X-energy's stock opened at $30.11 and closed at $29.20, up 27% from its initial public offering of $23 per share.
The company's valuation reached $11.5 billion at close, driven by investor optimism over the nuclear power startup's prospects.
Just five years ago, interest in nuclear startups would have been a surprise, given the industry's past struggles with delayed projects and massive cost overruns.
However, investors now appear bullish that X-energy has figured out a way to overcome these challenges, thanks in part to the AI-driven data center boom.
Data centers require tremendous amounts of electricity, and nuclear power is one option being explored to diversify energy sources.
X-energy's 80-megawatt reactor design aims to bring costs down through modularity, with Amazon committing to buy up to 5 gigawatts' worth of capacity over the next decade or so.