing fuel is one of the most important steps for any nuclear project,” said Liz Muller, CEO and Co-Founder of Deep Fission. “This agreement with Urenco enables us to move quickly toward commercialisation and scaling our technology with a high-quality fuel.”
Deep Fission’s proprietary design integrates conventional pressurized water reactor technology with deep borehole drilling techniques from the oil and gas sector and geothermal heat-transfer approaches. Each Gravity Reactor is installed one mile underground, where surrounding geology provides passive shielding and natural containment, reducing the need for above-ground megastructures.
Deep Fission recently broke ground on its pilot project in Parsons, Kansas, after signing an Other Transaction Agreement (OTA) with DOE. The Company has also announced a customer pipeline representing 12.5 GWe of future planned power.
“Urenco is pleased to support innovative nuclear companies like Deep Fission,” said John Kirkpatrick, Urenco USA’s Managing Director. “Advanced reactor developers are an important part of the future energy landscape, and we are focused on ensuring a reliable domestic supply of enriched uranium to support growth in this sector.”
The Deep Fission Gravity Nuclear Reactor uses the traditional pressurised water reactor design for its fuel assemblies and power control methods. Gravity reactors operate at the same approximately 315°C core temperature, while hydrostatic pressure from one-mile-deep column of water provides the same 160 atm of reliable pressure, safely and naturally.
The heat produced is transferred to a steam generator at depth to boil water. This novel deployment approach applies proven geothermal components and processes for energy transfer. Non-radioactive steam rises rapidly to the surface, where a standard steam turbine converts the energy to electricity.
Deep Fission was founded in 2023 by father-daughter team Elizabeth and Richard Muller, emerged from stealth mode in August 2024. In September 2025, the company went public through a reverse merger transaction with Surfside Acquisition raising $30m through a private placement offering. Surfside Acquisition, a special purpose acquisition company, merged with the company to form a new entity that retains the name Deep Fission. The Mullers earlier co-founded Deep Isolation in 2016 to develop the concept of placing canisters of radioactive waste hundreds of metres underground via a borehole.
