Fukushima – overview

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This page last updated 17 April 2011.

1. What happened at Fukushima?
2. How serious were the accidents, and was there a meltdown?
3. What health effects are likely?
4. Is there a safe level of radiation?
5. What other effects can be expected?
6. Are there ay similarities between Fukushima, Chernobyl and Three Mile Island?
7. How dependent is Japan on nuclear power?
8. Are modern reactors safer than the ageing Fukushima boiling water reactors?
9. What does the future hold for nuclear power now?
10. Are Australia’s uranium companies in any way responsible for Fukushima?
11 Videos of the Fukushima disaster

1. What happened at Fukushima?

The March 11 earthquake and tsunami wreaked havoc on TEPCO’s Fukushima Daiichi nuclear plant on the north-east coast of Japan. Electricity supply from the grid was lost, and back-up generators and water pumps were incapacitated by the tsunami. Insertion of control rods automatically shut down three operating reactors (the other three were offline for maintenance) but the reactor cores still required active cooling. Likewise, spent fuel stores within the reactor buildings required active cooling.

Short-life batteries provided power to operate cooling systems but later efforts to use portable generators had mixed success. Problems arose because of incompatible generator connectors, high radiation levels restricting access to the reactor buildings and surrounds, and damage to the cooling systems as a result of the earthquake and tsunami. Fresh water supplies were depleted, hence the use of corrosive sea water which will ensure that the affected reactors never operate again.

With cooling systems failing or operating intermittently, temperature and pressure readings increased within some of the reactor pressure vessels, within the concrete containment structures which contain the steel pressure vessels, and within spent fuel pools. Unorthodox cooling methods – helicopter water drops, fire engines and water cannons − had mixed success.

Water boiled, leaving fuel elements exposed in four reactors and in some spent fuel pools.

At reactors #1, #2 and #3, pressure from the reactor vessels rose several times to the point that it required release of radioactive steam to the outer building.

Nuclear fuel interacted with water to produce hydrogen which collected at the top of buildings housing some of the reactors. In reactor buildings #1 and #3, hydrogen explosions blew apart the outer shell of the reactor buildings. In the reactor #2 building, a hydrogen explosion occurred due to pressure build up in the pressure suppression chamber beneath the reactor.

Pressure and temperature readings fluctuated, as did water levels in reactor vessels and spent fuel pools. Some measuring instruments were destroyed.

A fire erupted in the reactor #4 building − this was one of the reactors that was offline for maintenance when the earthquake and tsunami hit. The #4 spent fuel pool was of greatest concern because it contained the most amount of spent fuel − 250 tonnes compared to 50−100 tonnes in reactors #1, #2 and #3. In the #4 spent fuel pool, fuel was exposed, hydrogen produced, and a hydrogen explosion occurred.

Spent fuel pool problems were also evident in reactors #1, #2 and #3. It appears likely that spent fuel rather than reactor cores may be responsible for most of the radiation releases to the environment. As late as March 20, the International Atomic Energy Agency reported that it still lacked data on water levels and temperatures for the spent fuel pools at reactors #1, #2, #3 and #4. In reactor #3 there was concern that the pool may have been compromised by the explosion. In reactor #4 there was concern that fire had damaged the pool.

At the time of writing (April 4), efforts to stem leaks of highly radioactive liquid are meeting with little success.

The emergency response involved some difficult dilemmas. For example, water was required for cooling, but the injection of water also increased the risk of a ‘criticality accident’ involving a restart of nuclear chain reactions (which would have generated still more radioactivity and heat and exacerbated existing problems).

High temperature and pressure readings were recorded in reactors #5 and #6, with the spent fuel pools being of particular concern, but the situation was slowly brought under control. Holes were deliberately created to vent hydrogen to reduce the risk of explosions.

It seems there was little or no damage to the common spent fuel pool or to the dry spent fuel storage building at Fukushima Daiichi.

TEPCO has announced that four reactors will be permanently shut-down and decommissioned (easier said than done) and that plans for two new reactors at the Fukushima Daiichi site have been cancelled. The fate of reactors #5 and #6 is uncertain.

At the nearby Fukushima Daini plant, which has four reactors, cooling was compromised and overheating occurred in three reactors, but the situation was fairly quickly brought under control.

2. How serious were the accidents, and was there a meltdown?

On the International Nuclear and Radiological Event (INES) scale of the International Atomic Energy Agency, the accidents and incidents at reactors #1, #2 and #3 were rated a Level 7 “Major Accident”. Level 7 is the most serious level on INES and is used to describe an event comprised of “A major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures.” The reactor #4 accident is rated Level 3 (‘Serious Incident’). The problems experienced at Fukushima Daini reactors #1, #2 and #4 were rated Level 3 on the INES scale.

Fuel degradation and melting is very likely to have occurred. In that limited sense there were ‘meltdowns’ in some reactors and spent fuel pools − but it is an imprecise and sometimes unhelpful term. A complete reactor meltdown would be of no consequence unless it resulted in significant radiation releases. Radiation releases, in turn, are of no consequence (to humans, at least) if they do not result in direct exposure or exposure via contaminated food or water.

3. What health effects are likely?

Workers have suffered serious injuries and in some cases large radiation exposures (though insufficient to cause the symptoms of acute radiation poisoning).

In terms of the broader public health impact, explosions and fires are the last things you want to see in nuclear reactors − they provide a means for widespread dispersal of radionuclides. Radiation readings within and beyond the reactor plant fluctuated considerably. To give an example, one reading indicated that a member of the public 20 kms from the reactors would have received their annual ‘allowable’ limit in just three hours. Elevated radiation levels were detected as far away as Tokyo and beyond.

On the other hand, while there may have been some damage to containment vessels in one or two reactors, the damage fell far short of the complete obliteration of containment at Chernobyl. Spikes in radiation readings were just that − only within the nuclear plant were high readings detected over a significant period of time. Much of the radiation appears to have been short-lived (as opposed the large release of long-lived radionuclides from the reactor core at Chernobyl). The decision to establish a 20 km evacuation zone reduced human exposures to radiation as did the later decision to evacuate some more distant locations with relatively high contamination (conversely, there is controversy as to whether the Japanese government ought to have established wider evacuation zones and to have done so more quickly). The government supplied stable iodine tablets to people leaving the 20 km evacuation zone and recommended precautionary measures in the 20−30 km zone.

To estimate the death toll from Fukushima, it will be necessary to estimate the total human radiation exposure as a result of the accidents. The standard risk estimate for low level radiation can then be applied. It is far too early to be attempting those calculations for Fukushima, but we can apply the logic to Chernobyl. Total radiation exposure from Chernobyl was 600,000 Sieverts according to the International Atomic Energy Agency and thus an estimated 30,000 people will die, nearly all of them because of cancers induced by low level radiation exposure. Plausible estimates of the Chernobyl death toll range from 9,000 to 93,000.

The Japanese Nuclear and Industrial Safety Agency estimates that the amount of radioactive material released to the atmosphere is approximately 10 percent of the 1986 Chernobyl accident.

Overall, many, many thousands of people must have received very small doses of radiation as a result of the Fukushima emergency. It seems likely that the estimated death toll will be far smaller than Chernobyl. However the situation is still fluid, with ongoing radioactive leaks and ongoing difficulties cooling the reactors. Radiation releases are continuing — indeed a TEPCO official said at a media conference on April 13 that: ”The radiation leak has not stopped completely and our concern is that it could eventually exceed Chernobyl.”

4. Is there a safe level of radiation?

A great deal of the commentary around the Fukushima emergency has implied that low level radiation exposure is safe or harmless. However the overwhelming weight of scientific opinion holds that there is no threshold below which ionising radiation poses no risk − this is the ‘linear no-threshold’ model.

The Committee on the Biological Effects of Ionising Radiation of the US National Academy of Sciences comprehensively studied the issue and concluded that “the risk of cancer proceeds in a linear fashion at lower doses without a threshold and … the smallest dose has the potential to cause a small increase in risk to humans.”

The issue is inherently complex and thus the Committee noted that the linear no-threshold may understate or overstate the true risks of low-level radiation: “It should be noted however, that even with the increased sensitivity the combined analyses are compatible with a range of possibilities, from a reduction of risk at low doses to risks twice those upon which current radiation protection recommendations are based.”

5. What other effects can be expected?

In addition to the health impacts, other effects of the Fukushima accidents include: the expense and trauma of relocating approximately 200,000 people; a big hit to the tourism industry and a significant broader economic impact; and horror stories emerging from the exclusion zone such as hospital patients being left to suffer and die as staff fled.

6. Are there any similarities between Fukushima, Chernobyl and Three Mile Island?

They were different types of accidents.

Chernobyl involved a steam explosion in an operating reactor which quickly exposed the reactor core to the environment, followed by a protracted graphite fire which spread radiation far and wide.

Three Mile Island involved significant nuclear fuel melting in the reactor core, but this was largely contained.

Fukushima resulted from limited access to electricity and compromised water cooling systems (as a result of an earthquake and tsunami), leading to a cascade of events including exposure of fuel and spent fuel as water levels fell, fires, explosions, and emergency responses compromised by radiation levels, fresh water shortages, etc.

In terms of their health effects, Three Mile Island led to only small radiation releases and exposures; the impact of Fukushima will be greater; and Chernobyl was the worst of the accidents.

7. How dependent is Japan on nuclear power?

Before Fukushima, 55 reactors supplied 30% of Japan’s electricity. Two reactors were under construction and 12 more were planned. At least four of the Fukushima Daiichi reactors, and possibly all six, will never operate again. It is unclear how the Fukushima emergency will affect Japan’s nuclear power expansion plans.

A pattern of mismanagement, accidents and scandals in Japan’s nuclear industry is reflected in public opinion. A 2005 survey by the International Atomic Energy Agency found that just 21 percent of Japanese citizens supported the construction of new reactors; 76 percent were opposed. Of the 18 countries surveyed, only four were more strongly opposed to the construction of new nuclear reactors. In Japan as elsewhere, the Fukushima emergency is bound to weaken support for nuclear power.

8. Are modern reactors safer than the ageing Fukushima boiling water reactors?

Mostly, yes. But there are numerous other boiling water reactors with similar vulnerabilities as the Fukushima reactors.

All reactor types − existing an envisaged − have their vulnerabilities. If you want to dig into these debates, check out some industry literature and compare it with the analyses of NGOs such as the International Panel on Fissile Materials, the Union of Concerned Scientists or the Tokyo-based Citizens Nuclear Information Centre.

To give an example of a problem in the making, many reactors are being built in China which would not meet licensing requirements in the US or Western Europe. That problem is compounded by secrecy, by uneven and often inadequate training of workers, by the jailing of nuclear industry whistleblowers, and by tight constraints on media reporting.

Claims that the Japanese boiling water reactors were accident-prone and in no way representative of the rest of the global nuclear power fleet would have been more convincing had they been made before the Fukushima disaster. Before Fukushima, this is what the US Nuclear Regulatory Commission said: “All nuclear power plants are built to withstand environmental hazards, including earthquakes. Even those plants that are located outside of areas with extensive seismic activity are designed for safety in the event of such a natural disaster.” TEPCO made equally unequivocal comments.

As far as possible, comparative safety assessments generate data on deaths per gigawatt-year of electricity output. Unfortunately, some of the greatest hazards − such as global warming arising from fossil fuel usage, and the WMD proliferation risks associated with nuclear power − cannot be meaningfully quantified.

9. What does the future hold for nuclear power now?

Global nuclear power capacity has been stagnant for the past 20 years. Before the Fukushima accidents, nuclear power was expected to increase by 20−40% from 2010 to 2030. Now, expansion by anything more than 20% by 2030 seems unlikely − and the pattern of stagnation may persist. Ziggy Switkowski has said that the Fukushima emergency has done “a great deal of damage” to the nuclear industry and that the industry will take a “long, long time” to recover community trust.

Growth can be anticipated in a few countries − China, South Korea, Russia and India − but beyond those countries all bets are off. The nuclear industry’s hopes of establishing a toe-hold in numerous countries currently without nuclear power have likely been dealt a serious blow.

There was little indication of significant nuclear power expansion in North America or Western Europe before Fukushima (notwithstanding the hype) and the prospects for expansion are weaker now. In Australia, the Labor Government and the Coalition have ruled out the development of nuclear power.

By 2030, a large majority of reactors will be approaching the end of their operating lives or will be have been recently commissioned. This will be of concern because of the ‘bathtub effect’ − reactors are more accident-prone at the beginning and end of their lives.

10. Are Australia’s uranium companies in any way responsible for Fukushima?

Uranium mining companies in Australia refuse to say whether or not they supply the scandal-plagued TEPCO, operator of the Fukushima plant. However it is known that Australia exports large volumes of uranium to Japan − nearly 2500 tonnes in 2008 − and TEPCO is certainly one of the customers.

The uranium industry angrily rejects any suggestion of culpability. According to a March 18 statement from the Australian Uranium Association: “The Australian uranium industry has led the global nuclear industry’s efforts to create a framework of stewardship for the safe and responsible management of uranium throughout the nuclear fuel cycle.”

However “efforts to create a framework for stewardship” is managerial jargon shrouding the inaction of the industry. The Australian uranium industry sat on its hands and did nothing even as it was revealed that TEPCO and other Japanese nuclear utilities had systematically and routinely falsified safety data and breached safety regulations for decades, even as a 2007 report detailed 97 incidents of ‘malpractice’ at Japan’s nuclear power plants, and even as the ability of Japan’s nuclear plants to withstand earthquakes came under criticism from industry insiders.

11. Videos of the Fukushima disaster

Two corporate videos below – after you press play, press the red cc button for English subtitles.

Jim Green
Friends of the Earth, Australia