Hydrogen sulfide present in Fukushima contaminated water tanks

safe_image.php.jpg
January 7, 2019
Mako Oshidori reported from a recent TEPCO press conference that the company has admitted to finding hydrogen sulfide in some of the contaminated water tanks at Fukushima Daiichi.
 
The instances of hydrogen sulfide was found in newer welded tanks in the G3 tank farm in August.
TEPCO found levels up to 50 ppm in some of the tanks.
If it oxidizes to sulfuric acid it can corrode steel and concrete storage equipment including the water tanks.
 
TEPCO claims that the cause of the hydrogen sulfide gas was due to anaerobic bacterial decomposition. Hydrogen sulfide gas is a corrosion concern for the contaminated water tanks.
 
This is a problem from a human health standpoint for workers in the area. TEPCO cites a level of at least 50 ppm. They do not report the exact concentrations over 50 ppm. Health effects can happen at doses lower than 50 ppm. As exposure doses increase so do the health dangers. High concentrations can cause rapid death. With tanks creating this gas byproduct the risk exists of a worker accidentally coming in contact with a concentrated amount of this gas. Workers in the tank farms do not wear respirators, only paper particle filtration masks.
 
TEPCO stated they would continue to investigate the conditions in the on site tanks for gas and corrosion.
 

Fukushima Daiichi H4 Tank Farm Dismantled, Contents Transferred

31 May 2017 water tanks dismantled b.jpg

 

On May 26 Tepco finished dismantling the 56 tanks from the H4 tank farm. Tepco mentioning some soil remediation having being done, but providing no details about it.

Those tanks were used to contain contaminated water and sludge from the reactors and the contaminated water treatment systems.

Those tanks panels having not been welded but only bolted with rivets, caused numerous leals in 2013. Those tanks panels were removed and sent to an automated cutting system for further dismantling and storage as radioactive waste. Their content was transfered to other more recent tanks, those welded.

http://www.tepco.co.jp/cc/press/2013/1232456_5117.html

http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170526_03-j.pdf

ggiujkl.jpg

ggiujkl.jpg

Fukushima nuclear plant still plagued by tainted water 6 years after meltdowns

1

Workers bring in a new water tank, right, as a replacement for an old contaminated water tank at TEPCO’s No. 1 nuclear power plant in the town of Okuma in Fukushima Prefecture on Feb. 24, 2017

OKUMA, Fukushima — With two weeks to go until the sixth anniversary of the disaster at Tokyo Electric Power Co. (TEPCO)’s Fukushima No. 1 Nuclear Power Plant here, the Mainichi Shimbun visited the plant on Feb. 24, obtaining a first-hand view of working conditions and the persisting problem of tainted water.

The number of areas on the plant site requiring full face masks has decreased considerably, and the overall working environment has improved greatly. However, the issue of having to replace the tanks that hold radioactively contaminated water lingers.

Dealing with contaminated water requires significant manpower. According to TEPCO, about half of the approximately 6,000 people working daily at the No. 1 nuclear power plant are involved in handling contaminated water.

There are roughly 1,000 tanks of contaminated water inside the No. 1 plant site, forming a forest of containers with nowhere else to go.

2

A worker makes checks with a hammer on an impermeable wall near TEPCO’s No. 4 reactor in the town of Okuma in Fukushima Prefecture on Feb. 24, 2017

During the immediate aftermath of the nuclear disaster in 2011, a considerable number of tanks known as flanges were placed within the site. However, as concerns continue to grow about contaminated water leaking from these tanks due to dilapidation, TEPCO has taken action and is working on dismantling them.

Although covering the ground at the No. 1 plant with concrete has made it possible to work in about 90 percent of the site without a protective uniform, all those working near the old tanks must wear full face masks and Tyvek suits as the tanks once held highly contaminated water. Wearing this kind of protective clothing makes the work much harder to perform — as it can be difficult to breathe — and it is physically exhausting, even in the middle of winter.

Hiroshi Abe, 55, of Shimizu Corp. — the company overseeing the dismantling work — states, “As we work toward recovery from the disaster, we want to ensure that all workers are protected from radiation exposure and injuries.”

Presently, the level of radiation in the vicinity of the buildings housing the No. 1, No. 2, and No. 3 reactors is high. During the Mainichi Shimbun’s visit to the site on Feb. 24, the radiation level near the No. 3 reactor was found to be more than 300 microsieverts per hour, and near the No. 2 reactor building, it was discovered to be 137.6 microsieverts per hour.

3.jpg

A radiation measuring device shows a reading of 137.6 microsieverts per hour near TEPCO’s No. 2 reactor in the town of Okuma in Fukushima Prefecture on Feb. 24, 2017.

Furthermore, an “ice wall,” which was built to restrict the flow of contaminated water underground, has not been as effective as initially expected.

A spokesman for TEPCO, Takahiro Kimoto, who accompanied the Mainichi Shimbun on this visit, said, “Nearly six years have passed since the disaster. Our decommissioning work is now about to enter the main stage of extracting melted fuel.”

However, with TEPCO and the government’s decommissioning work set to continue until around 2041-2051, there is still a long way to go until they can reach the “main stage.”

http://mainichi.jp/english/articles/20170225/p2a/00m/0na/010000c

 

 

TEPCO Delays Replacing Tainted Water Tanks

Screen-Shot-2016-02-21-at-9.27.49-AM-1024x676.png

 

Tokyo, Sept. 28 (Jiji Press)–Tokyo Electric Power Company Holdings Inc. <9501> has effectively given up replacing tainted water storage tanks at its Fukushima No. 1 nuclear power station with safer ones at an early date, it was learned Wednesday.


It is believed to be the first time that the power firm has abandoned a deadline in its decommissioning work timetable, revised in June last year.


TEPCO now expects to finish the work in June 2018 at the earliest, according to documents submitted to a panel of the Nuclear Regulation Authority.


TEPCO initially planned to finish replacing the storage tanks with welded low-leakage ones early in the current business year through March 2017.


TEPCO remains unable to stop increases in the amount of radioactive water. The amount of contaminated water stored in the current tanks with a higher risk of leakage stood above 110,000 tons as of Thursday.

http://jen.jiji.com/jc/eng?g=eco&k=2016092800865

TEPCO to reuse tanks holding radioactively contaminated water at Fukushima plant

fukushimawatertanks.jpg

 

 

Tokyo Electric Power Co. (TEPCO) will reuse highly contaminated tanks at the crippled Fukushima No. 1 Nuclear Power Plant to store radioactively contaminated water after treatment, company sources said.

The company will return contaminated water to flange-type tanks that had held such water after removing radioactive materials from the water using the Advanced Liquid Processing System (ALPS). This is because TEPCO has failed to prevent contaminated water from being generated on the premises of the plant or to secure enough storage tanks to hold treated water.

TEPCO had submitted the reuse plan to the Nuclear Regulation Authority, which approved it on July 6 or earlier. TEPCO is set to begin reusing contaminated tanks as early as this month.

Flange-type tanks are assembled by tightening multiple steel plates with bolts. Since such tanks have higher risks of leaking contaminated water, TEPCO is gradually replacing them with tanks assembled by welding steel plates together.

TEPCO is trying to freeze underground soil to surround reactor buildings at the Fukushima power plant to prevent underground water from flowing beneath them and becoming contaminated with radioactive materials.

However, as the efforts have proven ineffective, the utility has decided to reuse flange-type tanks, which it had initially planned to dismantle.

Massive amounts of water are flowing onto the premises of reactor buildings at the atomic power station, generating some 400 tons of radioactively contaminated water a day. TEPCO uses ALPS to purify contaminated water, but the system cannot remove radioactive tritium.

The power company has stored the treated water mainly in welded-type tanks. There are already 1,000 water tanks on the premises of the power station.

http://mainichi.jp/english/articles/20160707/p2a/00m/0na/003000c

Dismantling of Contaminated Water Tanks in Fukushima Daiichi

TEPCO explains how they will go about taking down the many bolt together tanks at the disaster site, to be replaced with welded tanks in what is becoming a crowded patch of land on the plant grounds.

1  Example drawing of the tank preparation process including an air filtration system

and the spraying of dust inhibitor s prior to disassembly

2

 Interior of a drained tank with sprayer installed

3

 Tank with plastic tarp roof

4

 Partially disassembled tank portion

5

Tank before final sludge draining

6

Drained tank before removal

7

Building where tank sections will be cut down

8

 Transport of tank sections for cutting

9

Band saws for cutting down tank sections

10

Inside saw system

11

HEPA dust system installed on the saw.

Tepco says the remaining scrap will be loaded into steel containers and will be stored on site.

Source: Tepco

http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_150623_04-j.pdf

Nuclear cleanup at Fukushima plant stymied by water woes

Japan Nuclear Water WoesTanks storing contaminated water are seen at the Fukushima No. 1 nuclear power plant

in Fukushima Prefecture on Nov. 12.

November 13, 2014

OKUMA, Fukushima Prefecture–More than three years into the massive cleanup of Japan’s tsunami-damaged nuclear power plant, only a tiny fraction of the workers are focused on key tasks such as preparing for the dismantling of the broken reactors and removing radioactive fuel rods.

Instead, nearly all the workers at the Fukushima No. 1 nuclear power plant are devoted to an enormously distracting problem: a still-growing amount of contaminated water used to keep the damaged reactors from overheating. The amount has been swelled further by groundwater entering the reactor buildings.

Hundreds of huge blue and gray tanks to store the radioactive water, and buildings holding water treatment equipment are rapidly taking over the plant, where the cores of three reactors melted following a 2011 earthquake and tsunami. Workers were building more tanks during a visit to the complex on Nov. 12 by foreign media, including The Associated Press.

“The contaminated water is a most pressing issue that we must tackle. There is no doubt about that,” said Akira Ono, head of the plant. “Our effort to mitigate the problem is at its peak now. Though I cannot say exactly when, I hope things start getting better when the measures start taking effect.”

The numbers tell the story.

6,000 WORKERS

Every day, about 6,000 workers pass through the guarded gate of the Fukushima No. 1 plant on the Pacific coast–two to three times more than when it was actually producing electricity.

On a recent work day, about 100 workers were dismantling a makeshift roof over one of the reactor buildings, and about a dozen others were removing fuel rods from a cooling pool. Most of the rest were dealing with the contaminated water, said Tatsuhiro Yamagishi, a spokesman for Tokyo Electric Power Co., the utility that owns the plant.

The work threatens to exhaust the supply of workers for other tasks, since employees must stop working when they reach annual radiation exposure limits. Experts say it is crucial to reduce the amount and radioactivity of the contaminated water to decrease the risk of exposure to workers and the environmental impact before the decommissioning work gets closer to the highly contaminated core areas.

40 YEARS

The plant has six reactors, three of which were offline when disaster struck on March 11, 2011. A magnitude-9.0 earthquake triggered a huge tsunami which swept into the plant and knocked out its backup power and cooling systems, leading to meltdowns at the three active reactors.

Decommissioning and dismantling all six reactors is a delicate, time-consuming process that includes removing the melted fuel from a highly radioactive environment, as well as all the extra fuel rods, which sit in cooling pools at the top of the reactor buildings. Workers must determine the exact condition of the melted fuel debris and develop remote-controlled and radiation-resistant robotics to deal with it.

Troubles and delays in preparatory stages, including the water problem and additional measures needed to address environmental and health concerns in removing highly radioactive debris from atop reactor buildings that exploded during meltdowns, have pushed back schedules on the decommissioning roadmap. Recently, officials said the government and TEPCO plan to delay the planned start of fuel removal from Units 1 and 2 by about 5 years.

The process of decommissioning the four reactors is expected to take at least 40 years.

500,000 TONS

The flow of underground water is doubling the amount of contaminated water and spreading it to vast areas of the compound.

Exposure to the radioactive fuel contaminates the water used to cool the melted fuel from inside, and much of it leaks and pours into the basements of the reactors and turbines, and into maintenance trenches that extend to the Pacific Ocean. Plans to freeze some of the most toxic water inside the trench near the reactors have been delayed for at least 8 months due to technical challenges.

The plant reuses some of the contaminated water for cooling after partially treating it, but the additional groundwater creates a huge excess that must be pumped out.

Currently, more than 500,000 tons of radioactive water is being stored in nearly 1,000 large tanks which now cover large areas of the sprawling plant. After a series of leaks last year, the tanks are being replaced with costlier welded ones.

That amount dwarfs the 9,000 tons of contaminated water produced during the 1979 partial meltdown of the Three Mile Island nuclear plant in the United States. At Three Mile Island, it took 14 years for the water to evaporate, said Lake Barrett, a retired U.S. nuclear regulatory official who was part of the early mitigation team there and has visited the Fukushima plant.

“This is a much more complex, much more difficult water management problem,” Barrett said.

10 TRILLION YEN

An estimated 2 trillion yen ($18 billion) will be needed just for decontamination and other mitigation of the water problem. Altogether, the entire decommissioning process, including compensation for area residents, reportedly will cost about 10 trillion yen, or about $90 billion.

All this for a plant that will never produce a kilowatt of energy again.

About 500 workers are digging deep holes in preparation for a taxpayer-funded 32 billion yen ($290 million) underground “frozen wall” around four reactors and their turbine buildings to try to keep the contaminated water from seeping out.

TEPCO is developing systems to try to remove most radioactive elements from the water. One, known as ALPS, has been trouble-plagued, but utility officials hope to achieve its daily capacity of 2,000 tons when they enter full operation next month following a final inspection by regulators.

Officials hope to treat all contaminated water by the end of March, but that is far from certain.

Source: Asahi Shimbun

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201411130092