Fukushima dome roof takes shape, but radiation remains high — The Asahi Shimbun

” High radiation levels are still limiting recovery work at the Fukushima No. 1 nuclear plant, a stark reality that reporters saw firsthand when they observed efforts to remove risk factors there.

Media representatives were invited into the plant in early December to see construction work, with the building of a domed roof over the No. 3 reactor building as the main focus.

However, they were only allowed to stay on top of the roof for 20 minutes due to high radiation levels.

The roof is being put together directly above the storage pool for spent fuel. The dome is designed to prevent the spewing of radioactive materials when the fuel is actually removed from the pool.

The original roof of the No. 3 reactor building was severely damaged by a hydrogen explosion in the days following the March 11, 2011, Great East Japan Earthquake and tsunami, which led to the crippling of the Fukushima No. 1 plant.

Spent fuel still remains in the storage pools located on the top floors of the No. 1 to No. 3 reactor buildings.

Plans call for removing the spent fuel first from the No. 3 reactor building.

Although the dome will help prevent the spread of radioactive materials, building parts and other debris as well as some equipment have still not been completely removed from the storage pool, which holds 566 fuel rods.

The collapsed roof and walls were removed to allow for the construction of the domed roof, which began in the summer. The domed roof is about 17 meters high, and a crane was also installed under it in November.

Plans call for the removal of the spent fuel from the No. 3 building to begin in the middle of the next fiscal year.

Internal radiation exposure levels were measured before media representatives headed to the No. 3 reactor building. They were also required to don protective clothing as well as a partial face mask covering the mouth and nose from about 100 meters from the building.

Radiation levels close to the building were 0.1 millisieverts per hour.

An elevator installed into the scaffolding next to the reactor building took the media representatives to the roof, which had been covered with metal plates.

The so-called operating floor looked like any other newly constructed building roof, a sharp contrast to the twisted metal parts that covered the building shortly after the nuclear accident.

Tokyo Electric Power Co., the plant’s operator, captured video footage from within the reactors for the first time in July. Debris that appears to be melted nuclear fuel was found in various parts of the containment vessel.

To the south of the No. 3 reactor building stands the No. 4 reactor building, from where all the spent nuclear fuel has been removed.

To the north is the No. 2 reactor building, which avoided a hydrogen explosion. Beyond the building, cranes and other large equipment are working in preparation for the removal of debris from the No. 1 reactor building.

TEPCO officials cautioned media representatives about standing too long right next to the storage pool, which could be seen located about six meters below the roof. Debris was found within the pool while insulating material floated on the pool surface.

The radiation level near the pool was 0.68 millisieverts per hour. While that was a major improvement from the 800 millisieverts per hour recorded in the immediate aftermath of the nuclear accident close to seven years ago, it was still too high to allow for a stay of longer than 20 minutes. ”

by Chikako Kawahara, The Asahi Shimbun

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Botched gauge settings might have contaminated Fukushima groundwater from April onward: Tepco — The Japan Times

” The discovery of falsely configured monitoring equipment at the stricken Fukushima No. 1 nuclear power plant means the groundwater flowing underneath it might have gotten contaminated from April onward, Tokyo Electric said Friday.

The utility said incorrect gauge settings were used to measure groundwater levels in six of the wells near reactors 1 and 4. This resulted in groundwater readings about 70 cm higher than reality, which means the beleaguered power utility has been mismanaging the groundwater there for months.

To prevent tainted water from leaking from the plant, Tokyo Electric Power Company Holdings Inc. installed water gauges so it could keep the groundwater levels in the wells a meter higher than the contaminated water in the buildings.

Tepco adjusts the amount of water in wells called subdrains around the buildings to keep the groundwater higher than the tainted water inside them, which prevents it from flowing out. If the groundwater levels sink below the level of the radioactive water, it might leak out.

On Friday, Tepco said the estimated groundwater level in one of the six subdrain wells close to reactor 1 fell below the level in the reactor building at least eight times during the five-day period to May 21 because the gauges were set incorrectly.

Groundwater levels were 2 mm to 19 mm lower than the level in the buildings, Tepco said, adding that it does not know precisely how long each of these problematic situations lasted because water level data is collected by the hour.

Tepco said groundwater levels in five other wells affected by the incorrect settings did not fall below the levels in the nearby reactor buildings.

All six are in the area surrounded by an underground ice wall designed to prevent groundwater leakage.

According to Tepco, the incorrect settings date as far back as April 19. The earliest error affected the gauge in a well where groundwater fell to hazardous levels.

In the world’s worst nuclear disaster since Chernobyl, reactors 1, 2 and 3 at the plant experienced core meltdowns and reactors 1, 3 and 4 were severely damaged by hydrogen explosions following a massive offshore earthquake that spawned large tsunami in March 2011. ”

by Jiji, Kyodo via The Japan Times

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Fukushima’s decommissioning delays, challenges and unknowns remain roadblocks to cleanup — Beyond Nuclear

” Six and a half years after the Fukushima Daiichi triple meltdown, Japan’s government, the nuclear regulator and Tokyo Electric Power Company’s (TEPCO) most rudimentary plan of attack for recovery from radioactive catastrophe is delayed again. The first steps of decommissioning cannot legitimately begin until undamaged but highly radioactive “spent” fuel assemblies are removed from vulnerable reactor storage ponds, sufficiently cooled and re-contained in qualified dry storage casks.  Then, there are the three melted fuel cores that still must be located, retrieved and somehow re-contained. Where all of the massive radioactive contamination will go is a mystery.  In fact, there are an alarming number of challenges, continuing delays and unknowns that remain before securing the destroyed nuclear power station site and halting the ongoing release of radioactivity to the land, water and air.

Among the most immediate concerns is the management of 1007 highly radioactive and thermally hot irradiated nuclear fuel assemblies still in the two cooling pools perched atop the destroyed Units 1 and 2 outside of any containment structure. Each of the site’s six-units has an elevated nuclear waste storage pond. The site has a large common pool located near Unit 4. The government recently admitted that previously unknown, possibly undisclosed, damage in these irradiated fuel storage ponds and radioactive contamination has again delayed the plan to move the dangerous fuel assemblies by at least another three years, now 2023. Unit 3 remains on schedule in 2018 to begin the two-year transfer of 514 irradiated fuel assemblies from its rooftop storage pool to a jam-packed common onsite pool located at ground level. This common pool and its massive radioactive inventory requires reliable cooling power.  Unit 4 completed a three-year project to transfer its irradiated fuel into the common pool in 2014. The common pool now has 6,726 irrradiated fuel assemblies with a maximum design capacity of 6,840. As this common pool is already densely packed, it is ever more critical that Japan expedite the transfer of the sufficiently cooled irradiated nuclear fuel into qualified, individualized dry storage casks that can passively cool the hot nuclear waste without the need for water and electrical power. Currently, only 1,412 irradiated assemblies have been secured in onsite dry cask storage. These dry casks further need to be hardened against another natural disaster and possible terrorism.

The recurring delays at securing the irradiated fuel currently in wet pool storage (individual units to the common pool) and then into scientifically-qualified and hardened dry cask storage systems raises concern for public health, safety and the environment given the prospect of another large nearby earthquake causing a loss of cooling with the risk of a nuclear waste fire and radioactive releases. A 6.9 magnitude offshore earthquake on November 21, 2016 caused a temporary loss of cooling to wet storage systems at Fukushima Daiichi. Significant earthquakes of 6.0 to 6.9 magnitude occur in Japan on average 17 times per year, roughly one-tenth of all large earthquakes in the world. More severe earthquakes must be anticipated. The loss of cooling power and water to some or all of the more than 11,577 hot nuclear waste assemblies onsite outside of containment remains a significant public health, safety and environmental concern.

Japan is still technologically conceptualizing the “most challenging part” of Fukushima Daiichi’s decommissioning and the recovery of three missing melted reactor cores if and when they can be located. The unprecedented operation has now been delayed until 2019.  A viable technology for scooping up melted nuclear fuel does not yet exist. Re-containment and removal of the melted fuel cores is key to addressing the ongoing massive buildup of radioactive water now estimated at 800,000 tons that is being stored in growing onsite tank farms.  Groundwater flowing down into the reactor wreckage must be constantly pumped out, partially filtered of radioactivity and stored onsite in the large tanks. The tank farms themselves represent an additional environmental threat in the event of another severe earthquake that could rupture the structures with a radioactive flood into the ocean. ”

by Beyond Nuclear

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The Fukushima nuclear meltdown continues unabated — Helen Caldicott, Independent Australia

Helen Caldicott sums up the situation here:

” Recent reporting of a huge radiation measurement at Unit 2 in the Fukushima Daichi reactor complex does not signify that there is a peak in radiation in the reactor building.

All that it indicates is that, for the first time, the Japanese have been able to measure the intense radiation given off by the molten fuel, as each previous attempt has led to failure because the radiation is so intense the robotic parts were functionally destroyed.

The radiation measurement was 530 sieverts, or 53,000 rems (Roentgen Equivalent for Man). The dose at which half an exposed population would die is 250 to 500 rems, so this is a massive measurement. It is quite likely had the robot been able to penetrate deeper into the inner cavern containing the molten corium, the measurement would have been much greater.

These facts illustrate why it will be almost impossible to “decommission” units 1, 2 and 3 as no human could ever be exposed to such extreme radiation. This fact means that Fukushima Daichi will remain a diabolical blot upon Japan and the world for the rest of time, sitting as it does on active earthquake zones.

What the photos taken by the robot did reveal was that some of the structural supports of Unit 2 have been damaged. It is also true that 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 fell on the molten core beneath. But units 1, 2 and 3 also contain cooling pools with very radioactive fuel rods — numbering 392 in Unit 1, 615 in Unit 2, and 566 in Unit 3; if an earthquake were to breach a pool, the gamma rays would be so intense that the site would have to be permanently evacuated. The fuel from Unit 4 and its cooling pool has been removed.

But there is more to fear.

The reactor complex was built adjacent to a mountain range and millions of gallons of water emanate from the mountains daily beneath the reactor complex, causing some of the earth below the reactor buildings to partially liquefy. As the water flows beneath the damaged reactors, it immerses the three molten cores and becomes extremely radioactive as it continues its journey into the adjacent Pacific Ocean.

Every day since the accident began, 300 to 400 tons of water has poured into the Pacific where numerous isotopes – including cesium 137, 134, strontium 90, tritium, plutonium, americium and up to 100 more – enter the ocean and bio-concentrate by orders of magnitude at each step of the food chain — algae, crustaceans, little fish, big fish then us.

Fish swim thousands of miles and tuna, salmon and other species found on the American west coast now contain some of these radioactive elements, which are tasteless, odourless and invisible. Entering the human body by ingestion they concentrate in various organs, irradiating adjacent cells for many years. The cancer cycle is initiated by a single mutation in a single regulatory gene in a single cell and the incubation time for cancer is any time from 2 to 90 years. And no cancer defines its origin.

We could be catching radioactive fish in Australia or the fish that are imported could contain radioactive isotopes, but unless they are consistently tested we will never know.

As well as the mountain water reaching the Pacific Ocean, since the accident, TEPCO has daily pumped over 300 tons of sea water into the damaged reactors to keep them cool. It becomes intensely radioactive and is pumped out again and stored in over 1,200 huge storage tanks scattered over the Daichi site. These tanks could not withstand a large earthquake and could rupture releasing their contents into the ocean.

But even if that does not happen, TEPCO is rapidly running out of storage space and is trying to convince the local fishermen that it would be okay to empty the tanks into the sea. The Bremsstrahlung radiation like x-rays given off by these tanks is quite high – measuring 10 milirems – presenting a danger to the workers. There are over 4,000 workers on site each day, many recruited by the Yakuza (the Japanese Mafia) and include men who are homeless, drug addicts and those who are mentally unstable.

There’s another problem. Because the molten cores are continuously generating hydrogen, which is explosive, TEPCO has been pumping nitrogen into the reactors to dilute the hydrogen dangers.

Vast areas of Japan are now contaminated, including some areas of Tokyo, which are so radioactive that roadside soil measuring 7,000 becquerels (bc) per kilo would qualify to be buried in a radioactive waste facility in the U.S..

As previously explained, these radioactive elements concentrate in the food chain. The Fukushima Prefecture has always been a food bowl for Japan and, although much of the rice, vegetables and fruit now grown here is radioactive, there is a big push to sell this food both in the Japanese market and overseas. Taiwan has banned the sale of Japanese food, but Australia and the U.S. have not.

Prime Minister Abe recently passed a law that any reporter who told the truth about the situation could be [jail]ed for ten years. In addition, doctors who tell their patients their disease could be radiation related will not be paid, so there is an immense cover-up in Japan as well as the global media.

The Prefectural Oversite Committee for Fukushima Health is only looking at thyroid cancer among the population and by June 2016, 172 people who were under the age of 18 at the time of the accident have developed, or have suspected, thyroid cancer; the normal incidence in this population is 1 to 2 per million.

However, other cancers and leukemia that are caused by radiation are not being routinely documented, nor are congenital malformations, which were, and are, still rife among the exposed Chernobyl population.

Bottom line, these reactors will never be cleaned up nor decommissioned because such a task is not humanly possible. Hence, they will continue to pour water into the Pacific for the rest of time and threaten Japan and the northern hemisphere with massive releases of radiation should there be another large earthquake. ”

by Helen Caldicott

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Possible causes of Fukushima frozen wall failures — SimplyInfo

While Nuclear Street focuses on the 90 percent of the ice wall at Fukushima No. 1 that is working (in the previous post), Simply Info analyzes the possible cause of the failure of the other 10 percent of the ice wall to freeze.

Read article

Near miss at Fukushima is a warning for U.S., panel says — Richard Stone, Science

” Japan’s chief cabinet secretary called it “the devil’s scenario.” Two weeks after the 11 March 2011 earthquake and tsunami devastated the Fukushima Daiichi Nuclear Power Plant, causing three nuclear reactors to melt down and release radioactive plumes, officials were bracing for even worse. They feared that spent fuel stored in the reactor halls would catch fire and send radioactive smoke across a much wider swath of eastern Japan, including Tokyo.

Thanks to a lucky break detailed in a report released today by the U.S. National Academies, Japan dodged that bullet. The near calamity “should serve as a wake-up call for the industry,” says Joseph Shepherd, a mechanical engineer at the California Institute of Technology in Pasadena who chaired the academy committee that produced the report. Spent fuel accumulating at U.S. nuclear reactor plants is also vulnerable, the report warns. A major spent fuel fire at a U.S. nuclear plant “could dwarf the horrific consequences of the Fukushima accident,” says Edwin Lyman, a physicist at the Union of Concerned Scientists, a nonprofit in Washington, D.C., who was not on the panel.

After spent fuel is removed from a reactor core, the fission products continue to decay radioactively, generating heat. Many nuclear plants, like Fukushima, store the fuel onsite at the bottom of deep pools for at least 5 years while it slowly cools. It is seriously vulnerable there, as the Fukushima accident demonstrated, and so the academy panel recommends that the U.S. Nuclear Regulatory Commission (NRC) and nuclear plant operators beef up systems for monitoring the pools and topping up water levels in case a facility is damaged. It also calls for more robust security measures after a disaster. “Disruptions create opportunities for malevolent acts,” Shepherd says.

At Fukushima, the earthquake and tsunami cut power to pumps that circulated coolant through the reactor cores and cooled water in the spent fuel pools. The pump failure led to the core meltdowns. In the pools, found in all six of Fukushima’s reactor halls, radioactive decay gradually heated the water. Of preeminent concern were the pools in reactor Units 1 through 4: Those buildings had sustained heavy damage on 11 March and in subsequent days, when explosions occurred in Units 1, 3, and 4.

The “devil’s scenario” nearly played out in Unit 4, where the reactor was shut down for maintenance. The entire reactor core—all 548 assemblies—was in the spent fuel pool, and was hotter than fuel in the other pools. When an explosion blew off Unit 4’s roof on 15 March, plant operators assumed the cause was hydrogen—and they feared it had come from fuel in the pool that had been exposed to air. They could not confirm that, because the blast had destroyed instrumentation for monitoring the pool. (Tokyo Electric Power Company, the plant operator, later suggested that the hydrogen that had exploded had come not from exposed spent fuel but from the melted reactor core in the adjacent Unit 3.) But the possibility that the fuel had been exposed was plausible and alarming enough for then-NRC Chairman Gregory Jaczko on 16 March to urge more extensive evacuations than the Japanese government had advised—beyond a 20-kilometer radius from the plant.

Later that day, however, concerns abated after a helicopter overflight captured video of sunlight glinting off water in the spent fuel pool. In fact, the crisis was worsening: The pool’s water was boiling away because of the hot fuel. As the level fell perilously close to the top of the fuel assemblies, something “fortuitous” happened, Shepherd says. As part of routine maintenance, workers had flooded Unit 4’s reactor well, where the core normally sits. Separating the well and the spent fuel pool is a gate through which fuel assemblies are transferred. The gate allowed water from the reactor well to leak into the spent fuel pool, partially refilling it. Without that leakage, the academy panel’s own modeling predicted that the tops of the fuel assemblies would have been exposed by early April; as the water continued to evaporate, the odds of the assemblies’ zirconium cladding catching fire would have skyrocketed. Only good fortune and makeshift measures to pump or spray water into all the spent fuel pools averted that disaster, the academy panel notes.

At U.S. nuclear plants, spent fuel is equally vulnerable. It is for the most part densely packed in pools, heightening the fire risk if cooling systems were to fail. NRC has estimated that a major fire in a U.S. spent fuel pool would displace, on average, 3.4 million people from an area larger than New Jersey. “We’re talking about trillion-dollar consequences,” says panelist Frank von Hippel, a nuclear security expert at Princeton University.

Besides developing better systems for monitoring the pools, the panel recommends that NRC take another look at the benefits of moving spent fuel to other storage as quickly as possible. Spent fuel can be shifted to concrete containers called dry casks as soon as it cools sufficiently, and the academy panel recommends that NRC “assess the risks and potential benefits of expedited transfer.” A wholesale transfer to dry casks at U.S. plants would cost roughly $4 billion. ”

by Richard Stone, Science

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