At the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station, which caused the worst accident in history, investigations and preparations are underway to remove the melted "nuclear fuel debris", while construction work to release the treated water that continues to accumulate has been completed. is approaching.
At the Fukushima Daiichi Nuclear Power Plant, power was lost due to the huge earthquake and tsunami, and nuclear fuel melted down in three reactors, causing a "meltdown" and releasing a large amount of radioactive material.
In the reactors and containment vessels of Units 1 to 3, "nuclear fuel debris" remains, which is melted nuclear fuel mixed with structures, and the water used for cooling and groundwater become contaminated water. It continues to increase at a pace of 100 tons per day.
As of March 2, the amount of treated water containing radioactive substances such as tritium that remains after treating this contaminated water has reached approximately 1.33 million tons. I expect the tank to be full.
The government plans to start releasing it into the sea from spring to summer this year after diluting it to 1/40 of the standard, and the construction of the undersea tunnel used for release is expected to be completed in June.
On the other hand, there are deep-rooted voices of opposition, mainly from fishermen and others, and the issue is whether the government and TEPCO can gain the understanding of the parties concerned as the discharge into the ocean is imminent.
In addition, the start of the removal of "nuclear fuel debris", which is considered to be the biggest difficulty in decommissioning, is planned for Unit 2 after October this year.
The initial extraction is positioned as a trial, and the plan is to extract several grams using a robotic arm.
However, the total amount of "nuclear fuel debris" from Units 1 to 3 is estimated to be as high as 880 tons, and there is no concrete path for how to retrieve it.
Akira Ono, CEO of TEPCO's Fukushima Daiichi Decommissioning Engineering Company, said in an interview on March 1, "Fuel debris retrieval and treated water issues are unavoidable in advancing decommissioning. The first year may be a turning point in determining whether future decommissioning work can be carried out safely and steadily."
What is Fukushima Daiichi Nuclear Power Plant?
On March 11, 2011, at TEPCO's Fukushima Daiichi Nuclear Power Station, Units 1 to 3 of the six reactors were in operation, while the remaining three reactors were shut down for periodic inspections.
Around 2:46 pm, a huge earthquake with a magnitude of 9.0 occurred off the Tohoku coast.
All three operating reactors were shut down.
Due to the effects of the earthquake, transmission towers collapsed, which cut off the supply of electricity from the outside, and the emergency generators started up. The building containing such items was flooded.
All power needed to cool the nuclear fuel has been lost.
A few hours later, it is believed that a meltdown occurred at Unit 1, where the nuclear fuel melted away, and around 3:30 p.m. An explosion occurred.
Furthermore, meltdowns occurred in Units 3 and 2 one after another.
In Unit 3, a hydrogen explosion occurred shortly after 11:00 a.m. on March 14, and in Unit 2, although a hydrogen explosion did not occur, there is a possibility that the containment vessel was severely damaged. A large amount of radioactive material is believed to have been released outside.
In addition, Unit 4, which had been stopped, exploded shortly after 6:00 a.m. on the 15th due to hydrogen flowing from the exhaust pipe connected to Unit 3.
According to the international standards that indicate the seriousness of the accident, it is the most serious "Level 7".
It was the worst accident in history, along with the 1986 accident at the former Soviet Union's Chernobyl nuclear power plant in present-day Ukraine.
[Changes in nuclear power policy and issues]
Shift in nuclear power policy 1 Extension of operation
After the accident at Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station, the government revised the law to limit the operating period of nuclear power plants to 60 years, and has expressed the view that it is ``not envisioned'' for new construction or expansion. .
The government has changed the direction of these policies significantly.
The content was to maximize the use of nuclear power plants with top priority on safety.
In the Basic Energy Plan, which sets out the direction of the government's energy policy announced in 2021, the government clearly states that "Nuclear power gives top priority to safety, and we will reduce our dependence on nuclear power as much as possible while expanding renewable energy." doing.
The government claims that this plan and the new policy are not inconsistent, but as the energy crisis worsens due to the global decarbonization movement and Russia's military invasion of Ukraine, the restart will be accelerated. In order to continue to use nuclear power plants, we have stepped in to substantially extend the operation period and change policies regarding new construction and expansion, and the nuclear power policy has undergone the most significant change since the nuclear accident.
One of the pillars of the policy to "maximize the use of nuclear power plants" newly announced in February 2023 is the suspension period due to examination etc. for the maximum operating period of 60 years after the nuclear accident. was to change it so that it could be driven practically beyond the upper limit by excluding .
In response to this, the Nuclear Regulation Authority decided on a new system for confirming the safety of nuclear power plants according to the number of years of aging. has not yet been determined and is currently under consideration.
Change in Nuclear Policy 2 Next-Generation Reactors and Restarts
Another pillar of the new nuclear power policy is that after the nuclear accident, the government expressed its view that it would approve the construction, expansion, and rebuilding of nuclear power plants, which it had said was "unforeseen."
Specifically, it included the development and construction of next-generation nuclear reactors for rebuilding on the premises of decommissioned nuclear power plants.
These next-generation reactors are envisioned to be of five types:
▼Innovative light water reactors
▼Small light water reactors
▼Fast reactors ▼High
temperature gas-cooled reactors
▼Nuclear fusion reactors I'm having an issue with my face.
Furthermore, in order to accelerate the restart of nuclear power plants, the government has also announced a policy to take the national government at the forefront.
These seven reactors are
: Tohoku Electric Power Company's Onagawa Nuclear Power Station No. 2 in Miyagi Prefecture,
Tokyo Electric Power Company's Kashiwazaki-Kariwa Nuclear Power Station Units 6 and 7 in
Niigata Prefecture, Japan Atomic Power Company's Tokai No. 2 Nuclear Power Plant in Ibaraki Prefecture
, and Fukui Prefecture. Kansai Electric Power's Takahama Nuclear Power Station Units 1 and 2. Chugoku
Electric Power Company's Shimane Nuclear Power Station Unit 2 in Shimane Prefecture.
Many issues surrounding nuclear power
While the government has come up with a policy to promote the use of nuclear power plants, troubles related to the safety of nuclear power plants are also occurring.
In January 2023, at Unit 4 of the Takahama Nuclear Power Plant in Fukui Prefecture, the reactor will automatically shut down when an alarm is issued indicating that the amount of neutrons in the reactor, which indicates the state of nuclear fission, has suddenly decreased during operation. Something went wrong.
According to Kansai Electric Power's investigation so far, one of the 48 control rods fell into the reactor due to an electrical failure, partially suppressing the nuclear fission reaction, reducing the amount of neutrons and issuing an alarm. It is
Shinsuke Yamanaka, Chairman of the Nuclear Regulation Authority, pointed out, ``Since the trouble is in a very important part of the nuclear reactor, we want you to investigate the cause and deal with it with a sense of urgency.'' I'm looking for workarounds etc.
In addition, in 2021, at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture, which is aiming to restart operations, there have been a series of anti-terrorism problems such as unauthorized entry by employees into the main control room and inadequate equipment to detect intrusion from the outside. Found in
Based on this, the Nuclear Regulation Authority has issued an administrative disposition to effectively prohibit the operation of the Kashiwazaki-Kariwa Nuclear Power Station to TEPCO, and additional inspections to investigate the status of improvement measures are continuing. We plan to compile the test results by the end of May.
However, Chairman Yamanaka of the Regulatory Commission confirmed that there were deficiencies in the equipment to detect intrusions from the outside during inspections, and he acknowledged that it would be difficult for TEPCO to make improvements in a short period of time. So, it is difficult to lift the administrative disposition in May, and it is expected that it will take a certain amount of time if the inspection is continued.
In addition, there are areas that have problems with evacuation plans in preparation for a nuclear power plant accident that will lead to protecting the lives of residents.
Municipalities surrounding the Tokai Daini Nuclear Power Plant in Ibaraki Prefecture have not made progress in formulating a wide-area evacuation plan, which is essential for protecting the safety of residents.
Approximately 940,000 people, the largest number in Japan, live within a 30-kilometer radius around the Tokai No. 2 Nuclear Power Plant, where immediate evacuation or shelter-in-place is required in the event of an accident.
In order to protect the safety of residents, it is necessary to have a wide-area evacuation plan that stipulates routes to avoid traffic jams and securing evacuation destinations. As of the end of February, only 5 out of 14 municipalities around the nuclear power plant were affected.
Furthermore, policy issues related to the “nuclear fuel cycle” remain unresolved.
The reprocessing plant under construction in Rokkasho Village, Aomori Prefecture, has repeatedly postponed the completion date, and the "pu-thermal" that uses "MOX fuel" containing plutonium in general nuclear power plants is not progressing as planned.
In addition, the selection of a disposal site for so-called "nuclear waste", which is a high-level radioactive waste made by mixing glass with radioactive liquid waste after reprocessing of spent nuclear fuel, is uncertain. In the policy of nuclear power generation policy, we will strengthen efforts to solve these problems.
[A long-standing issue in nuclear policy: “Nuclear waste” with no exit]
A long-standing issue in nuclear power policy is the problem of high-level radioactive waste, so-called "nuclear waste," which is produced after power generation at nuclear power plants.
In order to select a disposal site for "nuclear waste", the government and businesses have strengthened their efforts, such as publishing a map showing scientifically promising sites and holding explanatory meetings, etc., and research for selection is progressing. Although some local governments have already taken action, further progress is unclear, and the situation continues where no exit is in sight.
What is "Nuclear Waste"?
Nuclear power plants generate spent nuclear fuel during operation, and in Japan, the pillar of nuclear power policy is the "nuclear fuel cycle," in which plutonium and uranium are extracted from these fuels and reused as fuel.
The reprocessing process leaves waste liquid containing radioactive materials that cannot be reused.
In order to chemically stabilize this waste liquid, it is mixed with glass and hardened to form high-level radioactive waste, so-called "nuclear waste". must be isolated for tens of thousands of years from
For this reason, the government has decided to set up a disposal site for "nuclear waste" in the ground deeper than 300 meters and bury it, but the situation has continued that the selection of the site has not progressed.
Selection of a difficult disposal site
In order to promote the selection of this final disposal site, a law was enacted in Japan in 2000, and a business operator called NUMO (Nuclear Waste Management Organization) solicited candidate sites from municipalities nationwide, and the national government also distributed them to local governments where surveys were conducted. We created a system to provide money and began full-scale efforts to select a disposal site.
After that, in 2007, Toyo Town in Kochi Prefecture applied for a survey for selection, but it was withdrawn due to objections from residents.
Since then, there have been no concrete moves to apply, and the selection of candidate sites has been difficult. In 2012, the Atomic Energy Commission, which makes proposals for the country's nuclear policy, said that efforts to obtain public consensus were insufficient. In addition, I summarized the view that the country should take the lead in selecting candidate sites.
In response to this, in 2014
, in addition to the conventional method of waiting for applications from local governments,
the national government introduced a method of presenting scientifically promising areas and requesting surveys for the selection of disposal sites to multiple local governments. I decided to include it.
As a gateway to this, in July 2017 we released a map called the "Scientific Characteristics Map," which indicates promising areas by color-coding the country based on scientific criteria such as the presence of volcanoes and active faults.
In this map, the areas designated as "areas with a relatively high possibility of confirming favorable characteristics" for disposal sites amounted to two-thirds of the national land area.
The government and NUMO did not press local governments to decide whether to accept the survey, and after publishing the map, they held briefing sessions in various places to deepen their understanding of the disposal of "nuclear waste."
However, after the briefing session started, in October 2017, it became clear that a company entrusted by NUMO had recruited university students with the promise of a reward, and inappropriate operations were revealed, and the briefing session was temporarily suspended. became.
In principle, NUMO took measures to prevent recurrence, such as directly managing the operation, and then resumed briefing sessions, which are still held in various places.
Two municipalities in Hokkaido applied
Under these circumstances, in 2020, there was a big movement toward selecting a disposal site.
For the first time after the publication of the "Scientific Characteristics Map", Suttsu Town and Kamoenai Village in Hokkaido announced that they would accept surveys for selection, and in November 2020, NUMO began surveys for the first time in Japan in two municipalities. is.
the investigation process
The survey is carried out in three stages, and currently, the first stage, "literature survey", is being conducted to investigate the presence or absence of active faults and volcanoes based on the information in the materials, so to speak, such as research data so far. .
The period is about two years, and if there is no problem with this survey, after obtaining the understanding of the prefectural governor and the head of the local government, the geology and groundwater conditions will be investigated by boring surveys over about four years. ” is performed.
Furthermore, the same procedure is followed to analyze the strata in detail, and proceed to a "precision survey" to investigate the stability of the strata in the future over a period of about 14 years, after which the final survey results will be compiled.
As for the construction of the actual disposal site, the national government will make a decision based on the results of the survey, listening to the opinions of the residents and the thoughts of the prefectural governments.
The government fully respects the opinion of the region in any stage of the investigation, and if they disagree, it will not proceed to the next stage of the investigation.
Progress to the next investigation stage is not foreseeable
The “literature survey” in two municipalities in Hokkaido, which started in November 2020, has passed the target of two years, and NUMO will summarize the evaluation in the future.
In order to proceed to the next stage, in addition to each town and village, the understanding of the governor of Hokkaido is necessary, but Governor Naomichi Suzuki has expressed opposition to the investigation in any municipality, and there is no prospect. .
The national government aims to expand the survey area, but there is no exit in sight
On the other hand, other than the two local governments in Hokkaido, there is no movement to apply for surveys aimed at selecting disposal sites, and it is difficult to say that interest is growing nationwide.
In countries such as France and Finland, where the selection of disposal sites is progressing, the government has indicated a policy aiming to increase the survey area, based on the fact that the site was narrowed down after conducting surveys in about 10 areas.
In February 2023, for the first time in eight years, we decided to revise our basic policy for the realization of final disposal of "nuclear waste" and put together a proposal for new initiatives.
As a specific initiative,
▽ the government will visit more than 100 local governments nationwide together with NUMO and electric power companies, and
▽ will set up a new forum for consultation with the top of the local government where the nuclear power plant is located. .
It is unclear whether these efforts will lead to progress in the investigation, and as the government shifts its nuclear policy toward maximizing the use of nuclear power plants, there continues to be no end in sight for the issue of disposal of "nuclear waste." .