Members of the media take in the No. 1 reactor at the Fukushima No. 1 power plant in Fukushima Prefecture on Thursday.
OKUMA, FUKUSHIMA PREF. – While a recent investigation found what may be melted nuclear fuel rods in reactor No. 2 containment vessel at the Fukushima No. 1 plant, that information isn’t nearly enough to devise an effective method for removing it, the chief of the plant told reporters during a media tour Thursday.
“We put in cameras and robots and obtained valuable images, though they were partial . . . but it’s still unclear what is really going on there,” said Shunji Uchida, who became chief of the crippled plant last July. “We first need to know the situation of the debris.”
Last month, the utility inserted a 10.5-meter rod with a camera on its tip into a hole in the No. 2 reactor’s primary containment vessel and discovered black lumps sticking to the grating directly underneath the suspended pressure vessel, which holds the core.
Tepco claims it is still unsure whether the lumps are really melted fuel that burned through the bottom of the pressure vessel. Although it is still years away from actually trying to remove the fuel, Tepco, the government and related parties are planning to decide on a basic strategy this summer and go into more detail next year.
Uchida described last month’s surveillance operation as “just peeking.”
Engineers are playing with the idea of refilling the primary containment vessel with water during debris cleanup operations to reduce the intensity of the radiation, but since the PCV was probably damaged during the meltdown crisis in March 2011, the water that’s being pumped in 24/7 to keep the fuel cool is just leaking back out.
According to past analyses, some of the melted fuel rods penetrated the pressure vessel and fell into the containment vessel surrounding it after the March 11 quake and tsunami caused a station blackout at the plant, crippling all cooling functions.
This Week’s Featured Interview:
- Dr. Helen Caldicott on why Fukushima will never be able to be cleaned up; the devastating health impacts of radiation; and why the 2020 Tokyo Olympics are a really really bad idea.
- Dr. Caldicott Links:
KGO Radio: Host Pat Thurston recently interviewed Arnie Gundersen, chief engineer for Fairewinds Energy Education on KGO radio to discuss the latest challenging news from Japan about the Fukushima Daiichi atomic power reactor including the high levels of radiation emanating from the reactors, all the failed robotic expeditions, where we should go from here, as well as how ongoing radioactive releases from the Fukushima Daiichi site may be impacting the west coast of the United States.
BBC Newsday: BBC Radio interviewed nuclear engineer Arnie Gundersen to discuss TEPCO’s attempts to send a special robot into Fukushima Daiichi Reactor #2 in Japan to investigate the obstacles in the way of TEPCO’s progress determining the location and condition of the atomic fuel. Unfortunately even this specially designed robot failed in its attempt to clear the path for additional investigations as the nuclear radioactivity was so high, it shut down the robots before they could complete their mission.
Enviro News: The astronomical radiation readings at Fukushima Daiichi Reactor #2 of 530 Sv/hr complicate the already complex task of decommissioning the plant. These levels are so radioactive that a human would be dead within a minute of exposure and specially designed robots can only survive for about 2 hours. Fairewinds chief engineer Arnie Gundersen says that the best solution would be to entomb the reactors, similar to the sarcophagus entombing Chernobyl, for at least 100-years, otherwise the radiation level that workers would be exposed to is simply too dangerous.
Read the whole article here
Are the meltdowns at Fukushima Daiichi over? The answer is no. Made all the more prevalent a year out from it’s initial release by the recent robotic expeditions into Reactor #2 which gave us a clearer picture on just how deadly the radiation levels are, watch Chief Engineer and nuclear expert Arnie Gundersen inform viewers on what’s going on at the Japanese nuclear meltdown site, Fukushima Daiichi. As the Japanese government and utility owner Tokyo Electric Power Company push for the quick decommissioning and dismantling of this man-made disaster, the press and scientists need to ask, “Why is the Ukrainian government waiting at least 100 years to attempt to decommission Chernobyl, while the Japanese Government and TEPCO claim that Fukushima Daiichi will be decommissioned and dismantled during the next 30 years?”
Like so many big government + big business controversies, the answer has nothing to do with science, and everything to do with politics and money. To understand Fukushima Daiichi, you need to follow the money.
Tepco uses the RISER quadcopter drone to visually map gamma radiation in the unit 3 turbine building. The RISER quadcopter drone is equipped with GPS, HD cameras and the N-Visage 3D gamma radiation detector which produces color images of radiation. It has a small size 3d gamma camera.
The N-Visage 3D gamma radiation detector technology has been used previously to examine the refueling floor of unit 2 and some other areas of the reactor buildings.
The RISER quadcopter drone has a maximum radiation resistance of 10 mSv/hr so it won’t be used into the more dangerous areas of the site.
Our Rainbow Warriors Facebook group started in 2011 as an FB group about the Fukushima catastrophe, its old name was the “Fukushima 311 Watchdogs”. In June 2012, after an exhausting first year the Fukushima 311 Watchdogsgroup was dissolved, and one month later was reborn as the Rainbow Warriors, with a broader scope of interests, environment protection, climate change etc. https://www.facebook.com/groups/277245265712386/
However the ongoing Fukushima catastrophe still remains one of our our major concerns.
The Fukushima 311 Watchdogs has survived as a community FB page:
Fukushima 311 Watchdogs https://www.facebook.com/fukushima311watchdog/
and as a blog: Fukushima 311 Watchdogs https://dunrenard.wordpress.com/
This coming March 11th will be the 6th Anniversary of the beginning of the still ongoing nuclear catastrophe. Many people have disappeared along the way since March 2011, however among those who were with us right from the beginning, the Fukushima Watchers, the Fukushima Watchdogs, some haven’t yet forgotten and are still here with us.
3.11.2017 FUKUSHIMA SIXTH ANNIVERSARY ONGOING DISASTER.
TAKE ACTION: #FUKU+6 Anniversary is happening 3.11.17 … six years since the #Fukushima nuclear meltdown and ongoing poisoning of our oceans began … our air land food water have been contaminated. #Fukushima continues to spew radioisotopes into the Pacific Ocean threatening vital marine life, ecosystems and the food chain. Japan continues to burn radioactive debris and dump it into the Pacific spreading poison into the atmosphere. Join the FUKU+6 actions and events fb page taking place worldwide. Act in solidarity, please click on this image, download it, and make it your cover pic, and help spread the word. https://www.facebook.com/groups/3.11fukushimasixthanniversaryactions/601393323403623/?ref=notif¬if_t=like¬if_id=1487640969842420
It looks like its too radioactive for robots to survive. I wonder how they will do this work now?
Tokyo, Feb. 20 (Jiji Press)–A failed robot survey of melted nuclear fuel that has dropped through the bottom of a damaged reactor pressure chamber at the Fukushima No. 1 nuclear plant complicates the formulation of a policy in the summer for taking out the fuel debris.
The removal of the molten nuclear fuel is regarded as the most demanding challenge in the decommissioning of the disaster-stricken plant’s reactors, said to take 30 to 40 years.
Tokyo Electric Power Company Holdings Co. <9501>, the manager of the plant in Fukushima Prefecture, northeastern Japan, is discussing the drawing up of a broad policy outline before conducting an additional survey to work out a detailed plan for the nuclear fuel removal, company officials said.
TEPCO’s initial plan called for a self-propelled survey robot, dubbed scorpion, to enter the No. 2 reactor’s containment vessel and travel on a 7.2-meter rail to reach a metal grating directly beneath the reactor’s damaged pressure chamber. The robot would have surveyed the extent of damage to the chamber, while locating melted nuclear fuel that is believed to have dropped through the metal grating to the bottom of the containment vessel and shooting the fuel’s images.
The No. 2 reactor is one of the three units that suffered meltdown due to the failure of their cooling systems caused by the March 2011 earthquake and tsunami.
It is unclear why there is less radioactivity under the reactor vessel, when it is where there should be the most.
A robot was expected to solidify ways to clean up the No. 2 reactor at the Fukushima No. 1 nuclear plant, but its short-lived mission raised puzzling questions that could derail existing decommissioning plans.
The robot, Sasori, was abandoned in the melted-down reactor after it became stuck in deposits and other debris that are believed to have interfered with its drive system.
But it did take radiation measurements that indicate Tokyo Electric Power Co., operator of the plant, was too optimistic about the state and location of the melted fuel within the reactor. The melted fuel, in fact, may be spread out all over the reactor’s containment vessel.
Scientists had believed the melted nuclear fuel fell through the reactor’s pressure vessel and landed on metal grating and the floor of the containment vessel.
The results of Sasori’s investigation, coupled with previous data taken from possible images of the melted fuel, show the situation within the reactor is much worse than expected. And a fresh investigation into the reactor is now nowhere in sight.
A remote-controlled video camera inserted into the reactor on Jan. 30 took what are believed to be the first images of melted fuel at the plant, which suffered a triple meltdown after the March 2011 Great East Japan Earthquake and tsunami.
Based on the images, TEPCO estimated 530 sieverts per hour at a point almost halfway between the metal grating directly beneath the pressure vessel and the wall of the containment vessel. Black lumps on the grating are believed to be melted fuel.
A different robot sent in on Feb. 9 to take pictures and prepare for Sasori’s mission estimated 650 sieverts per hour near the same spot.
Both 530 and 650 sieverts per hour can kill a person within a minute.
Sasori, equipped with a dosimeter and two cameras, on Feb. 16 recorded a reading of 210 sieverts per hour near the same location, the highest figure measured with instruments in the aftermath of the disaster.
Sasori was supposed to travel along a rail connecting the outer wall of the containment vessel with the metal grating to measure radiation doses and shoot pictures inside, essential parts of work toward decommissioning the reactor.
After traveling only 2 meters, the robot became stuck before it could reach the metal grating.
TEPCO at a news conference repeatedly said that Sasori’s investigation was not a “failure” but had produced “meaningful” results.
However, an official close to TEPCO said, “I had great expectations for Sasori, so I was shocked by how it turned out.”
Hiroaki Abe, professor of nuclear materials at the University of Tokyo who has studied TEPCO’s footage, tried to explain why high doses were estimated between the pressure vessel and the containment vessel.
“Instead of directly landing on the rail, the melted nuclear fuel may have flown off after it reacted violently with the concrete, which had a high moisture content, at the bottom of the containment vessel, just like what happens when lava pours into the sea,” Abe said.
But he said this scenario raises a puzzling question, considering the estimated radiation readings near the area below the pressure vessel were down to 20 sieverts per hour, according to an analysis of the video footage.
“If nuclear fuel debris had splattered around, the radiation levels at the central area below the pressure vessel must be extremely high,” he said. “In addition, deposits on the rail would have taken the shape of small pieces if they were, in fact, flying nuclear fuel debris. The findings are puzzling.”
Images by the remote-controlled camera also showed that equipment in the lower part of the pressure vessel was relatively well preserved, indicating that the hole at the bottom of the vessel is not very large.
“How to remove nuclear fuel debris will all depend on how much remains inside the pressure vessel and how much fell out,” Abe said.
Toru Obara, professor of nuclear engineering at the Tokyo Institute of Technology, stressed the need to retrieve substances from the bottom of the robots or elsewhere.
“We could get clues as to the state of the melted nuclear fuel and the development of a meltdown if we could figure out which materials mixed with the nuclear fuel,” he said.
The surveys by the camera and robots were conducted from a makeshift center at the No. 2 reactor. The center’s walls are made from radiation-blocking metal.
TEPCO and the government plan to determine a method to remove nuclear fuel debris in fiscal 2018 before they proceed with the actual retrieval process at one of the three destroyed reactors.
One possible method involves filling the containment vessels with water to prevent radioactive substances from escaping.
The latest robot seeking to find the 600 tons of nuclear fuel and debris that melted down six year ago in Japan’s wrecked Fukushima Dai-Ichi power plant met its end in less than a day.
The scorpion-shaped machine, built by Toshiba Corp., entered the No. 2 reactor core Thursday and stopped 3 meters (9.8 feet) short of a grate that would have provided a view of where fuel residue is suspected to have gathered. Two previous robots aborted similar missions after one got stuck in a gap and another was abandoned after finding no fuel in six days.
After spending most of the time since the 2011 disaster containing radiation and limiting ground water contamination, scientists still don’t have all the information they need for a cleanup that the Japanese government estimates will take four decades and cost 8 trillion yen ($70.6 billion). It’s not yet known if the fuel melted into or through the containment vessel’s concrete floor, and determining the fuel’s radioactivity and location is crucial to inventing the technology needed to remove it.
“The roadmap for removing the fuel is going to be long, 2020 and beyond,” Jacopo Buongiorno, a professor of nuclear science and engineering at the Massachusetts Institute of Technology, said in an e-mail. “The re-solidified fuel is likely stuck to the vessel wall and vessel internal structures. So the debris have to be cut, scooped, put into a sealed and shielded container and then extracted from the containment vessel. All done by robots.”
Read more: Robots are being utilized to clean up U.K.’s nuclear waste
To enter a primary containment vessel, which measures about 20 meters at its widest, more than 30 meters tall and is encased in meters of concrete, outside air pressure is increased to keep radiation from escaping and a sealed hole is opened that the robot passes through. Three reactors at the plant suffered meltdowns, and each poses different challenges and requires a custom approach for locating and removing the fuel, said Tatsuhiro Yamagishi, Tokyo Electric Power Co. Holdings Inc. spokesman.
The machines are built with specially hardened parts and minimal electronic circuitry so that they can withstand radiation, if only for a few hours at a time. Thursday’s mission ended after the robot’s left roller-belt failed, according to Tokyo Electric, better known as Tepco. Even if it had returned, this robot, like all others so far designed to aid the search for the lost fuel, was expected to find its final resting place inside a reactor.
No. 1 Unit
Hitachi Corp. in the next two months plans to send a machine into the No. 1 reactor core that scientists hope can transmit photos of the fuel and measure radiation levels.
The snake-like robot will lower a camera on a wire from a grate platform in the reactor to take photos and generate 3-D models of the bottom of the containment vessel. This will be the third time Hitachi sends in this robot design.
While the company is hopeful this robot will find some of the fuel, it will likely be unable to find all of it, according to Satoshi Okada, a Hitachi engineer working on the project. The company is already planning the next robot voyage for after April.
“We are gathering information so that we can decide on a way to remove the fuel,” said Okada. “Once we understand the situation inside, we will be able to see the way to remove the fuel.”
No. 2 Unit
On Thursday, Toshiba’s scorpion-like robot entered the reactor and stopped short of making it onto the containment vessel’s grate. While Tepco decided not to retrieve it, the company views the attempt as progress.
“We got a very good hint as to where the fuel could be from this entire expedition” Tepco official Yuichi Okamura said Thursday at a briefing in Tokyo. “I consider this a success, a big success.”
Tepco released images last month of a grate under the No. 2 reactor covered in black residue that may be the melted fuel — one of the strongest clues yet to its location. The company measured radiation levels of around 650 sieverts per hour through the sound-noise in the video, the highest so far recorded in the Fukushima complex.
A short-term, whole-body dose of over 10 sieverts would cause immediate illness and subsequent death within a few weeks, according to the World Nuclear Association.
The Hitachi and Toshiba robots are designed to handle 1,000 sieverts and no robot has yet been disabled due to radiation.
“Radiation levels near the fuel are lethal,” said MIT’s Buongiorno, who holds the university’s Tepco chair, a professorship based on an initial donation by the company 10 years ago. There are no formal affiliations or obligations for the faculty who receive the chair, he said.
Because the No. 2 unit is the only one of the three reactors that didn’t experience a hydrogen explosion, there was no release into the atmosphere and radiation levels inside the core are higher compared to the other two units, according to the utility.
No. 3 Unit
Tepco’s balance sheet has been strapped by ballooning Fukushima cleanup costs and slumping national power demand. All of the company’s nuclear power plants remain shut since it halted the No. 6 reactor at its Kashiwazaki Kariwa station in March 2012. The company is seeking drastic changes in top management in consultation with the Japanese government, TV Asahi reported Friday, without attribution.
The utility has focused on removing spent fuel in the upper part of the reactor building, which Toshiba aims to extract with a claw-like system. This fuel didn’t melt and is still in a pool that controls its temperature.
The used-fuel in No. 3 is scheduled to begin removal before the end of the decade, the first among the three reactors that melted down. Toshiba is developing another robot to search for melted fuel, planned to enter sometime in the year ending March 2018. The company hasn’t announced yet the design or strategy.
Year over year, ever since 2011, the Fukushima Daiichi nuclear meltdown grows worse and worse, an ugly testimonial to the inherent danger of generating electricity via nuclear fission, which produces isotopes, some of the most deadly poisonous elements on the face of the planet.
Fukushima Daiichi has been, and remains, one of the world’s largest experiments; i.e., what to do when all hell breaks lose aka The China Syndrome.
Scientists still don’t have all the information they need for a cleanup that the government estimates will take four decades and cost ¥8 trillion. It is not yet known if the fuel melted into or through the containment vessel’s concrete floor, and determining the fuel’s radioactivity and location is crucial to inventing the technology to remove the melted fuel.1
As it happens, “”inventing technology” is experimental stage stuff. Still, there are several knowledgeable sources that believe the corium, or melted core, will never be recovered. Then what?
According to a recent article, “Potential Global Catastrophe of the Reactor No. 2 at Fukushima Daiichi,” February 11, 2017 by Dr. Shuzo Takemoto, professor, Department of Geophysics, Graduate School of Science, Kyoto University: The Fukushima nuclear facility is a global threat on level of a major catastrophe.
Meanwhile, the Abe administration dresses up Fukushima Prefecture for the Tokyo 2020 Olympics, necessitating a big fat question: Who in their right mind would hold Olympics in the neighborhood of three out-of-control nuclear meltdowns that could get worse, worse, and still worse? After all, that’s the pattern over the past 5 years; it gets worse and worse. Dismally, nobody can possibly know how much worse by 2020. Not knowing is the main concern about holding Olympics in the backyard of a nuclear disaster zone, especially as nobody knows what’s happening. Nevertheless and resolutely, according to PM Abe and the IOC, the games go on.
Along the way, it’s taken Tokyo Electric Power Company (TEPCO) nearly six years to finally get an official reading of radiation levels of the meltdown but in only one unit. Analysis of Unit #2 shows radiation levels off-the-charts at 530 Sieverts, or enough to kill within minutes, illustrative of why it is likely impossible to decommission units 1, 2, and 3. No human can withstand that exposure and given enough time, frizzled robots are as dead as a door nail.
A short-term, whole-body dose of over 10 sieverts would cause immediate illness and subsequent death within a few weeks, according to the World Nuclear Association.1
Although Fukushima’s similar to Chernobyl Exclusion Zone in some respects, where 1,000 square miles has been permanently sealed off, Fukushima’s different, as the Abe administration is already repopulating portions of Fukushima. If they don’t repopulate, how can the Olympics be held with food served from Fukushima and including events like baseball held in Fukushima Prefecture?
Without question, an old saw – what goes around comes around – rings true when it comes to radiation, and it should admonish (but it doesn’t phase ‘em) strident nuclear proponents, claiming Fukushima is an example of how safe nuclear power is “because there are so few, if any, deaths” (not true). As Chernobyl clearly demonstrates: Over time, radiation cumulates in bodily organs. For a real life example of how radiation devastates human bodies, consider this fact: 453,391 children with bodies ravaged, none born at the time of the Chernobyl meltdown in 1986, today receive special healthcare because of Chernobyl radiation-related medical problems like cancer, digestive, respiratory, musculoskeletal, eye disease, blood disease, congenital malformation, and genetic abnormalities. Their parents were children in the Chernobyl zone in 1986.2
Making matters worse yet, Fukushima Daiichi sets smack dab in the middle of earthquake country, which defines the boundaries of Japan. In that regard, according to Dr. Shuzo Takemoto, professor, Department of Geophysics, Graduate School of Science, Kyoto University:
The problem of Unit 2… If it should encounter a big earth tremor, it will be destroyed and scatter the remaining nuclear fuel and its debris, making the Tokyo metropolitan area uninhabitable. The Tokyo Olympics in 2020 will then be utterly out of the question.3
Accordingly, the greater Tokyo metropolitan area remains threatened for as long as Fukushima Daiichi is out of control, which could be for generations, not years. Not only that, Gee-Whiz, what if the big one hits during the Olympics? After all, earthquakes come unannounced. Regrettably, Japan has had 564 earthquakes the past 365 days. It’s an earthquake-ridden country. Japan sits at the boundary of 4 tectonic plates shot through with faults in zigzag patterns, very lively and of even more concern, the Nankai Trough, the candidate for the big one, sits nearly directly below Tokyo. On a geological time scale, it may be due for action anytime within the next couple of decades. Fukushima Prefecture’s not that far away.
Furthermore, the Fukushima Daiichi nuclear complex is tenuous, at best:
All four buildings were structurally damaged by the original earthquake some five years ago and by the subsequent hydrogen explosions so should there be an earthquake greater than seven on the Richter scale, it is very possible that one or more of these structures could collapse, leading to a massive release of radiation as the building falls on the molten core beneath.4
Complicating matters further, the nuclear site is located at the base of a mountain range. Almost daily, water flows from the mountain range beneath the nuclear plant, liquefying the ground, a sure-fire setup for cascading buildings when the next big one hits. For over five years now, radioactive water flowing out of the power plant into the Pacific carries isotopes like cesium 134 and cesium 137, strontium 90, tritium, plutonium americium and up to 100 more isotopes, none of which are healthy for marine or human life, quite the opposite, in fact, as those isotopes slowly cumulate, and similar to the Daleks of Doctor Who fame (BBC science fiction series, 1963-present) “Exterminate! Exterminate! Exterminate!”
Isotopes bio-concentrate up the food chain from algae to crustaceans to small fish to big fish to bigger humans. Resultant cancer cells incubate anytime from two years to old age, leading to death. That’s what cancer does; it kills.
Still, the fact remains nobody really knows for sure how directly Fukushima Daiichi radiation affects marine life, but how could it be anything other than bad? After all, it’s a recognized fact that radiation cumulates over time; it’s tasteless, colorless, and odorless as it cumulates in the body, whether in fish or further up the food chain in humans. It travels!
An example is Cesium 137, one of the most poisonous elements on the planet. One gram of Cesium 137 the size of a dime will poison one square mile of land for hundreds of years. That’s what’s at stake at the world’s most rickety nuclear plant, and nobody can do anything about it. In fact, nobody knows what to do. They really don’t.
When faced with the prospect of not knowing what to do, why not bring on the Olympics? That’s pretty good cover for a messy situation, making it appear to hundreds of thousands of attendees, as well as the world community “all is well.” But, is it? Honestly….
The Fukushima nuclear meltdown presents a special problem for the world community. Who knows what to believe after PM Abe lied to the IOC to get the Olympics; see the following headline from Reuters News:
“Abe’s Fukushima ‘Under Control’ Pledge to Secure Olympics Was a Lie: Former PM,” Reuters, September 7, 2016.
Abe gave the assurances about safety at the Fukushima plant in his September 2013 speech to the International Olympic Committee to allay concerns about awarding the Games to Tokyo. The comment met with considerable criticism at the time… Mr. Abe’s ‘under control remark, that was a lie,’ Koizumi (former PM) now 74 and his unruly mane of hair turned white, told a news conference where he repeated his opposition to nuclear power.
As such, a very big conundrum precedes the 2020 games: How can the world community, as well as Olympians, believe anything the Abe administration says about the safety and integrity of Fukushima?
Still, the world embraces nuclear power more so than ever before as it continues to expand and grow. Sixty reactors are currently under construction in fifteen countries. In all, 160 power reactors are in the planning stage and 300 more have been proposed. Pro-Nuke-Heads claim Fukushima proves how safe nuclear power is because there are so few, if any, deaths, as to be inconsequential. That’s a boldfaced lie.
Here’s one of several independent testimonials on deaths because of Fukushima Daiichi radiation exposure (many, many, many more testimonials are highlighted in prior articles, including USS Ronald Reagan sailors on humanitarian rescue missions at the time):
It’s a real shame that the authorities hide the truth from the whole world, from the UN. We need to admit that actually many people are dying. We are not allowed to say that, but TEPCO employees also are dying. But they keep mum about it.5
- “Chernobyl’s Legacy: Kids With Bodies Ravaged by Disaster”, USA Today, April 17, 2016).
- Shuzo Takemoto, “Potential Global Catastrophe of the Reactor No. 2 at Fukushima Daiichi”, February 11, 2017.
- Helen Caldicott: “The Fukushima Nuclear Meltdown Continues Unabated”, Independent Australia, February 13, 2017.
- Katsutaka Idogawa, former mayor of Futaba (Fukushima Prefecture), “Fukushima Disaster: Tokyo Hides Truth as Children Die, Become Ill from Radiation – Ex-Mayor”, RT News, April 21, 2014.
The latest data on doses taken by workers at the Fukushima Daiichi nuclear plant are available online at the Ministry of Health, Labor and Social Affairs. They were provided by TEPCO. The company has reset all meters to zero by April 1, 2016.
Since that date, and until 31 December 2016, 14,643 workers have been exposed to ionizing radiation at the site of the accidented plant, out of which 13,027 were subcontracted workers (89%). There were 9,484 in December alone, out of which 8,463 were subcontracted workers
The average dose received during these 9 months was 2.14 mSv (2.29 mSv for subcontracted workers and 0.94 mSv for TEPCO employees). The highest dose was 38.76 mSv and a subcontracted worker took it. It should be noted that 93 subcontracted workers have already received a dose higher than 20 mSv. The highest dose taken by a TEPCO employee is 11.63 mSv.
By way of comparison, let us recall that the annual limit dose for the public is 1 mSv per year under normal conditions. For workers, it is 50 mSv per year without exceeding 100 mSv over 5 years. In France, it is strictly 20 mSv per year for workers.
Translated by Hervé courtois from L’ACROnique de Fukushima‘s article : http://fukushima.eu.org/dernieres-donnees-sur-les-doses-prises-par-les-travailleurs-a-la-centrale-de-fukushima-dai-ichi/
Robot stuck in Fukushima No. 2 reactor on 1st try, abandoned. Damage inside No. 2 reactor building at Fukushima plant greater than expected
The Sasori robot is stuck inside the containment vessel of Fukushima No. 1 nuclear power plant’s No. 2 reactor on Feb. 16. (Provided by International Research Institute for Nuclear Decommissioning)
Robot stuck in Fukushima No. 2 reactor on 1st try, abandoned
In the latest hitch in efforts to decommission reactors at the Fukushima No. 1 nuclear power plant, a robotic surveyor became mired in deposits and was lost on its maiden journey on Feb. 16.
Tokyo Electric Power Co., which operates the plant in Fukushima Prefecture, had to abandon the Sasori (scorpion) robot after it became stuck inside the containment vessel of the power station’s No. 2 reactor that morning.
The highly touted probe was specially developed for the important task of surveying the interior of the crippled reactor and collecting data to assist in removing the melted fuel.
But with the environment inside too treacherous for a key component in the process, TEPCO’s decommissioning project seems to have come to a standstill.
According to the utility, the robot entered the containment vessel around 8 a.m. It traveled along a 7.2-meter-long rail connecting the outer wall of the containment vessel with its central portion immediately beneath the pressure vessel.
But about 5 meters into its mission, the robot’s controls started to become less responsive. TEPCO believes it was due to deposits and other debris that are blocking the rail entering its drive system.
The operator tugged on the electrical cable connected to the robot and had it pull back to an area along its path with less obstacles, but it ultimately became stuck there.
The robot measured the radiation levels in the area at 210 sieverts per hour, which is lethal enough to kill a human in two minutes. Earlier, the company had estimated the level in the area at 650 sieverts per hour from video footage captured on Feb. 9 by another robot that paved the way for the Sasori.
With the robot completely immobilized, TEPCO gave up on retrieving it around 3 p.m. The operator cut the electric cable and closed the tunnel bored into the wall of the containment vessel, entombing the robot inside.
The probe was cast aside to the edge of the 0.6-meter-wide rail so that it would not impede future surveyor robots.
Had everything gone according to plan, TEPCO would have sent the Sasori onto the grating in the heart of the containment vessel, which is covered in black chunks believed to be melted fuel rods that fell from the pressure vessel above.
The utility had hoped to measure the dosage of these radioactive lumps, as well as capture images of the underside of the pressure vessel, which contains holes from when the nuclear fuel burned through it in the meltdown that was triggered by the Great East Japan Earthquake and tsunami in 2011.
Damage inside No. 2 reactor building at Fukushima plant greater than expected
Damage within the No. 2 reactor building at the Fukushima No. 1 Nuclear Power Plant was found to be greater than expected, based on images sent back by a robot sent into the structure by plant owner Tokyo Electric Power Co. (TEPCO) in a mission that concluded Feb. 16.
The operation used a self-propelled scorpion-shaped robot, with the goal of investigating the inside of the reactor’s containment vessel and the area directly beneath the reactor, but the area under the reactor was not reached. The No. 2 reactor building was thought to be comparatively undamaged compared to the No. 1 and No. 3 reactor buildings, where hydrogen explosions occurred. Worse damage than expected was discovered, however, such as holes in the grating foothold inside the containment vessel.
At a press conference, TEPCO official Yuichi Okamura stressed, “This investigation was the first of its type in the world and uncovered information about the debris inside. The mission wasn’t a failure.”
The robot’s camera also took footage of the condition of pipes in the structure, and image processing could make these pictures clearer. However, the robot’s treads stopped moving after it proceeded over 2 meters along a rail, and TEPCO was not able to use it to check the melted nuclear fuel.
TEPCO plans to decide as early as this summer on how to remove the melted fuel from the No. 1 through No. 3 reactors and start the decommissioning process in earnest. The results of the investigation were to be used as base data for the decommissioning, but with it having not produced an overall understanding of the No. 2 reactor building’s interior, a new investigation will probably be sought.
However, no plan for the next investigation has been decided, and it may begin with the development of a new robot. TEPCO plans to send in a different robot to the No. 1 reactor building next month. For the No. 3 reactor building, a robot capable of moving in water is being developed because there is a large amount of contaminated water at the bottom of its containment vessel.
While the press reported Scorpion’s mission as a failure, it provided useful data before being abandoned. It collected some radiation readings and a number of useful images.
The robot seems to have become stranded on a pile of debris on the rail. Radiation data from along this inspection route provided only one radiation reading, no telemetry as other videos had. Tepco’s video is heavily edited but still provides some useful information.
A reminder, these readings are the result of venturing into the more deadly areas of the reactor where they have been unable to previously, no resulting from an increase of radiation. While this is much lower than the earlier camera estimates of radiation it is still extremely high and quite deadly.
Arond the same area where the high radiation source was found, TEPCO stated they found a 210 Sv/h reading with the on board radiation sensor.
New images from inside the pedestal were obtained as were some images looking up into the containment structure.
Image below from TEPCO. White ghosting on the image is likely due to radiation levels rather than steam. The existing melt hole in the pedestal floor grate can be partially seen in the upper mid section of the image. A very thick amount of fuel debris can be see in the lower right section of the image. The mark “clean” on this image with an arrow indicates an area where the floor grate may have failed after the molten fuel had splattered on the area. Further below, more fuel debris and structures can be seen.
The red circle shows an area where it appears fuel debris was moved or blocked by a fallen piece of sheet steel.
In both images, sections of light colored piping can be seen below the area where the grate is missing. On the far left of the image a partially melted section of flexible conduit can be seen.
This appears to indicate that high temperatures within the pedestal were very localized.
TEPCO handout for this work
Tepco released a new image of the reactor 2: at least three holes in the platform and still no corium.
The platform is made of metal (grating), just below the tank, intended to access the control rods. The bottom of the containment is a little over 3 m below.
Tepco’s document in Japanese:
A robot shown in this photo by the International Research Institute for Nuclear Decommissioning was put inside reactor 2 at the Fukushima No. 1 nuclear plant on Thursday
Robot stops working in Fukushima reactor
The operator of the crippled Fukushima Daiichi nuclear power plant says it suspended a survey by a robot at one of its reactors after the device stopped working.
Tokyo Electric Power Company, or TEPCO, sent the scorpion-shaped robot into the containment vessel of the plant’s No. 2 reactor on Thursday.
The company believes fuel in the reactor melted through its core during the 2011 accident and accumulated at the bottom of the facility’s containment vessel.
The survey was aimed at getting a close look at what could be fuel debris — a mixture of nuclear fuel and melted parts of the reactor.
The robot was also expected to measure radiation and temperatures there to gather data for scrapping the reactor.
TEPCO officials say the device was advancing on a metal rail leading to a central area below the reactor’s core, but stopped moving before it could reach the center.
The officials say they decided to give up the robot and cut its remote-control cable.
TEPCO plans to analyze data collected by the robot and figure out how to carry out future probes.
Robot survey of crippled Fukushima reactor ends in failure
The operator of the crisis-hit Fukushima Daiichi nuclear power plant said Thursday its attempt to take a close look at the crippled No. 2 reactor using a scorpion-shaped robot ended in failure due to a technical flaw.
A track glitch meant the self-propelled robot was unable to climb over obstacles, Tokyo Electric Power Company Holdings Inc. said. It gave up on retrieving the robot by cutting its remote control cables.
TEPCO, however, said, “We have received new important information about the radiation level and temperature inside the (reactor) containment vessel,” emphasizing it did not view Thursday’s survey as a failure.
Latest probe of reactor 2 fails after Fukushima robot blocked by obstacles
A renewed attempt to survey reactor 2 at the damaged Fukushima No. 1 nuclear power plant failed Thursday when the latest robot probe became obstructed.
The robot was inserted into the primary containment vessel at around 7:50 a.m. to approach the metal grating directly underneath the pressure vessel, where a black mass has been found.
Tokyo Electric Power Company Holdings Inc. had hoped to take a closer look at what could be melted nuclear fuel, but it was forced to abandon the operation shortly after 3 p.m.
The robot didn’t reach its objective, Tepco said, and the utility eventually severed its controller cable.
Having detected an extraordinarily high radiation level —estimated at 650 sieverts per hour — in a preparatory survey, Tepco had hoped to obtain more precise readings, images and data needed to remove fuel and other debris to decommission the plant.
In previous surveys, the utility found deposits on the grating believed to be nuclear debris and a 1-sq.-meter hole believed to have been created by molten fuel escaping from the pressure vessel.
Challenges dogged the latest attempt from the start. There was little clear surface for the robot to move around, and the radiation could kill the unit as with the preliminary surveys.
Next month, Tepco plans to survey the No. 1 reactor.
Operation of communication about the “scorpion” robot which will be sent to the confinement enclosure of reactor n ° 2
TEPCO and its partners launched a communication operation about the “scorpion” robot, which will be sent to the containment reactor of reactor n ° 2 in an attempt to locate the corium, ie the highly radioactive molten fuel, mixed with debris. It is not certain that the mission will be a success, the cleaning robot having lasted only two hours in this enclosure because of the extreme radiations, without being able to finish its task.
A press release announces what we already know and insists on the challenges: “every step is a new challenge for TEPCO, but TEPCo welcomes the challenges”. The company would be almost happy with the accident? It is accompanied by a promotional video with a comparison to the kendô fights posted on its Facebook page.
The Japanese nuclear industry wants to place itself on the decommissioning market and highlights the technologies being developed. This robot was designed by IRID, Toshiba and TEPCO. IRID benefits from public funds. As for Toshiba, it is almost bankrupt because of its nuclear branch and TEPCO is financially in a bad shape.
1. Current conditions of Unit 2 Primary Containment Vessel (PCV)
Nuclear fuel in the Primary Containment vessel (PCV) was exposed to the air and melted from the impact of March 2011 Great Earthquake.
As a result of the accident analysis, it was found that a portion of melted nuclear fuel might have been fallen inside the pedestal.
To remove fuel debris, it is necessary to investigate the PCV and clarify the conditions of debris and surrounding structures.
2. Outline of Unit 2 PCV investigation
[Purpose]: To obtain feedback information (deformation of platform, etc.) for the design and
development of next investigation devices inside the pedestal
To inspect conditions on the platform inside pedestal, fuel debris fallen to the CRD housing, and conditions of structures inside pedestal.
[Investigation point]: Platform and Control Rod Drive (CRD) will be investigated from the platform inside pedestal
3. Work steps for Unit 2 PCV investigation
4. Preparatory investigation results from X-6 penetration to CRD rail
4. Preparatory investigation results at the entrance of pedestal area
4. Preparatory investigation results of pedestal area
5. Additional results expected from the self-propelled investigation device
6. Investigation by the self-propelled investigation device to the end of CRD rail
6. Investigation by the self-propelled investigation device to the end of CRD rail
Reference: Investigation results on the platform inside the pedestal
Technical information for the media is available here:
In Japanese about the upcoming mission http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170215_08-j.pdf
And about radiation protection measures http://www.tepco.co.jp/nu/fukushima-np/handouts/2017/images1/handouts_170215_09-j.pdf
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