From Chernobyl to Fukushima: the hazardous journey of nuclear power

22 ဧပြီလ 2011
Article

Three partial core meltdowns and other crises have precipitated a nuclear nightmare. This is a wake-up call for the world.

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It was a mere coincidence, if a tragic one, that the Fukushima nuclear disaster in Japan happened just a few weeks short of the 25th anniversary of the Chernobyl catastrophe in Ukraine, which falls on this April 26. Chernobyl is the world’s worst-ever industrial accident, far worse than the Bhopal gas leak disaster of December 1984. Some 3,000 to 3,500 people perished in Bhopal in the first week of the chemical accident. The death-toll from the illnesses caused by that exposure has since risen to an estimated 15,000 to 20,000.

In Chernobyl, the number of additional cases of cancers and leukaemias caused by radiation is estimated to range from 34,000 to 140,000, leading to 16,000 to 73,000 fatalities. Some studies, including one published by the New York Academy of Sciences, put the number of fatalities at more than 10 times higher than the last figure.

A disaster waiting to happen

In many ways, however, the Fukushima disaster was not a coincidence at all. It was only waiting to happen. A part of that inevitability is attributable to the siting of as many as six reactors in a highly seismic area close to a subduction zone, where tsunamis tend to occur. Some of it is explained by the flaws of the Boiling Water Reactor design of the United States multinational General Electric. Yet another part is attributable to the questionable operating practices and accident management of the station operator, Tokyo Electric Power Co (TEPCO).

However, some of the inevitability arose, as we see below, from the nature of nuclear technology and its inherent hazards. The bitter truth is, all existing nuclear reactors in the world, regardless of the type of fuel and coolant they use, and irrespective of their configuration, are vulnerable to serious accidents with potentially catastrophic radioactivity releases.

The Fukushima reactors were not designed to cope simultaneously with a huge earthquake of magnitude 9 on the Richter scale and a tsunami. TEPCO knew this. In 1995, 2002 and 2007, it had to shut down reactors at several of its stations. In 2007, there was a radioactivity release from the Kashiwazaki-Kariwa plant, the world’s largest nuclear power station. But TEPCO concealed this and other material facts on nearly 200 occasions.

Other Japanese operators too have practised deception. For instance, in 1995, one of them released an altered video of a fire at a fast-breeder reactor—an even more hazardous reactor type than normal ones—to conceal the damage. They all got away with this because of their collusive relationship with the regulator, Japan’s Nuclear and Industrial Safety Authority.

The course of events

What happened at Fukushima on March 11? The three operating reactors (of a total of six) shut down, as planned, when the earthquake happened. The back-up power supply came on, as planned, through diesel generators. But an hour later, the generators failed, probably because they had been flooded by the tsunami. In a serious lapse in safety design, the generators were located at a low level instead of at an elevation. There was a tiny battery back-up, which could have operated the valves of the control rods which can damp down a nuclear fission reaction. But that soon failed. There was a full station blackout. The reactors were now headed for serious trouble.

With loss of coolant water, the reactors’ cores heated up and some fuel was damaged, leading to a build-up of extremely flammable hydrogen. A series of explosions took place in the reactor buildings, which wrecked their walls and roofs, making radioactivity releases likelier. The top priority now was to cool the reactors with water—freshwater or even seawater—with specially procured, dedicated, powerful pumps.

TEPCO relied on fire pumps which were ineffectual. According to some analysts, TEPCO, anxious to save the reactors, delayed pumping seawater into them: seawater corrodes reactors, which then would have to be written off. Helicopters were deployed to pour seawater over the reactors, but much of it was lost to the wind.

The reactors kept heating up and their cores lost water cover, leading first to significant leaks, and then to large-scale releases of radioactivity. To contain the overpressure from building up to a dangerous point, the plant engineers periodically released steam carrying radioisotopes into the atmosphere. It also contained molecules in which a part of the normal hydrogen had been replaced by its toxic heavy isotope, tritium.

By the end of the first week, Reactors 1, 2 and 3 were in acute distress, with overheated and exposed fuel. The much-feared nightmare, a partial core meltdown, was coming true.

Inadequate solutions and a flimsy plan B

Two new complications soon arose. Following the General Electric design, the reactors’ intensely radioactive spent fuel was stored in water pools in the reactor building itself. This water must also be cooled, but wasn’t. The spent fuel heated up and the water evaporated, leading to further releases of dangerous isotopes like iodine-31, caesium-137 and strontium-90. The situation became particularly grim in one of the reactors (Number 4) which had been shut down before March 11. The roof of its spent-fuel pool blew off, adding to radioactivity releases.

The second complication was also rooted in design. Reactor 3 burnt a mix of plutonium and uranium oxides (MOX) as fuel instead of the normal slightly enriched uranium. The use of MOX is known to generally “increase the consequences of severe accidents in which large amounts of radioactive gas and aerosol are released compared to the same accident in a reactor using non-MOX fuel …, according to an expert of the Union of Concerned Scientists of the US.As a result, the number of latent cancer fatalities resulting from an accident could increase by as much as a factor of five for a full core of MOX fuel ….” Reactor 3 therefore may have contributed more than the other reactors to the radioactivity releases from Fukushima.

Also in play was yet another design-related problem, that of a structurally weak primary containment, the steel vessel which encloses the reactor. General Electric’s Mark-I containment is considered by experts to be “unusually vulnerable” to failure in the event of a core-meltdown accident. “A recent study by the US government-run Sandia National Laboratories shows that the likelihood of containment failure in this case is nearly 42 percent. The most likely failure scenario involves the molten fuel burning through the reactor vessel, spilling onto the containment floor, and spreading until it contacts and breaches the steel containment-vessel wall.

An invisible tsunami of radiation

During the first few days of the crisis, radiation levels in the reactor control room were reportedly 8,000 times the maximum permissible. Radioactivity at the station gate soon recorded an alarming 1,000 millisieverts an hour, several thousand times the highest permissible radiation dose for plant employees (30-50 millisieverts a year).

By the second week of the crisis, milk and vegetables in Fukushima and nearby prefectures were found to have higher-than-permissible concentrations of iodine-131 and caesium-137. Radiation from the reactors had spread hundreds of kilometres away. Tapwater in Tokyo, 220 km away, was found to have been radioactively contaminated, and the government advised people not to give it to babies. People were evacuated from a zone with a 20-kilometre radius from the plant, while those living between a 20-km and 30-km radius were advised to leave.

Many independent experts believe that the evacuation zone should have been extended. The US Embassy in Japan, following the Nuclear Regulatory Commission’s assessment, advised evacuation for American citizens living within 80 km. By the third week of the crisis, caesium-137 concentrations at a distance of 40 km from Fukushima had reached up to 3.7 megabecquerels per square metre (the becquerel is a unit that measures the rate of disintegrations per second).

This is more than double the level of 1.48 units, which was set as the threshold for evacuation in Chernobyl. A region 30 to 40 kilometres northwest of Fukushima recorded a dose rate above 125 microsieverts per hour, a level at which immediate evacuation is often advised.

No reliable estimates have yet emerged of the number of people exposed to radionuclides from Fukushima, or the doses they absorbed. Such exposure carries a high health risk, including cancers and leukaemias. Iodine-131 has a short half-life (the time during which it naturally decays to half its original mass) of 8 days. It gets rapidly absorbed in the thyroid gland. Caesium-137 behaves much like potassium and is absorbed in a wide range of tissues. Strontium-90 is attracted to bones, being chemically similar to calcium. Caesium-137 and strontium-90 both have half-lives of about 30 years. They will have a significant presence even a century from now.

More problems arise

The crisis took a turn for the worse in its third week. Although engineers reached electric power to the station, they only succeeded in turning on lights. Most other systems, including instrumentation that allows workers to know what is happening in the reactor cores and spent-fuel pools, did not operate. The reactor cores were not adequately cooled. Nor did their spent-fuel pools. Reactors 1, 2 and 3 are estimated to contain 1,496 bundles of fuel. The spent-fuel pools of the four reactors have 2,724 bundles.

A 20-centimetre crack developed in a shaft carrying cables to the Reactor 1 building, from which large quantities of highly irradiated water leaked. As its water tankage got filled, TEPCO dumped over 10,000 tonnes of radioactive water into the sea.

Seawater radioactivity in Fukushima’s immediate vicinity reached concentrations millions of times higher than permissible levels. TEPCO engineers made several attempts to plug the crack with desperate means such as using newspapers and even sawdust, but did not succeed for three days. On April 6, TEPCO announced that the leak was plugged. But it is not clear if the seal is reliable and can withstand mounting pressure from a trench filled with highly radioactive water.

Fukushima has released a large quantity of toxic radioisotopes. According to one estimate, based on data from the monitoring stations of the Comprehensive Test Ban Treaty Organisation, a United Nations body, roughly 20 percent of the iodine-131 and 50 percent of the caesium-137 released in the Chernobyl accident were released from Fukushima within the first few days. A later estimate says the two releases are about the same. Fukushima’s inventory of caesium is 40 times higher than Chernobyl’s.

A columnist in Nature (April 5) writes: “The implications of the available data on contamination are far-reaching. … [It] seems likely that in some areas, food restrictions could hold for decades, particularly for wild foodstuffs such as mushrooms, berries and freshwater fish.

One month after the Fukushima crisis began, it remains unresolved. Reactors 1, 2 and 3 have undergone a partial core meltdown. US energy secretary Steve Chu estimates the Reactor 1 core damage at 70 percent. And the energy department says the damage is 33 percent in Reactor 2. Reactor 3 warrants great concern because of MOX fuel. The spent-fuel pools too continue to pose problems. Four reactors will be written off. But their entombment will pose new problems.

TEPCO and NISA have subjected workers at Fukushima to high radiation doses by rewriting the rule book and raising the maximum permissible one-time dose from 50 millisieverts to 250 millisieverts. Trenches outside the reactor buildings, especially Reactor 2, are full of highly contaminated water, with radiation levels of 1,000 millisieverts an hour—high enough to cause acute radiation syndrome within an hour.

Says a UCS scientist: “The volume of radioactive water is so large that [workers] are running out of places to store it. To cut down on the volume of water they need to remove and store, they are trying to reduce the amount of water they pump into the reactors to cool the fuel in the cores. But without that cooling, the fuel … has been heating up. This leads to a buildup of pressure in the reactor that may require additional venting of radioactive gas to the atmosphere. If the heating becomes great enough, it can also lead to additional fuel damage and further release of radioactive gases ….

The Fukushima crisis will be with us for several years. As yet, there are no reliable estimates of the quantity of the fuel that may have melted. But it may be substantial.

Fukushima has shocked the world public, upset energy generation plans in many countries, and precipitated what is likely to be the greatest-ever crisis of the global nuclear industry. The industry already faces stagnation and decline. Nuclear power generation peaked worldwide in 2006-07 and has been declining by 2 percent annually.

The US nuclear industry has not had a new reactor order since 1973. It never recovered from the Three Mile Island (TMI) accident of 1979. Chernobyl dealt a body blow to the European nuclear industry. Chernobyl could be attributed to shoddy design and operational practices in industrially backward Ukraine. Fukushima happened in a country that has the world’s third largest fleet of nuclear reactors and is technologically highly advanced.

It could happen again

The sequence of events at Fukushima may be special, even unique. But a station blackout can happen for a variety of reasons, without a natural disaster. Engineers who have designed, operated and licensed nuclear reactors say all existing reactor types can undergo a catastrophic accident—with different sequences but the same end-result. Nuclear reactors are extremely complex, and internally, tightly coupled high-temperature high-pressure systems. A small mishap in one sub-system gets quickly transmitted and magnified, throwing the reactor into a crisis that can neither be anticipated nor controlled.

It is delusional to think that the Fukushima disaster was caused by the earthquake and tsunami. They merely triggered a crisis in reactors that were vulnerable to a grave accident in the first place. Many other nuclear disasters, including loss-of-coolant accidents and core meltdown, such as Chalk River (Canada, 1952), Windscale (UK, 1967), Three Mile Island (US, 1979) and Chernobyl (1986), were caused by operator error, equipment degradation or failure, failure of emergency backup, and loss of power. Natural disasters only make nuclear accidents more likely.

The nuclear industry has persistently underestimated the probability of a core-damage accident. In 1975, the Rasmussen Report said the probability was one in 20,000 years of reactor operation in the US. But TMI happened within 500 years of operation. The estimate was soon revised to one accident in 1,000 years. But a core-damage accident has happened once every 8 years in the world since 1970.

The US has responded to Fukushima by ordering a safety review of all its 104 reactors, including as many as 23 General Electric BWRs. Since TMI, the US has recorded 17 “near-misses” or serious accidents in nuclear reactors—including four since 1990. These were all “significant precursors” of core damage.

Germany, Switzerland and China have suspended their nuclear programmes. Germany has rescinded its recent decision to extend the phaseout of all nuclear reactors by 12 years. Many other countries, including, Turkey, Syria, Jordan, Poland, Egypt, Bangladesh, Brazil, Israel, Saudi Arabia, Nigeria and the UAE, which had announced plans to build new reactors, are likely to put them on hold. Nigeria has already cancelled them.

Areva of France, the world’s largest nuclear corporation, has said that the Fukushima crisis is likely to cause delays in the construction of its new European Pressurised Reactor. The first EPR under construction, in Finland, has been delayed by 42 months, and is 90 percent over budget and mired in bitter litigation. Areva’s own EPR in France, at Flamanville, could face a moratorium on its construction, according to Electricite de France.

India's head in the sand 

Among all the countries with substantial nuclear power expansion plans, India alone has not announced a “pause-and-review” approach. India’s Department of Atomic Energy remains complacent and basically denies the gravity of the Fukushima catastrophe. Its first response to the core damage, leading to a hydrogen explosion, was: “It was purely a chemical reaction and not a nuclear emergency….” DAE secretary Srikumar Banerjee described the unfolding disaster as “an unusual situation due to natural disaster”.

Nuclear Power Corporation chairman SK Jain was even more blasé: “There is no nuclear accident or incident …. It is a well-planned emergency preparedness programme …to contain the residual heat after … an automatic shutdown.

A fortnight later, the DAE admitted that the Japanese disaster was serious, but said such accidents cannot happen in India; the DAE’s safety systems are superior. It even denied the possibility in respect of two reactors at Tarapur, of the same design (General Electric’s Boiling Water Reactor) as Fukushima’s. The DAE said its installations would withstand major earthquakes and tsunamis. Jain boasted: “We have got total knowledge … of the seismic activities. Worst seismic events and tsunami have been taken into consideration in our designs.” But TEPCO had made similar claims.

The DAE’s record of safety is embarrassingly bad for a small nuclear programme which contributes less than 3 percent to national electricity generation. The DAE has exposed hundreds of workers to radiation doses above the maximum permissible limit, including over 350 by the early 1980s at Tarapur alone.

DAE installations have witnessed serious accidents. In 1993, a fire broke out at Narora, less than 200 km from Delhi. It started in the turbine room because of unsafe practices against which the manufacturer had warned. It spread to the reactor building. The management panicked and violated emergency protocols. The fire ended accidentally, not by design.

At Kaiga, a containment dome being built over a reactor—the last line of defence in case of a radioactivity leak—collapsed. The design and construction methods were faulty. It is too frightening to think of the consequences had this happened with a working reactor.

In 1995, the Rajasthan Atomic Power Station leaked radioactive waste into a lake for two months. In 2003, six workers at the Kalpakkam reprocessing plant were exposed to excessive radiation doses—admittedly “the worst accident in radiation exposure in the history of nuclear India”.

Kaiga also witnessed suspected sabotage in November 2009, when workers were found to have high levels of tritium in their urine. Tritium, a heavy isotope of hydrogen, is toxic and raises the likelihood of cancer. According to the plant authorities, it was spiked into a drinking-water cooler. The saboteurs were never identified. Nor is it known how they had access to the tritium, and how they could insinuate it into the sealed cooler.

The DAE refuses to acknowledge the thorny problem of nuclear wastes, generated at every stage of the so-called “nuclear fuel cycle”, from uranium mining to reactor operation to spent-fuel storage or reprocessing. High-level wastes remain hazardous for thousands of years. Science has no way of safely storing them for long periods, let alone neutralising them.

The DAE has got away with unsafe practices because it is not subject to public scrutiny or regulation. India has no independent authority that can evolve standards and regulate reactors for safety. The Atomic Energy Regulatory Board is toothless and dependent for its budget, equipment and personnel on the DAE. The Atomic Energy Act 1962 allows the DAE to conceal any information it likes.

Changes to the Indian nuclear power policy

After Fukushima, the Indian government has come under public pressure to review the nuclear programme. A recent statement signed by 60 eminent citizens said: “We strongly believe that India must radically review its nuclear power policy for appropriateness, safety, costs, and public acceptance, and undertake an independent, transparent safety audit of all its nuclear facilities, which involves non-DAE experts and civil society organisations. Pending the review, there should be a moratorium on all further nuclear activity, and revocation of recent clearances for nuclear projects.” (Available at www.cndpindia.org)

The government is still resistant to proposals to pause and review its nuclear programme. But Prime Minister Manmohan Singh has hinted at limited change. He reminded DAE scientists on March 29: “The people of India have to be convinced about the safety and security of our own nuclear power plants. We should bring greater openness and transparency in the decision-making processes … and improve our capacity to respond to the public desire to be kept informed about decisions and issues that are of concern to them. I would like to see accountability and transparency in the functioning of our nuclear power plants.

He added: “I have already directed a technical review of all safety systems of our nuclear power plants using the best expertise available ….” However, it is not clear if this review will be done by an independent body which includes non-DAE experts and civil society organisations. The only significant commitment by Singh is to “strengthen the AERB and make it a truly autonomous and independent regulatory authority ….” India may separate the AERB from the DAE. But to be effective, a reorganised AERB must include independent experts and not brainwashed scientists who believe that nuclear power is inherently safe, indispensable and desirable. But even a reformed AERB won’t be enough. If India wants to avert nuclear disaster, it must radically rethink its nuclear power policy.