12 Février 2012
TOKYO (Kyodo) -- Tokyo Electric Power Co. said Sunday the temperature at the bottom of the No. 2 reactor at its crippled Fukushima No. 1 nuclear plant rose further to 82 C, but the reactor has not gone critical.
While the thermometer reading at shortly after 2 p.m. marked a new high since the reactor attained a cold shutdown in December, the utility known as TEPCO said it has confirmed that sustained nuclear reactions are not taking place in the reactor as no radioactive xenon has been detected inside its containment vessel.
TEPCO reported the latest development immediately to the Nuclear and Industrial Safety Agency of the Economy, Trade and Industry Ministry as the temperature exceeded the limit of 80 C designated by the company's safety regulation for maintaining a cold shutdown, it said.
It is considered desirable to keep the temperature below 80 C, while the bottom of a reactor pressure vessel must be kept below 100 C in a stable cold shutdown, in view of the margin of error of thermometers, according to TEPCO officials.
TEPCO plans to increase the amount of water injected as a coolant by 3 tons per hour and pour 1 ton of boric acid later Sunday to prevent any event of criticality.
As a reason for what is causing the temperature rise, TEPCO said it is possible the water flow is unstable and thus failing to cool the reactor stably, while also saying it will check the thermometer for any irregularities. The temperature was measured at 78.3 C at 10 a.m. and fell to 75.4 C at 11 a.m.
The decline occurred after TEPCO on Saturday night increased the amount of water being injected into the reactor to 14.6 tons per hour from 13.6 tons, after seeing the temperature rise to 73.3 C at 9 p.m. It reached 74.9 C at 11 p.m. Saturday. The temperature readings began rising on Feb. 1.
One of the three thermometers at the bottom of the reactor's pressure vessel stayed between 67 C and 71 C from Friday evening to Saturday evening after hitting 73.3 C on Monday.
Readings from two other thermometers that check the temperature at the bottom of the No. 2 reactor vessel were around 35 C, TEPCO said.
The Nos. 1 to 3 reactors at the Fukushima No. 1 plant in northeastern Japan experienced meltdowns as a result of the loss of key cooling functions in the wake of the devastating earthquake and tsunami on March 11 last year.
Temperature rising at No.2 reactor
The temperature at the No.2 reactor of the Fukushima Daiichi nuclear power plant keeps rising even after the injection of more cooling water on Saturday night.
The plant operator, Tokyo Electric Power Company, or TEPCO, says a thermometer at the bottom of the reactor registered 78.3 degrees Celsius at 10 AM on Sunday.
The reading began to rise in late January to around 70 degrees. TEPCO pumped in more water to push down the temperature, but it rose again on Saturday night to 74.9 degrees.
The temperature continued to climb on Sunday morning to hit its highest level since last December, when the government and TEPCO declared all the reactors were at a state of cold shutdown, with their temperatures below 100 degrees.
TEPCO denied the possibility of nuclear criticality, saying 2 other thermometers at the bottom of the reactor show temperatures at around 35 degrees.
It adds that continuous nuclear fission would generate radioactive xenon, but gas samples collected from near the reactor found the element below the detection limit.
TEPCO is set to dump in boric acid to prevent any nuclear criticality later on Sunday and increase the volume of cooling water by 3 tons per hour.
Under new guidelines, the company must keep reactor temperatures at 80 degrees or below, given thermometers' margin of error of up to 20 degrees.
FUKUSHIMA--The Fukushima No. 2 nuclear power plant was "near meltdown" after being hit by tsunami following the Great East Japan Earthquake on March 11, according to the head of the plant.
The No. 2 plant, on the border of Naraha and Tomioka towns in Fukushima Prefecture, was opened to the media Wednesday for the first time since the disaster. It is 12 kilometers from the Fukushima No. 1 nuclear power plant, which suffered a meltdown. Both facilities are operated by Tokyo Electric Power Co.
Plant chief Naohiro Masuda, in charge of plant operations since the crisis, told reporters Wednesday, "The No. 2 plant almost suffered the same fate as No. 1 [which led to a severe crisis]."
On March 11, a 9-meter-high tsunami struck the No. 2 plant, while the No. 1 plant was hit by a 13-meter-high tsunami. The tsunami caused the No. 2 plant's seawater pumps, used to cool reactors, to fail. Of the plant's four reactors, three were in danger of meltdown.
Luckily, one external high-voltage power line still functioned, allowing plant staff in the central control room to monitor data on internal reactor temperatures and water levels.
By March 15, the No. 2 plant's four reactors reached a state of cold shutdown without any leakage of radioactive materials.
"[At that point, the situation at the No. 2 plant] was considerably different from the No. 1 plant where it was difficult to know what was going on," Masuda, 53, said.
However, despite intense efforts by all employees, it took a long time to stabilize the reactors.
On March 11, about 2,000 employees of the No. 2 plant worked to stabilize the reactors. Some employees connected 200-meter sections of cable, each weighing more than a ton, over a distance of nine kilometers.
Masuda noted the timing of the disaster was critical in saving the plant.
"We were lucky it happened on a Friday afternoon [and not on a weekend]," he said.
Masuda pointed out only 40 employees would have been at the plant if the earthquake had occurred in the evening or on a weekend.
"[In that case] it would be have been difficult for us to deal with the disaster," he said.
The Fukushima prefectural government conducted an on-site inspection at the No. 2 plant on Wednesday and repeated a request to TEPCO to decommission the facility.
Masuda did not elaborate and said, "At the moment, I can only say we'll maintain a state of cold shutdown."
The No. 2 plant's No. 1 reactor began operating in 1982. Following the Great East Japan Earthquake, a Nuclear Emergency Situation Declaration was issued for both the No. 1 and No. 2 plants. The declaration was lifted for the No. 2 plant in December.
A team of Fukushima prefectural officials visited the Fukushima No. 2 nuclear plant on Feb. 8, marking the first prefectural inspection of the plant since the March 11, 2011 disasters forced it to shut down.
"Right now, the most important tasks are to keep the reactors in cold shutdown and cool the spent fuel rods while preparing safety measures to deal with any unexpected problems," said the deputy head of the prefecture's living environment division following the inspection. "I felt that work there to maintain emergency power supplies and prevent flooding of the plant buildings was progressing."
The reactors at the Fukushima No. 2 plant -- about 11 kilometers south of the disaster-struck Fukushima No. 1 nuclear complex -- stopped automatically when the Great East Japan Earthquake hit and are now in cold shutdown, but the plant was very nearly the site of a second nuclear crisis.
In circumstances similar to those at the No. 1 plant, the cooling systems in three of Fukushima No. 2's four reactors failed when the March 11 tsunami hit and knocked out their backup generators. Unlike the situation at the No. 1 plant, however, staff at the No. 2 station managed to patch into external power before the reactor cores could seriously overheat.
In December last year, the government's Nuclear and Industrial Safety Agency officially declared the nuclear emergency at the plant over, while Tokyo Electric Power Co. -- operator of both the Fukushima No. 1 and 2 plants -- has submitted a plan to the agency for maintaining cold shutdown.
Fukushima Prefecture is calling for the shutdown of all nuclear stations in the prefecture, including Fukushima No. 2.
However, Fukushima No. 2 plant director Naohiro Masuda suggested it's too soon to discount restarting the reactors there, saying, "Under present circumstances, it's impossible to say how the reactors here will be dealt with in the future. For now, we have to maintain a steady cold shutdown by transitioning from the temporary cooling equipment we now have in place to proper, permanent equipment."
The abnormal rise in temperature in a reactor at the Fukushima No. 1 nuclear power plant has stopped, apparently because more water has been injected into the crippled reactor, according to Tokyo Electric Power Co.
TEPCO said the temperature at the base of the No. 2 reactor's pressure vessel had fallen to 68.5 C at 5 p.m. Tuesday after earlier peaking at 73 C. However, the cause of the increased temperature remained unclear.
Junichi Matsumoto, acting head of TEPCO's headquarters regarding nuclear plant locations, said increasing the amount of water injected hourly into the reactor by three tons to 13.5 tons since 4:30 a.m. Tuesday seemed to be having an effect.
"[The temperature] has begun falling after peaking," Matsumoto said.
Keeping the temperature at the base of the reactors at 100 C or less is a stable state known as cold shutdown. Reaching cold shutdown was a precondition for enabling the government to declare in December that the crisis at the nuclear plant had been brought under control.
TEPCO's guideline stipulates the temperature should be kept at 80 C or lower to allow for possible measurement errors.
The reactor will need to be monitored carefully because the condition inside the reactor's inner part containing melted nuclear fuel is not clear, and the reason for the temperature rise has yet to be pinpointed.
Currently, cooling water is injected into the No. 2 reactor via two piping systems--the coolant water supply system that can deliver water to the vessel's base, and the reactor core water spray system that aims water directly at the reactor core.
The temperature in the pressure vessel's base began rising from 45 C around Jan. 26, when the water injection balance of the two systems was changed several times during pipe repair work.
One of three thermometers installed around the base recorded a temperature increase of nearly 30 C over a little more than 10 days, reaching as high as 73 C at one time.
According to TEPCO, the volume of water being injected was far less than usual. It is possible that the way water was injected into the reactor might have changed around the time of the pipe repairs, and that water did not reach some of the fuel.
TEPCO also speculated that the fuel, which had melted and then solidified, might have cracked due to some shock or dropped down and changed shape.
Tokyo Electric Power Co. has increased the amount of water being injected into the No. 2 reactor at the Fukushima No. 1 nuclear power plant because the temperature at the base of the pressure vessel has been rising, the company said Tuesday.
The 13.5 tons being injected each hour to cool the reactor--an increase of three tons--is the most since the government announced the crippled plant had achieved a stable state of cold shutdown in December.
According to the utility, after increasing the amount of water being injected at 4:30 a.m. Tuesday, the temperature at the vessel's base has been fairly constant: It was 72.2 C at 5 a.m. and 69 C at 10 a.m. The temperature at the base of the vessel had been 45 C as of Jan. 27, but began rising earlier this month. TEPCO is investigating the cause of the higher temperature.
Temperature decreasing inside Fukushima reactor
Tokyo Electric Power Company says it has been able to lower the temperature inside the No.2 reactor at the troubled Fukushima Daiichi nuclear power plant by increasing the amount of water being injected into it.
TEPCO had been struggling to deal with rising temperatures inside the reactor. A thermometer located at the bottom of the reactor read 45 degrees Celsius on January 27th, but rose to over 70 degrees on Sunday. The cause is unknown, and two other thermometers at the reactor have shown no such increase.
TEPCO said on Wednesday that the temperature inside the reactor was 66.7 degrees at 5 AM, 5.5 degrees lower than a day earlier. The temperature gradually declined after the company increased the rate of water injection by 3 tons to 13.5 tons per hour on Tuesday.
Such a high rate of injection has not been used since just after the nuclear crisis began last March.
TEPCO says the temperature inside the reactor rose slightly to 68 degrees at 10 AM, but it is still dropping overall.
The utility cannot determine the exact situation inside the reactor or the cause of the temperature rise.
The utility says it will continue to monitor the situation closely while maintaining the current rate of water injection.
By REIJI YOSHIDA - http://www.japantimes.co.jp/text/nn20120208f1.html
In December, Prime Minister Yoshihiko Noda announced the "conclusion" of the meltdown crisis at the Fukushima No. 1 nuclear plant, saying Tokyo Electric Power Co. was managing to keep the three crippled reactors cool, as well as the facility's spent fuel pools.
But a former special adviser to Naoto Kan, who was prime minister when the crisis started, warned that the situation is far from resolved and said Fukushima has exposed a raft of serious nuclear problems that Japan will have to confront for years.
"I would say (the crisis) just opened Pandora's box," Hiroshi Tasaka, who has a doctorate in nuclear engineering and is now a professor at Tama University, said in a recent interview with The Japan Times.
He was one of a select group who glimpsed the secret worst-case scenario document written up by the Japan Atomic Energy Commission on March 25 that was later reportedly quashed by the government.
According to the scenario, the biggest risk during the meltdown crisis wasn't the reactors themselves but the spent fuel pools sitting atop them, particularly the one above reactor 4, which still contains about 1,500 nuclear fuel assemblies, Tasaka said.
Unlike reactors 1, 2 and 3, the No. 4 unit was offline for regular checks when disaster struck on March 11 and thus didn't suffer a meltdown. But its fuel rods were in the pool outside the reactor, and its coolant water fell dangerously low.
Adding to the danger is that the fuel pool is now directly exposed to the outside environment after a hydrogen explosion blew off the upper part of the reactor building on March 15, Tasaka noted.
The potential heat from the pool was also much higher than other pools because 204 of the 1,535 assemblies were still "new ones" that had been temporarily removed from reactor 4 for regular checks.
The Fukushima crisis has highlighted the dangers of spent fuel pools, which are outside the robust primary containment vessels of the reactors themselves, Tasaka said.
Under the current circumstances, the nation has no prospect of starting up the experimental high-level nuclear waste processing facility in Rokkasho, Aomori Prefecture, because of both technical difficulties and the sentiments of antinuclear activists.
This means utilities must store their spent fuel assemblies in cooling pools at their respective reactor sites as a "temporary measure." This situation greatly increased the danger at Fukushima No. 1 on March 11.
"The storage capacities of the spent fuel pools at the nation's nuclear power plants are reaching their limits," Tasaka wrote in a new book, "Kantei Kara Mita Genpatsu Jiko No Shinjitu" ("The Truth About the Nuclear Accident as Viewed From the Prime Minister's Office").
According to Tasaka, the utilities' fuel pools were about 70 percent full on average in 2010, but the figure was 80 percent at Fukushima No. 1.
The makeshift cooling systems set up at Fukushima No. 1 to stabilize the stricken reactors and fuel pools have greatly reduced the possibility of another catastrophe, Tasaka said, but the ad hoc system for decontaminating the coolant water is nevertheless generating large amounts of highly contaminated waste every day.
Making matters worse, the government doesn't have any place to permanently store it, he wrote.
Tasaka is also deeply concerned about the "groundless optimism" displayed by bureaucrats and business leaders as they rush to restart dozens of reactors that remain halted for safety checks since March 11.
"I understand quite well the intentions of the government, which now wants to send out a message of hope. But at this stage, all the risks should be put on the table," he said.
The nation's nuclear regulators must carry out drastic reforms to regain the people's trust. This is an imperative for the government if it wants to keep pushing nuclear power, Tasaka said.
He recalled viewing the government's worst-case scenario in late March. He was officially appointed special adviser to the prime minister on March 29.
The document detailed a hypothetical Fukushima crisis worst case: Eventual contamination from the plant would require the government to assist residents in the Tokyo area to evacuate if they wanted to voluntarily "migrate," based on the same evacuation protocols adopted for the 1986 Chernobyl accident.
The scenario assumed another hydrogen explosion would occur in the reactor 1 building and radiation would force all of the workers at the plant to evacuate.
All of the pools storing hundreds of nuclear fuel assemblies would eventually lose their cooling ability and the assemblies would melt down and breach the pools.
According to Kyodo News, the simulation was "so shocking" that top government officials decided to keep the paper secret by treating it as a mere personal document of Japan Atomic Energy Commission Chairman Shunsuke Kondo, who compiled the simulation. The government only gave it official recognition at the end of December, according to Kyodo.
More than 10 months after he saw the worst-case scenario paper, Tasaka is still not sure if such scary information should immediately be made public during a nuclear plant crisis.
The assumed worst case was extreme and people did not need to immediately flee the Tokyo area even in March or April, Tasaka said. Disclosing the simulation could have caused panic in the capital, he said.
Tasaka was obliged to keep secret what he learned through his work at the prime minister's office and was not in a position to decide what information was to be made public during the crisis.
He said he decided to start talking about the worse-case scenario only after Kan mentioned some of its highlights during an interview with the media in September.
Tasaka believes the media and government should lay some ground rules in advance on what sensitive information should be made clear in a nuclear crisis.
February 07, 2012
Temperature remains high at damaged reactor
An unknown rise in temperature at one of the reactors at the damaged Fukushima nuclear plant is troubling its operator. Tokyo Electric says the temperature hasn't gone down even after it increased the volume of cooling water on Tuesday.
One of the thermometers at the bottom of reactor No. 2 at the Fukushima Daiichi plant gradually rose to about 70 degrees Celsius since January 27th. It had stayed around 45 degrees before.
In an effort to lower the temperature, the operator increased the amount of water sprayed on the nuclear fuel by 3 tons to 13.5 tons per hour Tuesday morning.
But Tokyo Electric said readings were down only about 3 degrees after some 5 hours of operation, hardly showing signs of improvement.
The utility said the flow of water in the reactor may have changed after plumbing work in late January, causing difficulties in cooling part of the melted nuclear fuel.
It added that no temperature rise has been observed at 2 other thermometers in the same reactor and that it will continue to carefully monitor the reactor.
TEPCO has been unable to visually confirm conditions inside the reactors since the nuclear disaster last March because of high radiation.
TOKYO (Kyodo) -- Workers at the crippled Fukushima Daiichi power plant on Tuesday raised the amount of water injected into the No. 2 reactor to the highest level since the plant achieved a stable state of cold shutdown in December, as concerns grew over the rising temperature recently detected at the bottom of the reactor's pressure vessel.
Following the move, the temperature measured at the same spot on the vessel dropped to 69.0 C at 10 a.m. from 72.2 C logged at 5 a.m., Junichi Matsumoto, spokesman for plant operator Tokyo Electric Power Co. told a press conference, but added that the company needs more time to assess the effect of the latest step.
"It is difficult to judge whether the temperature is rising or dropping unless we monitor the development for about a day," Matsumoto said.
TEPCO said it increased the amount of injected water at 4:24 a.m. Tuesday. The No. 2 reactor is now being cooled with the injection of 13.5 tons of water per hour, up from 10.5 tons.
Nuclear disaster minister Goshi Hosono told a press conference that TEPCO is making utmost efforts to lower the temperature.
Touching on last month's change in the amount of coolant water at the No. 2 reactor for pipe replacement, which is believed to have affected the temperature, Hosono said, "This was a process to enhance stability, but it has become clear that there is a possibility of (replacement work) creating an unstable situation temporarily."
"We have to consider in an even more careful way," he said.
TEPCO's Matsumoto said he believes the No. 2 reactor is maintaining a state of cold shutdown, because the temperature is not rising continuously. Readings on two other thermometers checking the temperature of the bottom of the pressure vessel were around 40 C as of 10 a.m.
A cold shutdown is defined by the Japanese government as a situation in which the bottom part of a reactor pressure vessel is kept below around 100 C and radiation exposure from the release of radioactive substances is significantly held down.
At the Fukushima Daiichi plant in northeastern Japan, the Nos. 1 to 3 reactors have suffered meltdowns as a result of the loss of their key cooling functions in the wake of the devastating earthquake and tsunami on March 11 last year.
TEPCO is now injecting water into the three crippled reactors through a new water circulation system installed after the accident.
February 06, 2012
Temperature at No.2 reactor remains high
Attempts to cool the temperature in the No. 2 reactor of the disabled Fukushima Daiichi nuclear power plant have only partially succeeded despite the injection of more cooling water.
The temperature in the reactor has gradually risen from about 45 degrees Celsius registered on January 27th.
In the past 4 days, the temperature has climbed more than 20 degrees to above 70 degrees.
The plant operator, Tokyo Electric Power Company began pumping more water into the reactor at around 1:30 AM on Monday. But at 7 AM, the temperature stood at 73.3 degrees and at 5 PM, 69.2 degrees.
The utility firm says 2 other thermometers elsewhere in the reactor gave readings of about 44 degrees.
TEPCO says the rise in temperatures indicate that the flow of water in the reactor may have changed direction after plumbing work, and is no longer able to properly cool down the melted down nuclear fuel.
However, the utility says radioactive xenon has not been detected in gases around the reactor, and that nuclear criticality is not taking place.
The government and TEPCO announced in December that the 3 troubled reactors at the Fukushima plant had reached a state of cold shutdown with their temperatures below 100 degrees. But the situation inside the reactors remains unclear.
New regulations established after the state of cold shutdown was achieved require the utility to keep temperatures inside the reactors below 80 degrees.
TEPCO says it will increase the amount of water being injecting into the reactor to see if the temperature in the reactor drops.
The government's Nuclear and Industrial Safety Agency says there is a need for a comprehensive study to determine whether the reactor is actually in a state of cold shutdown. It says a brief reading of over 80 degrees on one of the thermometers does not necessarily mean there is trouble in the cooling system.
Meanwhile, the Chairman of the Nuclear Safety Commission, Haruki Madarame, says that a recurrence of nuclear criticality is unlikely.
But he criticized TEPCO and the nuclear safety agency for their handling of the matter. He says they are failing to properly explain the state of the reactors to the people.
Temperature rises at Fukushima No.2 reactor
The operator of the Fukushima Daiichi nuclear plant says the temperature in the No.2 reactor remains high despite the injection of additional water.
A thermometer at the bottom of the reactor showed 73.3 degrees Celsius on Monday morning. It was around 45 degrees on January 27th and 71.7 degrees at 4 PM on Sunday.
Tokyo Electric Power Company began injecting 10.6 tons of water per hour from around 1:30 AM on Monday. That's one ton more per hour than before.
The utility says 2 other thermometers placed at the bottom of the reactor have been giving readings of about 44 degrees.
It says the flow of water in the reactor may have changed after plumbing work, causing difficulties in cooling the nuclear fuel.
In December last year, the government and TEPCO declared the 3 reactors at the Fukushima Daiichi plant had been successfully put into a state of cold shutdown as their temperatures had fallen below 100 degrees. But the situation inside the reactors remains unknown.
TEPCO says the regulations set after the state of cold shutdown was achieved require the utility to keep temperatures inside the reactors below 80 degrees.
So it says the No.2 reactor is still in the state of cold shutdown.
February 04, 2012
TOKYO (AP) -- Leaks of radioactive water have become more frequent at Japan's crippled nuclear power plant less than two months after it was declared basically stable.
The problem underlines the continuing challenges facing Tokyo Electric Power Co. as it attempts to keep the Fukushima Dai-ichi nuclear plant under control. A massive earthquake and tsunami badly damaged the plant last March, resulting in the melting of three reactor cores.
Workers spotted a leak Friday at a water reprocessing unit which released enough beta rays to cause radiation sickness,TEPCO spokesman Junichi Matsumoto said. He said no one was injured and the leak stopped after bolts were tightened on a tank.
Matsumoto said TEPCO also found that 8.5 tons of radioactive water had leaked earlier in the week after a pipe became detached at Unit 4, one of the plant's six reactors. The company earlier had estimated that only a few gallons (liters) had leaked.
He said officials are investigating the cause of that leak, but that it was unlikely the pipe had been loosened by the many aftershocks that have hit the plant.
The structural integrity of the damaged Unit 4 reactor building has long been a major concern among experts because a collapse of its spent fuel cooling pool could cause a disaster worse than the three reactor meltdowns.
Cold winter weather has also caused water inside pipes to freeze elsewhere at the plant, resulting in leaks in at least 30 locations since late January, Matsumoto said.
Officials have not detected any signs of radioactive water from the leaks reaching the surrounding ocean. Sandbag walls have been built around problem areas as a precaution. [don’t worry, everything is safe]
More than 100,000 people around the plant fled their homes after the disaster due to radiation fears.
The government announced in December that the plant had reached "a cold shutdown condition" and is now essentially stable.
On Monday, six inspectors from the government's Nuclear and Industrial Safety Agency will begin an inspection of the plant to ensure its continued stability. They will study the reactors' cooling functions and measures to prevent explosions and nuclear chain reactions, among other steps to keep the plant under control, officials said.
February 03, 2012
NHK World English
Safety checks to begin at Fukushima Daiichi plant
Japan's nuclear safety agency will begin inspecting the Fukushima Daiichi nuclear plant from Monday to see if it can safely remain in a state of cold shutdown.
Officials from the Nuclear and Industrial Safety Agency plan to check equipment and contingency preparations by examining manuals and interviewing workers during their three-week inspections.
Among the seven types of equipment to be checked is a reactor cooling system that recycles decontaminated water from the facility.
Another is a nitrogen-injection system to prevent hydrogen explosions within the disabled reactors.
Agency officials say they will open the onsite inspections to the media. The checks will be the first safety tests required under law since the March 11th accident.
The government declared on December 16th that the Fukushima Daiichi reactors had achieved a state of cold shutdown.
This means reactor temperatures have stabilized below 100 degrees Celsius, and the release of radioactive substances has been contained.
February 02, 2012
TOKYO (Kyodo) -- Tokyo Electric Power Co. said Wednesday that 8.5 tons of radioactive water leaked from the No. 4 reactor of the crisis-hit Fukushima Daiichi power plant because a pipe connected to the reactor dropped off, but added that the liquid has not flowed outside the reactor building.
At the time of the devastating earthquake and tsunami last March 11, the reactor's fuel rods were in its spent fuel pool due to maintenance work that was taking place. The water contains radioactive materials as it is mixed up with water that is in contact with the fuel in the spent fuel tank.
According to the utility known as TEPCO, water was found to have leaked onto the floor of the No. 4 unit building at 10:30 p.m. Tuesday. The leak was stopped at 10:43 p.m. by closing a valve, officials said.
The total amount of leakage from the reactor was initially estimated to be 6 liters, but the utility revised the figure later Wednesday, adding that the leakage appears to have started at around 5 p.m. Monday.
The pipe may have dropped off because water inside increased in volume as it turned into ice due to cold temperatures.
The utility plans to check whether there are similar cases in the other crippled reactors.
The Nos. 1 to 3 reactors have fuel inside, which is believed to have melted in the early phase of the nuclear crisis because the plant lost its cooling functions following the natural disasters.
The No. 4 unit also lost the function to cool its spent fuel pool, but no serious damage is believed to have occurred in the fuel stored there.
TOKYO (Kyodo) -- Tokyo Electric Power Co. said Wednesday that it has found radioactive water leaking from a broken pipe connected to the No. 4 reactor of the crisis-hit Fukushima Daiichi power plant, but added that the liquid has not flowed outside the reactor building.
At the time of the devastating earthquake and tsunami last March 11, the reactor's fuel rods were in its spent fuel pool due to maintenance work that was taking place. The water contains radioactive materials as it is mixed up with water that is in contact with the fuel in the spent fuel tank.
According to the utility known as TEPCO, about 6 liters of water were found to have leaked onto the floor of the No. 4 unit building at 10:30 p.m. Tuesday. The leak was stopped at 10:43 p.m. by closing a valve, officials said.
The utility is looking into the cause of the damage to the pipe and believes it may have some connection with the recent cold weather or the explosions that took place at the plant in the early phase of the nuclear crisis.
The density of radioactive substances included in the water is estimated at 35.5 becquerels per cubic centimeter, according to TEPCO.
January 31, 2012
NHK World English
Govt plans Fukushima decontamination test-run
Japan's Environment Ministry has unveiled a model project designed to decontaminate areas with high levels of radiation around the crippled Fukushima Daiichi nuclear plant.
In a test-run for a wider clean-up, the ministry will first try to decontaminate 3 closed sections of a national expressway running through the no-entry zone near the plant.
The ministry last week announced a 2-year plan to decontaminate by March 2014 some evacuation zones where radiation levels have dropped below 50 millisieverts per year.
Radiation levels over a total 5 kilometers of expressway slated for the new project have ranged from a little to substantially above 50 millisieverts a year.
The ministry plans to assess the project's effectiveness in a test-run from the middle of March through July.
January 30, 2012
More water leaks found at Fukushima nuclear plant
NHK World English
More water leaks have been found at the troubled Fukushima Daiichi nuclear power plant.
Tokyo Electric Power Company told reporters on Monday morning that it has discovered 2 additional water leaks at the nuclear plant.
This comes after it was announced on Sunday that nearly 8 tons of water was found to have leaked in 14 locations at the plant.
One of the 2 new findings involves about 30 liters of water that has leaked from a device that is removing salt from contaminated water. The other leak is from a valve of a pipe that is injecting water into a reactor.
TEPCO says leaked water has neither spilled out of the plant, nor flowed into the sea.
The utility firm is trying to determine whether water in some of the pipes froze and cracked the pipes, or loosened the pipes' connections.
It plans to quickly implement preventive measures, including carrying out more patrols early in the morning and wrapping insulation around the pipes and other equipment. !!!!!!!
The temperature on Monday morning around the plant dropped to minus 8.7 degrees Celsius.
January 29, 2012
TEPCO ordered to prevent water leaks at reactors
NHK World English
Japan's nuclear safety agency has instructed the operator of the Fukushima Daiichi nuclear plant to prevent water leaks at the plant.
The move follows the discovery of water leaks on Sunday in 14 locations at the damaged plant.
Tokyo Electric Power Company says about 40 liters of water leaked from a cooling system for a spent fuel pool at the No. 4 reactor, forcing the system to stop for one hour and 40 minutes. The utility also says that 7 tons of water leaked from the No. 6 reactor.
The company says that the leakages apparently occurred after frozen water in pipes loosened the pipes' connections or broke some parts.
The company adds that the leaked water did not contain radioactive materials or had already been processed to remove them.
Similar water leaks occurred in 3 locations at the plant on the previous day.
Responding to the agency's call for preventive measures, TEPCO has decided to conduct frequent checks on early mornings when temperatures often drop below zero and protect pipes from the cold with insulation materials or heaters, if necessary.
The utility says measures are already in place to protect critical systems, such as those used for cooling reactors.
Frozen water blamed for leaks at Fukushima plant
Tokyo Electric Power Company has found water leaks in 14 locations at the Fukushima Daiichi nuclear plant.
The utility says the leaks apparently occurred after frozen water ruptured the pipes and the leaked water did not contain any radioactive materials.
Tokyo Electric said about 40 liters of water leaked from a cooling system for a spent fuel pool at the No.4 reactor on Sunday, but the flow stopped when workers closed the valve.
The company said the leak forced the system to stop for one hour and 40 minutes, but the pool's temperature did not rise.
Tokyo Electric said 7 tons of water had leaked from the No.6 reactor.
The temperature fell to minus 8 degrees Celsius on Sunday morning near the damaged plant.
Ruptured pipes caused 3 water leaks on the previous day.
Tokyo Electric official Junichi Matsumoto admitted that the utility failed to take sufficient steps to prevent frozen pipes. He said it will take quick action to protect the pipes from the cold weather.