Amazon-backed nuclear startup X-energy has closed an oversubscribed $700 million Series D financing round led by Jane Street.

Proceeds from the funding round will be directed to the company’s supply chain and commercial pipeline, supporting an order book of more than 11GW, equivalent to roughly 144 advanced small modular reactors (SMRs).

New investors included ARK Invest, Galvanize, Hood River Capital, Point72, Reaves Asset Management, and XTX Ventures, alongside existing backers such as Ares Management, Corner Capital, Emerson Collective, NGP, and Segra Capital.

“The success of this financing round allows us to deepen partnerships with critical deployment partners and invest in a robust and reliable supply chain to successfully deliver projects with our customers,” said X-energy CEO J. Clay Sell.

X-energy founder and executive chairman, Kam Ghaffarian, added that the round “is a strong affirmation of the role X-Energy expects to play in shaping the future of energy.”

X-energy is developing the Xe-100 advanced small modular reactor. Xe-100 is a pebble-bed, high-temperature gas-cooled reactor. Fuel pebbles – about the size of a billiard ball – power the reactor, with each pebble containing thousands of uranium fuel particles. The company’s first four-unit Xe-100 plant is planned at Dow’s Seadrift Operations site in Texas and is under review by the US Nuclear Regulatory Commission.

Amazon has directly invested in the company and secured the option to deploy more than 5GW of Xe-100 projects in the US by 2039, starting with the Cascade Advanced Energy Facility in Washington state.

When constructed, the facility is expected to comprise three 320MW sections to make up the complete 960MW plant. The first 320MW block will comprise four of X-energy’s 80MWe (electric) and 200MWt (thermal) Xe-100 SMRs.

Following the initial phase, the partners will have the option to expand to 12 units, reaching 960MW of capacity. Construction at the site is expected to commence by the end of the decade, with operations to start sometime in the 2030s.

Amazon struck the initial deal with Energy Northwest and X-energy to develop the site last year. X-energy also plans to deploy 6GW in the UK with Centrica.

The company is also constructing a US-based facility to produce TRISO-X fuel, designed to deliver scalable, safer, and reliable power for industrial and energy applications.

Earlier this year, X-energy and Amazon signed an agreement with South Korea’s Doosan Enerbility and Korea Hydro & Nuclear Power Co. to accelerate the deployment of new SMRs in the US. As part of the collaboration, the companies aim to mobilize up to $50 billion in public and private investments for Xe-100 projects and to expand SMR supply chain capacity to support its growth.

Amazon is not the only major tech firm to back SMRs over the last two years. A swathe of other data center operators and hyperscalers have supported the technology. Notable examples include Google, Data4, Oracle, Switch, and Equinix.