What the damage to the Fukushima plant portends for Japan—and th…
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What the damage to the Fukushima plant portends for Japan—and the world
Reliving the horror their grandparents knewONE danger of earthquakes, from Tokyo to San Francisco, has always been the flames that rise from the wreckage when fires are unleashed from their hearths. In Japan they have been called the “flowers of Edo”. But no earlier flames have been as foreboding as those that have erupted sporadically from the stricken Fukushima Dai-ichi nuclear power station. The horrifying spectacle will not end the planet’s nuclear endeavours. It could, however, reshape them radically.
Of the nuclear plants that provide about a third of Japan’s electricity (see chart), Fukushima Dai-ichi is not the first to be paralysed by an earthquake. But it is the first to be laid low by the technology’s dependence on a ready supply of water for cooling. To be near water is usually to be near the sea. And in this case, that meant right in the path of a tsunami.
The immediate impact of the catastrophic failures at Fukushima is not yet clear. It is worse than America’s near-disaster at Three Mile Island in 1979, which was fairly swiftly brought under control. But it is highly unlikely to be as devastating as the accident at Chernobyl in Ukraine in 1986, which sent a radioactive cloud across Europe that caused the deaths of an uncertain number of people, possibly well into the thousands.
The 40-year-old reactors in the nuclear power station run by the Tokyo Electric Power Company faced a disaster beyond anything their designers were required to imagine, and shut themselves down appropriately. They might have got through comparatively unscathed, as did the reactors at Fukushima Dai-ni, a similar plant farther along the coast. But at the Fukushima Dai-ichi plant things went wrong in many ways.
Nuclear reactors are protected by what plant designers call “defence in depth”. Some of these defences are simple barriers. The nuclear fuel is encased in hard alloys to construct fuel rods; the reactor core that these rods make up, and the water it sits in, are contained within a steel pressure vessel. That in turn sits within a larger steel structure, the primary containment vessel. Around it sits the steel and concrete secondary containment structure.
Other defences are actions, rather than things. The first action to be taken in the case of an earthquake is an emergency shutdown, which is achieved by thrusting control rods that sit below the reactor in its pressure vessel up into the reactor’s core. The control rods soak up the neutrons that mediate the chain reaction which produces most of a reactor’s energy, shutting it down. But other reactions will continue for a while; straight after shutdown, a reactor like those at Fukushima Dai-ichi is still a heat engine as powerful as a fair-sized jet engine at full throttle, locked in a small tight box. Things can get hot pretty quickly if there is no way of keeping it cool.
And after the tsunami hit, Fukushima Dai-ichi lost its cool. Generators stopped; electrical switching equipment was flooded. Attempts failed to get the cooling system working with batteries and generators from elsewhere. The emergency power eventually ran out altogether.
The Fukushima Dai-ichi plant uses boiling-water reactors, which are basically electric kettles where the nuclear reactor is the heating element at the bottom. If the kettle can’t be turned off and its spout is bunged up because the steam is radioactive, the situation inside will deteriorate. The amount of water will decrease, until eventually the nuclear core at the bottom is uncovered. It then gets even hotter even quicker, and bits of it will start to melt and react with the steam. The steam, meanwhile, will become ever more plentiful, and pressure will build up to a potentially explosive level. This seems to have happened to some extent in all three reactors.
In reactor 1, and later in reactor 3, steam contaminated with some radioactive elements was allowed out of the pressure vessel and into the larger containment vessel that surrounds it. There hydrogen in the released gas met a spark and exploded, blowing the roofs off the buildings but not, it seemed at the time, damaging the containment systems. With the primary containment vessel of reactor 1 still too full of steam, the radical decision was made to flood it with sea water to absorb the heat. The sea water was also laced with boric acid, which can soak up stray neutrons that the control rods miss.
Fukushima Dai-ichi: trying to explainReactor 3’s pressure vessel was then treated the same way, as, eventually, was reactor 2’s. But at some point, according to the company’s reports, reactor 2 boiled dry, and also—the two things possibly connected—suffered damage to the doughnut at the bottom of the containment vessel in an explosion on Tuesday morning. That is why it was reactor 2 which, by March 15th, was posing the greatest threat. Later it was reported that the containment was compromised at reactor 3 as well.
At around this stage the problems of the deteriorating plant began to spread. On March 15th, and again on the 16th, fires started in the building housing reactor 4. The reactor was safely off-line for maintenance when the quake struck, but there is spent fuel in storage tanks in the building, as elsewhere in the plant. This, too, needs to be covered with water that is circulated so as to keep things cool. At reactor 4 and reactor 3 spent fuel may have been exposed to the air. After the fire, radiation levels inside the plant soared. At this point, the level outside the plant was fairly high too. At one stage an unprotected person at the main gate would have received the maximum allowable yearly dose for a nuclear-industry worker in a matter of hours.
Conflicting reports of how much radiation was spreading farther afield were enough to cause panic. Matters worsened when America announced that it thought radiation levels were extremely high, and could severely constrain efforts to control the situation. On March 17th these included the use of helicopters and possibly water cannon to top up the water in the spent-fuel stores, bulldozing new access paths and yet more efforts to supply the plant with reliable electricity from the grid.
Chain reaction
The Japanese are now sure to reconsider their reliance on nuclear power, which is currently provided by 55 reactors, many similar in design to those now in trouble. Despite high spending on solar power over the years, the only real alternatives are imported natural gas or dirty coal. In the short term, with large parts of the country’s nuclear-generating capacity shut down, more gas will have to be imported. If the long term has a lot less nuclear power in it, there will be a corresponding need for gas and probably coal.
What of the rest of the world? Industry boosters had hopes of a nuclear renaissance as countries try to cut back on carbon emissions. There has been talk of a boom like that of the 1970s, when 25 or so plants started construction each year in rich countries. Not any more. Public opinion will surely take a dive. At the least, it will be difficult to find the political will or the money to modernise the West’s ageing reactors, though without modernisation they will not get any safer. The searing images from Fukushima, and the sense of floundering haplessness, will not be forgotten even if final figures reveal little damage to health.
The German government has declared a three-month moratorium on its controversial plan, agreed only last autumn, to prolong the life of its nuclear plants. This is likely to lead to the shutdown of its seven oldest plants and their permanent removal from the power grid. America’s never more than limited enthusiasm for new nuclear plants may disappear altogether.
If there was nothing else the matter, the nuclear industry might be able to weather a not-too-bad final outcome at Fukushima. After all, new reactors are said, with some justification, to be a lot safer. And most countries have the option of building them in seismically inactive zones, a luxury Japan does not enjoy. Even old reactors in the West, such as America’s boiling-water reactors, have been revamped in such a way as to preclude, it is thought, anything like the power outage that doomed the similar reactors at Fukushima Dai-ichi. But something else is the matter. Although the new reactors may be much safer than the old ones, they are a lot more expensive.
It is hard to say how much more expensive, since so few are being built. Generous loan guarantees have failed to get any commissioned so far in America. Two are under construction in western Europe, and both are over-budget. The labour of getting safety approvals makes investors jittery. And natural gas is abundant, far cheaper and relatively clean.
Yet the world will not necessarily turn en masse against nuclear power. Although events at Three Mile Island halted construction of nuclear plants in America, elsewhere—in France and, strikingly, in Japan—it continued. France, which has 58 nuclear reactors, seems to see the disaster in Japan as an opportunity rather than a setback for its nuclear industry. President Nicolas Sarkozy sang the industry’s praises on March 14th, saying that French-built reactors have lost international tenders because they are expensive: “but they are more expensive because they are safer.”
But the region where nuclear power is set to grow fastest, and seems least likely to be deterred, is the rest of Asia. Of the 62 plants under construction in the world, two-thirds are in Asia. Russia plans another ten. By far the most important nascent nuclear power is China, which has 13 working reactors and 27 more on the way. China has announced a pause in nuclear commissioning, and a review. But its leaders know that they must move away from coal: the damage to health from a year of Chinese coal-burning dwarfs any caused by the nuclear industry. And if anyone can build cheap, one-size-fits-all nuclear plants, it is probably the Chinese.
If the West turns its back on nuclear power and China ploughs on, the results could be unfortunate. Nuclear plants need trustworthy and transparent regulation, a clear distinction between operators and regulators and well enforced building codes. The Fukushima plant lacked some of those. China can offer none.
<The Economist>,2011/03/17
Reliving the horror their grandparents knewONE danger of earthquakes, from Tokyo to San Francisco, has always been the flames that rise from the wreckage when fires are unleashed from their hearths. In Japan they have been called the “flowers of Edo”. But no earlier flames have been as foreboding as those that have erupted sporadically from the stricken Fukushima Dai-ichi nuclear power station. The horrifying spectacle will not end the planet’s nuclear endeavours. It could, however, reshape them radically.
Of the nuclear plants that provide about a third of Japan’s electricity (see chart), Fukushima Dai-ichi is not the first to be paralysed by an earthquake. But it is the first to be laid low by the technology’s dependence on a ready supply of water for cooling. To be near water is usually to be near the sea. And in this case, that meant right in the path of a tsunami.
The immediate impact of the catastrophic failures at Fukushima is not yet clear. It is worse than America’s near-disaster at Three Mile Island in 1979, which was fairly swiftly brought under control. But it is highly unlikely to be as devastating as the accident at Chernobyl in Ukraine in 1986, which sent a radioactive cloud across Europe that caused the deaths of an uncertain number of people, possibly well into the thousands.
The 40-year-old reactors in the nuclear power station run by the Tokyo Electric Power Company faced a disaster beyond anything their designers were required to imagine, and shut themselves down appropriately. They might have got through comparatively unscathed, as did the reactors at Fukushima Dai-ni, a similar plant farther along the coast. But at the Fukushima Dai-ichi plant things went wrong in many ways.
Nuclear reactors are protected by what plant designers call “defence in depth”. Some of these defences are simple barriers. The nuclear fuel is encased in hard alloys to construct fuel rods; the reactor core that these rods make up, and the water it sits in, are contained within a steel pressure vessel. That in turn sits within a larger steel structure, the primary containment vessel. Around it sits the steel and concrete secondary containment structure.
Other defences are actions, rather than things. The first action to be taken in the case of an earthquake is an emergency shutdown, which is achieved by thrusting control rods that sit below the reactor in its pressure vessel up into the reactor’s core. The control rods soak up the neutrons that mediate the chain reaction which produces most of a reactor’s energy, shutting it down. But other reactions will continue for a while; straight after shutdown, a reactor like those at Fukushima Dai-ichi is still a heat engine as powerful as a fair-sized jet engine at full throttle, locked in a small tight box. Things can get hot pretty quickly if there is no way of keeping it cool.
And after the tsunami hit, Fukushima Dai-ichi lost its cool. Generators stopped; electrical switching equipment was flooded. Attempts failed to get the cooling system working with batteries and generators from elsewhere. The emergency power eventually ran out altogether.
The Fukushima Dai-ichi plant uses boiling-water reactors, which are basically electric kettles where the nuclear reactor is the heating element at the bottom. If the kettle can’t be turned off and its spout is bunged up because the steam is radioactive, the situation inside will deteriorate. The amount of water will decrease, until eventually the nuclear core at the bottom is uncovered. It then gets even hotter even quicker, and bits of it will start to melt and react with the steam. The steam, meanwhile, will become ever more plentiful, and pressure will build up to a potentially explosive level. This seems to have happened to some extent in all three reactors.
In reactor 1, and later in reactor 3, steam contaminated with some radioactive elements was allowed out of the pressure vessel and into the larger containment vessel that surrounds it. There hydrogen in the released gas met a spark and exploded, blowing the roofs off the buildings but not, it seemed at the time, damaging the containment systems. With the primary containment vessel of reactor 1 still too full of steam, the radical decision was made to flood it with sea water to absorb the heat. The sea water was also laced with boric acid, which can soak up stray neutrons that the control rods miss.
Fukushima Dai-ichi: trying to explainReactor 3’s pressure vessel was then treated the same way, as, eventually, was reactor 2’s. But at some point, according to the company’s reports, reactor 2 boiled dry, and also—the two things possibly connected—suffered damage to the doughnut at the bottom of the containment vessel in an explosion on Tuesday morning. That is why it was reactor 2 which, by March 15th, was posing the greatest threat. Later it was reported that the containment was compromised at reactor 3 as well.
At around this stage the problems of the deteriorating plant began to spread. On March 15th, and again on the 16th, fires started in the building housing reactor 4. The reactor was safely off-line for maintenance when the quake struck, but there is spent fuel in storage tanks in the building, as elsewhere in the plant. This, too, needs to be covered with water that is circulated so as to keep things cool. At reactor 4 and reactor 3 spent fuel may have been exposed to the air. After the fire, radiation levels inside the plant soared. At this point, the level outside the plant was fairly high too. At one stage an unprotected person at the main gate would have received the maximum allowable yearly dose for a nuclear-industry worker in a matter of hours.
Conflicting reports of how much radiation was spreading farther afield were enough to cause panic. Matters worsened when America announced that it thought radiation levels were extremely high, and could severely constrain efforts to control the situation. On March 17th these included the use of helicopters and possibly water cannon to top up the water in the spent-fuel stores, bulldozing new access paths and yet more efforts to supply the plant with reliable electricity from the grid.
Chain reaction
The Japanese are now sure to reconsider their reliance on nuclear power, which is currently provided by 55 reactors, many similar in design to those now in trouble. Despite high spending on solar power over the years, the only real alternatives are imported natural gas or dirty coal. In the short term, with large parts of the country’s nuclear-generating capacity shut down, more gas will have to be imported. If the long term has a lot less nuclear power in it, there will be a corresponding need for gas and probably coal.
What of the rest of the world? Industry boosters had hopes of a nuclear renaissance as countries try to cut back on carbon emissions. There has been talk of a boom like that of the 1970s, when 25 or so plants started construction each year in rich countries. Not any more. Public opinion will surely take a dive. At the least, it will be difficult to find the political will or the money to modernise the West’s ageing reactors, though without modernisation they will not get any safer. The searing images from Fukushima, and the sense of floundering haplessness, will not be forgotten even if final figures reveal little damage to health.
The German government has declared a three-month moratorium on its controversial plan, agreed only last autumn, to prolong the life of its nuclear plants. This is likely to lead to the shutdown of its seven oldest plants and their permanent removal from the power grid. America’s never more than limited enthusiasm for new nuclear plants may disappear altogether.
If there was nothing else the matter, the nuclear industry might be able to weather a not-too-bad final outcome at Fukushima. After all, new reactors are said, with some justification, to be a lot safer. And most countries have the option of building them in seismically inactive zones, a luxury Japan does not enjoy. Even old reactors in the West, such as America’s boiling-water reactors, have been revamped in such a way as to preclude, it is thought, anything like the power outage that doomed the similar reactors at Fukushima Dai-ichi. But something else is the matter. Although the new reactors may be much safer than the old ones, they are a lot more expensive.
It is hard to say how much more expensive, since so few are being built. Generous loan guarantees have failed to get any commissioned so far in America. Two are under construction in western Europe, and both are over-budget. The labour of getting safety approvals makes investors jittery. And natural gas is abundant, far cheaper and relatively clean.
Yet the world will not necessarily turn en masse against nuclear power. Although events at Three Mile Island halted construction of nuclear plants in America, elsewhere—in France and, strikingly, in Japan—it continued. France, which has 58 nuclear reactors, seems to see the disaster in Japan as an opportunity rather than a setback for its nuclear industry. President Nicolas Sarkozy sang the industry’s praises on March 14th, saying that French-built reactors have lost international tenders because they are expensive: “but they are more expensive because they are safer.”
But the region where nuclear power is set to grow fastest, and seems least likely to be deterred, is the rest of Asia. Of the 62 plants under construction in the world, two-thirds are in Asia. Russia plans another ten. By far the most important nascent nuclear power is China, which has 13 working reactors and 27 more on the way. China has announced a pause in nuclear commissioning, and a review. But its leaders know that they must move away from coal: the damage to health from a year of Chinese coal-burning dwarfs any caused by the nuclear industry. And if anyone can build cheap, one-size-fits-all nuclear plants, it is probably the Chinese.
If the West turns its back on nuclear power and China ploughs on, the results could be unfortunate. Nuclear plants need trustworthy and transparent regulation, a clear distinction between operators and regulators and well enforced building codes. The Fukushima plant lacked some of those. China can offer none.
<The Economist>,2011/03/17