Fukushima nuclear disaster: Japan to release radioactive water into sea this year
By Grace Tsoi BBC News 13 Jan 23,
Japan says it will release more than a million tonnes of water into the sea from the destroyed Fukushima nuclear power plant this year.
After treatment the levels of most radioactive particles meet the national standard, the operator said.
The International Atomic Energy Agency (IAEA) says the proposal is safe, but neighbouring countries have voiced concern.
The 2011 Fukushima disaster was the worst nuclear accident since Chernobyl.
Decommissioning has already started but could take four decades.
“We expect the timing of the release would be sometime during this spring or summer,” said chief cabinet secretary Hirokazu Matsuno on Friday, adding that the government will wait for a “comprehensive report” from IAEA before the release.
Every day, the plant produces 100 cubic metres of contaminated water, which is a mixture of groundwater, seawater and water used to keep the reactors cool. It is then filtered and stored in tanks.
With more than 1.3 million cubic metres on site, space is running out.
The water is filtered for most radioactive isotopes, but the level of tritium is above the national standard, operator Tepco said. Experts say tritium is very difficult to remove from water and is only harmful to humans in large doses.
However, neighbouring countries and local fishermen oppose the proposal, which was approved by the Japanese government in 2021.
The Pacific Islands Forum has criticised Japan for the lack of transparency.
“Pacific peoples are coastal peoples, and the ocean continues to be an integral part of their subsistence living,” Forum Secretary General Henry Puna told news website Stuff.
“Japan is breaking the commitment that their leaders have arrived at when we held our high level summit in 2021.
“It was agreed that we would have access to all independent scientific and verifiable scientific evidence before this discharge takes place. Unfortunately, Japan has not been co-operating.”……. more https://www.bbc.com/news/world-asia-64259043
Fukushima water to be released into ocean in next few months, says Japan
Guardian, Justin McCurry in Tokyo, 13 Jan 23,Authorities to begin release of a million tonnes of water from stricken nuclear plant after treatment to remove most radioactive material
The controversial release of more than a million tonnes of water from the wrecked Fukushima Daiichi nuclear plant will begin in the northern spring or summer, Japan’s government has said – a move that has sparked anger among local fishing communities and countries in the region.
The decision comes more than two years after the government approved the release of the water, which will be treated to remove most radioactive materials but will still contain tritium, a naturally occurring radioactive form of hydrogen that is technically difficult to separate from water.
Japanese officials insist the “treated” water will not pose a threat to human health or the marine environment, but the plans face opposition from fishermen who say it risks destroying their livelihoods, almost 12 years after a magnitude-9.0 earthquake triggered a huge tsunami that killed more than 18,000 people along Japan’s north-east coast…………………………………….
South Korea and China have voiced concern about the discharge, while the Pacific Islands Forum said recently it had “grave concerns” about the proposed release.
Writing in the Guardian, the forum’s secretary general, Henry Puna, said Japan “should hold off on any such release until we are certain about the implications of this proposal on the environment and on human health, especially recognising that the majority of our Pacific peoples are coastal peoples, and that the ocean continues to be an integral part of their subsistence living”.
The South Korean government, which has yet to lift its ban on Fukushima seafood, has said that releasing the water would pose a “grave threat” to marine life. Fishing unions in the area oppose the release, warning it would cause alarm among consumers and derail more than a decade of efforts to reassure the public that Fukushima seafood is safe to eat…………… more https://www.theguardian.com/environment/2023/jan/13/fukushima-water-to-be-released-into-ocean-in-next-few-months-says-japan
Fukushima, Our ongoing accident.
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 memories
The 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.
Bring voices from the coast into the Fukushima treated water debate
PNAS Leslie Mabon and Midori Kawabe 28 Oct 22, More than a decade has passed since the accident at the Fukushima Dai’ichi nuclear power plant in Japan—but the most contentious aspect of bringing the site under control is only just beginning. The Japanese Government has approved plant operator TEPCO’s plan to release treated water into the Pacific Ocean. That water is currently being stored onsite and retains some radioactive substances after treatment. The decision to release this water has provoked political contention and societal concern. South Korea, China, and Taiwan, as well as international environmental nongovernmental organizations, have expressed strong concern; and fisheries cooperatives in Japan remain opposed to the releases for fear of possible reputational impacts on Fukushima seafood.
TEPCO are confirming specific details of the release process, and an International Atomic Energy Agency (IAEA) task force has made multiple visits to the Fukushima Dai’ichi site at the behest of the Japanese Government and TEPCO. The releases are scheduled to start in 2023 and run for many years………………………………………
Even if TEPCO and the government minimize environmental impacts through careful management of the process, as some international experts believe possible (3), the indirect socioeconomic impacts of the treated water releases on Fukushima’s coastal fishing communities are likely to be experienced over the long term. Proposals made by the community of researchers and institutions working at the science–policy interface for Fukushima treated water must be informed by a deep understanding of the local community context—and they must be responsive to the concerns of local stakeholders. We believe local community concerns can be more fully incorporated into decision making for treated water at Fukushima Dai’ichi………………….
Local Influence
Within Japan, the government expert committees advising the management of treated water are dominated largely—albeit not exclusively—by engineering and physical science expertise (4). Despite fisheries cooperatives’ long-standing and vocal opposition to the releases, plant operator TEPCO explained in August 2021 that they had not at that point had direct consultations with fisheries representatives regarding the discharges (5). Formal dialogue between the operator and the fisheries sector in Fukushima on the topic of releases did not start until TEPCO and the Japanese Government had determined most of the technical details. This left little room for the plans to be adjusted in response to any concerns from Fukushima’s fishers or coastal residents…………………………
Both within Japan and internationally, Fukushima’s fishers and coastal residents, although not completely absent, have received limited consideration as stakeholders. Fishers and residents tend to be caricatured as being concerned over rumors and reputational damage to Fukushima seafood owing to the treated water releases (9, 10)—or as harboring “irrational” safety fears over the relatively small amounts of radioactivity from pollutants such as tritium that are contained in the tanks currently storing treated water onsite (e.g., 3)………….
Missing Local Context
The Japanese Government is unlikely to reverse their decision to release treated water. Even so, it’s important to recognize that fishing is both an economic activity and the subject of deep emotional investment on the Fukushima coast. ……………………………….more https://www.pnas.org/doi/10.1073/pnas.2205431119
Fukushima: Japan attempts to safely remove nuclear fuel from crippled reactors
DW 22.09.2022, Julian Ryall (Tokyo)
More than a decade after the second-worst nuclear disaster in history, engineers want to construct a huge water-filled tank around one of the damaged reactors and carry out underwater dismantling work.
Nuclear experts pondering the safest way to decommission the three crippled reactors at the Fukushima Daiichi atomic energy plant have devised a new plan to recover highly radioactive debris at the site, with even anti-nuclear campaigners giving the proposal their qualified support.
They warn, however, that the situation at the plant — on the northeast coast of Japan— remains precarious more than a decade since three of the six reactors suffered meltdowns after an offshore earthquake of magnitude 9 triggered a series of powerful tsunamis.
In their latest annual strategy report on progress at the plant, experts at the Nuclear Damage Compensation and Decommissioning Facilitation Office (NDF) have proposed the construction and filling with water of a massive concrete tank to completely enclose one of the reactor buildings. ………………………………………. more https://www.dw.com/en/fukushima-japan-attempts-to-safely-remove-nuclear-fuel-from-crippled-reactors/a-63200659
Fukushima Plants Showing ‘Unusual Growing Patterns’
NewsWeek, BY ROBYN WHITE ON 8/31/22 , Japan’s Fukushima, the site of the world’s second-worst nuclear disaster, is showing “unusual growing patterns” among vegetation in the area because of the radiation contamination.
…………………… Tim Mousseau, a professor of biological sciences at the University of South Carolina and a radiation expert, told Newsweek that a “vast region near the power plant” is still “significantly contaminated” but that levels are much lower than they used to be. However, the effects of radiation continue to be seen in the plants in the area, he said.
“There have been a few studies of the plants showing effects of the radiation. For example, it has been shown that Japanese fir trees show unusual growth patterns similar to that observed for pine trees in Chernobyl,” Mousseau said. “Such effects are still open for study, as they are preserved in the growth form of the plant/tree as long as it is still living.”
He continued, “Many areas are still contaminated above levels that most would consider safe for people to live, although most of the region is now relatively safe for short visits.”
Carmel Mothersill, a radiobiologist and the Canada research chair in environmental radiobiology, said that remediation efforts have also affected the area’s vegetation.
………. Mousseau also said that the ongoing effects of the contamination and “other human disturbances” remain largely unknown, as “research in the region has dropped off dramatically in the past years because of COVID and Japan’s restrictions on visitors from outside the country.”
“Assuming Japan removes travel restrictions, more research will be conducted,” he said
While some areas are opening back up to the public, most of the Fukushima area remains evacuated, Mothersill said…….. https://www.newsweek.com/fukushima-plants-unusal-gorwing-patterns-1738525
Robot issue delays fuel removal from Fukushima nuclear plant
The operator of the wrecked Fukushima nuclear power plant says it is postponing the start of the removal of highly radioactive melted fuel from its damaged reactors because of delays in the development of a remote-controlled robotic arm
abc news, By, MARI YAMAGUCHI Associated Press, August 25, 2022, Tokyo Electric Power Company Holdings had originally planned to begin removing melted fuel from the Unit 2 reactor at the Fukushima Daiichi plant last year, 10 years after the disaster triggered by a massive earthquake and tsunami on March 11, 2011.
That plan was postponed until later this year, and now will be delayed further until about autumn next year because of additional work needed to improve the performance of the robotic arm, TEPCO said.
The giant arm, jointly developed by Veolia Nuclear Solutions of Britain and Japan‘s Mitsubishi Heavy Industries, has been transported to Japan and is being adjusted at a testing facility south of the Fukushima plant…………………… https://abcnews.go.com/Technology/wireStory/robot-issue-delays-fuel-removal-fukushima-nuclear-plant-88839281
Tepco delays removing Fukushima nuclear debris
TOKYO, Aug 24 (Reuters) – Tokyo Electric Power Company Holdings (Tepco) (9501.T) is considering abandoning a plan to start removing nuclear debris from a reactor in its wrecked Fukushima Daiichi nuclear power plant by the end of the year, Kyodo reported on Wednesday.
The plan will be postponed for about a year due to a delay in the development of a robot arm that will be used to remove the debris, the report said citing unnamed sources………………….. more https://www.reuters.com/business/environment/tepco-considering-delay-removing-fukushima-nuclear-debris-kyodo-2022-08-24/
The shadows grow longer in Fukushima
By WANG XU in Tokyo | China Daily, 15 Aug 22,
As Tokyo tries to woo residents back, plans to dump toxic water pose more perils
For Setsuko Matsumoto, 71, there will be no return to her hometown in Fukushima prefecture－that is despite the determined efforts of the Japanese government to win her over to the idea that it is safe to do so. And that goes for the many like Matsumoto who cannot countenance how they can once again live in neighborhoods that were devastated by the earthquake and tsunami more than a decade ago.
Having run a hair salon for almost 30 years in Futaba, a town 4 kilometers from the crippled Fukushima Daiichi nuclear power plant, Matsumoto believes the place has no future. The government would have her believe otherwise. On Aug 30, it will lift the last of the restrictions imposed that have prevented former residents from living in the region permanently. It claims radiation levels arising from the nuclear accident in March 2011 are now low enough to be deemed safe.
“I don’t think that the town will be able to go on, even with the return of some elderly residents,” says Matsumoto.
Although 11 years have passed since the Fukushima plant’s cooling systems were severely damaged in the disaster, triggering the meltdown of three reactors and the release of large amounts of radiation, Matsumoto has her reasons for not moving back.
“Residing in Futaba is not an option for me,” she says. “The lack of shopping and medical care opportunities can’t be solved anytime soon and I don’t have a reason to relocate to a place with a worse living environment.”
Over the years, there have been sustained efforts－both from the top down and the bottom up－aimed at driving Fukushima’s reconstruction and revitalization. Seemingly limitless funds have been spent on that process, from the national government all the way down to township levels. These efforts are all bound up in the Japanese government’s economic and political ambitions to show the world that it has succeeded in managing the nuclear crisis.
Yet that strong desire to change Fukushima into something resembling its old form, or even something better, has encountered resistance from the likes of Matsumoto, who have lived with the effects of trauma for more than a decade.
As a result of the disaster, some 160,000 people like Matsumoto were evacuated from the Fukushima region. What the authorities had to contend with was a level-7 nuclear accident, the highest on the international scale of nuclear and radiological events. By the end of 2021, some 40,000 of them were still unable to return to their homes. But, with Futaba, the last of dozens of places ending their status as no-go zones, the government still faces a challenge in regaining the people’s trust.
In a survey conducted by Japan’s Reconstruction Agency and others, only 11.3 percent of respondents said they wanted to return to Futaba while more than 60 percent said they already decided not to return.
The town aims to attract 2,000 people back in the next five years but in a trial for overnight stays, beginning in January, has seen only 15 former residents have applied.
In a report in 2020, Miranda Schreurs, a professor and chair of environmental and climate policy at the Technical University of Munich, Germany, argues that the situation in Fukushima remains precarious because problems like the removal of radioactively contaminated waste, and issues such as incineration, still need to be addressed.
“It will still take many years to win back confidence and trust in the government’s messages that the region is safe,” Schreurs says in the report, adding that intergenerational equity is also an issue. The next generations will be left with the burden of completing the highly dangerous and complex decommissioning work at the Fukushima plant, she said.
The plans for Fukushima’s future also bump up against the government’s divisive decision to proceed with a plan to discharge the radioactive water from the plant into the Pacific Ocean. The water has been used to cool the highly radioactive, damaged reactor cores and would be sufficient to fill about 500 Olympic-sized swimming pools. Under Tokyo’s schedule, the ocean disposal will begin next spring.
Those plans present another blow to those former Fukushima residents who may be wanting to return to their old communities……………………………………………
In Japan, the condemnations of official policy, along with petitions calling for the reversal of the decision, have been constant since the ocean discharge plan was confirmed by the government in April last year.
Among the environmental groups denouncing the plan is FoE Japan. In a statement, it says the Japanese government and TEPCO had much earlier made written commitments on the matter, that “without the understanding of relevant personnel, no actions will be taken”. However, the government still decided to go ahead with the ocean discharge without seeking advice from the parties involved, the statement says.
Civil society groups in the most-affected prefectures submitted a petition to Japan’s Ministry of Economy, Trade and Industry and TEPCO in March. Reaffirming their opposition to the release of the contaminated water, they demanded that the government pursue other alternatives. Consumer groups and fisheries associations are at the forefront of this action.
The petition has collected some 180,000 signatures from residents in prefectures such as Fukushima, Iwate and Miyagi.
Under the government’s plan, the authorities will gradually discharge the still-contaminated water from next spring. Japan insists there are no alternatives to the ocean discharge. It says that by the end of 2022 there will be no space left at the site for storage. Moreover, after a treatment process known as the Advanced Liquid Processing System, or ALPS, the radioactive tritium－a radioactive isotope of hydrogen－will be the only radionuclide in the water and that it is harmless.
However, many environmental scientists and environmentalists are scathing in their condemnation of Japan’s narrative, saying it is misinformation aimed at creating a false impression that the consequences of the 2011 nuclear disaster are short-lived.
A report in 2020 by the environmental group Greenpeace says the narrative has been constructed to serve financial and political reasons.
“Long after the Yoshihide Suga (and Shinzo Abe) administrations are historical footnotes, the negative consequences of the Fukushima Daiichi meltdown will remain a present and constant threat most immediately to the people and environment of Fukushima, but also to the rest of Japan and internationally,” says the report, referring to Suga as the then prime minister whose government approved the disposal plan a year ago.
According to the Greenpeace report, there is no technical, engineering or legal barrier to securing storage space for ALPS-treated contaminated water. It is only a matter of political will and the decision is based on expediency－the cheapest option is ocean discharge.
“The discharge of wastewater from Fukushima is an act of contaminating the Pacific Ocean as well as the sea area of South Korea,” says Ahn Jae-hun, energy and climate change director at the Korea Federation for Environment Movement, an advocacy group in Seoul.
“Many people in South Korea believe that Japan’s discharge of the Fukushima wastewater is a wrong policy that threatens the safety of both the sea and humans.”
Shaun Burnie, a senior nuclear specialist with Greenpeace Germany, says the Fukushima contaminated water issue comes under the United Nations Convention on the Law of the Sea as it is a form of pollution to international waters.
There are strong grounds for individual countries to file a legal challenge against Japan’s plan, Burnie says. http://www.chinadaily.com.cn/a/202208/15/WS62f99f00a310fd2b29e7224e_1.html
Construction begins at Fukushima plant for water release
The construction of facilities needed for a planned release of treated radioactive wastewater into the sea next year from the damaged Fukushima nuclear power plant has begun despite opposition from the local fishing community
abc news, by MARI YAMAGUCHI Associated Press, August 04, 2022, TOKYO — The construction of facilities needed for a planned release of treated radioactive wastewater into the sea next year from the damaged Fukushima nuclear power plant began Thursday despite opposition from the local fishing community.
Plant workers started construction of a pipeline to transport the wastewater from hillside storage tanks to a coastal facility before its planned release next year, according to the plant operator, Tokyo Electric Power Company Holdings.
The digging of an undersea tunnel was also to begin later Thursday.
Construction at the Fukushima Daiichi plant follows the Nuclear Regulation Authority’s formal approval last month of a detailed wastewater discharge plan that TEPCO submitted in December.
The government announced last year a decision to release the wastewater as a necessary step for the plant’s ongoing decommissioning…………………..
Local fishing communities and neighboring countries have raised concerns about potential health hazards from the radioactive wastewater and the reputation damage to local produce, and oppose the release.
Scientists say the impact of long-term, low-dose exposure to not only tritium but also other isotopes on the environment and humans are still unknown and that a release is premature.
The contaminated water is being stored in about 1,000 tanks that require much space in the plant complex. Officials say they must be removed so that facilities can be built for its decommissioning. The tanks are expected to reach their capacity of 1.37 million tons in autumn of 2023…………………….
TEPCO and the government have obtained approval from the heads of the plant’s host towns, Futaba and Okuma, for the construction, but local residents and the fishing community remain opposed and could still delay the process. The current plan calls for a gradual release of treated water to begin next spring in a process that will take decades………………..
High anxiety as Japan takes another step toward releasing wastewater from crippled Fukushima nuclear plant into sea.
China, South Korea, Taiwan, Hong Kong and Macau) still have import bans in place.
concern about whether the discharge of enormous amounts of wastewater could set a bad precedent for dealing with future nuclear accidents.
CBS News BY LUCY CRAFT, 25 July 22, Tokyo — The fishing industry around Japan’s Fukushima coast expressed disappointment and resignation over the weekend as long-expected plans to start releasing treated wastewater into the ocean from the crippled Fukushima Daiichi nuclear power plant moved one step closer to reality. The drastic measure has been adopted as the only practical way out of a dilemma that’s plagued the damaged plant for more than a decade……………………..
The unprecedented, controversial disposal operation is likely to take decades.
Since the massive 2011 earthquake and tsunami triggered meltdowns in three of the plant’s reactors, operator Tepco has struggled to manage the vast amount of contaminated water — a combination of reactor cooling water, rainwater and groundwater, all irradiated as it flows through the highly-radioactive melted reactor cores – accumulating at the facility.
As a stopgap, the grounds surrounding the damaged reactors have been converted into a giant tank farm, with more than 1,000 storage vessels holding 1,310,000 tons of wastewater.
Tepco has long warned that it will run out of storage space as soon as spring 2023, and that the structures are hampering the technologically challenging work of decommissioning the plant. The temporary storage solution is also highly vulnerable to any future natural disasters……………
Before construction of the undersea tunnel can even begin, however, Tepco’s proposal must win backing from the regional government in Fukushima Prefecture and the two affected towns of Okuma and Futaba. A Fukushima fish processing company representative told the Asahi newspaper, “to be honest, even if we oppose this, I don’t feel like we have any chance of overturning the decision.”
After years of painstaking efforts to convince the Japanese public and the rest of the world that their seafood is safe, the local fishing industry fears the ocean release will tarnish their brand anew. Tokyo has promised to buy catches if the industry suffers reputational damage.
Of the 55 countries and regions that imposed restrictions on imported Japanese food after the Fukushima Daiichi catastrophe — including the U.S. — five (China, South Korea, Taiwan, Hong Kong and Macau) still have import bans in place.
Regulators solicited public comment and said they had received more than 1,200 responses, including people voicing concern over whether the undersea tunnel would be earthquake-safe, and what was being done to protect workers.
Tokyo has said levels of tritium — the one isotope that can’t be filtered out — will be diluted to below 1/40th of the allowable level for discharge in Japan, and 1/7th the WHO ceiling for drinking water.
Still, some experts have called for greater transparency, fearing unintended consequences of the operation. There is also concern about whether the discharge of enormous amounts of wastewater could set a bad precedent for dealing with future nuclear accidents. https://www.cbsnews.com/news/japan-fukushima-daiichi-nuclear-plant-wastewater-release-into-sea-approved/
Stiff resistance by fishing unions to Japan’s move to dump Fukushima nuclear wastewater into the ocean.
The impact of Japan’s 2011 earthquake and tsunami still ripples through
the country as the nation continues the decommissioning process of the
wrecked Fukushima Daiichi nuclear power plant. In addition to mass
evacuations of the surrounding area, the plant’s meltdown also uncovered
failings by its operator to take proper precautions, resulting in hefty
fines for four former executives.
The latest move involving the failed
plant has brought fresh criticism as Japan’s nuclear regulators approved
a plan to release water from the plant into the ocean, the government said
on Friday. The water, used to cool reactors in the aftermath of the 2011
nuclear disaster, is being stored in huge tanks in the plant, and amounted
to more than 1.3 million tonnes by July. The regulators deemed it safe to
release the water, which will still contain traces of tritium after
treatment, the foreign ministry said in a statement.
Plant operator Tokyo
Electric Power Company (Tepco) would face additional inspections by
regulators, it added. Tepco plans to filter the contaminated water to
remove harmful isotopes apart from tritium, which is hard to remove. Then
it will be diluted and released to free up plant space and allow
decommissioning to continue. The plan has encountered stiff resistance from
fishing unions in the region, which fear its impact on their livelihoods.
Neighbours China, South Korea and Taiwan have also voiced concern.
Irish Independent 24th July 2022
Japan’s nuclear regulator formally approves release of Fukushima wastewater to the Pacific
Japan’s nuclear regulator on Friday formally approved a plan to release
more than a million tonnes of treated water from the crippled Fukushima
nuclear power plant into the ocean.
The plan has already been adopted by
the government and endorsed by the International Atomic Energy Agency
(IAEA), but plant operator TEPCO must still win over local communities
before going ahead. The country’s Nuclear Regulation Authority approved
TEPCO’s plan, according to a foreign ministry statement, which said the
government would ensure the safety of the treated water as well as the
“reliability and transparency of its handling”.
Daily Mail 22nd July 2022
Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident.
Abstract
Understanding the actual situation of radiocesium (137Cs) contamination of trees caused by the Fukushima nuclear accident is essential for predicting the future contamination of wood. Particularly important is determining whether the 137Cs dynamics within forests and trees have reached apparent steady state. We conducted a monitoring survey of four major tree species (Japanese cedar, Japanese cypress, konara oak, and Japanese red pine) at multiple sites. Using a dynamic linear model, we analyzed the temporal trends in 137Cs activity concentrations in the bark (whole), outer bark, inner bark, wood (whole), sapwood, and heartwood during the 2011–2020 period. The activity concentrations were decay-corrected to September 1, 2020, to exclude the decrease due to the radioactive decay. The 137Cs concentrations in the whole and outer bark samples showed an exponential decrease in most plots but a flat trend in one plot, where 137Cs root uptake is considered to be high. The 137Cs concentration ratio (CR) of inner bark/sapwood showed a flat trend but the CR of heartwood/sapwood increased in many plots, indicating that the 137Cs dynamics reached apparent steady state within one year in the biologically active parts (inner bark and sapwood) and after several to more than 10 years in the inactive part (heartwood). The 137Cs concentration in the whole wood showed an increasing trend in six plots. In four of these plots, the increasing trend shifted to a flat or decreasing trend. Overall, the results show that the 137Cs dynamics within forests and trees have reached apparent steady state in many plots, although the amount of 137Cs root uptake in some plots is possibly still increasing 10 years after the accident. Clarifying the mechanisms and key factors determining the amount of 137Cs root uptake will be crucial for predicting wood contamination.
Introduction
After the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March of 2011, a wide area of forests in eastern Japan was contaminated with radionuclides. In particular, radiocesium (137Cs) has the potential to threaten the forestry and wood production in the contaminated area for many decades because it was released in large amounts (10 PBq)1 and has a relatively long half-life (30 years). Radiocesium levels for some wood uses are strictly regulated in Japan (e.g., 40 Bq kg−1 for firewood2 and 50 Bq kg−1 for mushroom bed logs3), meaning that multipurpose uses of wood from even moderately contaminated areas are restricted. Although a guidance level of radiocesium in construction wood has not been declared in Japan, the permissible levels in some European countries (370–740 Bq kg−1)4,5,6 suggest that logging should be precautionary within several tens of kilometers from the FDNPP, where the 137Cs activity concentration in wood potentially exceeds 1,000 Bq kg−1 [refs. 7,8]. To determine whether logging should proceed, the long-term variation in wood 137Cs concentration must be predicted as accurately as possible. Many simulation models successfully reproduce the temporal variations in the early phase after the FDNPP accident, but produce large uncertainties in long-term predictions9. To understand the 137Cs dynamics in forests and trees and hence refine the prediction models, it is essential to provide and analyze the observational data of 137Cs activity concentrations in tree stem parts.
Accident-derived 137Cs causes two types of tree contamination: direct contamination by 137Cs fallout shortly after the accident, and indirect contamination caused by surface uptake from directly contaminated foliage/bark10,11 and root uptake from contaminated soil12. The 137Cs concentration in bark that pre-exists the accident was affected by both 137Cs drop/wash off from bark surfaces and 137Cs uptake because the bark consists of a directly contaminated outer bark (rhytidome) and an indirectly contaminated inner bark (phloem). Given that the 137Cs content was 10 times higher in the outer bark than in the inner bark in 201213 and the 137Cs concentration in the whole bark decreased during the 2011–2016 period at many study sites8, the temporal variation in the whole bark 137Cs concentration during the early post-accident phase must be mainly contributed by drop/wash off of 137Cs on the outer bark surface.
In contrast, stem wood (xylem) covered by bark was contaminated only indirectly. Although 137Cs distribution in sapwood (outer part of stem wood; containing living cells) and heartwood (inner part of stem wood; containing no living cells) is non-uniform and species-specific8,13,14,15, the 137Cs concentration in whole wood depends on the amount of 137Cs uptake. Because the dissolvable 137Cs on the foliar/bark surface decreased significantly within 201116, the main route of 137Cs uptake since 2012 is likely root uptake rather than surface uptake. A monitoring survey during 2011–2016 showed that the temporal trend in the whole wood 137Cs concentration can be increasing, decreasing, or flat8, suggesting that 137Cs root uptake widely differs among sites and species.
Meanwhile, many simulation models have predicted an initial increase in the whole wood 137Cs concentration after the accident, followed by a gradual decline9. The initial increase is attributable to the increase in soil 137Cs inventory, and the following decline is mainly attributed to radioactive decay, dilution by wood biomass increment, and immobilization in the soil. Therefore, the trend shift from increasing to decreasing is a good indicator that shows the 137Cs dynamics within the forest have reached apparent steady state, which is characterized by slower changes in 137Cs concentration, bioavailability, and partitioning in the forest12,17,18. However, the timing of the trend shift predicted by the models have large uncertainty, varying from several years to a few decades from the accident9. Moreover, the trend shift has not been confirmed by observational data after the FDNPP accident. Although our monitoring survey cannot easily identify the key driving factors of the temporal trends, it can directly discern the trend shift from increasing to decreasing, and the timeframe of the increasing trend. The confirmation of the trend shift will accelerate the understanding of key factors of 137Cs root uptake, because important parameters such as transfer factor and CR are originally defined for a steady state condition18.
The present study aims to clarify the temporal trends of 137Cs concentrations in bark and wood of four major tree species (Japanese cedar, Japanese cypress, konara oak, and Japanese red pine) at multiple sites during the 10 years following the FDNPP accident. Detecting a trend shift from increasing to decreasing in the wood 137Cs concentration was especially important to infer whether the 137Cs dynamics within the forest have reached apparent steady state. We update Ohashi et al.8, who analyzed the monotonous increasing or decreasing trends during 2011–2016, with observational data of 2017–2020 and a more flexible time-series analysis using a dynamic linear model (DLM). The DLM is suitable for analyzing data including observational errors and autocorrelation, and has the advantage of being applicable to time-series data with missing years. For a more detailed understanding of bark contamination and the 137Cs dynamics in tree stems, we also newly provide data on the 137Cs concentrations in the outer and inner barks. The temporal trends in the 137Cs CRs of outer bark/inner bark, heartwood/sapwood, and inner bark/sapwood were analyzed to confirm whether the 137Cs dynamics within the trees have reached apparent steady state.
Materials and methods
Monitoring sites and species
The monitoring survey was conducted at five sites in Fukushima Prefecture (sites 1–4 and A1) and at one site in Ibaraki Prefecture (site 5), Japan (Fig. 1). Sites 1, 2, and A1 are located in Kawauchi Village, site 3 in Otama Village, site 4 in Tadami Town, and site 5 in Ishioka City. Monitoring at sites 1–5 was started in 2011 or 2012, and site A1 was additionally monitored since 2017. The tree species, age, mean diameter at breast height, initial deposition density of 137Cs, and sampling year of each sample at each site are listed in Table 1. The dominant tree species in the contaminated area, namely, Japanese cedar (Cryptomeria japonica [L.f.] D.Don), Japanese cypress (Chamaecyparis obtusa [Siebold et Zucc.] Endl.), konara oak (Quercus serrata Murray), and Japanese red pine (Pinus densiflora Siebold et Zucc.) were selected for monitoring. Japanese chestnut (Castanea crenata Siebold et Zucc.) was supplementally added in 2017. The cedar, cypress, and pine are evergreen coniferous species, and the oak and chestnut are deciduous broad-leaved species. Sites 1 and 3 each have three plots, and each plot contains a different monitoring species. Site A1 has one plot containing two different monitoring species, and the remaining sites each have one plot with one monitoring species, giving ten plots in total.
Sample collection and preparation
Bulk sampling of bark and wood disks was conducted by felling three trees per year at all sites during 2011–20168,25 and at sites 3–5 and A1 during 2017–2020. Partial sampling from six trees per year was conducted at sites 1 and 2 during 2017–2020 (from seven trees at site 2 in 2017) to sustain the monitoring trees. All the samples were obtained from the stems around breast height. During the partial sampling, bark pieces sized approximately 3 cm × 3 cm (axial length × tangential length) were collected from four directions of the tree stem using a chisel, and 12-mm-diameter wood cores were collected from two directions of the tree stem using an automatic increment borer (Smartborer, Seiwa Works, Tsukuba, Japan) equipped with a borer bit (10–101-1046, Haglöf Sweden, Långsele, Sweden). Such partial sampling increases the observational errors in the bark and wood 137Cs concentrations in individual trees26. To mitigate this error and maintain an accurate mean value of the 137Cs concentration, we increased the number of sampled trees from three to six. The sampling was conducted mainly in July–September of each year; the exceptions were site-5 samples in 2011 and 2012, which were collected irregularly during January–February of the following year. The collected bark pieces were separated into outer and inner barks, and the wood disks and cores were split into sapwood and heartwood. The outer and inner bark samples during 2012–2016 were obtained by partial sampling of barks sized approximately 10 cm × 10 cm from 2–3 directions on 2–3 trees per year.
The bulk samples of bark, sapwood, and heartwood were air-dried and then chipped into flakes using a cutting mill with a 6-mm mesh sieve (UPC-140, HORAI, Higashiosaka, Japan). The pieces of the outer and inner bark were chipped into approximately 5 mm × 5 mm pieces using pruning shears, and the cores of the sapwood and heartwood were chipped into semicircles of thickness 1–2 mm. Each sample was packed into a container for radioactivity measurements and its mass was measured after oven-drying at 75 °C for at least 48 h. Multiplying this mass by the conversion factor (0.98 for bark and 0.99 for wood)8 yielded the dry mass at 105 °C.
Radioactivity measurements
The radioactivity of 137Cs in the samples was determined by γ-ray spectrometry with a high-purity Ge semiconductor detector (GEM20, GEM40, or GWL-120, ORTEC, Oak Ridge, TN). For measurements, the bulk and partial samples were placed into Marinelli containers (2.0 L or 0.7 L) and cylindrical containers (100 mL or 5 mL), respectively. The peak efficiencies of the Marinelli containers, the 100-mL container, and the 5-mL container were calibrated using standard sources of MX033MR, MX033U8PP (Japan Radioisotope Association, Tokyo, Japan), and EG-ML (Eckert & Ziegler Isotope Products, Valencia, CA), respectively. For the measurement of the 5-mL container, a well-type Ge detector (GWL-120) was used under the empirical assumption that the difference in γ-ray self-absorption between the standard source and the samples is negligible27. The measurement was continued until the counting error became less than 5% (higher counting errors were allowed for small or weakly radioactive samples). The activity concentration of 137Cs in the bark (whole) collected by partial sampling was calculated as the mass-weighted mean of the concentrations in the outer and inner barks; meanwhile, the concentration in the wood (whole) was calculated as the cross-sectional-area-weighted mean of sapwood and heartwood concentrations. The activity concentrations were decay-corrected to September 1, 2020, to exclude the decrease due to the radioactive decay.
Discussion
Causes of temporal trends in bark 137Cs concentration
The 137Cs concentration in the whole bark decreased in many plots, clearly because the outer bark 137Cs concentration decreased. However, the whole bark 137Cs concentration showed a relatively small decrease or even a flat trend in some plots (site-2 cedar and site-1 cypress and oak). In the site-1 cypress plot, where the whole bark 137Cs concentration decreased relatively slowly, the inner bark 137Cs concentration notably increased. Similarly, although we lack early phase monitoring data in the site-2 cedar and site-1 oak plots, the inner bark 137Cs concentration in both plots is considered to have increased prior to monitoring because the sapwood 137Cs concentration increased in both plots and the CR of inner bark/sapwood was constant in all other plots. Therefore, the low-rate decrease or flat trend in the whole bark 137Cs concentration in some plots was probably caused by an increase in the inner bark 137Cs concentration, itself likely caused by high 137Cs root uptake (as discussed later).
The 137Cs concentration in the outer bark decreased in all four plots monitored since 2012 (site-1 and site-3 cedar, site-1 cypress, and site-3 pine), confirming the 137Cs drop/wash off from the bark surface. The constant (exponential) decrease in three of these plots indicates that the 137Cs drop/wash off was still continuing in 2020 but with smaller effect on the outer bark 137Cs concentration. In contrast, the decrease in the site-1 cypress plot seemed to slow down since around 2017. Furthermore, Kato et al.32 reported no decrease in 137Cs concentration in the outer bark of Japanese cedar during the 2012–2016 period. Such cases cannot be fitted by a simple decrease of the outer bark 137Cs concentration. As a longer-term perspective, in the outer bark of Norway spruces (Picea abies) affected by the Chernobyl nuclear accident, the biological half-life of 137Cs concentration was extended in areas with higher precipitation, suggesting that high root uptake of 137Cs hinders the decreasing trend33. The present study showed that 70–80% or more of the 137Cs deposited on the bark surface (outer bark) was removed by drop/wash off after 10 years from the accident and that the 137Cs CR of outer bark/inner bark became constant in some plots. These facts suggest that the longer-term variations in outer bark 137Cs concentration will be more influenced by 137Cs root uptake, although it is uncertain whether root uptake caused the slowing down of the decrease rate seen in the site-1 cypress plot. Further studies are needed to understand the 137Cs concentration in newly formed outer bark and to determine the 137Cs CR of outer bark/inner bark at steady state.
Causes of temporal trends in wood 137Cs concentration
The temporal trends of the 137Cs concentration in the whole wood basically corresponded to those in the sapwood. The exceptions were the site-3 and site-4 cedar plots, where the sapwood 137Cs concentration did not increase but the whole wood 137Cs concentration was raised by the notable increase in the heartwood 137Cs concentration. This behavior can be attributed to a species-specific characteristic of Japanese cedar, which facilitates Cs transfer from sapwood to heartwood8,15,34. The present study newly found that the increase in the 137Cs CR of heartwood/sapwood in the cedar plots became smaller or shifted to a flat trend around 2015–2016, indicating that 137Cs transfer between the sapwood and heartwood has reached apparent steady state at many sites 10 years after the accident. Therefore, after 2020, the whole wood 137Cs concentration in cedar is unlikely to increase without a concomitant increase in the sapwood 137Cs concentration.
The increasing trends in the 137Cs concentrations in whole wood and sapwood (site-2 cedar, site-1 cypress, and site-1 and site-3 oak plots) are seemingly caused by the yearly increase in 137Cs root uptake; however, the wood 137Cs concentration can also increase when the 137Cs root uptake is constant or even slightly decreases each year. This behavior can be shown in a simple simulation of the temporal variation in the wood 137Cs content (the amount of 137Cs in stem wood of a tree). If the 137Cs dynamics within a tree have reached steady state and the proportion of 137Cs allocated to stem wood become apparently constant, the wood 137Cs content in a given year can be considered to be determined by the amount of 137Cs root uptake and the amount of 137Cs emission via litterfall. The flat 137Cs CR trend of inner bark/sapwood during 2012–2020 (see Fig. 5) indicates that the 137Cs dynamics, at least those between the inner bark and sapwood, reached apparent steady state within 2011. Here we assume that (1) the annual amount of 137Cs root uptake is constant, (2) the proportion of 137Cs allocated to stem wood is apparently constant, and as assumed in many forest Cs dynamics models17,35,36,37, (3) a certain proportion of 137Cs in the stem wood is lost via litterfall each year. Under these conditions, the simulated amount of 137Cs emission balanced the amount of 137Cs root uptake after sufficient time, and the wood 137Cs content approached an asymptotic value calculated as [root uptake amount × allocation proportion × (1/emission proportion − 1)]. Note that the asymptotic value increases with increasing root uptake amount and decreasing emission proportion and does not depend on the amount of 137Cs foliar/bark surface uptake in the early post-accident phase. Nevertheless, the amount of 137Cs surface uptake in the early phase critically determines the trend of the wood 137Cs content. More specifically, the trend in the early phase will be increasing (decreasing) if the surface uptake is smaller (larger) than the asymptotic value. Finally, the temporal variation of the 137Cs concentration in wood is thought to be the sum of the dilution effect of the increasing wood biomass and the above-simulated variation in the wood 137Cs content. Therefore, in the early post-accident phase, the wood 137Cs concentration will increase when the wood 137Cs content increases at a higher rate than the wood biomass. As the wood 137Cs content approaches its asymptotic value (i.e., steady state), its increase rate slows and the dilution effect proportionally increases. Then, the wood 137Cs concentration shifts from an increasing trend to a decreasing trend. The trends of the 137Cs concentrations in whole wood and sapwood in the site-3 oak plot follow this basic temporal trend, which is similarly predicted by many simulation models9.
In other plots with the increasing trend (site-2 cedar and site-1 cypress and oak), the increase in the 137Cs concentrations in whole wood and sapwood became smaller or shifted to a flat trend around six years after the accident; however, it did not shift to a decreasing trend. This lack of any clear shift to a decreasing trend, which was similarly seen at sites with hydromorphic soils after the Chernobyl nuclear accident38,39, cannot be well explained by the above simulation. A core assumption of the simulation that the yearly amount of 137Cs root uptake is constant is probably violated in these plots, leading to underestimations of the root uptake amount. Although the inventory of exchangeable 137Cs in the organic soil layer has decreased yearly since the accident, that in the mineral soil layer at 0–5 cm depth has remained constant40. In addition, the downward migration of 137Cs has increased the 137Cs inventory in the mineral soil layer below 5-cm depth41,42. If the steady state 137Cs inventory of the root uptake source can be regarded as sufficient for trees, any increase in the 137Cs root uptake is likely explained by expansion of the root distribution and the increase in transpiration (water uptake) with tree growth. When the wood 137Cs content increases at a similar rate to the wood biomass, the increasing trend will not obviously shift to a decreasing trend. Therefore, assuming the 137Cs allocation and emission proportions in the mature trees do not change considerably with time, the amount of 137Cs root uptake is considered to be increasing yearly in these four plots.
In the remaining plots with the decreasing or flat trend (site-1 cedar, site-4 cedar without outliers, site-5 cypress, and site-3 pine), according to the above simulation, the amount of initial 137Cs surface uptake was larger than or similar to the asymptotic value, i.e. the amount of 137Cs root uptake is relatively small and/or the proportion of 137Cs emission via litterfall is relatively high. However, the amount of 137Cs root uptake in the plots with the flat trend is possibly increasing because the flat trend has not shifted to a decreasing trend. In these plots, although it is difficult to confirm apparent steady state of the soil–tree 137Cs cycling because of the lack of an initial increasing trend, the recent flat trends in the 137Cs CRs of heartwood/sapwood and inner bark/sapwood indicate that the 137Cs dynamics, at least within the trees, have reached apparent steady state.
Various factors were found to increase the 137Cs root uptake after the Chernobyl nuclear accident; for example, high soil water content, high soil organic and low clay content (i.e., low radiocesium interception potential [RIP]), low soil exchangeable K concentration, and high soil exchangeable NH4 concentration12,43. After the FDNPP accident, the 137Cs transfer from soil to Japanese cypress and konara oak was found to be negatively correlated with the soil exchangeable K concentration44,45 and the 137Cs mobility is reportedly high in soils with low RIP46. However, neither the soil exchangeable K and Cs concentrations nor the RIP have explained the different 137Cs aggregated transfer factors (defined as [137Cs activity concentration in a specified component/137Cs activity inventory in the soil]) of Japanese cedars at sites 1–446,47. Because the 137Cs dynamics within the forest and trees in many plots reached apparent steady state at 10 years after the FDNPP accident, the 137Cs aggregated transfer factor is now considered to be an informative indicator of the 137Cs root uptake. Therefore, a comprehensive analysis of the 137Cs aggregated transfer factor and the soil properties at more sites than in the present study will be important to understand key factors determining the amount of 137Cs root uptake by each tree species at each site.
Validity and limitation of the trend analyses
Although the application of the smooth local linear trend model failed in plots monitored for less than five years, it was deemed suitable for analyzing the decadal trend because it removes annual noises, which are probably caused by relatively large observational errors (including individual variability)26. Moreover, the algorithm that determines the trend and its shift between 2 and 4 delimiting years was apparently reasonable, because the detected trends well matched our intuition. However, when judging a trend, the algorithm simply assesses whether the true state values significantly differ between the delimiting years. Therefore, it cannot detect changes in the increase/decrease rate (i.e., whether an increasing/decreasing trend is approaching a flat trend). For example, the whole bark 137Cs concentration in the site-1 cypress plot was determined to decrease throughout the monitoring period. In fact, the decrease rate slowed around 2014 and the decreases were slight between 2014 and 2020 (see Fig. 2). Similarly, the sapwood 137Cs concentration in the site-1 cypress and oak plots was determined to increase throughout the monitoring period, but the increase rate has clearly slowed since around 2017. To more sensitively detect the shift from an increasing/decreasing trend to a flat trend, other algorithms are required. Nevertheless, this algorithm is acceptable for the chief aim of the present study; that is, to detect a trend shift from increasing to decreasing.
Conclusions
In many plots monitored at Fukushima and Ibaraki Prefectures, the 137Cs concentrations in the whole and outer bark decreased at almost the same yearly rate for 10 years after the FDNPP accident, indicating that the direct contamination of the outer bark was mostly but not completely removed during this period. Moreover, the 137Cs concentration in the whole bark decreased at relatively low rates or was stable in plots where the 137Cs root uptake was considered to be high. This fact suggests that indirect contamination through continuous root uptake can reach the same magnitude as direct contamination by the accident.
In all of our analyzed plots, the 137Cs CR of inner bark/sapwood has not changed since 2012, indicating that 137Cs transfer among the biologically active parts of the tree stem had already reached apparent steady state in 2011. In contrast, the 137Cs CR of heartwood/sapwood in six out of nine plots increased after the accident. In four of these plots, the 137Cs CR of heartwood/sapwood plateaued after 3–6 years; in the other two plots, the plateau was not reached even after 10 years. Therefore, saturation of 137Cs in heartwood (an inactive part of the tree stem) requires several years to more than one decade.
The 137Cs concentration in the whole wood showed an increasing trend in six out of nine plots. In four of these plots, the increasing trend shifted to a flat or decreasing trend, indicating that the 137Cs dynamics in many forests reached apparent steady state at 10 years after the accident. However, the lack of the clear shift to a decreasing trend indicates that the 137Cs root uptake is probably still increasing in some plots. Continuous monitoring surveys and further studies clarifying the complex mechanisms of 137Cs root uptake in forests are needed in order to refine the simulation models and improve their prediction accuracy.
Japan OKs plan to release Fukushima nuclear plant wastewater
Japan’s nuclear regulator has approved plans by the operator of the wrecked Fukushima nuclear plant to release its treated radioactive wastewater into the sea next year, saying the outlined methods are safe and risks to the environment minimal
By Mari Yamaguchi Associated Press, May 18, 2022,
………. There is still concern in the community and neighboring countries about the potential health hazards of the release of the wastewater that includes tritium — a byproduct of nuclear power production and a possible carcinogen at high levels.
The government and TEPCO say more than 60 isotopes selected for treatment can be lowered to meet safety standards, except for tritium, but that it is safe if diluted. Scientists say impact of long term low-dose exposure to the environment and humans are unknown, and that tritium can have a bigger impact on humans when consumed in fish than in water.
,,,,,,,,,, Under the plan, TEPCO will transport water that has been treated to below releasable levels through a pipeline from the tanks to a coastal facility, where the water is diluted with seawater.
From there, the water will enter an undersea tunnel to be discharged at a point about 1 kilometer (0.6 mile) from the plant to ensure safety and minimize the impact on local fishing and the environment, according to TEPCO.
The plan will become official after a 30-day public review, a formality that is not expected to overturn the approval.
………..The contaminated water is being stored in about 1,000 tanks at the damaged plant, which officials say must be removed so that facilities can be built for its decommissioning. The tanks are expected to reach their capacity of 1.37 million tons next year — slower than an earlier estimate of later this year……….. https://abcnews.go.com/Technology/wireStory/japan-oks-plan-release-fukushima-nuclear-plant-wastewater-84800836
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