APS News

Fukushima’s Legacy Debated

By Michael Lucibella

A year after the meltdown at the Fukushima Daiichi power plant, its legacy still divides scientists over the future of nuclear power. At this year’s March Meeting, a special session organized by the Forum on Physics in Society, the Forum on International Physics and the Division of Condensed Matter Physics brought the two sides to the forefront.

Stephen Kuczynski, CEO of Southern Nuclear Operating Company, defended his industry. His company recently received the first new construction license to build a new nuclear power plant in the United States since the Three Mile Island incident in 1979.

“It’s the safest industry that you can work in. The workers at our power plants are the safest in any industry,” Kuczynski said. “We also have layers of oversight… There [are] multiple layers to detect if there is a change or degradation in the safety culture, and we can take action.”

However, concerns about safety persist. On the same panel, following Kuczynski’s remarks, Edwin Lyman from the Union of Concerned Scientists laid out his organization’s reservations about the safety of nuclear power in the US.

“The question does come up: ‘Can it happen here?’ There’s been a lot of debate on this issue, whether it was a Japan-specific event, whether the US was better prepared than Japan to deal with this kind of contingency. In our view, complacency is as prevalent here in the United States as it is in Japan,” Lyman said. “US nuclear plants were not designed or intended to survive major natural disasters, multiple system failures or terrorist attacks.”

Following the crisis at Fukushima, leaders of the US nuclear industry put together a study titled “The Way Forward” to review what happened in Japan and prevent such an accident in the United States. The document that emerged included a strategy for coping with potential accidents, which the industry referred to as its FLEX plan. According to the plan, plants acquire self-contained portable pumps, generators, batteries, compressors, hoses and equipment to clear debris. The equipment is kept onsite to deal with a catastrophic event that knocks out external power. The idea is to use the batteries, hoses and other equipment to keep water flowing over spent fuel rods and the reactor cores, preventing them from overheating.

“Let’s just assume that we’re not smart enough to know every single possible external event; let’s develop strategies to deal with whatever they are,” Kuczynski said. “It may be a flood, it may be a seismic activity, it may be something that we’re just not thinking about at this point in time. But can we develop strategies to extend battery life, make sure our sources of AC power are secure, and can transport water so our ultimate heat sink can be functional? That is the whole purpose around FLEX.”

Lyman said that the FLEX program did not address some of the fundamental issues that contributed to the disaster at Fukushima. He said he was concerned that a major catastrophic event, like the tsunami that struck the Japanese plant, could still knock out all of the emergency equipment stored onsite.

“The US nuclear industry has proposed a program which they call FLEX, which essentially involves buying lots of commercial grade, off-the-shelf equipment like diesel generators that anyone can buy for their home, and storing them at various places, on and off reactor sites, in the hope that no matter what event might come, that at least some equipment somewhere will survive and you’ll be able to get it to the site and use it,” Lyman said. “It’s really not clear how much additional safety we’re getting from the industry’s program. And the NRC has not yet issued its guidlines as to how that equipment should be regulated.”

The designs of reactors were also the subject of contention. The reactors slated for construction at Southern Nuclear’s new plant are the first to use a much touted, third generation nuclear reactor, the Westinghouse AP1000. It’s been designed with a number of passive safety features built in that don’t need any power or operators to shut down fission reactions and start cooling the core. The system is supposed to keep the reactor from going critical for three days if emergency power hasn’t been restored.

“In the AP1000 there is a pool of water on top of the containment, so if it’s needed, it will stream and it will exchange the heat and that pool of water is there for at least a three day period,” Kuczynski said. “All we need to do is fill it back up; it’s a very simple evolution. And that’s just gravity, that’s just convection, that’s just normal heat transfer.”

The robustness of that 72 hour estimate was disputed by Lyman. He said that overall the plans developed by the nuclear industry lacked vision and flexibility for disasters outside of the imaginations of designers. Prior to the disaster in Japan, no one had developed contingency plans for such severe damage inflicted upon a nuclear plant. Lyman said that such is also the case with the new Westinghouse reactors; their safety is predicated on the entire system remaining mostly intact.  One potential flaw he pointed to was if the pool of water used for cooling is punctured there would be no contingency to prevent the reactor from going critical.

“We hear a lot about the AP1000s that can cope with a 72 hour station blackout. But really that’s only under the design basis of certain conditions,” Lyman said. “So if you have something that’s beyond the design basis of the plant, a seismic event or major flooding, then you might not be able to count on that 72 hour plan.”


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