Nuclear startup Deep Fission is heading to the public markets, filing for a Nasdaq initial public offering that could raise about $157 million to fund its plan to bury small reactors deep underground and sell their power to AI data centers. The company filed its S-1 with the US Securities and Exchange Commission on May 20.
Inside the $157 million offering
Deep Fission is offering 6 million shares at an expected price of $24 to $26 each, with a 30-day option for underwriters to buy up to 900,000 additional shares. At the top of the range, the deal would value the company at roughly $1.66 billion. The company has applied to list on the Nasdaq Global Market under the ticker symbol "FISN." It says it intends to use the proceeds for working capital and to advance engineering, research, licensing and construction of its first pilot reactor.
A second trip to the public markets
The filing carries a sense of deja vu. In September 2025, Deep Fission completed a reverse merger with Surfside Acquisition, a Delaware shell company, raising $30 million in a concurrent private placement at $3 a share. According to reporting on the new S-1, that listing was public in name only, as the stock never actually traded, and the company is now pursuing a more traditional IPO route.
Mile-deep reactors for the AI era
Deep Fission's pitch is unusual: rather than building reactors at the surface, it plans to place them in boreholes roughly a mile underground, using the surrounding rock and pressure as natural containment. The company says it began drilling the first of three test wells in March, with a target depth of up to 6,000 feet and an eight-inch diameter, far narrower than the 30-to-50-inch boreholes it will need at commercial scale. It has also drawn an $80 million equity investment, including $20 million from data center developer Blue Owl, which signed a non-binding agreement for future power plants. The race to power AI is fueling broader nuclear momentum, including advanced fission projects like NANO Nuclear's KRONOS microreactor.
A going-concern warning clouds the debut
The S-1 paints a challenging financial picture. Deep Fission's accumulated deficit grew to $88.1 million as of March, up from $56.2 million, and its cash and equivalents fell about $6.4 million, or roughly 7%, in six weeks. The filing repeats a "going concern" warning, cautioning that the company could run out of money within 12 months if the IPO does not close. Its timeline to reach reactor criticality has also slipped. The offering follows a wave of nuclear listings, as fission developer X-energy went public last month in an upsized IPO, and arrives alongside other headline filings such as SpaceX's record IPO filing and Unitree's Shanghai listing.
Reporting based on coverage from TechCrunch, Bloomberg, and Deep Fission's SEC filings.