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D'coda Dcoda

"Now They Tell Us" Series: TEPCO Admits Reactor 1 Corium May Be 65 Centimeters into the... - 0 views

ex-skf.blogspot.com/...ll-us-series-tepco-admits.html

shared by D'coda Dcoda on 01 Dec 11 - No Cached
  • There you go! It took TEPCO only 8 and a half months to say what many people have been saying at least for 8 months.The corium has long escaped the Reactor Pressure Vessel AND the Containment Vessel of Reactor 1 (that much TEPCO has actually admitted, but..), and has eaten into the concrete pedestal to about 65-centimeter deep.For Reactors 2 and 3, TEPCO thinks (hopes, wishes...) that a good chunk of the corium dropped from the RPV onto the CV. No mention whether the corium there is eating into the concrete or not.From NHK News (11/30/2011; quick translation, subject to revision):
  • Significant amount of melted fuel in the Containment Vessel
  • It has been discovered by TEPCO's analysis that the significant amount of Reactor 1's melted fuel pierced through the steel Reactor Pressure Vessel and dropped onto the Containment Vessel, then melted the concrete at the bottom of the CV. It is estimated that the melted fuel may have eaten into the concrete to maximum 65 centimeters deep.
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  • Using different methods, TEPCO and various other research institutions have been analyzing the state of the melted fuel based on the reactor temperatures and the amount of water being poured into the reactors, and the results were announced on November 30 at a workshop held by the national government.
  • In Reactors 1 thorugh 3 of Fukushima I Nuclear Power Plant, core meltdowns have occurred, and it is considered that part of the melted fuel has dropped from the RPVs to the CVs. However, the details are not yet known even after more than 8 months since the accident started.
  • For Reactors 2 and 3, TEPCO also estimates that part of the fuel has dropped to the Containment Vessels, showing how severe the accident has been.
  • TEPCO's result shows that, in the most severe case, all of the fuel would have melted, of which a significant portion pierced through the bottom of the Reactor Pressure Vessel and dropped onto the Containment Vessel.
  • There is a concrete platform [pedestal] at the bottom of the Containment Vessel, which is then covered with steel plates
  • When the melted fuel drops to the bottom of the Containment Vessel, a core-concrete reaction takes place at a high temperature, melting the concrete. In the worst case, in Reactor 1, the melted fuel could reach 65 centimeters deep into the concrete.
  • At the thinnest part of the concrete, it is only 37 centimeters to the outer steel plate of the Containment Vessels. This is a very severe accident.
  • TEPCO also estimates that in the worst cases for Reactors 2 and 3, 57% and 63% of the fuel have melted, respectively, and part of the fuel dropped onto the Containment Vessels.
D'coda Dcoda

U.S. nuke regulators weaken safety rules [20Jun11] - 0 views

www.bellinghamherald.com/...-regulators-weaken-safety.html

shared by D'coda Dcoda on 15 Nov 11 - No Cached
  • Federal regulators have been working closely with the nuclear power industry to keep the nation's aging reactors operating within safety standards by repeatedly weakening standards or simply failing to enforce them, an investigation by The Associated Press has found.Officials at the U.S. Nuclear Regulatory Commission regularly have decided original regulations were too strict, arguing that safety margins could be eased without peril, according to records and interviews.The result? Rising fears that these accommodations are undermining safety -- and inching the reactors closer to an accident that could harm the public and jeopardize nuclear power's future.
  • Examples abound. When valves leaked, more leakage was allowed -- up to 20 times the original limit. When cracking caused radioactive leaks in steam generator tubing, an easier test was devised so plants could meet standards.Failed cables. Busted seals. Broken nozzles, clogged screens, cracked concrete, dented containers, corroded metals and rusty underground pipes and thousands of other problems linked to aging were uncovered in AP's yearlong investigation. And many of them could escalate dangers during an accident.
  • Despite the problems, not a single official body in government or industry has studied the overall frequency and potential impact on safety of such breakdowns in recent years, even as the NRC has extended dozens of reactor licenses.Industry and government officials defend their actions and insist no chances are being taken. But the AP investigation found that with billions of dollars and 19 percent of America's electricity supply at stake, a cozy relationship prevails between industry and the NRC.Records show a recurring pattern: Reactor parts or systems fall out of compliance. Studies are conducted by industry and government, and all agree existing standards are "unnecessarily conservative."
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  • Regulations are loosened, and reactors are back in compliance."That's what they say for everything ...," said Demetrios Basdekas, a retired NRC engineer. "Every time you turn around, they say, 'We have all this built-in conservatism.' "The crisis at the decades-old Fukushima Dai-ichi nuclear facility in Japan has focused attention on nuclear safety and prompted the NRC to look at U.S. reactors. A report is due in July.But the factor of aging goes far beyond issues posed by Fukushima.
  • Commercial nuclear reactors in the United States were designed and licensed for 40 years. When the first were built in the 1960s and 1970s, it was expected that they would be replaced with improved models long before their licenses expired.That never happened. The 1979 accident at Three Mile Island, massive cost overruns, crushing debt and high interest rates halted new construction in the 1980s.Instead, 66 of the 104 operating units have been relicensed for 20 more years. Renewal applications are under review for 16 other reactors.As of today, 82 reactors are more than 25 years old.The AP found proof that aging reactors have been allowed to run less safely to prolong operations.
  • Last year, the NRC weakened the safety margin for acceptable radiation damage to reactor vessels -- for a second time. The standard is based on a reactor vessel's "reference temperature," which predicts when it will become dangerously brittle and vulnerable to failure. Through the years, many plants have violated or come close to violating the standard.As a result, the minimum standard was relaxed first by raising the reference temperature 50 percent, and then 78 percent above the original -- even though a broken vessel could spill radioactive contents."We've seen the pattern," said nuclear safety scientist Dana Powers, who works for Sandia National Laboratories and also sits on an NRC advisory committee. "They're ... trying to get more and more out of these plants."
  • Sharpening the pencilThe AP study collected and analyzed government and industry documents -- some never-before released -- of both reactor types: pressurized water units that keep radioactivity confined to the reactor building and the less common boiling water types like those at Fukushima, which send radioactive water away from the reactor to drive electricity-generating turbines.The Energy Northwest Columbia Generating Station north of Richland is a boiling water design that's a newer generation than the Fukushima plants.Tens of thousands of pages of studies, test results, inspection reports and policy statements filed during four decades were reviewed. Interviews were conducted with scores of managers, regulators, engineers, scientists, whistleblowers, activists and residents living near the reactors at 65 sites, mostly in the East and Midwest.
  • AP reporters toured some of the oldest reactors -- Oyster Creek, N.J., near the Atlantic coast 50 miles east of Philadelphia and two at Indian Point, 25 miles north of New York City on the Hudson River.Called "Oyster Creak" by some critics, this boiling water reactor began running in 1969 and is the country's oldest operating commercial nuclear power plant. Its license was extended in 2009 until 2029, though utility officials announced in December they will shut the reactor 10 years earlier rather than build state-ordered cooling towers. Applications to extend the lives of pressurized water units 2 and 3 at Indian Point, each more than 36 years old, are under NRC review.Unprompted, several nuclear engineers and former regulators used nearly identical terminology to describe how industry and government research has frequently justified loosening safety standards. They call it "sharpening the pencil" or "pencil engineering" -- fudging calculations and assumptions to keep aging plants in compliance.
  • Cracked tubing: The industry has long known of cracking in steel alloy tubing used in the steam generators of pressurized water reactors. Ruptures have been common in these tubes containing radioactive coolant; in 1993 alone, there were seven. As many as 18 reactors still run on old generators.Problems can arise even in a newer metal alloy, according to a report of a 2008 industry-government workshop.
  • Neil Wilmshurst, director of plant technology for the industry's Electric Power Research Institute, acknowledged the industry and NRC often collaborate on research that supports rule changes. But he maintained there's "no kind of misplaced alliance ... to get the right answer."Yet agency staff, plant operators and consultants paint a different picture:* The AP reviewed 226 preliminary notifications -- alerts on emerging safety problems -- NRC has issued since 2005. Wear and tear in the form of clogged lines, cracked parts, leaky seals, rust and other deterioration contributed to at least 26 of the alerts. Other notifications lack detail, but aging was a probable factor in 113 more, or 62 percent in all. For example, the 39-year-old Palisades reactor in Michigan shut Jan. 22 when an electrical cable failed, a fuse blew and a valve stuck shut, expelling steam with low levels of radioactive tritium into the outside air. And a 1-inch crack in a valve weld aborted a restart in February at the LaSalle site west of Chicago.
  • * A 2008 NRC report blamed 70 percent of potentially serious safety problems on "degraded conditions" such as cracked nozzles, loose paint, electrical problems or offline cooling components.* Confronted with worn parts, the industry has repeatedly requested -- and regulators often have allowed -- inspections and repairs to be delayed for months until scheduled refueling outages. Again and again, problems worsened before being fixed. Postponed inspections inside a steam generator at Indian Point allowed tubing to burst, leading to a radioactive release in 2000. Two years later, cracking grew so bad in nozzles on the reactor vessel at the Davis-Besse plant near Toledo, Ohio, that it came within two months of a possible breach, an NRC report said, which could release radiation. Yet inspections failed to catch the same problem on the replacement vessel head until more nozzles were found to be cracked last year.
  • Time crumbles thingsNuclear plants are fundamentally no more immune to aging than our cars or homes: Metals grow weak and rusty, concrete crumbles, paint peels, crud accumulates. Big components like 17-story-tall concrete containment buildings or 800-ton reactor vessels are all but impossible to replace. Smaller parts and systems can be swapped but still pose risks as a result of weak maintenance and lax regulation or hard-to-predict failures.Even mundane deterioration can carry harsh consequences.For example, peeling paint and debris can be swept toward pumps that circulate cooling water in a reactor accident. A properly functioning containment building is needed to create air pressure that helps clear those pumps. But a containment building could fail in a severe accident. Yet the NRC has allowed safety calculations that assume the buildings will hold.
  • In a 2009 letter, Mario V. Bonaca, then-chairman of the NRC's Advisory Committee on Reactor Safeguards, warned that this approach represents "a decrease in the safety margin" and makes a fuel-melting accident more likely.Many photos in NRC archives -- some released in response to AP requests under the federal Freedom of Information Act -- show rust accumulated in a thick crust or paint peeling in long sheets on untended equipment.Four areas stand out:
  • Brittle vessels: For years, operators have rearranged fuel rods to limit gradual radiation damage to the steel vessels protecting the core and keep them strong enough to meet safety standards.But even with last year's weakening of the safety margins, engineers and metal scientists say some plants may be forced to close over these concerns before their licenses run out -- unless, of course, new regulatory compromises are made.
  • Leaky valves: Operators have repeatedly violated leakage standards for valves designed to bottle up radioactive steam in an earthquake or other accident at boiling water reactors.Many plants have found they could not adhere to the general standard allowing main steam isolation valves to leak at a rate of no more than 11.5 cubic feet per hour. In 1999, the NRC decided to allow individual plants to seek amendments of up to 200 cubic feet per hour for all four steam valves combined.But plants have violated even those higher limits. For example, in 2007, Hatch Unit 2, in Baxley, Ga., reported combined leakage of 574 cubic feet per hour.
  • "Many utilities are doing that sort of thing," said engineer Richard T. Lahey Jr., who used to design nuclear safety systems for General Electric Co., which makes boiling water reactors. "I think we need nuclear power, but we can't compromise on safety. I think the vulnerability is on these older plants."Added Paul Blanch, an engineer who left the industry over safety issues, but later returned to work on solving them: "It's a philosophical position that (federal regulators) take that's driven by the industry and by the economics: What do we need to do to let those plants continue to operate?"Publicly, industry and government say that aging is well under control. "I see an effort on the part of this agency to always make sure that we're doing the right things for safety. I'm not sure that I see a pattern of staff simply doing things because there's an interest to reduce requirements -- that's certainly not the case," NRC chairman Gregory Jaczko said in an interview.
  • Corroded piping: Nuclear operators have failed to stop an epidemic of leaks in pipes and other underground equipment in damp settings. Nuclear sites have suffered more than 400 accidental radioactive leaks, the activist Union of Concerned Scientists reported in September.Plant operators have been drilling monitoring wells and patching buried piping and other equipment for several years to control an escalating outbreak.But there have been failures. Between 2000 and 2009, the annual number of leaks from underground piping shot up fivefold, according to an internal industry document.
D'coda Dcoda

#Fukushima I Nuke Plant: Water Entombment Is Back on the Table [01Sept11] - 0 views

ex-skf.blogspot.com/...ke-plant-water-entombment.html

shared by D'coda Dcoda on 01 Sep 11 - No Cached
  • Remember the time when the TEPCO/government complex pretended that it would fill the Containment Vessels of Reactors 1, 2 and 3 with water to cool the Reactor Pressure Vessels inside? It was late April, TEPCO started to pour an enormous amount of water in the RPV of Reactor 1 to fill the Vessel (as the water would leak into the CV). The operation was dubbed "water entombment".
  • We know how it quickly ended. TEPCO finally managed to actually measure the water level inside the CV and RPV of Reactor 1, and found that there was hardly any water in either of them - i.e. both the CV and the RPV of Reactor 1 were broken, kaput. Of 10,000 tonnes of water that TEPCO poured into the CV of Reactor 1, 3,000 tonnes were discovered in the basement.
  • But now, the water entombment is back in discussion in conjunction with decommissioning the reactors at Fukushima I Nuclear Power Plant, according to Mainichi Shinbun (8/31/2011).
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  • According to Mainichi, the plan submitted by TEPCO to a special committee of the Nuclear Safety Commission calls for the following steps: Clean up highly radioactive debris inside the reactor buildings;Identify and repair the damage to the Containment Vessels and the reactor buildings;Fill the Containment Vessels with water;Open the top lid of the Reactor Pressure Vessels and remove the melted fuel.
  • The NSC committee will consider the plan, and the government will decide on the final plan by January 2012. My questions: Step No.1: How? By whom? Step No.2: How? By whom? Step No.3: What's the point again? Step No.4: What melted fuel?
  • And no one knows, or rather, no one cares or wants to know, where exactly these melted blobs of fuel rods, control rods, instruments, metals, etc., are right now. TEPCO and the government will proceed as if they remain at the bottom of the Containment Vessel of each Reactor, if not still within the RPV. Inside the reactor buildings there are at least several spots as identified by TEPCO where the radiation levels are measured in sieverts/hour. Who is going to do the cleanup work, not to mention repairing the CVs and the building (I suppose they are thinking about the concrete foundations)?
D'coda Dcoda

Top Japan official: Very strong possibility there is nuclear fuel outside containment v... - 0 views

enenews.com/tainment-vessel-reactors-video

shared by D'coda Dcoda on 27 Dec 11 - No Cached
  • Goshi Hosono, Minister of State for the Nuclear Power Policy and Administration (Nuclear Accident Minister) with translator Recorded Dec. 19, 2011 Transcript Summary In regard to where the nuclear fuel might be there are 3 possibilities: Possibility 1: In pressure vessel Possibility 2: In containment vessel “The third possibility is it [nuclear fuel] might have worked it’s way out through the containment vessel and be underneath it” [...] “In regard to that third possibility that some fuel may have worked its way out of the containment vessel and gone underneath it, I think there’s a very strong possibility…we think there is a strong possibility that some fuel is in that location as well.”
D'coda Dcoda

Nuclear Engineer shares concerns about Brunswick Nuclear Leak [19Nov11] - 0 views

enformable.com/...ut-brunswick-nuclear-leak-from

shared by D'coda Dcoda on 21 Nov 11 - No Cached
  • The US Nuclear Regulatory Commission will begin a special inspection at Progress Energy‘s Brunswick-2 unit in North Carolina after the utility said Friday the reactor pressure vessel’s lid was not adequately tightened when it restarted earlier this week.  Most of us are also paying close attention to the events at Brunswick Nuclear Power Plant, and today I talked with a former nuclear engineer  Chris Harris about the recent developments.
  • The unit shut Wednesday morning after the reactor leaked. An investigation showed the inadequately tightened reactor vessel head was a potentially “significant” safety issue, Progress said in a report filed Friday with the NRC. Workers seeking the source of the leak found that at least 10 of the 64 bolts that secure the reactor vessel head to the pressure vessel were not fully tightened, Progress spokesman Ryan Mosier said in an email Friday.
  • The unit had been in a maintenance outage, was in the process of restarting and was operating at 7% power when workers discovered the leak in the reactor coolant system, Progress said in an event report filed Wednesday with NRC. When the leak exceeded 10 gal/minute, the unit was shut, Progress said.
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  • The Brunswick Nuclear Plant has two boiling-water reactors that generate 1,875 megawatts of electricity. Each of the Brunswick reactors is refueled once every 24 months, usually in the spring when the demand for electricity is relatively low. At the Brunswick Plant, 1 million gallons of water per minute are pumped from the Cape Fear River where it passes through the plant’s cooling system and then drops approximately  15 feet to the head of the outflow canal.
  • Refueling procedures are elaborate and well documented procedures, and one of the biggest questions is why the proper procedures were not followed, or were carried out incorrectly. The bolts need to be tensioned in a specific Torque Pattern, which generally includes multiple passes.  Refueling procedures require a crew of  at least 6 engineers, and additional Quality Control inspectors.
  • The Tensioning Tool is inspected and maintained, and is also part of the QC checklist.  This is not a simple situation where someone didn’t torque down the bolts correctly, as multiple personnel would have had to check and confirm the status prior to restart. In fact, according to Progress Energy’s 35 day outage schedule, the reassembly and reactor test are the 9th, and 10th steps of the process, and one can’t help but wonder why this was not detected before the reactor was re-pressurized. Chris had some very good questions regarding the Brunswick event, that I felt were worth sharing.
  • What testing was performed to determine that the RPV Head was Tensioned properly? What caused the improper Tensioning ? Procedure, Skill of the Craft? Aggressive Schedule? What are the Acceptance Criteria in the procedure for a properly tensioned head” How do you know that you meet the Acceptance Criteria?
  • Not only are the procedures and QC process in question, but the event also impacts operations and reliability of reactor components.  Chris highlighted a few questions that he felt were critical to ensure safe restart and operation.
  • Could there have been Foreign Material on the RPV Head Flange? What damage to surrounding equipment in the Drywell was sustained by the Steam/Water Leak? What is the condition of the Refueling Seal, now that it has been sprayed with Steamy/Hot Water? Did Hot/Steamy water find its way on the Outside of the Containment such that Corrosion in the future will be a problem? Did the steam leakage affect the Reactor Vessel Head Studs and their Threaded Holes (in the Reactor Vessel Flange) such that they will fail at a future date? At this point, Progress Energy is keeping fairly quiet about the specifics, and initially only revealed information of a “possible leak at the top of the reactor vessel”.  Monday morning should prove eventful not only for the Utility, but also for regulators.
D'coda Dcoda

Japanese Researcher Says Reactor 3's Fuel Melted Twice, Dropped to Containment Vessel [... - 0 views

ex-skf.blogspot.com/...esearcher-says-reactor-3s.html

shared by D'coda Dcoda on 09 Aug 11 - No Cached
  • From Asahi Shinbun (3:02AM JST 8/8/2011; not the literal translation): Fumiya Tanabe, former head of the research at Japan Atomic Energy Agency, will present the result of his research on Reactor 3 at Fukushima I Nuclear Power Plant in the upcoming Atomic Energy Society of Japan's conference next month.
  • Tanabe thinks the fuel melted and dropped to the bottom of the Reactor Pressure Vessel of Reactor 3 by March 14's explosion; then the melted fuel stayed there, cooled by more than 300-tonnes/day water. However, the amount of water injected dropped to only 24 tonnes per day from March 21 to 23, and 69 tonnes per day on March 24, probably due to increased pressure within the RPV. It caused the melted fuel to heat up again, and the fuel melted through the RPV and dropped onto the Containment Vessel (pedestal; see the diagram from Asahi).
  • According to Tanabe, the amount of water from March 21 to 24 was only about 11 to 32% of what was needed to remove the decay heat, and within one day the melted fuel would attain the melting temperature again.
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  • Tanabe thinks this massive "re-melting" caused the release of a large amount of radioactive materials into the environment which caused a spike in air radiation in wide areas of Tohoku and Kanto including Tokyo, and most of the re-melted fuel dropped from the RPV to the Containment Vessel.The article doesn't say what Tanabe thinks has happened to the melted fuel that dropped onto the Containment Vessel since.
  • But the article does say this:
  • TEPCO hopes to have a "cold shutdown" where the temperature at the bottom of the RPV is low [below 100 degrees Celsius] as the target for winding down the nuclear accident. But if the fuel core is mostly melted and has dropped down to the Containment Vessel, it may affect the "roadmap".
D'coda Dcoda

Plugging leaks will end crisis, not cold shutdown: analysts [12Sep11] - 0 views

search.japantimes.co.jp/...nn20110911f1.html

shared by D'coda Dcoda on 12 Sep 11 - No Cached
  • Ever since the nuclear crisis erupted six months ago, the public has been clamoring to know when the damaged reactors at the Fu ku shi ma No. 1 power plant will be brought under control and when the nightmare will end. The government and Tokyo Electric Power Co., which runs the crippled plant, are working to bring the three reactors into cold shutdown by mid-January.
  • Cold shutdown means the temperature at the bottom of the pressure vessel, which holds the core, has been lowered to less than 100 degrees. This critical milestone, known as "Step 2" in Tepco's road map for containing the crisis, would limit the release of radioactive materials from the plant to less than 1 millisievert per year, a level that poses no health risks.
  • Since work at the plant is proceeding relatively smoothly, it appears likely the mid-January target will be met. But Fukushima No. 1 will still have a long way to go before the flooded plant's reactors are stable enough to be considered safe, experts warn. The main reason is the abundance of highly radioactive water.
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  • "There are about 110,00 tons of contaminated water (in the plant) and the situation is still not completely under control because coolant water is leaking from the containment vessels. There is no guarantee that the irradiated water won't leak from the plant (and contaminate the environment)" if another natural disaster strikes, said Hisashi Ninokata, a professor of reactor engineering at the Tokyo Institute of Technology.
  • After achieving cold shutdowns of reactors 1, 2 and 3, the government may declare parts of the 20-km no-go zone around the plant safe. It may even let the evacuees return, as long as the area is decontaminated and crucial infrastructure restored.
  • But the longer the tainted water leaks, the more the radioactive waste will grow, leaving the Fukushima plant vulnerable to further disasters, Ninokata said. Before the Fukushima crisis can be said contained, the holes and cracks from which the water and fuel are escaping must be located and sealed. But this extremely difficult task could take years because the radiation near the reactors is simply too high to let workers get near them.
  • "It'll be too early to say that the situation has reached a stable phase even after Step 2 is completed," said Chihiro Kamisawa, a researcher at Citizens' Nuclear Information Center, a nonprofit group of scientists and activists opposed to nuclear power. When a reactor is in cold shutdown, the water cooling its fuel is still hot but no longer boiling, which significantly reduces the amount of radioactive emissions.
  • In late July, the temperature in reactor No. 1's pressure vessel fell below 100 degrees. On Monday, the same thing was achieved in reactor 3 after Tepco activated a system that pumps water deep into the containment vessel. But on Friday, reactor No. 2 was still boiling away with a reading of 112.6. "Efforts seem to be making smooth progress, and I think Step 2 is likely to be achieved by mid-January," said Shinichi Morooka, a Waseda University professor and reactor expert.
  • Another reason for optimism is the progress being made with the water decontamination system. The cleaning rate has greatly improved in the past few weeks and exceeded 90 percent of capacity last week. If the decontamination system ever reaches its full potential, it will allow Tepco to inject coolant at a higher rate and bring the melted cores to lower and stabler temperatures.
  • The government also plans to start decontaminating soil in various hot spots so the evacuees can return once the second step is completed. But some experts are questioning whether residents should be allowed to return so soon. The cracks and holes in the leaking reactors haven't even been pinpointed yet, let alone fixed, they say.
  • "As an engineer, I am worried (about the plan to let residents return) when it is still unclear what is really going on inside the reactors," said Morooka. For the time being, Tepco can only guess where the water is leaking from and which parts need repair, because radiation has prevented workers from fully exploring the buildings.
  • Spokesman Junichi Matsumoto said that since no extensive damage to the reactors was found during inspections of the first and second floors of the buildings, any holes or cracks are probably at the basement level. But with the basement floors flooded, Tepco's top priority is just to get the water out. Plans to fix the reactors aren't even being discussed yet, Matsumoto said.
  • Asked if the containment vessels can take another quake, the Tokyo Institute of Technology's Ninokata said he believes the impact would likely be distributed evenly through the structure without widening existing cracks or holes. But if the impact somehow focuses on parts damaged by the March 11 disasters, there could be further damage, he said. "The containment vessel is what really ensures the safety of a nuclear reactor," Ninokata said, warning that if radioactive materials are still leaking out, allowing residents to return would risk harming their health.
D'coda Dcoda

Confirmed: Tepco to drill hole in Reactor No. 2 containment vessel - Will start in Janu... - 0 views

enenews.com/el-will-start-in-january-video

shared by D'coda Dcoda on 27 Dec 11 - No Cached
  • TEPCO to conduct endoscopy of Fukushima reactors, NHK, Dec. 26, 2011: Tokyo Electric Power Company says it will use an industrial endoscope to study the inside of a damaged reactor at the Fukushima Nuclear power plant. [...] The firm will start drilling a hole in the northwest wall of the containment vessel at the No. 2 reactor next month so that the high-level radiation proof endoscope can be inserted through it. [...] See also: Ex-Fukushima Worker: Tepco to open up a hole in Reactor No. 2 containment vessel by year's end (VIDEO)
D'coda Dcoda

Whistle-blower talks, container vessel is melting like honeycomb [03Jan11] - 0 views

fukushima-diary.com/...ssel-is-melting-like-honeycomb

shared by D'coda Dcoda on 04 Jan 12 - No Cached
  • A whistle-blower of Tepco leaked the actual situation of Fukushima plant. He left his comments on a Japanese forum. Here are the messages.
  • Boring survey around reactor 2 is coming to the climax. As a result, the announcement of the government and Tepco has to be denied. If it’s soft material, they can do horizontal boring with such a weak equipment (like the top picture ) but when it comes to the concrete of the reactor building it’s impossible. They need to do boring with a foreign heavy equipment at an angle. They do boring to reach to under the container vessel. (like the bottom 2 pictures)
  • When they do boring where they don’t need to take a sample they drill roughly with this green rotary diamond bit but the dust is lethal because it’s too radioactive. When they need to take a sample, they change the diamond bit to hole saw type of bit. However, diamond is weak for the heat so when it’s hotter than 500℃ they use the standard type of the tungsten carbide instead.    The bottom 3 pictures are the samples taken.
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  • Probably the iron part of the core is uranium pellet unreacted – not sure yet because it’s still before the analysis. It’s beyond the max reading of 500X100 CPM. These yellow concrete slags come out from under the building one after one. It means that the container vessel is melting like honeycomb at least – doesn’t it? Otherwise why would metal uranium comes out of there ?
  • Taking a part of the concrete slag sample. Put it into the lead case (Chiyoda technol) and take it to a lab. I don’t know if it’s because they gave sea water to cool down or because it’s brackish area, if natrium (sodium salt) of sea water made a chemical reaction with calcium carbonate in the concrete to become diuranate natrium (sodium diuranate) or not, it looks yellow as yellow cake
  • made up my mind to take out the slags from the shelter to take pictures of them. wore protective clothing. When it’s taken out, it was over 400 ℃ but now it’s cooled down to 100 ℃. Can you see this big metal crystal (extremely radioactive) and the oxidized concrete looking like yellow cake? Can you believe it is out of the container vessel. It’s over 500 mSv/h, my geiger counter went over the limit. was scared so put it back to the shelter soon as I took a couple of the pictures.
  • D'coda Dcoda on 04 Jan 12
     
    Lots of good photos
D'coda Dcoda

#Fukushima I Nuke Plant: Early Days of Confusion and Mistakes at the Plant Being Reveal... - 0 views

ex-skf.blogspot.com/...-nuke-plant-early-days-of.html

shared by D'coda Dcoda on 17 Aug 11 - No Cached
  • The Kan Administration set up a fact-finding commission in late May to figure out what went wrong at Fukushima I Nuclear Power Plant that led to the catastrophic accident, even if the accident is still ongoing as of August.The Kan Administration set up a fact-finding commission in late May to figure out what went wrong at Fukushima I Nuclear Power Plant that led to the catastrophic accident, even if the accident is still ongoing as of August. There were many critics who said "First thing first", which was to stop the emission of radioactive materials from the broken reactors and do whatever possible to reduce the amount of the contaminated water, and .. (list is endless). But the government, who is always eager to paint a positive picture that everything is according to schedule and going well, wanted the commission to "investigate" the accident to learn from the mistakes.
  • TEPCO was preoccupied with the condition of the reactor and the Containment Vessel, and didn't think of the risk of hydrogen explosion. "There was no one who could have predicted the explosion.
  • The Kan Administration set up a fact-finding commission in late May to figure out what went wrong at Fukushima I Nuclear Power Plant that led to the catastrophic accident, even if the accident is still ongoing as of August.The Kan Administration set up a fact-finding commission in late May to figure out what went wrong at Fukushima I Nuclear Power Plant that led to the catastrophic accident, even if the accident is still ongoing as of August. There were many critics who said "First thing first", which was to stop the emission of radioactive materials from the broken reactors and do whatever possible to reduce the amount of the contaminated water, and .. (list is endless). But the government, who is always eager to paint a positive picture that everything is according to schedule and going well, wanted the commission to "investigate" the accident to learn from the mistakes.
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  • The Kan Administration set up a fact-finding commission in late May to figure out what went wrong at Fukushima I Nuclear Power Plant that led to the catastrophic accident, even if the accident is still ongoing as of August.The Kan Administration set up a fact-finding commission in late May to figure out what went wrong at Fukushima I Nuclear Power Plant that led to the catastrophic accident, even if the accident is still ongoing as of August. There were many critics who said "First thing first", which was to stop the emission of radioactive materials from the broken reactors and do whatever possible to reduce the amount of the contaminated water, and .. (list is endless). But the government, who is always eager to paint a positive picture that everything is according to schedule and going well, wanted the commission to "investigate" the accident to learn from the mistakes.There were many critics who said "First thing first", which was to stop the emission of radioactive materials from the broken reactors and do whatever possible to reduce the amount of the contaminated water, and .. (list is endless). But the government, who is always eager to paint a positive picture that everything is according to schedule and going well, wanted the commission to "investigate" the accident to learn from the mistakes.
  • TEPCO was preoccupied with the condition of the reactor and the Containment Vessel, and didn't think of the risk of hydrogen explosion. "There was no one who could have predicted the explosion.
  • The Kan Administration set up a fact-finding commission in late May to figure out what went wrong at Fukushima I Nuclear Power Plant that led to the catastrophic accident, even if the accident is still ongoing as of August.
  • There were many critics who said "First thing first", which was to stop the emission of radioactive materials from the broken reactors and do whatever possible to reduce the amount of the contaminated water, and .. (list is endless). But the government, who is always eager to paint a positive picture that everything is according to schedule and going well, wanted the commission to "investigate" the accident to learn from the mistakes.
  • What better way to give the impression that the accident is over, than to form a commission to investigate the accident?
  • Still, the commission led by a Tokyo University professor (emeritus) and including 3 attorneys (one of them a UN committee member fighting for equal rights for women) and one novelist, has been interviewing (or "interrogating" is the word used in the Japanese press) TEPCO managers at Fukushima I Nuke Plant, and part of their findings have apparently been leaked to Mainichi Shinbun. The commission meetings are not open to the public.
  • From Mainichi Shinbun (2:31AM JST 8/17/2011), what TEPCO managers at the plant is saying:
  • About the explosion of Reactor 1 building at 3:36PM on March 12:
  • There was no manual for the vent operation. They figured out the procedure by studying the blueprint
  • TEPCO was preoccupied with the condition of the reactor and the Containment Vessel, and didn't think of the risk of hydrogen explosion. "There was no one who could have predicted the explosion.
  • EPCO was preoccupied with the condition of the reactor and the Containment Vessel, and didn't think of the risk of hydrogen explosion. "There was no one who could have predicted the explosion.
  • TEPCO was preoccupied with the condition of the reactor and the Containment Vessel, and didn't think of the risk of hydrogen explosion. "There was no one who could have predicted the explosion.""
  • D'coda Dcoda on 17 Aug 11
     
    Highlighter wasn't working properly, good idea to check the source doc for remainder that wouldn't copy
D'coda Dcoda

Asahi: Explosive hydrogen may be coming from melted fuel rods and "accumulating near th... - 1 views

enenews.com/essel-without-being-driven-out

shared by D'coda Dcoda on 26 Sep 11 - No Cached
  • Hydrogen accumulates in pipes at Fukushima’s No. 1 reactor, Asahi, September 24, 2011:
  • Hydrogen has accumulated to a level higher than previously thought in pipes connected to the No. 1 reactor containment vessel [...] The nitrogen injections are believed to have lowered the hydrogen concentration considerably, but some hydrogen, being lighter than nitrogen, may be accumulating near the top of the containment vessel without being driven out. [...] Nor could TEPCO measure how much hydrogen may have been generated in the containment vessel. [...] TEPCO said it is investigating the possibility that hydrogen has also accumulated in a similar manner at the plant’s No. 2 and No. 3 reactors. [...]
  • Where does TEPCO think the hydrogen is coming from?
  • ...1 more annotation...
  • TEPCO said most of the accumulated hydrogen was generated by a reaction under high temperatures between water vapor and the surface of nuclear fuel rods that were exposed after water was lost following the March 11 earthquake and tsunami. Even now, the damaged reactors may be generating small amounts of hydrogen as water decomposes through irradiation from the melted fuel rods.
D'coda Dcoda

Radiation expert says outcome of nuke crisis hard to predict, warns of further dangers ... - 0 views

mdn.mainichi.jp/...20110909p2a00m0na016000c.html

shared by D'coda Dcoda on 10 Sep 11 - No Cached
  • As a radiation metrology and nuclear safety expert at Kyoto University's Research Reactor Institute, Hiroaki Koide has been critical of how the government and Tokyo Electric Power Co. (TEPCO) have handled the nuclear disaster at the Fukushima No. 1 nuclear plant. Below, he shares what he thinks may happen in the coming weeks, months and years. The nuclear disaster is ongoing. Immediately after the crisis first began to unfold, I thought that we'd see a definitive outcome within a week. However, with radioactive materials yet to be contained, we've remained in the unsettling state of not knowing how things are going to turn out.
  • Without accurate information about what's happening inside the reactors, there's a need to consider various scenarios. At present, I believe that there is a possibility that massive amounts of radioactive materials will be released into the environment again. At the No. 1 reactor, there's a chance that melted fuel has burned through the bottom of the pressure vessel, the containment vessel and the floor of the reactor building, and has sunk into the ground. From there, radioactive materials may be seeping into the ocean and groundwater.
  • The use of water to cool down the reactors immediately after the crisis first began resulted in 110,000 cubic meters of radiation-tainted water. Some of that water is probably leaking through the cracks in the concrete reactor buildings produced by the March 11 quake. Contaminated water was found flowing through cracks near an intake canal, but I think that's just the tip of the iceberg. I believe that contaminated water is still leaking underground, where we can't see it. Because of this, I believe immediate action must be taken to build underground water barriers that would close off the nuclear power plant to the outside world and prevent radioactive materials from spreading. The important thing is to stop any further diffusion of radioactive materials.
  • ...5 more annotations...
  • The government and plant operator TEPCO are trumpeting the operation of the circulation cooling system, as if it marks a successful resolution to the disaster. However, radiation continues to leak from the reactors. The longer the circulation cooling system keeps running, the more radioactive waste it will accumulate. It isn't really leading us in the direction we need to go.
  • It's doubtful that there's even a need to keep pouring water into the No.1 reactor, where nuclear fuel is suspected to have burned through the pressure vessel. Meanwhile, it is necessary to keep cooling the No. 2 and 3 reactors, which are believed to still contain some fuel, but the cooling system itself is unstable. If the fuel were to become overheated again and melt, coming into contact with water and trigger a steam explosion, more radioactive materials will be released.
  • TEPCO says it is aiming to bring the No. 1, 2 and 3 reactors to cold shutdown by January 2012. Cold shutdown, however, entails bringing the temperature of sound nuclear fuel in pressure vessels below 100 degrees Celsius. It would be one thing to aim for this in April, when the government had yet to confirm that a meltdown had indeed taken place. But what is the point of "aiming for cold shutdown" now, when we know that fuel is no longer sound?
  • In the days ahead, the storage of enormous quantities of radiation-contaminated waste, including tainted mud resulting from the decontamination process, will become a major problem.
  • When the Three Mile Island accident took place in 1972, the melted nuclear fuel had stayed within the pressure vessel, making defueling possible. With Fukushima, however, there is a possibility that nuclear fuel has fallen into the ground, in which case it will take 10 or 20 years to recover it. We are now head to head with a situation that mankind has never faced before.
D'coda Dcoda

Reactors 1 & 2 have HOLES up to 50 meters, clean up notes [9Dec11] - 0 views

mdn.mainichi.jp/...20111208p2a00m0na016000c.html

shared by D'coda Dcoda on 10 Dec 11 - No Cached
  • expected to take more than 30 years to decommission crippled reactors at the Fukushima No. 1 Nuclear Power Plant, and workers tasked with the difficult mission would have to venture into "uncharted territory" filled with hundreds of metric tons of highly radioactive nuclear fuel,
  • After the expert committee of the Japan Atomic Energy Commission (JAEC) compiled a report on procedures to decommission the No. 1 to 4 reactors at the Fukushima No. 1 Nuclear Power Plant on Dec. 7, the actual work is expected to move into high gear after the turn of the year. As in the case of the 1979 Three Mile Island accident, the workers would try to remove melted nuclear fuel after shielding radiation with water, a technique called a "water tomb." But the work would have to be done in a "territory where humans have not stepped into before," said a senior official of Tokyo Electric Power Co. (TEPCO), the operator of the troubled Fukushima nuclear power station. The work is so difficult that it is expected to take more than 30 years to finish decommissioning the reactors.
  • Up to about 5,000 millisieverts per hour of radiation -- lethal levels -- have been detected in the reactor building of the No. 1 reactor.
  • ...5 more annotations...
  • The key part of the decommissioning work is to remove a total of 1,496 fuel rods from the No. 1 to 3 nuclear reactors and 3,108 fuel rods from nuclear fuel pools of the No. 1 to 4 reactors. The government and TEPCO are expected to start decommissioning the reactors early in the New Year after unveiling detailed plans around Dec. 16 that the nuclear plant has been brought under control by achieving a stable state called a ''cold shutdown.''
  • TEPCO said it would bring the nuclear plant under control by filling the reactors with water. But subsequent analysis of the accident suggested that the No. 1 and 2 reactors had holes of up to 50 square centimeters caused by hydrogen explosions and the like. In the work schedule announced in May, TEPCO said it had scrapped its plan to repair the containment vessels and suspended the work to fill them with water.
  • workers have been fighting an uphill battle to remove crumbled fuel. The reactors had been running without cooling water for a long time, and most of the fuel melted and apparently dropped into the containment vessel from the bottom of the pressure vessel at the No. 1 reactor
  • A single fuel rod contains about 170 kilograms of uranium, and a simple calculation suggests that about 254 tons of uranium in the reactors alone must be recovered. The distance between the upper lid and the bottom of a containment vessel is up to 35 meters. From that far away, the work has to be done to chop off and recover melted and crumbled fuel by using remote controlled cranes. Furthermore, the melted fuel is mixed with metal from fuel pellets and reactor parts.
  • "Because no one has seen the inside of the nuclear reactors, the timing of starting the work to recover nuclear fuel mentioned in the report is only a nonbinding target."
D'coda Dcoda

#Fukushima I Melted Fuel Probably No Longer in Containment Vessel Reactor 2 [09Aug11] - 0 views

ex-skf.blogspot.com/...nuke-plant-krypton-85-and.html

shared by D'coda Dcoda on 12 Aug 11 - No Cached
  • Half life of xenon-131m is about 12 days. The measurement of density of radioactive materials in the air inside the Reactor 2 Containment Vessel was delayed because there was water in the temporary sampling instrument that TEPCO installed outside the CV. It looks like they decided to measure the water anyway, as well as the air. According to the measurement, the air is more radioactive than the water inside the Containment Vessel, but less radioactive than the air inside the Reactor 1 CV.
  • So the melted fuel is probably not even inside the Containment Vessel in Reactor 2 either. But what's with krypton and xenon? I also read a tweet by one of the workers at the plant who said there is still radioactive iodine being released, even though TEPCO's monitoring says iodine-131 is not detected at the plant any more. From TEPCO's handout for the press on August 10:
D'coda Dcoda

Fuku I Hydrogen Gas Update: It Was 63% Concentration [28Sep11] - 0 views

ex-skf.blogspot.com/...ogen-gas-update-it-was-63.html

shared by D'coda Dcoda on 29 Sep 11 - No Cached
  • and no need to worry, TEPCO will take care of it.TEPCO also says since there is no oxygen in the pipe that leads to the Reactor 1 Containment Vessel, there is NO DANGER of explosion.(Uh huh. "There is no danger of explosion" was what they said to the fire department and the Self Defense Force right before Reactor 1 blew up, and then before Reactor 3 blew up.)
  • From Yomiuri Shinbun (9/28/2011):
  • TEPCO announced on September 28 that the concentration of hydrogen gas in the pipe that leads to the Containment Vessel of Reactor 1 at Fukushima I Nuclear Power Plant was 63%.
  • ...3 more annotations...
  • TEPCO says there is no danger of explosion because no oxygen was detected in the pipe. The company will inject nitrogen in the pipe on September 29 to expel hydrogen.
  • The high concentration of hydrogen was found in the pipe that was to be used as part of the filtering system to suppress the leak of radioactive materials in the Containment Vessel. TEPCO will measure the levels of hydrogen gas in the similar pipes in Reactors 2 and 3.
  • It is considered that hydrogen gas was generated when the nuclear fuel was heated to high temperature right after the accident and the cladding and water reacted. If there are more than 4% hydrogen and more than 5% oxygen in the atmosphere, the chance of explosion increases. It is possible that there is hydrogen gas in the upper part of the Containment Vessel and in other pipes. The company says it will take measures to address hydrogen gas before proceeding on any work from now on.Looking at TEPCO's handout for the press on September 28 (Japanese only for now), all they will do is to try to expel hydrogen in the pipe alone by injecting nitrogen from the far end of the pipe. They must be operating on the assumption that all the hydrogen in the pipe is from the initial zirconium cladding and water interaction, not the recent or on-going radiolysis, and once the hydrogen currently in the pipe is expelled, that will be the end of the story.
D'coda Dcoda

Experts split on how to decommission Fukushima nuclear plant [29Aug11] - 0 views

mdn.mainichi.jp/...20110828p2a00m0na002000c.html

shared by D'coda Dcoda on 30 Aug 11 - No Cached
  • What is actually going to take place at the Fukushima No. 1 Nuclear Power Plant, where word is that the four reactors that were crippled in the Great East Japan Earthquake and tsunami will eventually be decommissioned? The Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency (NISA) defines "decommissioning" as the process of removing spent fuel from reactors and dismantling all facilities. Ultimately, the site of a decommissioned reactor is meant to be reverted into a vacant lot.
  • In 1996, the then Japan Atomic Energy Research Institute (JAERI) -- now the Japan Atomic Energy Agency (JAEA) -- finished decommissioning its Japan Power Demonstration Reactor. The decommissioning process of the Tokai Nuclear Power Plant in the Ibaraki Prefecture village of Tokai began in 1998 and is set to end in fiscal 2020, while the No. 1 and No. 2 nuclear reactors at the Hamaoka Nuclear Power Plant in the Shizuoka Prefecture city of Omaezaki are slated for decommissioning by fiscal 2036. Around the world, only around 15 nuclear reactors have thus far been dismantled.
  • The standard decommissioning process entails six major steps: 1. Remove spent fuel rods, 2. Remove radioactive materials that have become affixed to reactor pipes and containers, 3. Wait for radiation levels to go down with time, 4. Dismantle reactors and other internal vessels and pipes, 5. Dismantle the reactor buildings, and 6. Make the site into a vacant lot.
  • ...17 more annotations...
  • "Cleaning," "waiting," and "dismantling" are the three key actions in this process. Needless to say, this all needs to be done while simultaneously containing radioactive materials.
  • In the case of the Tokai Nuclear Power Plant, the first commercial plant to undergo decommissioning, spent fuel was removed over a span of three years beginning in 1998, and was transported to Britain for reprocessing. Dismantling of the facilities began in 2001, with current efforts being made toward the dismantling of heat exchangers; workers have not yet begun to take the reactor itself apart. The entire process is expected to be an 88.5-billion-yen project involving 563,000 people.
  • Hitachi Ltd., which manufactures nuclear reactors, says that it "generally takes about 30 years" to decommission a reactor. The Hamaoka Nuclear Power Plant's No. 1 and No. 2 reactors operated by Chubu Electric Power Co. are also expected to take about 30 years before they are decommissioned.
  • In the case of the Fukushima No. 1 Nuclear Power Plant, meanwhile, the biggest challenge lies in how to remove the fuel, says Tadashi Inoue, a research advisor at the Central Research Institute of Electric Power Industry (CRIEPI), a foundation that conducts research on energy and environmental issues in relation to the electrical power industry.
  • "we must deal with rubble contaminated with radioactive materials that were scattered in the hydrogen blasts and treat the radiation-tainted water being used to cool nuclear fuel before we can go on to fuel removal."
  • Currently, the Fukushima plant's operator, Tokyo Electric Power Co. (TEPCO), is desperately trying to treat the contaminated water. Huge challenges remain with regards to the contaminated rubble, as radiation levels of over 10 sieverts per hour were found near outdoor pipes on the plant grounds just the other day. Exposure to such high levels would mean death for most people.
  • Each step in the process toward decommissioning is complicated and requires great numbers of people. It's a race against time because the maximum amount of radiation that workers can be exposed to is 250 millisieverts.
  • The breached reactor core is a bigger problem. It is believed that raising water levels inside the reactor has been difficult because of a hole in the bottom of the vessel. It will be necessary to plug the hole, and continue filling the vessel with water while extracting the melted fuel. How to fill the vessel with water is still being debated. If the reactor can be filled with water, steps taken after the 1979 Three Mile Island nuclear accident can serve as a guide because in that case, in which approximately 50 percent of the core had melted, workers were able to fill the reactor with water and remove the fuel within.
  • Two types of fuel removal must take place. One is to take out the spent fuel in the containment pools, and the other is to remove the melted fuel from the reactor cores. Because the radiation levels of the water in the spent fuel pools have not shown any significant changes from before the crisis, it is believed that the spent fuel has not suffered much damage. However, removing it will require repairing and reinstalling cranes to hoist the fuel rods out.
  • Prefacing the following as "a personal opinion," Inoue says: "Building a car that can protect the people inside as much as possible from radioactive materials, and attaching an industrial robotic arm to the car that can be manipulated by those people could be one way to go about it."
  • Inoue predicts that removal of spent fuel from the containment pools will begin about five years after the crisis, and about 10 years in the case of melted fuel from the reactor core. Work on the four reactors at the Fukushima plant will probably take several years.
  • "Unless we look at the actual reactors and take and analyze fuel samples, we can't know for sure," Inoue adds. Plus, even if workers succeed in removing the fuel, reprocessing it is an even more difficult task. A review of processing methods and storage sites, moreover, has yet to take place.
  • Meanwhile, at least one expert says he doesn't believe that workers will be able to remove the melted fuel from the crippled plant.
  • "If there's 10 sieverts per hour of radiation outside, then the levels must be much higher closer to the reactor core," says Tadahiro Katsuta, an associate professor at Meiji University and an expert in reactor engineering and reactor policy who was once a member of an anti-nuclear non-profit organization called Citizens' Nuclear Information Center (CNIC). "The fuel has melted, and we haven't been able to cool it consistently. If work is begun five or 10 years from now when radiation levels have not yet sufficiently gone down, workers' health could be at serious risk."
  • Katsuta predicts that it will probably take at least 10 years just to determine whether it is possible to remove the fuel. He adds that it could very well take 50 years before the task of dismantling the reactor and other facilities is completed.
  • What Katsuta has in mind is a Chernobyl-style concrete sarcophagus, which would entail cloaking the melted tomb with massive amounts of concrete. "How could we simultaneously dismantle four reactors that have been contaminated to the extent that they have by radioactive materials?" asks Katsuta. "Japan has little experience in decommissioning reactors, and this case is quite different from standard decommissioning processes. It's not realistic to think we can revert the site back to a vacant lot. I think we should be considering options such as entombing the site with concrete or setting up a protective dome over the damaged reactor buildings
  • what we face is a great unknown to all of mankind.
D'coda Dcoda

#Fukushima I Nuke Plant Reactor 3: Humans Entered Reactor Bldg and Did What Bots Coulnd... - 0 views

ex-skf.blogspot.com/...ke-plant-reactor-3-humans.html

Fuckishima japan nuclear energy

shared by D'coda Dcoda on 10 Jul 11 - No Cached
  • 6 TEPCO employees and 4 TEPCO affiliate company employees went to the reactor building of the Reactor 3 on July 8 afternoon. 2 TEPCO employees entered the building, measured the radiation at the location where the nitrogen injection hose would be installed (55 millisieverts/hour), and put a temporary coupler on the metal pipe that would be used for nitrogen injection.For that 9-minute job, they received 5.34 millisieverts radiation.Here's TEPCO's handout for the press on July 9. The English explanation reads like a Google translation (maybe it is) but you get the idea. (I looked at the Japanese handout.)
  • TEPCO seems to be in a great hurry to start the nitrogen injection into the Containment Vessel of the Reactor 3. At first I thought it was just a window-dressing effort for the national government who had decided, on some inexplicable reason or unreason, it would be safe enough for people to come back to their homes in the planned evacuation zone as long as the nitrogen gas was pumped into the Reactor 3 Containment Vessel, just so that the government could tell the citizens "See what we've done for you? It's now so much safer you can go back!"Or, the Reactor 3 is actually in danger of blowing up in a hydrogen explosion.They have hardly done any work on other reactors. The Reactor 1's basement water, last seen as gushing out 4 sieverts/hour steam through to the 1st floor, hasn't been touched. That water doesn't even go to the water treatment system. I haven't heard any news of TEPCO sampling the water for analysis. There's hardly any news on the Reactor 2, after they opened the double door and supposedly drove out the radioactive materials and moisture inside. They still don't know the water level (if any) inside the Reactor 2's Pressure Vessel, because the pressure gauge and water gauge don't work. As for the Reactor 4, they've been injecting water into the Reactor well and the equipment pool from the bottom of the Reactor Pressure Vessel, which seems peculiar. Other than that, and the photo of a hot-spring-like Spent Fuel Pool on the 5th floor, there's not much information coming out.
  • D'coda Dcoda on 10 Jul 11
     
    see article for amount of radiation they received
D'coda Dcoda

Shutdown of Fukushima Reactors Is Ahead of Schedule [Nov11] - 0 views

spectrum.ieee.org/...-reactors-is-ahead-of-schedule

shared by D'coda Dcoda on 28 Oct 11 - No Cached
  • Editor's Note: This is part of the IEEE Spectrum special report: Fukushima and the Future of Nuclear Power.
  • This past April, when the Japanese government and Tokyo Electric Power Co. (TEPCO) jointly unveiled their plan to bring the damaged reactors of the Fukushima Dai-ichi nuclear power plant to a cold shutdown and gain control of the release of radioactive materials, they set a tentative completion date for mid-January 2012. And "tentative" had to be the operative word, for the obstacles TEPCO faced—and to some extent still does face—are challenging in the extreme. They include:
  • Fuel rod meltdowns in reactors 1, 2, and 3 due to loss of cooling systems following the 11 March earthquake and tsunami; Severe damage to the upper levels of reactor buildings 1, 3, and 4 and slight damage to building 2, stemming from hydrogen explosions; High levels of radiation and contaminated rubble, making working conditions hazardous and difficult; Thousands of metric tons of contaminated water accumulating on the site and leaking out of the reactors.
  • ...5 more annotations...
  • Critics, however, were quick to question the stability of the system and its ad hoc design. The combination of filtering and decontamination technologies—mainly from the French nuclear giant Areva and the U.S. nuclear waste management company Kurion—includes some 4 kilometers of piping. The critics have a point. Even with the addition of a reportedly more robust system (to be used in parallel or as backup as needed) from Toshiba and IHI Corp., TEPCO admits the system underwent 39 disruptions between 10 July and 8 September. One consequence is that roughly 100 000 metric tons of water still need to be decontaminated.
  • It appears, however, that the process is now ahead of schedule. Environment Minister Goshi Hosono, who is also in charge of the Fukushima nuclear accident recovery, told the International Atomic Energy Agency's annual general conference in Vienna on 19 September that Japan was now aiming to complete a cold shutdown of the Fukushima plant by December 2011, instead of mid-January 2012. Progress was already evident in July, when Hosono announced that workers had completed step 1 of the two-step road map on schedule, reducing radioactive emissions and starting to bring down the core temperatures in reactors 1, 2, and 3. Hosono attributed the success to the construction of a new cooling system, which had begun pumping water into all three damaged reactors. In addition to cooling, the system also decontaminates the water accumulating in the basements of the reactor and turbine buildings. The contamination is the result of injected water coming into contact with the molten fuel in the pressure vessels.
  • Disruptions and remaining challenges notwithstanding, TEPCO has been making progress toward step 2 of the road map: a cold shutdown. According to TEPCO, that means achieving and maintaining a temperature of less than 100 °C as measured at the bottom of a reactor pressure vessel—the steel vessel containing the fuel rods—which itself is enclosed inside a protective containment vessel. A major advance came at the beginning of September, when TEPCO was able to start up the core spray lines to cool reactors 1 and 3. The core spray lines apply water directly to the cores from above, while the system installed in July has been cooling the cores by injecting water from the bottom. TEPCO has also begun increasing the amount of water being injected into reactor 2. The core spray line could not be used until recently because TEPCO first had to survey the subsystem's piping and valves. Given the high radiation in the area, this was difficult, but workers completed the job in July and confirmed the system's operability in August.
  • By late September, as a result of these efforts, the temperatures in all three reactors had dropped below 100 °C for the first time since the accident. As of 29 September, the temperatures for reactors 1, 2, and 3, respectively, were 77.5 °C, 99.7 °C, and 78.7 °C. "We are steadily bringing the postaccident situation under control," says Hosono. "To achieve step 2 this year, we'll move the schedule forward and do our best." But Yoshinori Moriyama, deputy director-general of Japan's Nuclear and Industrial Safety Agency (NISA) is cautious. "We need to maintain this state over the midterm," he says. "Temporary lower temperatures and the nonrelease of radioactive substances do not immediately mean that this is a cold shutdown." In order for NISA to declare a cold shutdown, the temperatures must remain stable and below 100 °C into December. So NISA won't officially declare a cold shutdown until near the end of 2011.
  • Despite these positive developments, nuclear experts point out that achieving a cold shutdown does not make the troubled plant completely safe, given that even spent fuel continues to generate heat for years after use. And upon achieving a cold shutdown, TEPCO must take on a new series of challenges. These include finding where the injected water is escaping, stopping those leaks, dealing with the accumulated contaminated water, removing and storing the thousands of spent fuel rods from the pools in reactors 1 to 4, and then figuring out a way to remove the melted fuel. The last is a task that could take a decade or more, according to experts.
D'coda Dcoda

TEPCO says no explosion occured at No.2 plant [29Nov11] - 0 views

www3.nhk.or.jp/...20111129_10.html

damage

shared by D'coda Dcoda on 29 Nov 11 - No Cached
  • NHK has obtained Tokyo Electric Power Company's interim report
  • The company concluded in the report that there was no explosion at the No. 2 reactor, and that a blast at the No. 4 reactor was mistakenly believed to have occurred at the No. 2.
  • Later that day, pressure inside the No. 2 reactor vessel dropped sharply, and radiation levels near the plant's main gate rose above 10 millisieverts per hour, then the highest level so far. The interim report fails to specify how the leakage occurred at the containment vessel, just saying that gas in the vessel was somehow released into the air.
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