On March 11 last year a magnitude 9.0 earthquake hit off the coast of Japan triggering a powerful tsunami.
Resulting waves reached heights of 40 metres and pushed a wall of seawater inland as far as 10 km in some regions. The human toll was immense, with over 15,000 people confirmed dead and an additional 4,000 missing.
Following the tsunami, 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 disaster, the Science Media Centres in New Zealand, Australia and the UK have rounded up comments from natural hazards and nuclear experts to examine the current situation and what lessons can be learnt.
NB: The AusSMC hosted an online briefing on this issue with Japanese, UK and Australian experts – a recording is available here.
All of the SMC expert round-ups and backgrounders issued in the wake of the earthquake a year ago have been collected here.
“In October 2011, my colleague Stuart Fraser and I interviewed local disaster prevention officials and emergency services officials in Iwate and Miyagi Prefectures in collaboration with local academics and researchers. We want to learn from the successes and problems that occurred during the tsunami evacuation on 11th March 2011.
“We found that people’s immediate evacuation in response to the ‘natural’ warning of long earthquake ground shaking (lasting more than 2 minutes) was vital in saving lives. Official warning broadcasts caused confusion when transmission failed due to power outages, and there was some public complacence following many previous false alarms. Many deaths resulted from people delaying evacuation, travelling into or through the evacuation zone unnecessarily, and trying to evacuate by car.
“We also found that ‘vertical evacuation’ — people taking refuge in sturdy multi-story buildings above the tsunami level — saved many lives. Our ongoing research is focussing on how to designate existing buildings, or design new ones, for vertical evacuation in New Zealand.”
Professor James Goff is Director of the Australia-Pacific Tsunami Research Centre and Natural Hazards Research Laboratory, University of New South Wales, comments:
“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.”
Jose C. Borrero, Senior Consultant, ASR Limited, Adjunct Assistant Professor, University of Southern California, Tsunami Research Center comments:
“I did a real time tsunami hazard assessment using computer simulations on the night of March 11th. This was the first time this technique had ever been done in New Zealand, and the results from my work were used to upgrade the tsunami threat levels in the northern part of the country.
“We (the tsunami research community) in New Zealand totally underestimated the extended duration of the tsunami hazard from this event. While the tsunami arrival was at 7 or so in the morning, the strongest effects were not seen until lunch time or later. This caused many problems and numerous close calls, particularly in Whitianga, Port Charles and Tutukaka.
“In Whitianga there were several near collisions as boaters taking part in a fishing tournament and power boat race that day returned to the harbour in the afternoon. At Port Charles (northern Coromandel Peninsula) there was overland flooding, and some houses were even inundated. People were in danger and were lucky the tsunami was not any bigger.
“I am currently adapting computer simulation tools to work with worldwide standard tsunami modelling systems. This is an effort to set up a real time tsunami model for far field events (this type of system will only work for tsunami coming from sources more than 4 hours away)
“There was a huge amount of data recorded in New Zealand waters, on tide gauges, observationally, on video and with current meters. between this event (Japan 2011) and the Chile 2010 event, we have a very thorough set of data with which to look at the overall far-field tsunami issue for New Zealand and we can use this data to get a much better understanding of what might happen fro future far-field events originating from other likely tsunamis sources around the Pacific Rim (Cascadia, Alaska or Northern Chile).”
Professor Paul Hunter, Professor of Health Protection (University of East Anglia) and Editor of the Journal of Water and Health, comments:
“The Japanese have put a lot of effort into rebuilding the main roads through the affected areas and clearing away the rubble. There are mountains of rubble waiting to be sorted and then sent to landfill (the rubble contains many valuable metals such as iron etc. that they will not want to waste). This will take quite a few years to complete. The main WWT plant that we visited is now able to do primary treatment and chlorination but will not be back to full effectiveness for about 4 years, though when complete will be a state of the art plant much improved on the old one.
“There is a major problem with rebuilding in some areas in that after the tsunami receded it took with it sediment and the land dropped 40 to 60 cm in many places which makes a lot of the land below the level of high tide. So issues with building sea walls or raising land levels. Indeed the rebuilt road have been raised up
“Another problem is that the rubble mountains are fermenting and are at risk of developing spontaneous fires.
“As regards infectious disease epidemiology, there does not appear to have been major problems although my colleagues are concerned about the impact of inadequately treated sewage discharge to sea and are monitoring the situation.”
“When the first measurements began to appear of contamination levels in land around Fukushima, it quickly became clear that evacuation of the population would be for the long term. Several hundreds of square km of land have radioactive caesium levels similar to those seen around Chernobyl, so clean-up is an enormous, perhaps impossible, task. Experience from Chernobyl showed that, with massive effort, decontamination of towns can be successful by re-surfacing roads and skimming off contaminated topsoil from lawns. But clean-up of large areas of fields and woodland wasn’t even tried because of the huge expense and amounts of waste it generates. More likely, as at Chernobyl, large areas surrounding Fukushima will remain contaminated for decades, some areas probably too contaminated for people to return to their homes.
“If a Chernobyl-style permanent exclusion zone is set up at Fukushima, will it be a nuclear wasteland, or will nature reclaim the abandoned lands ? There are already reports of bird populations being damaged by radiation at Fukushima, but trying to separate the relatively small impact of radiation from all the other factors which affect animal populations is tricky. At Chernobyl, 25 years on, we have seen – often contradictory – evidence of long-term damage to wildlife, but also reports claiming the area is like a nature reserve because people are no longer hunting , fishing or farming. In 1996, Belarussian scientists even introduced the rare European Bison into the exclusion zone and the population is thriving, as are other large mammals such as deer, wild boar and wolves.
“We can’t yet say what the future of the Fukushima exclusion zone will be until we know how far decontamination is possible, and how much residual radiation the evacuees are willing to return to. But my guess would be that we’ll see another permanent exclusion zone – much smaller than at Chernobyl – which eventually will return to nature. And, as at Chernobyl, in 25 years’ time scientists will still be arguing about whether the radiation is doing long term damage to the wildlife it contains.”
Professor Richard Wakeford, Visiting Professor at the Dalton Nuclear Institute, University of Manchester, comments:
“There can be no doubt that the accident at the Fukushima Dai-ichi nuclear power station has caused genuine concern among those living in Fukushima Prefecture, and throughout Japan, about the health effects resulting from exposure to radiation from the radioactive materials released into the environment. Ordinary people are not experts in radiation risks and their fears are driven by what they know of the radiation effects seen after the atomic bomb explosions at Hiroshima and Nagasaki and after the Chernobyl nuclear reactor accident. Unfortunately, some comments that have been made in the media have unnecessarily increased public concern.
“That the Fukushima Dai-ichi accident was very serious is beyond dispute, and the reasons for it must be fully investigated. However, in an accident such as this, the consequences can be limited by appropriate actions to control exposure to radiation.
“So, unlike at Chernobyl, there have been no deaths or early health effects among the emergency workers because their doses were carefully limited. The only clear direct health effect among people living around Chernobyl is thyroid cancer in those heavily exposed as children to radioactive iodine – this was mainly due to the children drinking heavily contaminated milk because a food ban was not introduced quickly enough by the Soviet authorities. Measurements of radiation from radioactive iodine in the thyroid glands of children living near Fukushima Dai-ichi indicate that monitoring of the environment and the banning of consumption of foodstuffs where necessary have avoided this problem of high intakes of radioactive iodine. The main component of radioactive iodine (iodine-131) is short-lived, effectively disappearing from the environment after three months, so this problem has now passed.
“The major issue for contamination of the environment now is radioactive caesium (caesium-134 and caesium-137), which exists in the environment for much longer than radioactive iodine. So, monitoring of radiation exposure and contamination of foodstuffs will have to continue for some time. Modern radiation measuring instruments are very sensitive, and it is possible to detect very small levels of radiation and radioactivity – for example, it is still possible to detect very low levels of caesium-137 in food from Chernobyl contamination and fallout from nuclear weapons testing. What matters is the levels of radiation and radioactivity, since radiation and radioactivity are a natural part of the world in which we live. Measures can be taken to reduce the amount of radioactive caesium in the environment (for example, by removing topsoil) and in foodstuffs (for example, by monitoring items of food from contaminated areas), so keeping radiation exposures to acceptable levels.
“By ensuring that the damaged reactors at Fukushima Dai-ichi are stabilised such that further significant releases of radioactive materials are very unlikely, by the judicious removal of radioactively contaminated materials from areas used by people (for example, areas in villages and towns), and by the careful monitoring of radioactive caesium in foodstuffs, the risk to health from the Fukushima Dai-ichi accident can be reduced to a level that for the great majority of people in Japan is very small compared to the risks experienced in everyday life, including the risk posed by other sources of radiation and radioactivity (mainly natural sources) that are part of the everyday existence of everyone in the world.”
Tony Irwin is a Chartered Engineer and is a visiting lecturer for the Masters course in Nuclear Science at Australian National University. Tony is Chairman of the Engineers Australia Nuclear Engineering Panel. Tony worked for British Energy in the UK for more than thirty years commissioning and operating eight nuclear power reactors. Following the Chernobyl accident he was a member of a World Association of Nuclear Operators (WANO) mission that reviewed operating practices at Russian RMBK reactors. He comments:
On the sequence of events:
“We now have a better understanding of what happened :
Event Sequence – Key Events
|Loss of all AC supplies||
+ 51 mins
+ 54 mins
+ 52 mins
|Loss of cooling||
+ 1 hr
+ 70 hrs
+ 36 hrs
|Water level drops to Top of Active Fuel (TAF)*||
+ 74 hrs
+ 40 hrs
+ 4 hrs
+ 77 hrs
+ 42 hrs
|Fire pumps inject freshwater||
+ 43 hrs
+ 25 hrs
+ 87 hrs
+ 68 hrs
|Fire pumps inject seawater||
+ 28 hrs
+ 77 hrs
+ 46 hrs
|Off-site electrical supplies restored||
– + 11-15 days –
– + 14-15 days –
*Estimated source: Tony Irwin
- First core damage estimated to have occurred within 4 hours of the earthquake and reactors 1,2 and 3 cores largely melted within the first 3 days
- Hydrogen explosions caused the main damage and release of radioactivity
- Reactors stable within 2 weeks
On the Fukushima site today:
“The four damaged reactors are in a stable cold shutdown state, cooled by water circulated through a treatment plant. Site clean-up, including removal of radioactive rubble, continues. A mid and long-term roadmap for the decommissioning of units 1-4 was issued in December 2011. Phase 1 prepares for the removal of spent fuel from the cooling ponds to commence by 2013. Phase 2 prepares for the removal of fuel debris from the reactor core to commence within 10 years. The final phase completes the decommissioning of the reactors in 30-40 years.
“There are still over 100,000 people evacuated from Fukushima Prefecture. In the areas within the 20km evacuation zone with an annual radiation dose of <20mSv/year, it is expected that people will be allowed to return in March 2012. For higher radiation areas, remediation is required before restrictions are lifted by perhaps 2014.”
On nuclear power in Japan today:
“Before the accident, there were 54 reactors operating in Japan supplying 29% of the electricity demand. Since the accident, as reactors have been shut down for routine inspection (every 13 months) they have not been allowed to restart pending a comprehensive assessment of the response of individual reactors to extreme accidents (‘stress tests”). To date, the Japanese safety authorities have not approved the restart of any reactor.
“As of March 2012, there are only 2 reactors operating. Japan trade deficit is at record levels as fuel imports have soared.”
On the world situation:
“The severity of the accident and the need to ensure reactor safety in extreme events was recognised worldwide. Germany took the political decision to immediately shutdown 8 old reactors, and all reactors by 2022. Most countries announced plans to continue with nuclear power and assess the safety of their reactors. For example, the UK has confirmed the safety of their existing nuclear power plants and has recently approved design certification for two types of new reactor to be built in the UK.”
On lessons learnt:
“Reactor cooling is essential and must be maintained irrespective of external conditions. Modern reactors, for example the Westinghouse AP-1000 have passive cooling systems that require no external supplies and would have survived even this severe accident. The safety of existing reactors is being assessed to ensure they have diverse and physically separated cooling systems and electrical supplies.”
Dr Don Higson is a retired nuclear safety specialist and Fellow of the Institution of Engineers Australia, Fellow of the Australasian Radiation Protection Society, comments:
“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 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. He comments:
“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.”
Dr Pradip Deb is a Senior Lecturer in Medical Radiations at RMIT University, comments:
“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.”
“The Fukushima incident rightly caught the immediate attention of the media and led to discussions and debate about numerous aspects of nuclear power, safety, command and control following major incidents and also the perception of risk to name just a few. The level of commentary was generally balanced although there were some instances of conspicuous scare-mongering albeit generally based on poor initial information provided to the media. The events that evolved over the months following the tsunami were often easy to explain forexperienced and knowledgeable scientists. It is too easy to condemn facts and subsequent interpretation that we as scientists feel have been explained incorrectly in the media, it is essential that we maintain an awareness of how specialised some of this knowledge is. I also feel very strongly that we have a moral duty to provide, accurate, timely and digestible input to assist in the understanding of the population as a whole.
“My specialisation falls into the broad division of radiation medicine and hence I had a role to play in interpreting the population risk from exposure to the released radiation. To me, the risk mitigation comprised the three tenets of time, distance and protection and with this in mind everything that could have reasonably been done by the Japanese authorities was done. The explanation of any risk that was present was far more difficult in that at low radiation doses, you cannot specify who will receive a health detriment or even what that detriment is and it was occasionally stated by some that such lack of precision was equivalent to ambivalence or even clandestine shrouding of the facts. It is my job to ensure that everything is done to measure and mitigate radiation risks and such accusations did occasionally hurt.
“However, I do feel that as experts in relevant fields, we also have a clear responsibility to take concerns seriously and furthermore we must have the tact, social feelings and adaptability to ensure our points are understood
“In summary, I feel that the [UK] media did an excellent job and repeatedly stated the need for accurate and timely comment. It should be borne in mind that the tsunami killed tens of thousands and has received relatively little coverage.”