Why Water-Cooled SMRs Will Win The New Nuclear Race

If nuclear power has a future, it will likely be small, modular and water cooled, according to an expert with global credentials in nuclear research.

“There are plenty of technologies now—50 different models around the world. Once one of them gets into a financially viable equation, that will capture the entire market,” said Alfredo Caro, a research professor at The George Washington University, “and I think that this will happen with water-cooled small reactors.”

The first small modular reactor design certified by the U.S. Nuclear Regulatory Commission, a design by NuScale certified this month, is water-cooled.

The economic advantages of small modular reactors (SMRs) are often cited: factory produced and shipped to installation sites, they may avoid the regulatory labyrinths, cost overruns and construction delays that plague traditional reactor projects.

The 50 designs and concepts under development include models cooled by sodium, lead, gas or molten salt, but Caro believes water-cooled SMRs will have an additional advantage: the lessons of history.

“Why? Because there are something like 20,000 reactor years of operational experience with water-cooled reactors and the fuel for those reactors,” he said Wednesday in a lecture hosted by the Security and Sustainability Forum.

“It would be very difficult to come out with something sodium-cooled, lead-cooled, fuel like a spherical, economically competitive against the traditional technology, so I think eventually we will see all the designs that are available that are water cooled, they have a niche,” he said.

“I believe personally that that will happen. There will be plenty of small reactors, water cooled. So the same technology that dominates so well today, with only three accidents in the entire 60 years of history.”

The three accidents Caro refers to are the three major accidents that have crippled the growth of the nuclear industry: Three Mile Island in 1979, Chernobyl in 1986, and Fukushima in 2011.

The Union of Concerned Scientists counts seven “serious” accidents, adding to those above: a partial meltdown in Michigan in 1966, an explosion in Idaho in 1961, a partial meltdown in Los Angeles in 1959, and a fire in Cumbria, United Kingdom in 1957.

Even so, nuclear ranks close to the mortality rate for solar and wind energy, far below coal oil and gas, in deaths per terawatt hour of electricity produced.

“Nuclear by far is the safest way to produce electricity,” Caro said, though his assessment did not include solar and wind. “However, the perception of risk is subjective.”

A greater obstacle is cost, he said: “On average it is more expensive than any other source.”

Rate payers in the UK will pay three times the average rate of electricity for 35 years to pay off the construction cost for Hinkley Point C nuclear power station, which is an estimated 11 years behind schedule.

“Clearly it is very difficult to justify the investment,” Caro said.

The most recent reactor to go online, Olkiluoto 3 in Finland, took 17 years to construct. “There is no way you can have an economic equation that closes favorably for the investor if the construction time is 17 years.”

These are the challenges SMRs are designed to address.

“History tells us that in the 60s and 70s when the current nuclear technology was developed, all the options from Generation IV were all tested, and the water-cooled reactor came as the winner because it was the cheapest. Once you have one technology that wins the economic competition, nothing can stop it. Today I think all commercial reactors are water cooled. The same I think will happen with the small modular reactor.”

Caro has directed the Atomic Center and Balseiro Institute in Argentina, and he worked for many other programs including the European Fusion Program at the Paul Scherrer Institute in Switzerland, the Fusion Program at Lawrence Livermore National Laboratory, and the Science of Nuclear Materials and Fuels team at Los Alamos National Laboratory. He also served as a program director for the National Science Foundation.

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