The most frightening part of a tsunami hitting a nuclear power plant is what comes after – radioactive leaks that contaminate the water around the plant are exceedingly difficult to contain. The clean up of the radioactive water around the Fukushima Daiichi nuclear plant in Japan, which was struck by a tsunami in 2011, is expected to take decades. MIT researchers have come up with an alternative; they propose building floating nuclear plants, far enough offshore to simply ride out a tsunami and emerge unscathed.

The new design proposed by Jacopo Buongiorno, Associate Professor of Nuclear Science and Engineering at MIT and his colleagues, calls for constructing sturdy floating platforms, similar to the ones that support offshore oil and gas rigs. Light-weight nuclear reactors could be built on top of these platforms in shipyards, and then towed to appropriate locations offshore. Mooring the platform to the seafloor, would, they say, ensure that the nuclear power plant remains unaffected by a tsunami's waves. A power transmission line could connect the plant to the electrical grid.

"Tsunamis and earthquakes are no longer a source of risk for the nuclear plant," explains Buongiorno. "Essentially the ocean shields the seismic waves and the tsunami waves in relatively deep water, say 100 meters (300 ft) deep, are not big, so they don't pose a hazard for the plant."

It also becomes easy to avoid the biggest issue that leads to radioactive contamination in a damaged nuclear plant, the overheating of the reactor cores that lead to a meltdown, something that would be impossible in the ocean, according to the team.

"It’s very close to the ocean, which is essentially an infinite heat sink, so it’s possible to do cooling passively, with no intervention," says Buongiorno. "The reactor containment itself is essentially underwater."

Designing the plant in such a way that the ocean water automatically cools the nuclear reactors would, the researchers claim, prevent any radioactive leaks and fuel rod meltdowns, since it is possible to remove heat indefinitely.

Cutaway view of the proposed plant shows that the reactor vessel itself is located deep underwater, with its containment vessel surrounded by a compartment flooded with seawater, allowing for passive cooling even in the event of an accident (Image: Jake Jurewicz/MIT-NSE)

The whole concept has been around for a while. The floating nuclear power plant that Russian scientists have been working on for several years is expected to be operational by 2016, but their nuclear plant is being built on a barge close to the shore.

The unique advantage of the MIT team's design, lies in mooring the nuclear power plants 5 to 7 miles (8 - 11 km) into the ocean, thereby giving the power plants the ability to weather any tsunami. Another advantage the distance offers is that the people on land won't have to relocate, in the event of an accident or an emergency out in the ocean. "The biggest selling point is the enhanced safety," says Buongiorno.

Decommissioning such a power plant could just be a matter of towing it away at the end of the nuclear reactor's lifetime. Since there's no size limit, floating nuclear power plants could rival their land-based counterparts; they could range anywhere from 50-megawatt plants to 1,000-megawatt plants, according to the scientists.

Placing them a few miles offshore, out of sight of cities would enable them to supply power reliably without posing any risk or using up valuable land resources. "The ocean is inexpensive real estate," says Buongiorno.

The researchers will be presenting their work at the Small Modular Reactors Symposium, hosted by the American Society of Mechanical Engineers, from April 15-17, at Washington, D.C.

Check out the concept video below.

Source: MIT