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Unclear debris map casts shadow over decommissioning of Fukushima plant

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Pebble-like sediment believed to be nuclear fuel debris is lifted by a special device inside the No. 2 reactor containment vessel at the Fukushima Daiichi Nuclear Power Station.
April 9, 2019
TOKYO — The government and Tokyo Electric Power Co. (TEPCO) are set to launch full-scale probes of the inside of the No. 1 through No. 3 reactors at the disaster-stricken Fukushima Daiichi Nuclear Power Station this fiscal year, in an attempt to determine which reactor to work on first to remove fuel debris — a critical step for decommissioning the facility.
However, the interior of the No. 2 reactor, which is most likely to be the first to go through the debris removal process, has turned out to be different from what had originally been expected, underscoring the difficulties entailing the removal work. Since many companies are involved in the process, how to pass down the know-how acquired over the course of the more than 30 year-decommissioning process also poses a challenge.
“At present, it is difficult to clearly say we are going to remove all fuel debris,” said Akira Ono, who leads the decommissioning project, at a regular press conference by TEPCO on March 28, while noting that the utility will not back down from its ultimate goal of full debris removal.
If TEPCO fails to take out all debris from the nuclear plant, the very premise for dismantling the facility and returning the plot to its original state will be undermined. Such a scenario would adversely affect the disaster recovery plans envisaged by the national government and the Fukushima Prefectural Government. While awareness about the difficulty of debris removal has been shared among concerned parties, the actual dismal situation had not been recognized until TEPCO conducted the first debris survey at the No. 2 reactor on Feb. 13.
In that survey, a remotely controlled special device that was injected into the No. 2 reactor’s containment vessel succeeded in lifting portions of sediment accumulated at the bottom, which were believed to be fuel debris. Officials involved were relieved because they “had been worried the material would not move at all,” according to Ono.
The radiation level of the material, measured at a distance of some 30 centimeters, was 7.6 sieverts per hour, far less than anticipated. If the sediment contained a good portion of nuclear fuel, the radiation doses ought to have been several hundred sieverts per hour, even eight years after the 2011 nuclear meltdowns.
This finding suggested that the sediment that TEPCO came in contact with in the survey was not the main nuclear fuel debris it was looking for. Many speculate that the surface of the sediment may mainly consist of metals including cladding tubes that used to cover nuclear fuels.
The question now is whether fuel debris exists beneath the surface of the sediment or if nuclear fuel still remains within the reactor pressure vessel, or even somewhere else. There are currently no prospects for TEPCO to ascertain an accurate distributions of debris.
The material that was lifted in the survey mostly comprised pebble-like sediment, weighing less than 1 kilogram in total. Meanwhile, fuel debris generated in the core meltdowns is estimated to total 237 metric tons at the No. 2 reactor alone and a combined 880 tons at the No. 1 through No. 3 reactors.
At the No. 2 reactor, TEPCO will conduct a more detailed survey on debris possibly in the latter half of this fiscal year and attempt to collect small amounts of samples. At the No. 1 reactor, several apparatus including a robot submarine will be used to launch a full-scale survey inside the reactor to try to collect debris this fiscal year. As for the No. 3 reactor, the power company is apparently planning to prioritize removal of spent fuel, as related devices have gone through a series of glitches.
Unlike the other reactors, the No. 2 reactor did not suffer a hydrogen explosion in the 2011 disaster. Therefore, the No. 2 reactor remains the primary candidate for the first full-scale debris removal work, which is hoped to start in 2021.
With regard to the No. 1 and No. 3 reactors, the utility has yet to be able to reach materials appearing to be debris. The decommissioning of the nuclear plant is scheduled to be completed in 2051, a full 40 years after the triple meltdowns, but a concrete path toward that goal is not yet in sight.
“We have no choice but to remove whichever debris we can,” said a senior official with the Ministry of Economy, Trade and Industry.
Naoyuki Takaki, professor of nuclear engineering at Tokyo City University, commented, “There could ultimately be a decision to stop debris removal after pulling out as much debris as possible. In that case, we would have no option but to consider building a sarcophagus like the one at the Chernobyl nuclear plant.”

April 14, 2019 Posted by | fukushima 2019 | , , , | Leave a comment

Fukushima Daiichi Urged To Prepare For Future Tsunamis; No Sarcophagus For Meltdowns

TEPCO urged to cut risk of radioactive water leak
Japan’s nuclear regulator has urged the operator of the crippled Fukushima Daiichi nuclear power plant to reduce the risk of leaking of highly radioactive water from the facility into the sea, in case of another tsunami.
About 60,000 tons of such water is believed to have pooled in reactor buildings at the plant. The operator, Tokyo Electric Power Company, or TEPCO, is injecting water into the buildings to cool melted nuclear fuel, and groundwater is flowing into their basements.
The Nuclear Regulation Authority instructed TEPCO at a meeting on Tuesday to urgently study measures to lower the amount and radiation levels of the water.
The authority proposed 2 measures to TEPCO. One is building more tanks to store the water, even though the plant has about one thousand tanks. The other is treating the water using a system designed to filter out radioactive material, and circulating the water in a cooling system.
NRA member Toyoshi Fuketa said the utility cannot keep the water in the buildings forever. He said TEPCO should handle the water problem either along with that of other radioactive water or first of all.
Following the NRA’s instruction, TEPCO is to report the results of its study at a meeting next month or later.

State minister rules out sarcophagus option
Japan’s state minister for industry has ruled out the option of sealing off disabled reactors at the Fukushima Daiichi nuclear plant with a Chernobyl-style sarcophagus.

July 27, 2016 Posted by | Fukushima 2016 | , , , | Leave a comment

There’s no end to Fukushima crisis while melted fuel remains

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Fukushima Governor Masao Uchibori, left, speaks with Vice Industry Minister Yosuke Takagi

A massive concrete structure encases the wrecked No. 4 reactor at the Chernobyl nuclear power plant, site of the catastrophic 1986 accident.

Dubbed the “sarcophagus,” it was erected to contain the fuel that could not be extracted from the crippled reactor.

I never expected this word (“sekkan” in Japanese) to crop up in connection with the 2011 Fukushima nuclear crisis.

Local governments raised objections to the use of this word in a report compiled by a government organ that supports the decommissioning of the Fukushima No. 1 nuclear power plant.

While the report discusses the extraction of melted fuel as a requirement, it is written in such a way as to suggest that the construction of a sarcophagus is an option that should not be dismissed out of hand.

This outraged the governor of Fukushima, Masao Uchibori, who lashed out, “Containing (the melted fuel) in a sarcophagus spells giving up hope for post-disaster reconstruction and for returning home.”

The government organ has since deleted the word from the report, admitting that it was misleading and that constructing a sarcophagus is not under consideration.

The report lacked any consideration for the feelings of local citizens. But more to the point, just deleting the word does not settle this case.

Even though five years have passed since the disaster, nothing has been decided yet on how to extract the melted fuel. How, then, can anyone guarantee that the fuel will never be “entombed”?

I am reminded anew of the sheer difficulty of decommissioning nuclear reactors. The Fukushima edition of The Asahi Shimbun runs a weekly report on the work being done at the Fukushima No. 1 plant.

The report portrays the harsh realities at the site, such as leaks of contaminated water and accidents involving workers. Efforts to decommission the crippled reactors continue day after day, but the task is expected to take several decades.

Elsewhere in Japan, the rule that requires nuclear reactors to be decommissioned after 40 years is becoming toothless, and preparations are proceeding steadily for restarting reactors that have remained offline.

“Normalcy” appears to be returning, but there is a huge gap between that and the unending hardships in the disaster-affected areas.

http://www.asahi.com/ajw/articles/AJ201607230013.html

July 23, 2016 Posted by | Fukushima 2016 | , , | Leave a comment

No Chernobyl type Sarcophagus for Fukushima Daiichi?

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Chernobyl new safe confinement construction

After news inadvertently leaked via NHK that the decommissioning authority (NDF) for Fukushima Daiichi was considering a Chernobyl type sarcophagus for the plant, there is now an effort by the authority to back it down.

At the same time the government is rushing to reopen as much of the evacuation zone as possible so they can terminate evacuation compensation for the roughly 100,000 evacuees of the disaster.

Minamisoma reopened closed parts of the district this week and there is now consideration for opening highly radioactive zones in Okuma near the plant in a few years.

Mayors for the impacted towns near the plant expressed obvious outrage to the media after hearing the news.

The media reports and public concern are due to it even being on the table and that alone raises some obvious concerns.

NDF calls the media reports that they are considering a sarcophagus to be “untruthful” but go on to admit that it is now among the considered options.

Obviously such a structure would not be a medium term effort unless it involved some significant new design and long term plan.

NDF also tries to frame a sarcophagus as a more “medium term” solution.

They did confirm that this isn’t a done deal, but is an option they are considering.

Following that news Japan’s state minister for industry has ruled out the option of sealing off disabled reactors at the Fukushima Daiichi nuclear plant with a Chernobyl-style sarcophagus.

Takagi said the government’s policy is to stand by the people of Fukushima, and that his ministry has told the decommissioning body to rewrite its technical report.

Responding to Uchibori, Takagi said the government has no intention of using such an option, and that completing the decommissioning process is the top priority.

The body said it remained committed to removing fuel debris from the reactors that suffered meltdowns in the March 2011 accident.

But it presented a technical report that left room for entombing the reactors in a massive metal and concrete structure.

Yosuke Takagi met Fukushima Governor Masao Uchibori in Tokyo on Friday.

Uchibori said he was shocked to hear the word “sarcophagus” and called the option unacceptable.

http://www3.nhk.or.jp/nhkworld/en/news/20160715_27/

https://www.youtube.com/attribution_link?a=yfLq5-_Bu4U&u=%2Fwatch%3Fv%3Ddmw_uFGEZmw%26feature%3Dshare

https://dunrenard.wordpress.com/2016/07/17/state-minister-rules-out-sarcophagus-option/

 

July 19, 2016 Posted by | Fukushima 2016 | , | Leave a comment

State minister rules out sarcophagus option

 

 

Japan’s state minister for industry has ruled out the option of sealing off disabled reactors at the Fukushima Daiichi nuclear plant with a Chernobyl-style sarcophagus.

Yosuke Takagi met Fukushima Governor Masao Uchibori in Tokyo on Friday.

Uchibori said he was shocked to hear the word “sarcophagus” and called the option unacceptable.

Two days earlier, a government body charged with decommissioning the plant operated by Tokyo Electric Power Company mentioned the sarcophagus method for the first time.

The body said it remained committed to removing fuel debris from the reactors that suffered meltdowns in the March 2011 accident. But it presented a technical report that left room for entombing the reactors in a massive metal and concrete structure.

Responding to Uchibori, Takagi said the government has no intention of using such an option, and that completing the decommissioning process is the top priority.

Takagi said the government’s policy is to stand by the people of Fukushima, and that his ministry has told the decommissioning body to rewrite its technical report.

http://www3.nhk.or.jp/nhkworld/en/news/20160715_27/

 

July 17, 2016 Posted by | Fukushima 2016 | , , , | Leave a comment

‘Stone coffin’ eyed for decommissioning Fukushima plant: report

The government-funded Nuclear Damage Compensation and Decommissioning Facilitation Corp. (NDF) eyes an option of covering the disaster stricken Fukushima No. 1 Nuclear Power Plant with concrete in the future as in the Chernobyl disaster, it has been learned.

In its first planning report drawn up on July 13, the NDF leaves room for adopting the “sarcophagus (stone coffin) method,” in which nuclear fuel debris that melted in the Fukushima crisis will be confined inside reactor buildings using concrete and other materials.

The NDF points out in the report that it will be difficult to manage such a sarcophagus safely over a long period of time, and emphasizes that it is planning to remove fuel debris from the Fukushima nuclear plant for now. However, the report also says, “It is appropriate to flexibly review the plan in accordance with the conditions inside (nuclear reactors and other parts) that will be revealed later.”

The report also states, “It is necessary to fully consider the uncertainties over passing down responsibilities for a long period of time and concerns over easy postponement from one generation to another.”

The sarcophagus method was adopted at the Chernobyl nuclear complex in the former Soviet Union in the wake of the core meltdowns there in 1986.

http://mainichi.jp/english/articles/20160714/p2a/00m/0na/009000c

July 14, 2016 Posted by | Fukushima 2016 | , , | Leave a comment

Reactor decommissioning plan cites ‘sarcophagus’

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Reactor decommissioning plan cites ‘sarcophagus’

The government body charged with decommissioning the reactors at the Fukushima Daiichi nuclear plant says it remains committed to removing the fuel but sealing off the buildings that house them could be an option.

The Nuclear Damage Compensation and Decommissioning Facilitation Corporation issued its latest report Wednesday on its plan.

It says 2 methods will be used to remove molten fuel depending on the condition of the reactors.

One entails filling the containment vessels with water to shield workers from radiation. The second does not use water.

The new plan also introduces the option of creating a “sarcophagus” to seal off the buildings with the nuclear fuel inside.

This method was used at the Chernobyl nuclear plant in Ukraine.

The plan favors removing the nuclear fuel because of the long-term safety issues involved with a sarcophagus. It urges a flexible review of all available options.

It also notes the importance of addressing long-term public concerns about the plan.

The government and the plant operator, Tokyo Electric Power Company, plan to decide by the middle of next year how to remove the fuel from the reactors. They hope to begin work at one of them by 2021.

http://www3.nhk.or.jp/nhkworld/en/news/20160713_25/

Fukushima mayors react to decommission plan

Reacting to the new plan, the heads of municipalities around the Fukushima Daiichi nuclear plant have urged the government to stick to its promise regarding nuclear waste disposal.

The mayor of the city of Minamisoma, Katsunobu Sakurai, said the government and TEPCO must be made to abide by their initial pledge to remove the fuel from Fukushima Prefecture. Until this is done, he said, the evacuees won’t feel that it’s safe to return home.

He warned against using the word “sarcophagus” lightly. He said its mention only points out the inadequacy of decommissioning technology.

The mayor of the town of Namie, Tamotsu Baba, said a sarcophagus should not be considered because engineers are hard at work figuring out ways to remove the fuel.

He said all they can do is to have faith that the initial pledge will be kept, even if it takes 30 or 40 years to remove the fuel.

The mayor of the town of Okuma, Toshitsuna Watanabe, also urged the government and the utility to stick to their disposal promise.

http://www3.nhk.or.jp/nhkworld/en/news/20160713_28/

July 13, 2016 Posted by | Fukushima 2016 | , , , , | Leave a comment