Deep Fission CEO Liz Muller on New, Underground Nuclear Reactors

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We can't talk about artificial intelligence without talking about the energy that you need to power the AI buildout. Isabel, growing electricity demand from AI and data centers is prompting a global need for different forms of energy. One company seeking to meet that need is Deep Fission. It's an advanced nuclear energy company developing small modular pressurized water reactors installed one mile underground. We're going to learn what all of this means. The company began trading on the NASDAQ priced at $16 per share under the ticker FISN. Pleased to say we're now joined by Liz Muller, co-founder and CEO of Deep Fission. She joins us from our San Francisco Bureau. We're also joined by Will Wade, Bloomberg News energy reporter, here with us back in New York. But Liz, let's start with you. Just give us the elevator pitch for Deep Fission. What is the company and why did you guys go public now?

**Liz Muller** (1:05)
Yeah, Deep Fission, as you noted, is a different deployment model using currently available advanced reactor technology. So pressurized water reactors are the most common type of nuclear reactor we have today. But when you deploy it in a borehole a mile underground, you can deploy it much faster. You don't have all the construction that you would have for a conventional above-ground nuclear reactor. And so you can build it faster and at a significantly lower cost.

**Isabelle Lee** (1:33)
So for viewers just hearing about this, what problem does putting reactors a mile underground actually solve in nuclear deployment today?

**Liz Muller** (1:42)
Yeah, it's really two issues. The first one is nuclear has historically been too expensive. There's just too much construction, too many parts that need to get built. When you build it underground, you're able to take advantage of the rock that already exists. You're able to take advantage of a column of water above you in the borehole that is creating pressure through the force of gravity.
So you don't need big expensive pressurizers. So the result is we're much lower cost and we're much faster in order to build.

**Will Wade** (2:13)
So Liz, what I like about your company is that it's taking existing technologies that we already have. We know how to dig holes, we know how to build reactors, and it puts them together in a way that nobody's done before.
You haven't done it before either, of course, it's still new, we're waiting to see it happen. But can you talk a little bit more about how that can save money?

**Liz Muller** (2:35)
Yeah. So you're exactly right. This is using proven technology that already exists. So pressurized water reactor technology and standard commercially available fuel. But combining that with deep borehole drilling, which is also something that is commercially available, and we know how to do.
And when you combine those two, that's where you get something really special and a different deployment model. Nuclear is already very safe above ground. But when you put it in a reactor a mile below ground, the safety profile is extraordinary. And that means that you can take out a lot of the cost as well as a lot of the time to build.

**Will Wade** (3:12)
It's an interesting idea. What sort of reaction have you had since you came up with this idea? Because I feel like it can go two ways. You can get people saying, oh my god, that's crazy. I've never heard of anything like this. Or you can get people saying, oh my god, I've never heard of anything like this. What a brilliant idea.

**Liz Muller** (3:29)
Yeah, I think we get both. So I think it does start out with a little bit of disbelief. Why are we the only reactor company that is taking this approach and doing something so different, which is building a mile underground? But then the more people start to understand what we're doing and that we're using existing proven technologies, the more people start to appreciate the benefits of being surrounded by billions of tons of rock so that nothing can get out of the borehole. Having that column of water that is a mile long above you in the borehole, it is creating the pressure on your reactor, but it's also your emergency core cooling system. And when you're a mile underground, there's nowhere for that water to go.
And so the safety profile, I think, also grows on people as they start to appreciate the differences and the benefits of building a reactor a mile underground.

**Isabelle Lee** (4:19)