Nuclear nightmare in Japan
On March 11, a catastrophic earthquake — one of the four largest in the past century — struck in the ocean east of Japan, sending a colossal tsunami against the shore. By March 21, the toll of dead and missing, mainly from the tsunami, was estimated at 22,000.
As Japan confronted what Emperor Akihito called the worst crisis since World War II, we began to hear that the six-reactor complex at the Fukushima Daiichi plant, located directly in the tsunami’s path, had lost electrical power. The emergency generators also failed, apparently due to water damage to them or their fuel supply.
As we focus on the nuclear disaster at Fukushima, we emphasize that as of now, the tsunami itself is the far larger human tragedy. But like the tsunami itself, the nuclear disaster may portend further problems in other places, and is likely to affect a trend toward greater use of nuclear power around the world.
Immediately, the arrow of trouble aimed at the most ominous type of nuclear accident: loss of cooling. Fission — splitting of radioactive elements that powers nuclear reactors — can stop when reactor operators flip a switch to insert control rods to absorb neutrons. This stops the chain reaction — the divison of uranium atoms that releases neutrons that split other atoms and generate heat — which is the whole point of building nuclear reactors to boil water and drive turbines.
But once the fission reactions cease, decay heat continues to be released from the unstable atoms that remain after fission, and it is this heat that must be removed by a cooling system after shutdown.
Past accidents have shown that decay heat can build up in seconds; and significant damage to the fuel and potentially reactor equipment can occur within minutes. The danger of such a “meltdown” is a major reason why nuclear designers and engineers focus so much effort on cooling the reactor core.
In the beginning, there was Three Mile Island
Japan, target of the only two atomic bombs used in war, is hardly the first nation to confront a “loss of coolant” emergency at a reactor. That happened on March 28, 1979, in the United States, where Pennsylvania’s Three Mile Island (TMI) reactor #2 began a partial melt-down.
Much later, the Nuclear Regulatory Commission concluded that the accident “was caused by a combination of personnel error, design deficiencies, and component failures.” As hundreds of alarms buzzed in the control room, operators, lacking a direct measurement of the water level inside the reactor, made a bad situation worse, the reactor went at least partly dry, and a large percentage of the fuel melted.
It’s safe to say the public reaction verged on panic as a bubble of explosive hydrogen built up inside the plant and evacuations were ordered.
The slow, dangerous removal of fuel revealed massive heating and damage inside the reactor. According to the book, “TMI 25 Years Later”1: “A large portion of the core melted and flowed into the lower vessel. Most of the core experienced temperatures of at least 1727° C, with certain parts reaching 2527°C.”
At these temperatures, the essential containment vessel can weaken and fail.
TMI, the above book concluded, neared a complete a meltdown. “No one can say for sure, but some experts say that had the accident continued for another 20 to 45 minutes, the [reactor] vessel would have heated up and the metal would have lost its strength, leading to a rupture,” preventing further cooling and allowing superheated fuel to melt through the reactor vessel and enter – and likely exit — the reactor building.
From there, it’s impossible to speculate how widely the radiation would have spread, the authors wrote, but this is what is called the China Syndrome — a runaway load of reactor fuel melting its way down into the earth. Oddly, “China Syndrome” – the movie — was released 12 days before the TMI meltdown.
TMI #2 has since undergone a major cleanup. Intact and damaged fuel has been moved to storage at Idaho National Engineering Laboratory. Reactor #1 is operating normally, and final removal of the destroyed #2 awaits the decommissioning of its companion.
According to the Nuclear Regulatory Commission: “Estimates are that the average dose to about 2 million people in the area was only about 1 millirem. To put this into context, exposure from a chest X-ray is about 6 millirem.”
Nevertheless, the alarm over TMI sent the U.S. nuclear industry into a tailspin.
Chernobyl – the unmitigated disaster
The Lord Voldemort of nuclear accidents started on April 26, 1986, when Chernobyl reactor #4 exploded, burned and melted down in a spectacular fire that spewed an estimated 50 tons of radioactive fuel over a swath of Eastern Europe. Unlike TMI (and the imperiled Japanese reactors) Chernobyl had no vessel to contain its fuel, and a giant fire – consuming the estimated 800 tons of graphite used to slow neutrons in the reactor — burned for more than a week as brave crews tried to damp it with sand, boron and lead.
Chernobyl was located in a part of the Soviet Union that is now in Ukraine.
The meltdown produced some of the worst radiation injuries in history, and hundreds of thousands were force-evacuated from an “exclusion zone” — roughly 30 kilometers in radius — around the smoking, radioactive hulk of #4.
Within months, the cooling reactor was hastily wrapped in a giant concrete “sarcophagus” (stone coffin) to contain further radiation. But the sarcophagus is leaking, says Leon West, a professor of mechanical engineering at the University of Arkansas, who has 40 years of experience in nuclear physics, radiation protection and nuclear engineering. “Chernobyl is still open and is still a threat to the local environment.”
“Construction has already begun on the New Safe Confinement,” says photographer Michael Foster Rothbart, who lived 12 miles from the exclusion zone between 2007 and 2009, “and although it keeps falling behind schedule, target finish date is 2013.”
Japan: Facing Three Mile Island or Chernobyl?
By March 21, 10 days after the tsunami, the owners of the Fukushima power plant reported that it had reconnected electric power to all six reactors. The disaster seems headed toward resolution, says Jeff Geuther, who manages a research reactor at Kansas State University. “My understanding is that the fuel [in the three recently operating reactors and the three spent-fuel pools at other reactors] is all under water. The radiation dose has been falling at the plant, an indication that water level has increased in the spent fuel pools.”
Although it’s not clear how much fuel has melted, Geuther says, “It’s fairly clear that the cladding [a thin sheathing on the fuel rods], at a minimum, had some damage. Iodine and cesium have been detected offsite; these are fission products that would be typically be trapped inside the cladding.”
By March 23, the utility reported that the lights were on in the control room of reactor #3, but work had not yet begun on monitoring equipment and reactor cooling pumps in the three reactors that were operating before the quake. By March 24, smoke was rising from several reactors, three plant employees were being treated for radiation exposure, and the zone of concern about radiation in drinking water had been expanded. The local populace remains under evacuation.
Near-term progress in stabilizing the Fukushima plant will be measured by
A near miss?
Two positive factors helped what looks like a near-miss at Fukushima. First, those reactors (unlike Chernobyl) had thick steel containment vessels, which, despite some reports of damage, seemed to hold up reasonably well.
Second, also unlike Chernobyl, Fukushima used water, not combustible graphite, to slow neutrons.
On the other hand, Fukushima faced systemic difficulties due to the precipitating natural disasters: After the epochal earthquake-towering tsunami sequence shut the reactors down, the electric grid died, killing the emergency cooling pumps.
Then the emergency diesel generators failed, and without cooling, the reactors quickly overheated. But with roads out and the nation tending to survivors and victims of the tsunami, the nuclear emergency festered for days, through a series of explosions, fires, bursts of radiation, and evacuations of plant workers.
At one point, just 50 workers were on hand to deal with multiple emergencies at several reactors and pools of spent fuel. The desperation was on display when helicopters tried to dump buckets of water into the fuel pools and fire trucks sprayed cooling water through explosion-blasted walls.
How many broken reactors?
Despite early fears that Fukushima was mimicking Chernobyl, it seems rather to be headed toward the less malignant TMI precedent, says West. “A big leak [like Fukushima] is not like the open-air nuclear bonfire of Chernobyl that spewed radioactive materials into the upper atmosphere. The extent of the release of radiation and the continuing difficulties with cooling of reactors and spent fuel has clearly put the Daiichi site at the TMI stage.”
As radioactive particles cross the Pacific on the jet streams, “California, Oregon, and Washington should start reporting measurable traces of radioactive materials in air samples,” says West, “but for the United States, this should be more like a Chinese test of a nuclear weapon and of no health consequence.”
Radiation has already been detected on milk and green vegetables near the reactor, and now in drinking water in Tokyo. “The Japanese will need to monitor and control agriculture products to minimize the risk to public health,” says West. “This will be similar to efforts in the United States during the 1950′s, when the U.S. was detonating nuclear weapons in Nevada,” and farmers were prohibited from selling milk for four days afterwards.
Japanese meltdowns, American reverbs
As Japan evacuated neighbors from the Fukushima plant, the U.S. Nuclear Regulatory Commission (NRC) advised American citizens in Japan to move at least 50 miles away. That’s much further than specified American evacuation plans, notes Vicki Bier, a professor of industrial engineering at the University of Wisconsin-Madison. “If the NRC is concerned up to 50 miles in Japan, that certainly calls into question emergency planning here, which is limited to 10 miles.”
On March 16, California Senators Barbara Boxer and Dianne Feinstein asked the NRC to review safety at two California plants located near earthquake faults. “Roughly 424,000 live within 50 miles of the Diablo Canyon and 7.4 million live within 50 miles of San Onofre Nuclear Generating Station,” the senators wrote.
And on Mar. 22, the Nuclear Regulatory Commission agreed to accelerate a safety review at Indian Point, a pair of reactors 30 miles from Manhattan.
Japan: How prepared, in reality?
How did such severe nuclear troubles arise in Japan, where “tsunami” was coined, and which is the world’s leader in earthquake engineering and disaster preparedness?
For starters, the tsunami was much bigger than expected. But we’ve also learned from the Associated Press (on March 24) that Japanese preparations focused on natural disasters.
Was the nuclear emergency made worse because six reactors were at one location? As we saw, radiation vented from one reactor caused the flight of workers trying to tame other reactors. But multiple siting had “always been considered to be a really good idea,” says West. “You have a collection of focused professionals with lots of resources [for example, to fight fires], so if one reactor has difficulties, you could take those excess resources and focus on that situation. … This is the first situation, where [multiple sitings] appears to need to be reexamined.”
Early reports point to a critical design failure at Fukushima, says Bier, an expert on risk assessment at nuclear plants. “They were designing for earthquake and tsunami, but not for this level of damage; you’ve got to give engineers some criteria; they can’t design for anything. They could have designed for what did happen, but they apparently decided it was too unlikely.”
Design: Where are the goalposts?
A specific weakness concerned the emergency diesel generators needed to run the pumps, which apparently were swamped by the tsunami, says Bier. “There is a lot we won’t know for months, but there is reasonable speculation about things that could be done differently at modest cost. You can’t prepare for every eventuality, but probably it would have been possible to get better protection for the diesels in a bunker or on higher ground.”
The systematic disruption and near chaos interfered with tasks like avoiding melt-downs in the pools holding spent fuel, which lack the containment usually found on reactors. As Fukushima proved, accidents can be made worse as effects are compounded: the real-life scenario included a combination of a Japan-record earthquake, massive tsunami damage, regional blackouts and radiation releases.
“The surrounding area was so damaged by earthquake and tsunami that it impeded the emergency response,” says Bier. “We have seen stories about people within the evacuation zone who could not evacuate because the roads are impassable or buildings have collapsed, and they were not sending in rescue teams because the radiation was too high. Certainly it was not anticipated that the damage would be this severe, or the radiation would be too severe to evacuate.”
Fukushima: End game
Will the six reactors at Fukushima Daiichi be dismantled, like TMI #2, or wind up inside a Chernobyl-style concrete coffin?
The three reactors that got emergency cooling with sea water are likely finished due to corrosion, not to mention possible explosion damage. “Salt water is a killer,” says Robert Rosner, professor of astronomy, astrophysics and physics at the University of Chicago. Rosner expects these reactors to be taken apart and trucked to long-term storage.
Although the age of the reactors – about 40 years – militates against spending large sums on refurbishment and updating, Japan now faces an electricity shortage, so Rosner expects one or two of the plants to return to service, at least for a while.
West, however, suggests that at least one reactor may wind up encased in concrete. “If I were an engineering manager, I would be looking at the possibility of stabilizing it to deal with all the issues” and then build an outer containment to isolate the reactor but allow service visits.
Credibility at stake
Assessing the long-term impact of Fukushima requires us to look at the technology’s unique place in the popular eye. Whether the nuclear industry likes it or not, nuclear carries plenty of emotional baggage. Nuclear physics produced the mushroom clouds over Hiroshima and Nagasaki long before it was used to make electricity. And because ionizing radiation is invisible, it’s a case where what you don’t know can hurt you.
Nuclear energy also arouses fear because power-plant neighbors cannot control it, says Nathan Hultman, an assistant professor of public policy at the University of Maryland. “A lot of research has looked at why people view risks differently, and both dread and the degree of control in nuclear are nerves that are touched very strongly. We feel safer driving cars than in an airplane, even though statistically, airplanes are much safer, because we feel in control in a car.”
The Japanese nuclear industry also faces credibility problems, Hultman notes.
Bungling, cover-ups define Japanese nuclear power
Associated Press, March 17, 2011
TOKYO (AP) – Behind Japan’s escalating nuclear crisis sits a scandal-ridden energy industry in a comfy relationship with government regulators often willing to overlook safety lapses.
Leaks of radioactive steam and workers contaminated with radiation are just part of the disturbing catalog of accidents that have occurred over the years and been belatedly reported to the public, if at all.
In one case, workers hand-mixed uranium in stainless steel buckets, instead of processing by machine, so the fuel could be reused, exposing hundreds of workers to radiation. Two later died.
“Everything is a secret,” said Kei Sugaoka, a former nuclear power plant engineer in Japan who now lives in California. “There’s not enough transparency in the industry.”
“Small nuclear accidents were covered up,” says Hultman. “Often the initial reaction was ‘Everything is just fine, the situation is normal,’ then it came out there was a deeper problem. Now we are in a situation where very bad things are happening, and people are not sure what to believe.”
Hultman adds that these issues are a likely fixture in the coming debate over nuclear power. “Nuclear is not the only way to boil water to generate electricity,” he says, and the discussion of energy sources must be broader than that. “Rather than say, ‘We must have nuclear,’ we need to talk about alternatives as well.”
The Fukushima debacle could further polarize a nuclear debate that was altered by both TMI and Chernobyl, says Hultman. “There is almost a religious division. People who believe it’s good think it will be the answer to all our problems, and people who don’t like it, really really don’t like it.”
An omen for the future?
The Fukushima disaster carries striking ironies. Japan was the only country at the receiving end of atomic bombs, and studies of survivors at Hiroshima and Nagasaki have been the basis for understanding the health effects of low-level radiation.
Historically, the Fukushima disaster occurred as nuclear was gaining so much traction as a low-carbon solution to global warming that some prominent environmentalists had begun to talk nuclear. “This is going to have a big effect on the rebound toward nuclear,” says West, who adds, “We just can’t burn our forests — and coal is an old forest — forever,” due to global warming.
Even technological disasters that loom large in the short run may eventually be seen as lessons, West says. “The crash of a major aircraft … does not mean that air travel should end, it means we need to tighten up our design.”
Rosner, however, suggests that nuclear, with its potential for widespread, long-term contamination, needs to live by different rules. “When you are engineering something where the consequences, if something goes wrong, are devastating, even though the probability is very small, you need to engineer to avoid the devastation. We’ve known how to do that for 50 years, but it was always just a bit too expensive on the front end, so the decision was made: The probability is so low, we are not going to worry about it.”
– David Tenenbaum
Terry Devitt, editor; S.V. Medaris, designer/illustrator; Jenny Seifert, project assistant; David J. Tenenbaum, feature writer; Amy Toburen, content development executive
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- Disturbing releases of iodine and cesium? ↩