information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise
20 Mars 2013
March 20, 2013
http://ajw.asahi.com/article/0311disaster/fukushima/AJ201303200018
Cooling systems were restored for four fuel storage pools at Japan's tsunami-damaged nuclear plant, more than a day after a power outage halted the supply of fresh cooling water and raised concerns about the safety of the facility, which still relies on makeshift equipment.
Tokyo Electric Power Co. said the cooling system at the last pool at the Fukushima No. 1 nuclear plant was repaired early on March 20. It said pool temperatures were well within safe levels and the reactors were unaffected.
TEPCO spokesman Yoshikazu Nagai said workers were still trying to determine the cause of the cooling failure, which began when a brief power blackout hit the plant on the evening of March 19.
About 50 workers in hazmat suits and full-face masks were mobilized to fix the cabling to three switchboards that were suspected of involvement in the problem. TEPCO also prepared a backup system in case the repairs didn’t fix the issue and “worse comes to worst,” company spokesman Masayuki Ono said earlier March 19.
A massive earthquake and tsunami on March 11, 2011, caused extensive damage to the plant. Massive radiation leaks at that time contaminated air, water and soil around the plant, causing some 160,000 residents to evacuate.
The latest power outage was a test for TEPCO to show if it has learned anything from the disaster. TEPCO, which has faced repeated cover-up scandals, was slammed by local media on March 19 for waiting hours to disclose the blackout.
Ono acknowledged the plant was vulnerable.
“The Fukushima plant still runs on makeshift equipment, and we are trying to switch to something more permanent and dependable, which is more desirable,” he said. “Considering the equipment situation, we may be pushing a little too hard.”
Ono said the utility did not immediately try to switch to a backup cooling system because doing so without finding and fixing the cause could lead to a repeat of the problem.
There is a backup cooling system but no backup outside power source. TEPCO has backup cooling systems with separate power sources for reactor cooling, but fuel storage pools only have emergency diesel generators as a backup. TEPCO said it will consider installing backup outside power for the pools.
The No. 3 and No. 4 reactors share a makeshift switchboard that sits on the back of a truck, but an upgrade to a permanent, safer location is being planned later this month. Reactor cooling water pumps also sit on the back of a truck, with hoses traveling several kilometers to reach the reactors.
“We have a ton of problems that still need to be taken care of to overcome the challenges that we have never experienced before,” Ono said. But he denied the power outage would affect the plant's long-term cleanup plans.
Regulators have raised concerns about the makeshift equipment and urged the plant to switch to a more permanent arrangement. The operator still has to remove melted, highly radioactive fuel from the reactors before fully decommissioning the plant, which officials say could take 40 years.
Chief government spokesman Yoshihide Suga sought to allay concerns.
“We have put in place measures that leave no room for worry,” Suga told a regular briefing.
The command center at the plant suffered a brief power outage before 7 p.m. March 18. Electricity was quickly restored there but not to equipment pumping water into the fuel pools.
The temperature in the four pools had risen slightly, but was well below the utility's target control temperature of 65 degrees, TEPCO said.
“We don't believe the Fukushima disaster is under control,” said Yuko Endo, chief of nearby Kawauchi village, part of which remains restricted because of radiation contamination, keeping hundreds of residents away from their homes. Officials are struggling to make the area livable again, but people cannot return home unless they feel confident about the plant's stability, he said.
http://mainichi.jp/english/english/newsselect/news/20130320p2g00m0dm001000c.html
TOKYO (Kyodo) -- Tokyo Electric Power Co. said Tuesday it has resumed cooling the spent fuel pools of the Nos. 1, 3 and 4 reactors at the crippled Fukushima Daiichi nuclear power plant, a day after the key system was suspended due to a suspected problem with a power switchboard.
The incident did not affect the injection of water into the Nos. 1, 2 and 3 reactors that suffered core meltdowns, but indicated that the situation remains vulnerable more than two years after the plant was ravaged by the quake-triggered tsunami on March 11, 2011.
TEPCO spokesman Masayuki Ono told a press conference that the utility has yet to nail down the cause of the incident as it has devoted its energy to restoration efforts.
Electricity went out at a total of nine facilities, including an installation to remove radioactive substances from water used to cool reactors and a cooling system for a common pool located inside another building at the site.
Ono admitted that it was the first time such a large number of facilities, including important devices, had suffered an electricity failure simultaneously since the plant was brought under control in December 2011.
TEPCO initially noticed the problem after electricity instantaneously went out at the plant's accident response center at 6:57 p.m. Monday.
TEPCO had placed the highest priority on restoring the cooling system of the No. 4 spent fuel pool, as the number of fuel assemblies stored in the tank is higher than those left in the pools of the Nos. 1, 2 and 3 units. It succeeded in resuming the system by 4:13 p.m. Tuesday.
The cooling system for the Nos. 1 and 3 spent fuel pools was also put back online on Tuesday.
The temperature of the No. 4 spent fuel pool stood at 30 C at 4:30 p.m., compared with 25 C at 4 p.m. a day earlier. TEPCO has set an upper limit of 65 C to secure safety during normal operations.
TEPCO said the cooling system of the common pool was restored shortly after midnight Tuesday, meaning the operation of all nine facilities has recovered. The pool stores a total of 6,377 fuel assemblies.
The company suspects a problem at a makeshift power switchboard caused the suspension of the cooling system. The equipment in question is the only remaining makeshift power switchboard at the plant, installed after the nuclear crisis, according to Ono.
Economy, Trade and Industry Minister Toshimitsu Motegi said at a press conference that he has instructed TEPCO to take every possible measure to address the problem at the plant.
Chief Cabinet Secretary Yoshihide Suga also said there is "no need to worry," but a Fukushima prefectural government official told TEPCO the same day that the incident has created "significant anxiety" among local people.
Given that it took TEPCO about three hours before announcing that the cooling system had been suspended, the company said it will seek to convey information more quickly on issues that could stir public concern.
AFP-JIJI, Kyodo
Technicians have restored power to all cooling systems at the reactors of the Fukushima No. 1 nuclear plant, operator Tepco said Wednesday after a blackout sparked a new crisis.
Equipment in pools used to cool used fuel became fully operational 12 minutes after midnight, some 30 hours after the blackout, Tokyo Electric Power Co. said.
Used nuclear fuel becomes dangerous if its temperature is allowed to rise uncontrollably to the point where a self-sustaining critical reaction begins, causing a meltdown.
The incident did not affect the injection of water into the reactors 1, 2 and 3 that suffered core meltdowns, but indicated that the situation remains vulnerable more than two years after the plant was ravaged by the quake-triggered tsunami on March 11, 2011.
The latest crisis began Monday night with a brief power outage at a building on the plant’s site that serves as the central command for work to contain the nuclear accident and to dismantle the reactors.
The initial glitch cut electricity to the cooling pools at three of four heavily damaged reactors as well as a common pool at 7 p.m. on Monday, according to Tepco.
By Tuesday evening engineers had managed to restart cooling systems in the three affected reactor pools, the utility said.
A separate cooling system for the common pool was restarted just after midnight Wednesday, ending the latest problem, the company said.
“At 0:12 a.m. today (Wednesday), the common pool cooling purification system was restarted,” Tepco said in a statement. “All of the systems have been restarted.”
Tepco has stressed that the glitch was fixed before any lasting damage was caused, saying the temperatures of all the fuel pools remained well below the safety limit of 65 degrees.
Company officials say there has been no major change to the level of radioactivity at nearby monitoring spots.
Monday’s outage knocked out power at a total of nine facilities, including an installation to remove radioactive substances from water used to cool reactors and a cooling system for a common pool located inside another building at the site.
Ono admitted that it was the first time such a large number of facilities, including important devices, had suffered an electricity failure simultaneously since the plant was brought under control in December 2011.
Tepco has yet to identify the cause of the blackout, but suspects a problem with a switchboard.
The firm says the incident did not affect the injection of cooling water into reactors whose cores melted down soon after the start of the 2011 nuclear crisis.
The meltdown of three of Fukushima’s six reactors occurred after an earthquake and huge tsunami on March 11, 2011, which shut off the power supply and cooling system.
Tepco drew flak for playing down the scale of the disaster in the first few months. It has since admitted it had been aware of the potential dangers of a big tsunami but did nothing for fear of the reputational and financial cost.
The latest incident rekindled public concern about whether the politically connected utility is being fully transparent.
Tepco informed the government’s regulatory agency about the blackout shortly after it started, but waited three hours before issuing a public press release.
Staff Writer
Critical cooling systems for four pools containing thousands of nuclear fuel assemblies at the Fukushima No. 1 power plant shut down due to a loss of power overnight Monday, highlighting the vulnerability of the ad hoc equipment set up after the meltdowns two years ago.
Tokyo Electric Power Co. said repairs to fully recover the cooling functions of the fuel pools at reactors 1, 3 and 4 were completed on Tuesday night. Meanwhile, the utility said another huge common fuel pool would be fully functional by 8 a.m. Wednesday.
Tepco was still trying to pinpoint the cause of the power loss Tuesday afternoon, raising concern about the soundness of the facilities at the badly damaged nuclear plant, where decommissioning work will take decades.
Tepco emphasized that it would take at least three more days for the water in the spent fuel pool in the damaged reactor 4 building, potentially the most dangerous one, to reach the threshold control temperature of 65 degrees, giving the operator ample time to restore power before the coolant water started to boil and evaporate.
The utility speculated that a makeshift switchboard set up after the meltdowns of reactors 1-3 probably malfunctioned Monday evening, causing two more switchboards and other equipment to automatically shut down.
It is thought that this led to the power loss to the cooling systems for the fuel pools in the reactor 1, 3 and 4 buildings as well as the large common pool, which contains 6,377 nuclear fuel assemblies, Tepco said.
The injection of coolant water into the damaged cores of reactors 1, 2 and 3 was not disrupted, Tepco said.
“We are still trying to identify the cause (of the power loss). We need to investigate further,” said Tepco executive Masayuki Ono, who served as a spokesman at the news briefing Tuesday morning.
Tepco announced the loss of cooling functions shortly after 10 p.m. Monday, about three hours after the power went out, drawing criticism from the media.
Tepco said the information was withheld because it took several hours to figure out which equipment was affected by the power disruption.
Chief Cabinet Secretary Yoshihide Suga, meanwhile, sought to ease concern by assuring the public that the plant has backup equipment on hand for worst-case scenarios.
“We are preparing (backup safety) measures so that you don’t need to worry,” Suga told a news conference Tuesday morning.
According to Tepco, fire engines are deployed at the Fukushima plant, and other water pumps are available as well to inject water into any of the pools in the event the cooling equipment goes down for an extended period.
Radiation monitoring posts in and around the Fukushima plant showed no abnormal readings, according to both Tepco and the government.
But the current problem pulls back the curtain on the unreliability of the cooling systems at the Fukushima plant.
Containing 1,533 fuel assemblies, the reactor 4 pool is the hottest of the four. Its water temperature was estimated at 30.5 degrees at 10 a.m. Tuesday, and would rise 0.368 degree per hour while the cooling system is out, Tepco said.
At 100 degrees, the water would boil and evaporate. If all the water was lost, the fuel assemblies would melt down andthe pool collapse, releasing vast amounts of radioactive material into the environment.
Tepco now plans to transfer all the fuel assemblies from the reactor 4 pool to the sturdier common pool by the end of this year.
But the cooling system for the common pool was also shut down by the recent power loss.
It is expected to take more than three decades to decommission the three troubled reactors at the Fukushima complex, which has six reactors. It has not been decided what will happen with the rest of the crippled plant. Tepco will have to keep the cooling systems running throughout the long process to prevent further meltdowns of the still-hot reactor cores.
Ono said that for now at least Tepco believes the makeshift switchboard either lost current or surged, tripping other switchboards and equipment connected to the network, and cutting power to the cooling systems.
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