A US-based advanced nuclear energy company placing small modular reactors (SMRs) in boreholes one mile underground has raised $80m (€67m) in new financing.

Deep Fission, whose headquarters are in California, said the financing was completed through the offer and sale of 5,333,333 restricted shares of common stock at a fixed price of $15.00 per share. Investors included Ed Eisler of US investment company EE Holdings and Mark Tompkins of UK-based venture capital firm Montrose Capital, who led the company’s previous financing round in September 2025.