Amazon-backed advanced nuclear developer X-energy has raised more than $1 billion in its initial public offering (IPO).

Based out of Rockville, Maryland, the company said that it sold 44.3 million shares as part of its upsized IPO at $23 apiece, which was above the marketed range of $16 to $19. In total, the company raised approximately $1.02bn. The company filed for the IPO late last month.

The company, which was founded in 2009, is a small modular reactor developer (SMR). Its flagship product, the Xe-100 advanced SMR, 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. Last week, the company announced that it would deploy SMRs in Pennsylvania and across the PJM power market, along with independent ​power provider Talen Energy.

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.

Last year, the company 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.

To fund the development of the SMR, the company has raised more than $700 million to date, with the latest round led by Amazon.

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.