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Presentation at the ERMSAR ConferenceCologne Germany; March 23, 2012

THE FUKUSHIMA DAIICHI ACCIDENTS CONSEQUENCES; LESSONS AND LARGER ISSUES

B. R. SehgalEmeritus Professor

Nuclear Power SafetyRoyal Institute of Technology

Stockholm, Swedenbsehgal@safety.sci.kth.se

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Outline The following topics will be discussed: The consequences Immediate lessons learned and recommendations Some larger issues raised for the nuclear enterprise the

world-over A Few conclusions

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Public consequences-1• Radioactive releases to atmosphere

– The Japanese government had provided data on the release of isotopes to the atmosphere. The releases are large and that is why the accident has been classed as level-7 accident, they however are in the range of 5-10% of those from Chernobyl.

• This may sound comforting. However, it should be realised that Chernobyl releases were dispersed over an enormously larger area than those of Fukushima accidents, due to the energetic plume release of Chernobyl.

• Thus, the burden of clean up, decontamination etc for the 30-50 km radius may be similar as in Chernobyl. A fortunate occurrence was that part of the time the radioactive releases went towards the ocean. Perhaps entry to some land and forests may be restricted.

• One must be grateful to the Japanese government for evacuating the population in the vicinity of the Fukushima station; since no member of the public died or was injured due to radiation exposure.

• The accidents, however, are a social calamity since the people evacuated cannot go back to their homes for an unknown time period. The farmers cannot work their lands and all produce would have to be imported.

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Monitoring on-Site (1F)(conducted by TEPCO)

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Monitoring by MEXT and local nuclear emergency recponse HQ

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Public consequences-2Water contamination• The hydrogen explosion in unit 2 damaged the torus suppression pool

(SP) which contains hundreds of tons of water. This water was highly contaminated due to fission product released reaching the SP. This water leaked underground to the turbine building and later to a trench outside very close to the ocean shore.

• TEPCO managed to prevent the flow of this highly contaminated water to the ocean. Later water added to the units of 1-3 also leaked due to the holes in the vessels and also reached the turbine buildings of each of this reactors.

• TEPCO brought large capacity tanks to store the highly contaminated water. Perhaps the water mass is 150000 tons. TEPCO has constructed an Ion-exchange facility to remove the fission products from this large quantity of water.

• Perhaps, water with low radioactivity would have to be disposed- off in the ocean.

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Monitoring On-site (conducted by TEPCO)

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Monitoring on-Site (conducted by TEPCO)

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Public consequences-3

Economic consequences:• The economic consequences of the Fukushima accidents are beyond

belief. The TEPCO, an enormous electric utility company is going bankrupt; it has requested 1 trillion Yen (10 Billion Euros) loan from government to compensate the victims of the Fukushima accidents. But this is not sufficient.

• The Japanese government has recently published a plan to clean up the Fukushima site and decommission the station. The costs are estimated to be another 1 trillion yen and it would take 40 years.

• Another 1 trillion yen are earmarked for the clean up of land , houses, forests where radioactivity spread during the accident.

• There were many others costs to the nation; in terms of the effects of Fukushima on other companies' production, distribution etc. some of these effects were experienced by other economies as well.

• Economic costs of short electricity supply are still being incurred

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Wall Street Journal, December 22, 2011By PHRED DVORAK and MITSURU OBE TOKYO—Japan unveiled its plan to clean up the Fukushima Daiichi nuclear plant and return the surrounding region to normal, a 40-

year process that represents one of the most ambitious such efforts in history.The plan lays out a timetable to completely dismantle the plant, where reactors overheated dangerously following the March 11

earthquake and tsunami. It includes the development of robots to decontaminate the reactor buildings and technology to seal leaks in walls submerged in radioactive water.

The path laid out is arduous and slow: Officials estimate they won't finish plugging Fukushima Daiichi's leaky reactor buildings until 2018. Removing the melted fuel rods from three reactors will take 25 years, or until about 2036.

Plant operator Tokyo Electric Power Co. has estimated the decommissioning process will cost roughly ¥1 trillion ($12.8 billion), although that figure is expected to rise.

The decommissioning plan follows a proposal announced earlier this week, to start—as early as April—to return to their homes some of the 88,000 evacuees from areas nearest the plant, and to spend at least ¥1 trillion on decontaminating towns, parks and roads. It comes as the government also considers tightening food-safety standards to permit only one-fifth of the radioactive cesium that current rules allow.

Together, those proposals form the backbone of Japan's plan to deal with the long-term repercussions of the world's second-worst nuclear accident, following Chernobyl in 1986. Experts say the program will be extremely challenging to implement, in part because they aim to bring the region back, as much as possible, to the way it was before the accident.

"There is a strong call for us to put a lot of effort into decontamination, into restoring everything that can be restored, so people can live there again," said Goshi Hosono, Japan's minister overseeing the nuclear crisis, in an interview with The Wall Street Journal. "In order to restore things, we need to work on developing the technology, and devote plenty of money to whatever else is needed.''

See a timeline of how the Fukushima nuclear incident compares to other nuclear incidents.

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Eight months after the March 11 tsunami, the government opened the complex to the press on Nov. 12 for the first time. Read an account of the visit and see photos.

Part of Reactor No. 3 building is seen from a bus window on Nov 12.In many ways, Japan's cleanup and restoration plans are more ambitious and challenging than those following the nuclear accidents at Three Mile

Island in the U.S. and Chernobyl in the former Soviet Union. The 1979 accident at Three Mile Island was much smaller in scale, and emitted far less radioactive material into the atmosphere. The reactor's fuel

rods were damaged, but the vessels in which they were contained were intact. That is a very different situation than at Fukushima Daiichi, where the fuel in three reactors is thought to have burned holes in their immediately

surrounding pressure vessels, and in one case to have fallen all the way through to the bottom of the outer containment vessel. The reactor buildings and equipment at Fukushima Daiichi also are damaged and leaking radioactive water, something that didn't happen at Three Mile Island.

Experts say those differences present huge technological challenges—particularly in figuring out how to get to the bits of melted fuel. Those bits are likely scattered around the piping and other equipment at the bottom of the reactors' containment vessels "like bird droppings,'' says Tadashi Narabayashi, a professor of reactor engineering at Hokkaido University.

According to the government's blueprint for dismantling Fukushima Daiichi, engineers will first have to repair the reactor building leaks, which could take six years, then drain the buildings of radioactive water, which could take an additional two years.

Those estimates themselves are iffy, since nobody knows yet where the leaks are, says Hajimu Yamana, a professor of nuclear engineering at Kyoto University and head of a government panel studying how to dismantle the plant. "It's a bit of a stretch to say you'll do something in [a certain number of] years, when you don't know what it is you have to do,'' he said.

Not until 2022 does the plan foresee beginning the process of removing the melted fuel. Japan's cleanup plans also are more ambitious than those in place at Chernobyl, but for different reasons, experts say. In that accident, the lack of a

containment vessel surrounding the reactor meant radioactive materials from the accident were spread far and wide. Japanese officials point out that radiation released from Fukushima Daiichi is still only about 15% of what was emitted at Chernobyl.

But the Chernobyl cleanup plans were also simpler, experts say: Build a thick concrete container around the shattered reactor and move people away permanently. That won't work in Japan, where land is scarce and attachments to it are strong, says Mr. Hosono, the nuclear-crisis minister. "In this small country, people won't accept it if there is a big area where nobody is able to live,'' he says.

That means Japan is prepared to spend a lot of time, energy and money cutting up the contaminated plant and cleansing the site, so that people feel safe moving back near it. The government also has released ambitious plans to decontaminate surrounding areas to radiation levels that—while still many times what they were before the accident—are considered well below levels that scientists have found to be dangerous.

"We're trying to restore the land, even if living there doesn't raise health concerns,''

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Immediate lessons learned and recommendations

• The Fukushima accidents generated much response from agencies all over the world. The European country regulatory authorities ordered stress tests for the plants in their individual countries. The European commission followed by asking for reports from all the member countries. These are still in progress.

• The USNRC formed a task force. They reported their early evaluation in July 2011, followed by a later report. The recommendations made in July 2011 report are shown here

• The ANS established a committee whose report was released last week. I am a member. The recommendations made are made for the following issues:– Emergency power and cooling.– Emergency response– Hydrogen and containment– Spent fuel pools– Plant siting and site layout– Design basis selection

The ANS Committee recommendations are not too different than those of the USNRC Task Force

• There are many other groups making recommendations currently. Perhaps by end of 2012, things get clarified and consolidated.

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SUMMARY OF OVERARCHING RECOMMENDATIONS • This section presents the Task Force’s recommendations for improving the safety

of both operating and new nuclear reactors. It also addresses recommended improvements in the NRC programs for the oversight of reactor safety. The recommendations are based on the Task Force’s evaluations of the relevant issues identified from the Fukushima accident. Appendix A of this report proposes an implementation strategy and offers further details on these recommendations.

• The Task Force makes the following overarching recommendations: Clarifying the Regulatory Framework 1. The Task Force recommends establishing a logical, systematic, and coherent

regulatory framework for adequate protection that appropriately balances defense-in-depth and risk considerations. (Section 3)

Ensuring Protection 2. The Task Force recommends that the NRC require licensees to reevaluate and

upgrade as necessary the design-basis seismic and flooding protection of SSCs for each operating reactor. (Section 4.1.1)

3. The Task Force recommends, as part of the longer term review, that the NRC evaluate potential enhancements to the capability to prevent or mitigate seismically induced fires and floods. (Section 4.1.2)

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Enhancing Mitigation 4. The Task Force recommends that the NRC strengthen SBO mitigation capability at all operating and new

reactors for design-basis and beyond-design-basis external events. (Section 4.2.1) 5. The Task Force recommends requiring reliable hardened vent designs in BWR facilities with Mark I and

Mark II containments. (Section 4.2.2) 6. The Task Force recommends, as part of the longer term review, that the NRC identify insights about

hydrogen control and mitigation inside containment or in other buildings as additional information is revealed through further study of the Fukushima Dai-ichi accident. (Section 4.2.3)

7. The Task Force recommends enhancing spent fuel pool makeup capability and instrumentation for the spent fuel pool. (Section 4.2.4)

8. The Task Force recommends strengthening and integrating onsite emergency response capabilities such as EOPs, SAMGs, and EDMGs. (Section 4.2.5)

Strengthening Emergency Preparedness 9. The Task Force recommends that the NRC require that facility emergency plans address prolonged SBO and

multiunit events. (Section 4.3.1) 10. The Task Force recommends, as part of the longer term review, that the NRC pursue additional EP topics

related to multiunit events and prolonged SBO. (Section 4.3.1)11. The Task Force recommends, as part of the longer term review, that the NRC should pursue EP topics

related to decision making, radiation monitoring, and public education. (Section 4.3.2) Improving the Efficiency of NRC Programs 12. The Task Force recommends that the NRC strengthen regulatory oversight of licensee safety performance

(i.e., the ROP) by focusing more attention on defense-in-depth requirements consistent with the recommended defense-in-depth framework. (Section 5.1)

IRSN is considering also back-fits and systems for mitigation of consequences with secure location and protection.

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Some larger issues raised for

the nuclear power enterprise world-overOutline Introduction Risk, Probability, Consequences and the Public Frequency of the accidents! Has Fukushima negated the concept of the acceptance of

Residual Risk? Can current plants cope with Severe Accidents? Will lessons of Fukushima face Cost/Benefit rule in

implementation for current and future plants? What happened to Severe Accident Research, in particular

and Reactor Safety Research in general? Conclusions

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Introduction

The Fukushima accidents ( there were three) occured on March 11th to 13th, 2011; it took almost 6 months to stabilize them and reach cold shut-down.

These accidents are, and will be imprinted on the consciouness of the people of Japan. They were a man-made disaster on top of a nature –caused disaster

The accidents have, rightly, renewed the debate about suitability of nuclear power as a desired pillar of electrical

energy resource in the world.

Introduction (cont.) Already some relatively rich western European countries have

decided to forsake nuclear power as a long-term resource-base for electricity generation.

Perhaps their cost/benefit calculation is governed by public emotion, but such an important democratic decision by relatively large populations in Europe has to be considered seriously.

We should consider the larger issues and the practice of nuclear enterprise which may have led to such widespread release of radioactivity to the environment.

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Risk, Probability, Consequences and the Public

The nuclear power safety practice has rightly paid attention to the Risk = Probability × Consequences of nuclear power. However, the main concern of the nuclear enterprise has been with reduction of the accident probability or “prevention”. It should be recognized that the occurrence of an accident is the failure of all efforts on prevention. Also the public does not understand probability numbers like 10-6.

Perhaps the nuclear enterprise should concern itself with consequenses, and consider systems and actions to reduce the consequences. One example is filters on vents to reduce the radioactive releases.

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Risk, Probability, Consequences and the Public (cont.)

The WASH-1400 put most emphasis on fatalities in a large accident. Perhaps, what is more important for a large accident are the extent of the spread zone of the long-life radioactivity, ground contamination, evacuation and the social upheaval. The public is most upset if they have to move and if they cannot return to their homes.

Radioactivity is a fear complex in the mind of most populations. It is an unseen danger and this taboo can only be ameliorated through public education. It may be more effective to convince the public that very small doses for even long duration will not be a wide-spread health hazard than reducing the accident probability from 10-6 to 10-7. Comparing radioactivity doses to CT scan or tomography test is not productive, since the latter are by personal choice and are for a specific purpose

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Frequency of the accidents WASH – 1400 predicted one small consequence accident every 20000

reactor years, or an accident frequency of 5 × 10-5/RY. The strenuous efforts at prevention have claimed reduction in frequency to perhaps 1 × 10-6 /RY. With a population of ≈ 400 reactors, a minor consequence accident like TMI-2 may occur once every 50 years. However there have been one minor (TMI-2) and four accidents (Chernobyl and 3 Fukushima) of major public consequence. The Union of Concerned Scientists (UCS) stated that there may be an accident every 3-5 years.

The nuclear enterprise can not function with the frequency quoted by UCS, in spite of the climate change fears. Even, a TMI-2 type accident every 5 years with no ill effect on public will not be acceptable as were the boiler bursts in early days of steam power, there will be “what-if” questions and most probably people will be evacuated from their homes and the fear will be widespread.

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Frequency of the accidents (cont.)

Many people in nuclear enterprise believe that there will be no accidents anymore; “it cannot happen here”. But that has been shown to be a false belief. Accidents will happen, frequently or infrequently. We should reduce their consequences for the public.

In this context, education of Public to recognize the long term health hazards of fossil plants should be promoted vigorously, so that there is a realization that electricity is not available risk free.

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Has Fukushima negated the concept of the acceptance of Residual Risk?

The Concept of acceptance of Residual Risk has been invoked when an event in the accident scenario is considered to be highly improbable, coupled with the inability to estimate the consequences. Examples of such events could be: Ex-Vessel Steam Explosion; Base-Mat Melt-Through; Containment Failure a little bit after 24 hours.

The Fukushima accidents belong to the category of events of such low probability that they could have been considered as posing only residual risk. Perhaps, all “Long-Duration Station Black-Out (SBO)” events have been considered as posing only residual risk.

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Has Fukushima negated the concept of the acceptance of Residual Risk? (cont.)

In fact, the consequences of such events are not assessed. It is a grey area. But, Our inability to estimate the consequences for a very rare-high consequence event should not lead to its classification and acceptance as a residual risk.

The consequences of Fukushima accidents cannot be accepted as “Residual-Risk”. They are too large.

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Can current plants cope with Severe Accidents?

Severe accidents were not prescribed as safety design basis for current plants and they are not even so for the GEN III+ plants in USA and some other countries. Severe accident protection has been taken into account through AD HOC rules, the most prominent examples are the Hydrogen Rule, the Station Black-Out Rule, the ATWS Rule and some others. But, truly, severe accidents are considered as beyond design basis.

Promulgation of these Rules did not provide the protection needed for Fukushima. Nevertheless, Level-2 PRA are performed for many LWR plants and the computer codes MAAP, ASTEC and MELCOR, have provided very good insights. Most probably such analyses were also performed for the Fukushima plants.

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Can current plants cope with Severe Accidents? (cont.)

Perhaps a commitment to thoroughly analyze the safe performance (no large release, no hydrogen explosions) of the current plants in the most severe postulated accidents resulting from the internal and external initiators could be considered after the stress tests.

The results of such analyses (with peer review) may provide clues on improvements needed for current plants to protect the public against a low probability high consequence severe accident that could occur in future in some current LWR plant somewhere.

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Will lessons of Fukushima face Cost/Benefit rule in implementation for current and future plants?

The cost/benefit rule could become a large issue, if the lessons learned from the Fukushima accidents point to some expensive back-fits or major improvements needed for the current plants.

It is somewhat of a mystery, how the benefits are calculated. The lessons from Fukushima accidents would say that all the needed backfits, e.g., a tall long wall for tsunami protection, some diesel generators at higher elevation, water reservoir , fire-water pumps; portable diesel generators, compressed air/nitrogen cylinders, well-functioning vent valves, radioactivity filters, hydrogen recombiners (or igniters) in the reactor building, would have been of inconsequential costs compared to the benefits of avoiding severe accidents in three plants and the release of radioactivity to the environment. Just the magnitude of the loss of wealth for TEPCO in the stock market, in the first week of the accidents could compensate for all of the possible costs of the improvements/backfits.

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Will lessons of Fukushima face Cost/Benefit rule in implementation for current and future plants?

(cont.)

If the benefits are derived on the basis of a probabilistic argument, i.e., multiplying the actual benefits with the probability of the accident, cost/benefit could become greater than 1. However, all probabilistic estimates are not relevant, when a severe accident occurs. At that time the probability of the accident = 1.0

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What happened to Severe Accident Research, in particular and Reactor Safety Research in general?

Thirty years ago; soon after the TMI-2 accident, severe accident research took off with a flourish in USA and later in Japan, Europe and Korea. Currently only a few research projects are being conducted in Europe, Korea and perhaps one or two in USA. Clearly, the impression has been left that all needed knowledge has been acquired and what is left belongs to the residual-risk-category, or, to the code development category.

There is also no significant on-going research in the area of LWR design-base safety. Perhaps, for the design-basis accidents the computer codes may be able to predict the course of the accidents quite well. However, there may still be some surprises lurking underneath.

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What happened to Severe Accident Research, in particular and Reactor Safety Research in general? (cont.)

There is a substantial knowledge base still to be explored and acquired in the domain of severe accidents: their phenomenology, their energetics, their public consequences, their prevention, their stabilization and termination etc.

Last, but not the least are operator actions, errors, omissions, the circumstances in an accident etc., which all matter for the public consequences of a severe accident as it progresses. Operator actions can certainly “turn-off” a severe accident or make its consequences worse. We have 5 examples which led to accidents and perhaps several others (including those at Fukushima 5-6 and at other Japanese plants) which “turned-off” budding accidents.

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Conclusions

Certainly the nuclear power renaissance, which was about to spring forth, has been buried back in the ground by the cold frost of the Fukushima accidents

This may not be a permanent condition, since both developed and developing countries need electric power and coal is not a good choice from environmental and climate change considerations

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Conclusions (cont.)

It remains to be seen if some of the countries renouncing nuclear power, can construct sufficient and economic renewables to displace nuclear power, for ever.

Finally, it will depend on what an individual society will care to afford: abundance of electric power vs. fear of the effects of a possible nuclear power accident.

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Conclusions (cont.) It should be noted that the Fukushima accidents did not

cause any casualties and the long-term effects of radiation are not clearly known. However, there is a great fear of radioactivity in Public’s mind resulting in votes against nuclear power at the next election.

The fear of radioactivity in Public’s mind can be remedied only through education and that should be promoted.

The nuclear enterprise in the World should provide a proper, well-reasoned, constructive response to gain back the acceptance of Public.