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On March 11 last year a magnitude 9.0 (Mw) earthquake hit off the coast of Japan triggering a powerful tsunami and resulting in the most serious nuclear accident since Chernobyl. Over 15,000 people were confirmed dead as the tsunami inundated a total area of approximately 561 km2 (217 sq mi) in Japan. A series of fires and explosions within the Fukushima Daiichi nuclear power station triggered a full meltdown in three reactors whilst a fourth was significantly damaged by fire. The Fukushima Daiichi nuclear disaster was rated as a level 7 (major accident) on the international nuclear and radiological event scale. Now, one year after the disastrous events unfolded, nuclear and disaster experts examine the current situation and what lessons can be learnt.
Below are comments from Australian experts provided by the Australian Science Media Centre. The collaboration between the Australian Science Media and the Science Media Centre of Japan is supported by the Commonwealth through the Australia-Japan Foundation which is part of the Department of Foreign Affairs and Trade.
Dr Don Higson
Retired nuclear safety specialist and Fellow of the Institution of Engineers Australia, Fellow of the Australasian Radiation Protection Society
On Engineering
At Fukushima Daiichi, the reactors shut-down safely when struck by the fourth largest earthquake ever recorded. The nuclear emergency was due entirely to loss of on-site power supplies when the power station was inundated by a much larger tsunami than had been anticipated in its design. Clearly, the design of nuclear plants against the risk of flooding needs to be brought up to the level of design against seismic risk.
On the health effects
Rating the nuclear accident at Fukushima as 7 on the International Nuclear Event Scale (INES) has given the misleading impression that it was as bad as the Chernobyl accident. At Fukushima, no physical health effects of radiation have been observed among the general public and effects on workers have been far lower than those at Chernobyl. The INES was meant to aid public understanding of nuclear safety but has, in fact, made it more confused. The INES should be substantially modified or scrapped.
As at Chernobyl, the major public health effect of the Fukushima accident has been psychological, due to the forced relocation of population and exaggerated fears about radiation. In such circumstances, the public must be evacuated from the area as a precaution when it is not known how the situation will develop. However, they would be better off being allowed to return to their homes once it is certain that the situation is under control and that potential exposure levels are no greater than 20 mSv/y. Many people in the world are exposed naturally to higher levels of radiation than this without discernible adverse health effects. It is counterproductive to behave as though 20 mSv/y is a dangerous dose rate.
On the safety of nuclear power
Outside the former USSR, the nuclear industry continues to be one of the safest industries in which to work and the safest way to generate most of the electricity the world needs.
Dr John Price
Currently a consulting engineer. He was a member of the Safety Policy Unit of the National Nuclear Corporation UK where he studied major nuclear power accidents
After the Three Mile Island Accident of 1978, people like me who advocated nuclear power said two things about that incident: the safety systems at the station had contained the radiation and that ‘lessons had been learnt’. What Fukushima demonstrates is that no lessons are ever really learnt. These lessons are many and deep. As an example, there was a very practical lesson from Three Mile Island. Once the fuel cladding overheats, the zirconium metal in the cladding reacts with water to produce hydrogen gas.
The appearance of hydrogen gas during the accident at Three Mile Island caused major alarm, though in the end no damage. So why was no lesson learnt? At Fukushima the buildings of reactors 1 and 3 actually exploded violently while the world watched on television. Unit 2 also probably had a hydrogen explosion inside its containment and this may have caused leaks. Why, given the events of 1978, were the plants at Fukushima, and indeed nuclear plants worldwide, not fitted with the fairly simple means of dispersing hydrogen gas to prevent explosion?
I regard the damage caused by the hydrogen explosions to be the main reasons why recovery from the Accident at Fukushima will take a much, much longer time than some suggest. In a statement that went viral around the world in the week of the Fukushima accident, I said that clean-up will take 50 to 100 years. I still think this is the likely timeframe.
There have been other, more fundamental lessons which were not learnt. Can there ever be proper regulation of Nuclear Power, or indeed any other major risk? Are not the regulators always part of the cause of the accident? For non-nuclear examples, think of the Gulf of Mexico oil spill. Think of situations where people are permitted to build cities in areas subject to Tsunami. Think of recent financial crises. Whoever authorises something also has responsibility for its consequences. They own the benefits and they own the disasters.
Once the plant was agreed to be built, there were many bargains struck between the Japanese regulatory authorities and Tepco, the owner of the Fukushima plant. No matter which government department had been the regulator, no matter how independent the regulator might have wanted to be, compromises had to be made.
Here are some questions which we might hope should have been asked during regular licensing discussions:
· What emergency equipment should be provided for accidents beyond the design basis of the original design?
· What was to be the size of the Tsunami protection?
· Should Fukushima Units 1-4 have been operating in 2011?
All of these questions have associated major costs, whatever the answers. In each of these discussions, the regulator would want more and more expensive things, and Tepco would seek a financially possible compromise.
The last question, as to whether Daiichi 1-4 should have been operating in 2011, seems to have the easiest answer. No. It was an old superseded plant, in the wrong place. Fukushima Daiichi Unit 1 started operation in 1971 using 1960s designs. Units 2 to 4 also used the same design, though they are slightly larger. By the late 1970s, the designer of this type of plant, GE of USA, had already replaced Daiichi’s Mark 1 design of reactor with a design that they said was safer. By the 1990s even safer plants were being offered.
In retrospect, the decision as to whether the units should have had their licenses extended seems reasonably easy for Japan in the 1990s. Replacement could have been planned, new and safer plants could have been built. And nuclear energy would still be fulfilling its promise for Japan. Instead, a different decision was made. They fitted new tyres to their 1971 banger rather than buying the newer and much safer model. I assume that we will eventually find out what happened during regulatory discussions about the Daiichi plants in the 1990s. Whatever did happen in these discussions, the wrong decision was made for Japan, and for the world.
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