1 year ago
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Dec 19, 2022
What happens to the damaged reactors? The territories evacuated by 160 000 people? What are the new conditions for their return to the contaminated area since the lifting of the governmental aid procedures? Are lessons still being learned by our national operator for its own nuclear plants? We must not forget that a disaster is still unfolding in Japan and that EDF was supposed to upgrade its fleet on the basis of this feedback, which has still not been finalized.
Almost twelve years after the Fukushima disaster, Japan is still in the process of dismantling and ‘decontaminating’ the nuclear power plant, probably for the next thirty to forty years as well. In the very short term, the challenges are posed by the management of contaminated water.
All the contaminated water will be evacuated into the sea, by dilution over decades Each intervention in the accident reactors brings out new elements This has an impact on the schedule and the efficiency of the means used At the same time, the Japanese government’s objective is to rehabilitate the contaminated areas at any cost None of the French reactors is up to date with its safety level according to the post-Fukushima measures promulgated Japan will resume its nuclear policy, time having done its work on memoriesThe great water cycle
Although Japanese politicians claim that they have finally mastered the monster, the colossal task of cleaning up the site is still far from being completed to allow for the ultimate dismantling, with the length of time competing with the endless financing.
After so many years of effort, from decontamination to the management of radioactive materials and maneuvers within the dismantled plant, the actions on site require more and more exceptional means, exclusive procedures, and unprecedented engineering feats (such as robotic probes), while the nuclear fuel inside continues to be cooled permanently by water (not without generating, to repeat, millions of liters of radioactive water).
But the hardest part is yet to come: containing the corium, an estimated 880 tons of molten radioactive waste created during this meltdown of the reactor cores, and managing the thousands of fuel rods. So much so that the complete cleanup and dismantling of the plant could take a generation or more for a total estimated cost of more than 200 billion dollars (according to an assessment published by the German insurer Munich Re, Japan is 150 billion euros), a low range since other estimates raise the bill between 470 and 660 billion dollars, which is not in contradiction with the costs of an accident projected by the IRSN in France.
The removal of this corium will remain the most essential unresolved issue for a long time. Without it, the contamination of this area will continue. In February 2022, the operator Tepco (Tokyo Electric Power Company Holdings Inc.) tried again to approach the molten fuel in the containment of a reactor after a few more or less unsuccessful attempts, the radioactivity of 2 sieverts/hour being the end of everything, including electronic robots. This withdrawal seems quite hypothetical, even the Chernobyl reactor has never been removed and remains contained in a sarcophagus.
(source: Fukushima blog and Japan’s Nuclear Safety Authority NRA)
Until that distant prospect arrives, the 1.37 million tons of water will have filled the maximum storage capacity. This water was used to cool the molten fuel in the reactor and then mixed with rainwater and groundwater. The treatment via an Advanced Liquid Processing System (ALPS) is touted as efficient, but does not remove tritium. Relative performance: Tepco has been repeatedly criticized for concealing and belatedly disclosing problems with filters designed to prevent particles from escaping into the air from the contaminated water treatment system: 24 of the 25 filters attached to the water treatment equipment were found to be damaged in 2021, an already known defect that resulted in no investigation of the cause of the problem and no preventive measures after the filters were replaced.
The management of this type of liquid waste is a problem shared by the Americans. On site, experts say that the tanks would present flooding and radiation hazards and would hamper the plant’s decontamination efforts. So much so that nuclear scientists, including members of the International Atomic Energy Agency (IAEA) and the Japanese Nuclear Regulatory Authority, have recommended controlled release of the water into the sea as the only scientifically and financially realistic option.
In the end, contaminated water would have to be released into the sea through an underwater tunnel about a kilometer offshore, after diluting it to bring the concentration of tritium well below the percentage allowed by regulation (the concentration would be below the maximum limit of tritium recommended by the World Health Organization for drinking water). Scientists say that the effects of long-term, low-dose exposure to tritium on the environment and humans are still unknown, but that tritium would affect humans more when consumed in fish. The health impact will therefore be monitored, which the government already assures us it is anticipating by analyzing 90,000 samples of treated water each year.
Assessment studies on the potential impact that the release of stored contaminated water into the ocean could have therefore seem insufficient. For tritium, in the form of tritiated water or bound to organic matter, in addition to its diverse behavior according to these configurations, is only part of the problem. Some data show great variability in the concentrations of contaminants between the thousand reservoirs, as well as differences in their relative quantities: some reservoirs that are poor in tritium are rich in strontium 90 and vice versa, suggesting a high variability in the concentrations of other radionuclides and a dilution rate that is not so constant. All the ignorance currently resides on the still unknown interactions of the long-lived radioactive isotopes contained in the contaminated water with the marine biology. It is in order to remove all questions that a complete and independent evaluation of the sixty or so radioisotopes is required by many organizations.
As it stands, with the support of the IAEA so that dilution meets expectations, depending on currents, flows …, the release of contaminated materials would take at least forty years. Opponents of such releases persist in proposing an alternative solution of storage in earthquake-resistant tanks in and around the Fukushima facility. For them, “given the 12.3-year half-life of tritium for radioactive decay, in 40 to 60 years, more than 90% of the tritium will have disappeared and the risks will be considerably reduced,” reducing the direct nuisance that could affect the marine environment and even the food chain.
Modelling of marine movements could lead the waste to Korea, then to China, and finally to the Federated States of Micronesia and Palau. As such, each of the impacted countries could bring an action against Japan before the International Tribunal for the Law of the Sea to demand an injunction or provisional measures under international law.
Faced with these unresolved health issues, China, South Korea, Taiwan, local fishing communities continue to oppose this management plan, but the work is far from being completed and the problem of storage remains. Just like the ice wall built into the floor of the power plant, the release of contaminated water requires huge new works: the underwater pipe starts at about 16 meters underground and is drilled at a rate of five to six meters per day.
Time is of the essence. The tanks should reach their maximum capacity by the fall of 2023 (the volume of radioactive water is growing at a rate of about 130 to 140 tons per day). But above all, it is necessary to act quickly because the area is likely to suffer another earthquake, a fear noted by all stakeholders. With the major concern of managing the uranium fuel rods stored in the reactors, the risks that radioactivity will be less contained increase with the years.
In France, releases to the sea are not as much of a problem: the La Hague waste reprocessing site in France releases more than 11,000 terabecquerels per year, whereas here we are talking about 22 terabecquerels that would be released each year, which is much less than most of the power plants in the world. But we will come back to this atypical French case…
Giant Mikado
The operator Tepco has successfully removed more than 1500 fuel bundles from the reactor No. 4 of the plant since late 2014, but the hundreds still in place in the other three units must undergo the same type of sensitive operation. To do this, again and again, undertake in detail the clearing of rubble, the installation of shields, the dismantling of the roofs of buildings and the installation of platforms and special equipment to remove the rods… And ultimately decide where all the fuel and other solid radioactive debris will have to be stored or disposed of in the long term. A challenge.
The fuel is the biggest obstacle to dismantling. The solution could lie, according to some engineers, in the construction of a huge water-filled concrete tank around one of the damaged reactors and to carry out the dismantling work in an underwater manner. Objectives and benefits? To prevent radiation from proliferating in the environment and exposing workers (water is a radiation insulator, we use this technique in our cooling pools in France) and to maximize the space to operate the heavy dismantling equipment being made. An immersion solution made illusory for the moment: the steel structure enveloping the building before being filled with water is not feasible as long as radiation levels are so high in the reactor building, preventing access by human teams. In short, all this requires a multitude of refinements, the complexity of the reactors adding to the situations made difficult by the disaster.
Experience, which is exceptional in this field, is in any case lacking. What would guarantee the resistance of the concrete of the tanks over such long periods of time, under such hydraulic pressures? The stability of the soils supporting such structures? How can the concrete be made the least vulnerable possible to future earthquakes? How to replace them in the future?
All these difficulties begin to explain largely the delays of 30 to 40 to dismantle. The reactors are indeed severely damaged. And lethal radiation levels equivalent to melted nuclear fuel have been detected near one of the reactor covers, beyond simulations and well above previously assumed levels. Each of the reactors consists of three 150-ton covers, 12 meters in diameter and 60 centimeters thick: the radiation of 1.2 sieverts per hour is prohibitive, especially in this highly technical context. There is also no doubt that other hotspots will be revealed as investigations are carried out at the respective sites. The Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF), created in 2014, has the very objective of trying to formulate strategic and technical plans in order to proceed with the dismantling of said reactors. Given the physical and radiological conditions, the technical and logistical high-wire act.
Also, each plan is revised as information is discovered, as investigations are conducted when they are operable. For example, the reinforcing bars of the pedestal, which are normally covered with concrete, are exposed inside Reactor No. 1. The concrete support foundation of a reactor whose core has melted has deteriorated so badly that rebar is now exposed.
The cylindrical base, whose wall is 1.2 meters thick, is 6 meters in diameter. It supports the 440-ton reactor pressure vessel. The reinforcing rods normally covered with concrete are now bare and the upper parts are covered with sediment that could be nuclear fuel debris. The concrete probably melted under the high temperature of the debris. The strength of the pedestal is a major concern, as any defect could prove critical in terms of earthquake resistance.
Nothing is simple. The management of human material appears less complex.
Bringing back to life, whatever it takes
In the mountains of eastern Fukushima Prefecture, one of the main traditional shiitake mushroom industries is now almost always shut down. The reason? Radioactive caesium exceeding the government’s maximum of 50 becquerels per kilogram, largely absorbed by the trees during their growth. More than ten years after the nuclear disaster, tests have revealed caesium levels between 100 and 540 becquerels per kilogram. While cesium C134 has a radioactive half-life of about two years and has almost disappeared by now, the half-life of cesium C137 is about 30 years and thus retains 30% of its radioactivity 50 years after the disaster, and 10% after a century.
As more than two thirds of Fukushima prefecture is covered by forests, nothing seems favorable in the short term to get rid of all or part of the deposited radioactivity, as forests are not part of the areas eligible for ‘decontamination’, unlike residential areas and their immediate surroundings.
On the side of the contaminated residential and agricultural areas, ‘decontamination’ measures have been undertaken. But soil erosion and the transfer of contaminants into waterways, frequent due to typhoons and other intense rain events, are causing the radioactive elements to return, moving them incessantly. Scientists are trying to track radioactive substances to better anticipate geographical fluctuations in doses, but nothing is simple: the phenomena of redistribution of the initial contamination deposits from the mountains to the inhabited low-lying areas are eternal.
The Ministry of the Environment is considering the reuse of decontaminated soils (official threshold of 8,000 becquerels per kilogram), with tests to be conducted. For now, a law requires the final disposal of contaminated soil outside Fukushima Prefecture by 2045, which represents about 14 million cubic meters (excluding areas where radiation levels remain high). This reuse would reduce the total volume before legal disposal.
More generally, Japan has for some years now opted for the strategy of holding radiological contamination as zero and/or harmless. This is illustrated by the representative example of the financial compensation given to farmers, designed so that the difference between pre- and post-accident sales is paid to them as compensation for “image damage”, verbatim.
Finally, in the midst of these piles of scrap metal and debris, it is necessary to make what can be made invisible. Concerning radioactive waste for example, it must be stored in time. On the west coast of the island of Hokkaidō, the villages of Suttsu and Kamoenai have been selected for a burial project. Stainless steel containers would be stored in a vitrified state. But consultation with the residents has not yet been carried out. This is not insignificant, because no less than 19,000 tons of waste are accumulating in the accidental, saturated power plants, and must find a place to rest for hundreds of years to come.
In this sparsely populated and isolated rural area, as in other designated sites, to help with acceptance, 15 million euros are being paid to each of the two municipalities to start the studies from 2020. 53 million are planned for the second phase, and much more in the final stages. This burial solution seems inevitable for Japan, as the waste cannot remain at the level of the surface power plants and is subject at all times to the earthquakes that are bound to occur over such long periods (strong earthquakes have struck off the prefecture in 2021 and 2022). The degrees of dangerousness thus allow the government to impose a default choice, for lack of anything better.
On December 6, 2022, the Director General of the IRSN met with the President of Fukushima University and with a manager of the Institute of Environmental Radioactivity (IER). What was the objective? To show the willingness of both parties to continue ongoing projects on the effects of radioactive contamination on biodiversity and environmental resilience.
But France will not have waited for the health results of a disaster to learn and commit itself to take into account any improvement likely to improve the nuclear safety of its reactors. No ?
Experience feedback
After a few reactor restarts that marked a major change in its nuclear energy policy (ten nuclear reactors from six plants out of a total of fifty-four were restarted by June 2022), the Japanese government is nonetheless planning to build new generation nuclear power plants to support its carbon emission reduction targets. (A memorandum of understanding was signed by the Japan Atomic Energy Agency, Mitsubishi Heavy Industries and Mitsubishi FBR Systems with the American start-up TerraPower to share data for the Natrium fast neutron reactor project; the American company NuScale Power presented its modular reactor technology). But above all, the government is considering extending the maximum service life of existing nuclear reactors beyond 60 years. Following the disaster, Japan had introduced stricter safety standards limiting the operation of nuclear reactors to 40 years, but there is now talk of modernizing the reactors with safety features presented as “the strictest in the world”, necessarily, to meet safety expectations. Their program is worthy of a major refurbishment (GK).
But in France, where are we with our supplementary safety assessments?
The steps taken after the Fukushima disaster to reassess the safety of French nuclear facilities were designed to integrate this feedback in ten years. More than ten years after the start of this process of carrying out complementary safety assessments (CSA), this integration remains limited and the program has been largely delayed in its implementation.
Apparently, ten years to learn all the lessons of this unthinkable accident was not enough. Fear of the probable occurrence of the impossible was not the best motivation to protect the French nuclear fleet from this type of catastrophic scenario, based solely on these new standards. Concerning in detail the reality of the 23 measures identified to be implemented (reinforcement of resistance to earthquake and flooding, automatic shutdown in the event of an earthquake, ultimate water top-up for the reactor and cooling pool, detection of corium in the reactor vessel, etc.), the observation is even distressing: not a single reactor in operation is completely up to standard.
According to NegaWatt’s calculations, at the current rate of progress and assuming that funding and skills are never lacking, it would take until 2040 for the post-Fukushima standards to be finally respected in all French reactors. And even then, some of the measures reported as being in place are not the most efficient and functional (we will come back to the Diesels d’ultime secours, the DUS of such a sensitive model).
Even for the ASN, the reception of the public in the context of post-accident management could appear more important than the effectiveness of the implementation of the measures urgently imposed.
Then, let us complete by confirming that France and Japan have a great and long common history which does not stop in nuclear matters. Among this history, let us recall that Japan lacks facilities to treat the waste from its own nuclear reactors and sends most of it abroad, especially to France. The previous transport of highly radioactive Mox (a mixture of highly toxic plutonium oxide and reprocessed uranium oxide) to Japan dates back to September 2021, not without risk even for the British company specialized in this field, a subsidiary of Orano. The final request for approval for the completion of the Rokkasho reprocessing plant, an important partnership and technology transfer project, is expected in December 2022, although the last shipments to Japan suffered from defective products from Orano’s Melox plant, a frequent occurrence because of a lack of good technical homogenization of the products.
No one is immortal
In the meantime, the ex-managers of the nuclear power plant have been sentenced to pay 95 billion euros for having caused the disaster of the entire eastern region of Japan. They were found guilty, above all, of not having sufficiently taken into account the risk of a tsunami at the Fukushima-Daiichi site, despite studies showing that waves of up to 15 meters could hit the reactor cores. Precisely the scenario that took place.
Worse, Tepco will be able to regret for a long time to have made plan the cliff which, naturally high of 35 meters, formed a natural dam against the ocean and the relatively frequent tsunamis in this seismic zone. This action was validated by the Japanese nuclear safety authorities, no less culpable, on the basis of the work of seismologists and according to economic considerations that once again prevailed (among other things, it was a question of minimizing the costs of cooling the reactors, which would have been operated with seawater pumps).
The world’s fourth largest public utility, familiar with scandals in the sector for half a century, Tepco must take charge of all the work of nuclear dismantling and treatment of contaminated water. With confidence. The final total estimates are constantly being revised upwards, from 11,000 billion to 21,500 billion yen, future budgets that are borrowed from financial institutions, among others, with the commitments to be repaid via the future revenues of the electricity companies. A whole financial package that will rely on which final payer?
Because Tepco’s financial situation and technical difficulties are deteriorating to such an extent that such forty-year timetable projections remain very hypothetical, and the intervention of the State as a last resort is becoming more and more obvious. For example, the Japanese government has stated that the repayment of more than $68 billion in government funding (interest-free loans, currently financed by government bonds) for cleanup and compensation for the Fukushima Daiichi nuclear power plant disaster, owed by Tepco, has been delayed. Tepco’s mandatory repayments have been reduced to $270 million per year from the previous $470 million per year. It is as much to say that the envisaged repayment periods are as spread out as the Japanese debt is abysmal.
Despite this chaotic long-term management, the Japanese government has stated that it is considering the construction of the next generation of nuclear power plants, given the international energy supply environment and Japan’s dependence on imported natural resources. Once the shock is over, business and realpolitik resume.
On a human scale, only radioactivity is immortal.
