Australasian Science: Australia's authority on science since 1938

Fukushima: one year on

By Various experts

A year since a magnitude 9.0 earthquake hit the coast of Japan, triggering a powerful tsunami and resulting in the most serious nuclear accident since Chernobyl, nuclear and disaster experts examine the current situation and what lessons can be learnt.

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Dr Don Higson is a 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.”

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Dr John Price is 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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Dr Pradip Deb is a Senior Lecturer in Medical Radiations at RMIT University

“The Fukushima Daiichi accident has been one of the two major accidents in the international nuclear and radiological event scale (INES) in the last twenty five years (the other one was Chernobyl). The latest IAEA (international atomic energy agency) status report shows that the estimated external doses to the public from the cities within 20 kilometres from Fukushima Daiichi reactors are within the acceptance level for the public (1 mSv). Food monitoring data shows that in more than 99% samples (based on 14344 samples) the radioactive caesium and iodine isotopes (Cs-137 & Cs-134 and I-131) are within the acceptance level.

It is not practical to say that the world should be free of nuclear power. The next generation power reactors will be safer. The lesson we have learnt again is that it is radiophobia that harms us psychologically more than actual radiation doses do. Not only in the developing countries, but also in the technologically advanced countries, people are likely to believe unscientific reasoning about the effects of radiations. Topics of Radiation physics are currently not included in the school curriculum in most of the countries in the world, not even in Japan. To reduce radiophobia, the radioactivity and their effects should be understood by the general public. One way to make the public more trusting of radiation issues is teaching radiation physics starting from the school level science education.”

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Professor James Goff is Director of the Australia-Pacific Tsunami Research Centre and Natural Hazards Research Laboratory, University of New South Wales

“A year on from the 2011 Tohoku tsunami and we are still asking questions, more than we have answers to. I have been invited by Tohoku University in Sendai to attend a special ‘One-year Memorial of the 2011 Tohoku Earthquake and Tsunami Disaster’. This will happen on the same day as a ‘Forum for International Research Collaboration’. This will be the fourth visit by people from our centre. First in May to carry out some of the earliest international research on the tsunami – how big it was, what it left behind and so on. We visited again in August to revisit this work and to see how things had changed. Currently a member of our team, Dr Catherine Chague-Goff, is also on a Visiting Professorship to the University of Hokkaido. Why so much commitment? Essentially because we want to help the Japanese to understand the 2011 event, its precursors and other events in the region. However, we are also committed to helping our Japanese colleagues. Our centre has skills that the Japanese are interested in exploring and we are keen to work in collaboration with them to make this happen.

What have we learnt so far? Well, one of the more interesting finds in that for nearly 50% of its inundation distance inland the tsunami left almost no sand deposit, just mud and debris. Who cares? Well, if you are looking at how big and how often these events have happened in the past – you need to look for more than just the sand or else you might under-estimate things. Hence the interest in our work and what we have done elsewhere. We have also learnt a lot about the longer term after effects of these events. What one might call the ‘what are things like on the ground one year on’. Yes, much of the debris has been being cleared up, yes much of the evidence of destruction has been erased by diggers and work crews, but what seems a minor point is starting to become an issue - there is still a vast amount of salt in the soil and rice doesn’t like salt – and so in these places crops are hard to grow. There are implications here for long term recovery. Add to this things such as the loss of communities, poor roads, contaminated land and the sheer enormity of the devastated area and you can see that there is no simple fix.

We are returning to Sendai again to start putting the 2011 events in context. We really do need to know how big and how often these events occur because we don’t want to under-estimate the next one, not just in Sendai but for the whole of Japan. We also want to take these lessons with us to the rest of the Pacific so that we can do a better job there as well. Whether we can achieve this quickly or not remains to be seen. We all still have lots to learn.”

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Tatsujiro Suzuki is Vice-Chairman of the Atomic Energy Commission in the Japanese Cabinet office

“The present circumstances assure that Fukushima Daiichi is remarkably stable. However, the condition of the reactor core is not understood and there are still many mysteries about the nuclear reactor.

At present the main concern is the radioactive material being discharged in large quantities into the air. However, I think that this is a short-term concern. I feel as a future prospect, the treatment of contaminated water being generated in large quantities would be more important. The water is being processed; it however is not decreasing. The people at Fukushima Nuclear Power Plant are suffering a lot due to this. The influx has already entered the sea. Effort is being made to build a fence, however this would take time. Groundwater is flowing under the power plant; hence one has to keep watch on underground penetration. In the case of the contaminated water, a liquid waste disposal process has to be set up as it is a high level radioactive waste.

Robots started operating at the power plant a few days ago. However, in the long run, measures have to be taken against the discharge of nuclear fuel. According to an expert of the Atomic Energy Commission, it would take around 30 years for the complete containment of the Fukushima Daiichi accident. There are many matters which have not been experienced so far. Atomic energy experts as well as the best brains from the world over must come together to find the solution to this problem. The government is working towards forming such a system.

When we talk about the area outside the nuclear power plant, the contamination is spreading and a feeling of insecurity has developed amongst the citizens. Hence I think it is necessary that the government and the power company should have a deep sense of responsibility and should search their conscience. I think that the contamination outside the nuclear plant would not affect the health of the citizens. I, however, am extremely sorry that the entire country has fallen into despair due to this.

The government now is trying its best for decontamination. First of all, it is important to provide accurate information for monitoring. Disbelief still exists in the figures provided by the government. The government is putting in effort, but there might be problems in the approaches adopted. The style of communication is bad, the efficiency is poor, the process is not well designed; hence the residents are not feeling relaxed as yet. ICRP is also stating that the residents should be taken into confidence and then decisions should be made together. However the scene has not yet changed. Things are decided by the scientists all by themselves and then they are simply conveyed. The decision making process is not convincing. Therefore there exists a sense of distrust. And this has to be changed.

In the case of decontamination, the standards for external exposure (to radiation) have been set. The annual external exposure of any area should be less than 20mSv. If this isn't the case, people are not permitted to live there. However if it is less than the set standard, the residents can return to their homes. Hence, in the short run it is important that the areas with external exposure of 1~20mSv are decontaminated and made available for the residents. At present, data collection for decontamination has been stopped. It would, however, being full scale from April. As far as decontamination is concerned, there are challenging topics such as the hot spots (the area where the radiation dose is high locally) being jumbled up and the contamination levels desired by the agricultural people and those desired by the common man are different etc. Normally, monitoring is required to be done along with the residents before the decontamination. However it could not be done in this case. In addition, the present grid of monitoring is oversized. If possible it should be done within 100 meter ×100 meter. Even this is not feasible due to shortage of manpower. We would like to collaborate with various people and find out the best approach.

In the long run, it is necessary to differentiate between areas where residents can return and those where they cannot. This should be done at the earliest possible time. However, this needs a political decision. The residents build up expectations when the scientists state that “decontamination is possible”. However the areas where residents cannot return need to be clearly decided with the judgment of experts.

In addition, the citizens have a sense of distrust concerning the safety of other nuclear power plants. This was a tsunami and earthquake beyond the control of the safety standards. Hence now new standards should be created which would factor in such disasters. And the nuclear power plants must comply with these new standards. It is very difficult to create new safety standards in a short time span. Therefore, a stress test needs to be conducted. It seems that easy-to-follow restart criteria are not yet given. I think it is not necessary from an energy demand and supply point of view. However, if a new regulatory agency is formed then it would specify the standards of restart for the nuclear plants which are not operational at present. The new regulatory agency would do its best to convince the residents and make the nuclear plant operational.

Future energy policy of Japan
As far as energy policy is concerned, in the short run, the demand and supply measures for this summer must be formulated. Relevant data is now being collected. Investigations are also being made on the assumption that electricity generated using nuclear power would be zero.

In the long run, the only decision that has been made is that dependency on nuclear power plants would be reduced. Discussion over the future energy mix is not clear. The government has promised that it would provide the alternatives by this spring and things would get decided with a national debate in summer. As national debate is a new concept, it would require cooperation from the government as well as the entire nation including experts from various fields. We need to urgently find a process which would convince everyone that “The decision was taken after a debate”.

A significant philosophy needs to be formed to decide the energy mix with certain standards, as a society. I think apart from the debates by the government commission, it would be better if the debates are done everywhere and communicated to the government at the end.”

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Assistant Professor Hiroaki Koide is from the Kyoto University Research Reactor Institute

Things which have been learnt one year after the Fukushima disaster
We’ve realized that we don't know anything. If the accident was at a thermal power plant, it would have been possible to inspect the actual accident site and find out the details. However, in the case of a nuclear power plant disaster it is not possible as there are radioactive materials. The people who were promoting nuclear power generation so far say that the disaster was “unanticipated". As the accident was unanticipated, the measuring devices required to investigate the cause of the disaster are also not installed. Furthermore, the so-called measuring devices which were installed have broken down. It is of utmost importance to know the whereabouts of the nuclear fuel, and the melted reactor core. These facts however are not known.

Future prospects
If we talk about the scene at the nuclear plant, then the problem is that we don't know the extent the melted reactor core would spread to. It would be important to know the kind of measures that would have to be taken to prevent the spread of the contamination. If the melted reactor core drips underground and comes in contact with groundwater, radioactive material would spread in the environment. Therefore, it is important to set up barriers beforehand and prevent such contact.

Another problem is the spent nuclear fuel in the pool. Daiichi reactor 4 has been badly damaged. Efforts should be made to prevent further damage to this pool. This, however, is difficult due to frequent aftershocks and the high radiological dose levels. In the event of a big aftershock and the pool breaking down, the spent nuclear fuel would spread in the environment in the absence of a barrier. The workers have already started clearing up the debris. Moreover TEPCO might be looking at this problem as a top priority.”

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Assistant Professor Tetsuo Sawada is at Research Laboratory for Nuclear Reactors Energy Engineering at the Tokyo Institute of Technology

“Various events occurred within a week of the disaster. If the systems before the disaster are compared with those afterwards, does it develop as expected? If the condition of the reactor core is taken into account, then the fuel of the reactor cores is damaged from Daiichi reactor 1 to Daiichi reactor 3. And a significant proportion of the core fuel has melted. It is not very clear about the exact quantity of the core fuel that is damaged and whether it has spread in the furnace. There is a possibility that some fuel might have leaked out of the containment vessel and some quantity has melted. I think there is no marked change according to the circumstances reported by the Tokyo Electric Power Company (TEPCO) a few days after the Fukushima disaster. For example, if Daiichi reactor 1 is taken into consideration, then it is not clear whether the percentage of the core fuel that has melted is 70 or 100.

The problem of contamination and decontamination of any region due to radioactive material is a serious issue. It has been confirmed that in late March radioactive material was dispersed in areas including Itate, Fukushima Prefecture. The quantity of the discharged radioactive material and the dispersed radioactive material distribution has not changed a lot since then. Major emission into the environment stopped immediately after the disaster. However, the problem is coping with the substances that have already been discharged. Air dose rate observed in Minamisoma and Itate has not yet reduced. The matter has become serious as the circumstances are very difficult to comprehend and deal with. And it can be said that now the seriousness of the matter has increased from last March-April.

There is one more point which needs to be considered seriously. Areas within a 20-kilometer radius of the plant have been left uninhabited. This area was declared as a 'no-go’ zone. However, this area has been neglected over the past year. The rubble caused by the tsunami and the wreckages of houses due to the earthquake etc. are all lying untouched. If the situation continues like this then there would be much deterioration and decay. Furthermore, if there is new vegetation growth then it would advance the immobilization of the radioactive material. It has been also heard from the residents who have returned that the circumstances are getting worse due to the stand adopted.

How does one process and control the radioactive material that has been discharged into the environment? How can the people from the affected area cope with the radioactive material? These issues are very important. However, their solution is difficult. There was some information available from the knowledge gained following the Chernobyl accident, regarding the discharge of cesium in large quantities. However, I now comprehend the present circumstances and their gravity, after my frequent visits to Minamisoma and Itate, listening to the tales of residents after the actual discharge. It can be said that even my thoughts have changed.

An atomic energy regulatory agency is to be established in April. It seems that though the organizational structure of the agency would change, the content would be almost the same. I, however, am not clear as to how it should be. Neither am I in a position to comment on it. The future concern is the measures for the Daini power plant. There are frequent big earthquakes in this area following the earthquake in Sumatra in 2004. The possibility of a future earthquake of the same magnitude and that could possibly lead to a tsunami also exist. If such a situation occurs then the Fukushima power plant will become even more compromised. The circulatory system of the cooling pool of the reactors need to be maintained. It is necessary to have preventive measures in order to maintain the present cold shutdown, just in case something else goes wrong.

Lastly, there is another concern regarding the water shielding wall. At first, there was a situation when the water accumulated in the reactor building and the trench would not lessen even after being pumped out. The chances of groundwater leakage have been stated. Therefore it was decided to build a water shielding wall as a temporary measure. Since it would cost approximately 100 billion yen to build it, TEPCO took the stance that it would only build it if it got support from the Government. As a result the plan was cancelled. Even at this point in time, the relation between the groundwater flowing under the power plant and the water flowing outside it is not known. There might not be a leakage of contaminated water on a large scale. The question of quantity remains. I think there is a possibility of leakage being present at the moment.”

Source: AusSMC