- Email: [email protected]
Fukushima meltdown: the nuclear industry, one year on
SPECIAL REPORT / fukushima legacy
After the wave On 11 March 2011, one of the most powerful earthquakes on record hit north-east Japan. The resulting tsunami killed almost 20,000 people, and caused a meltdown at the Fukushima Daiichi nuclear plant. One year on, New Scientist looks at how the events at Fukushima have shaken up the nuclear industry, and at some of the implications for climate change and food production What now for safety? The crisis that unfolded at the Fukushima Daiichi nuclear plant after Japan’s megaquake and tsunami is rewriting the nuclear safety guide. There are some positives. Despite being shaken by an earthquake that exceeded the worst case assumed in their design, the reactors along Japan’s Pacific coast suffered no serious damage from the ground movement. Even the Onagawa plant, which sits closer to the megaquake’s epicentre than Fukushima, shut down with no major damage. Its resilience reflects a healthy margin of error in reactor seismic engineering. “Onagawa had the world’s best stress test, and it seems to have passed,” says Peter Yanev, a seismic risk consultant based in Orinda, California. That bodes well for the ability of reactors worldwide to withstand major earthquakes. Fukushima Daiichi was doomed by a decision to plan for only a 5.7-metrehigh tsunami – well short of the wave of up to 15 metres that engulfed the plant on 11 March 2011. In the light of this, regulators worldwide are reassessing whether other plants are vulnerable to catastrophic floods, caused by tsunami, swollen rivers or failed dams. It would have been prudent to note that tsunamis rising up to 38 metres had hit parts of Japan’s Pacific coast some 200 kilometres to the north, and to plan for a similar onslaught, says a team of nuclear safety, seismology and tsunami specialists who have analysed the information that was available to the plant’s designers (Bulletin of the Atomic Scientists, vol 67, p 37). Not only 8 | NewScientist | 10 March 2012
was the sea wall too low, but diesel generators needed to power emergency cooling systems, and the switching gear that connects the plant to the grid and controls core cooling, were not in “It would have waterproof buildings. Once they flooded, disaster was almost inevitable. been prudent to note that Simply installing more backup tsunamis of up generators won’t necessarily work, to 38 metres says Edwin Lyman, of the Union of had hit Japan’s Concerned Scientists in Cambridge, Pacific coast” Massachusetts. “The US nuclear industry is proposing to purchase lots of emergency equipment and distribute it around a plant, with the hope that something will be left working whatever happens,” says Lyman. But these extra generators may still be in harm’s way, he adds, because every plant has its own terrain and threats – be they hurricanes, earthquakes or floods. Far better, Lyman says, would be risk assessments to establish the safest sites for backup generators at each plant. Existing Swiss plants set a good example for flood-prone locations. Their reactors, threatened by Alpine rivers, have backup cooling systems in waterproof bunkers. They also have filtered venting systems so that even if cooling fails and pressure builds in the containment building, radioactive iodine and caesium can be removed from the steam before it is released. Had Fukushima Daiichi been designed All eyes are still to similar specifications, says Johannis on the Fukushima Daiichi nuclear Nöggerath, president of the Swiss power plant a Nuclear Society, “I’m convinced that it year after it was would have prevented the accident.” Peter Aldhous and Paul Marks n
hit by a tsunami
After the wave On 11 March 2011, one of the most powerful earthquakes on record hit north-east Japan. The resulting tsunami killed almost 20,000 people, and caused a meltdown at the Fukushima Daiichi nuclear plant. One year on, New Scientist looks at how the events at Fukushima have shaken up the nuclear industry, and at some of the implications for climate change and food production What now for safety? The crisis that unfolded at the Fukushima Daiichi nuclear plant after Japan’s megaquake and tsunami is rewriting the nuclear safety guide. There are some positives. Despite being shaken by an earthquake that exceeded the worst case assumed in their design, the reactors along Japan’s Pacific coast suffered no serious damage from the ground movement. Even the Onagawa plant, which sits closer to the megaquake’s epicentre than Fukushima, shut down with no major damage. Its resilience reflects a healthy margin of error in reactor seismic engineering. “Onagawa had the world’s best stress test, and it seems to have passed,” says Peter Yanev, a seismic risk consultant based in Orinda, California. That bodes well for the ability of reactors worldwide to withstand major earthquakes. Fukushima Daiichi was doomed by a decision to plan for only a 5.7-metrehigh tsunami – well short of the wave of up to 15 metres that engulfed the plant on 11 March 2011. In the light of this, regulators worldwide are reassessing whether other plants are vulnerable to catastrophic floods, caused by tsunami, swollen rivers or failed dams. It would have been prudent to note that tsunamis rising up to 38 metres had hit parts of Japan’s Pacific coast some 200 kilometres to the north, and to plan for a similar onslaught, says a team of nuclear safety, seismology and tsunami specialists who have analysed the information that was available to the plant’s designers (Bulletin of the Atomic Scientists, vol 67, p 37). Not only 8 | NewScientist | 10 March 2012
was the sea wall too low, but diesel generators needed to power emergency cooling systems, and the switching gear that connects the plant to the grid and controls core cooling, were not in “It would have waterproof buildings. Once they flooded, disaster was almost inevitable. been prudent to note that Simply installing more backup tsunamis of up generators won’t necessarily work, to 38 metres says Edwin Lyman, of the Union of had hit Japan’s Concerned Scientists in Cambridge, Pacific coast” Massachusetts. “The US nuclear industry is proposing to purchase lots of emergency equipment and distribute it around a plant, with the hope that something will be left working whatever happens,” says Lyman. But these extra generators may still be in harm’s way, he adds, because every plant has its own terrain and threats – be they hurricanes, earthquakes or floods. Far better, Lyman says, would be risk assessments to establish the safest sites for backup generators at each plant. Existing Swiss plants set a good example for flood-prone locations. Their reactors, threatened by Alpine rivers, have backup cooling systems in waterproof bunkers. They also have filtered venting systems so that even if cooling fails and pressure builds in the containment building, radioactive iodine and caesium can be removed from the steam before it is released. Had Fukushima Daiichi been designed All eyes are still to similar specifications, says Johannis on the Fukushima Daiichi nuclear Nöggerath, president of the Swiss power plant a Nuclear Society, “I’m convinced that it year after it was would have prevented the accident.” Peter Aldhous and Paul Marks n
hit by a tsunami