How come we have nuclear ships but not small nuclear power plants?

Some nuclear-energy enthusiasts argue that new kinds of smaller reactor are the key to reliable low-carbon energy. But U.S. naval might already rests on submarines and aircraft carriers with small reactors that run for decades. A reader recently got in touch with the obvious question: Why not just adapt naval technology for the grid?

This is familiar ground for Nick Touran.

“People ask me this question all the time,” he says. Touran has a Ph.D. in reactor-core design, worked for Bill Gates’s nuclear venture and runs the educational website whatisnuclear.com.

It turns out that civilian nuclear plants are an adaptation of naval technology. The story begins with Adm. Hyman G. Rickover, the gnomelike, blasphemous driving force behind the Navy’s nuclear program. Rickover likened himself to Attila the Hun and had young officers conduct job interviews on chairs with specially shortened front legs, banishing them to a closet if they disappointed him.

The design he favored for the first nuclear submarine, launched in 1954, was repurposed in the first full-scale nonmilitary nuclear plant, near Pittsburgh. It became the global standard.

But electricity from that 60-megawatt plant cost 10 times more than coal power. The solution was to go big. Making a reactor twice as large doesn’t double costs—it doesn’t need two safety systems or twice as much steel.

Touran listed other reasons why somehow plugging an aircraft carrier into the grid wouldn’t deliver cheap power. Naval reactors use highly enriched uranium (expensive and an extreme security risk) and are built to withstand combat. But economies of scale are a big factor.

Lately, though, the financing costs for bespoke, massively delayed megaprojects have outweighed those benefits. One hope for small reactors is that economies of mass production could make up for what’s lost in scale. Some alternative designs are better suited for miniaturization than Rickover’s favored pressurized water reactor, too.

The typical reactor generates a gigawatt of power. By contrast, one project that recently broke ground will generate up to 500 megawatts, and another will supply up to 50 megawatts. Some designs are far tinier.

Rickover summed up the challenge for atomic innovators in a 1953 memo that distinguished between “academic reactors” and “practical reactors.” The former are always cheap, use off-the-shelf components—and aren’t actually being built. The latter are complicated, expensive and behind schedule.

It’s academic

That rings true to Touran. He is enthusiastic about novel designs—and recently joined a nuclear-shipping startup—but thinks the best route to cheap nuclear power is figuring out how to build big plants efficiently.

Little reactors, meanwhile, could be tested in niche applications. A reactor on a ship provides power for an isolated community in the Russian Arctic. Other settings where higher costs could be tolerated include remote military outposts or in space.

As for the company that has made more than 400 reactors for the Navy, it’s hoping to benefit from any kind of nuclear renaissance.

Reporting its earnings this week, BWX Technologies talked about plans to sell nuclear fuel and components for various reactor designs. It is developing new micro reactors for the U.S. Army. But it’s also eyeing the next generation of large plants.

“We’re betting on the race, not on the horse,” CEO Rex Geveden said.

Thanks to WSJ subscriber Terry Milholland in Frisco, Tx., for the question that prompted this article. If there’s a climate- or energy-related question on your mind, let me know at [email protected]. And if somebody forwarded you this email, you can subscribe here.

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Today’s email was written by Ed Ballard in London. Contact him at [email protected]. Contact the team at [email protected].