Floating nuclear plants may withstand tsunamis

MIT scientists have come up with a new design for nuclear plants built on floating platforms, modelled after those used for offshore oil drilling, that could ride out deadly tsunamis.
When an earthquake and tsunami struck the Fukushima Daiichi nuclear plant complex in 2011, neither the quake nor the inundation caused the ensuing contamination, researchers said.
Rather, it was the after-effects - specifically, the lack of cooling for the reactor cores, due to a shutdown of all power at the station - that caused most of the harm.
The new power plant design could provide enhanced safety, easier siting, and centralised construction and could help avoid such consequences in the future, said researchers.

Such floating plants would be automatically cooled by the surrounding seawater in a worst-case scenario, which would indefinitely prevent any melting of fuel rods, or escape of radioactive material.
Such plants could be built in a shipyard, then towed to their destinations five to seven miles offshore, where they would be moored to the seafloor and connected to land by an underwater electric transmission line.

The concept takes advantage of two mature technologies: light-water nuclear reactors and offshore oil and gas drilling platforms.
Using established designs minimises technological risks, said Jacopo Buongiorno, an associate professor of nuclear science and engineering (NSE) at Massachusetts Institute of Technology (MIT).

A floating platform several miles offshore, moored in about 100 meters of water, would be unaffected by the motions of a tsunami; earthquakes would have no direct effect at all.
The biggest issue that faces most nuclear plants under emergency conditions - overheating and potential meltdown, as happened at Fukushima, Chernobyl, and Three Mile Island - would be virtually impossible at sea, said researchers.
"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. The reactor containment itself is essentially underwater," Buongiorno said.
At the end of a plant's lifetime, "decommissioning" could be accomplished by simply towing it away to a central facility. That would rapidly restore the site to pristine conditions, he said.

Such plants could be anywhere from small, 50-megawatt plants to 1,000-megawatt plants matching today's largest facilities.
Most operations would be similar to those of onshore plants, and the plant would be designed to meet all regulatory security requirements for terrestrial plants.
Buongiorno sees a market for such plants in Asia, which has a combination of high tsunami risks and a rapidly growing need for new power sources.
The concept is being presented at the Small Modular Reactors Symposium, hosted by the American Society of Mechanical Engineers.