Archives de juin 2012
The highest level of radiation to date has been detected inside the No.1 reactor at the tsunami-wrecked Fukushima Daiichi nuclear power plant in Japan.
The plant’s operator Tokyo Electric Power Company (TEPCO) said on Thursday it used endoscopes and dosimeters to examine the interior of the reactor. A record level of 10,300 millisieverts per hour was detected in the internal measurement carried out for the first time since the March, 2011 accident. The measurement was taken 20 centimeters above the surface of a contaminated water puddle in the reactor’s suppression chamber. This high level of radiation would be fatal for humans within 50 minutes.
A measurement of 1,000 millisieverts per hour was detected about four meters above the water surface, which is ten times higher than measured in the No.2 and No.3 reactors, Japanese media reported.
TEPCO official Junichi Matsumoto said he suspected that a higher radiation level in the No.1 reactor was caused by more fuel rods melting down than in other reactors.
He said robots would be used for damage assessment because it was unsafe for humans to work on the site.
Meanwhile, Officials from the Nuclear and Industrial Safety Agency apologized to Kawauchi village mayor Yuko Endo and communities around the plant for failing to release maps showing dangerous radiation areas. Residents of the village were forced to evacuate after the government designated 20-kilometer radius of the plant as no-entry zone.
The maps were provided by the United States days after the tsunami-triggered accident. U.S. Energy Department scientists used aerial surveys to compile the maps showing the spread of radiation around the stricken plant. The information was given to the Japanese Education and Science Ministry and the Nuclear and Industrial Safety Agency, the country’s nuclear watchdog, through the Foreign Ministry.The mayor said if the information were given to the village, people could have avoided evacuating into areas of high radiation. He also said more than a year has passed since the accident, and the apology meant nothing.
In a country as small, crowded and earthquake-prone as Japan, vetting nuclear reactors for safety is key — as the March 2011 accident at Fukushima Daiichi showed. Japan is the only economy, besides Taiwan, that has so many nuclear plants in quake zones.
- Japan Atomic Power Co.’s Tsuruga nuclear power plant.
So which of the country’s 50 reactors are safest to operate?
A bipartisan group of 10 lawmakers– all of whom support reducing Japan’s reliance on nuclear power– looked into that question. They ranked the reactors by nine criteria, including reactor age and type, accident records, average operating rates, quake vulnerability and proximity to large population centers.
They found the 10 safest reactors are run by three utilities — Kyushu Electric Power Co. (6), Shikoku Electric Power Co. (2) and Hokkaido Electric Power Co. (2). They are the smallest of Japan’s 10 utilities, and their plants are relatively new, and located far from large cities.
The worst performer is Japan Atomic Power Co.’s Tsuruga No. 1 reactor, which was recently found to have an active fault running right underneath.
Tsuruga is followed by Oi Nos. 1-2, Mihama Nos. 1-3, and Hamaoka Nos. 3-5. Of the worst 10, five are owned by Kansai Electric Power Co., and three by Chubu Electric Power Co., the nation’s second and third largest utilities. The still-operational reactors of Tokyo Electric Power Co., which runs Fukushima Daiichi, came in toward the middle of the rankings. But all Tepco’s reactors were on a second list of facilities the lawmakers thought should be scrapped, based on the risks of future earthquakes or damage done by recent quakes. Tepco’s remaining reactors have all suffered damage from earthquakes in 2007 and 2011.
The bottom 10 ranking reactors are all 30 years old or more, except for the three Hamaoka reactors, which are newer but sitting in a region with a high risk of being hit by a Magnitude 8 earthquake.
The list is still a preliminary, the lawmakers’ group says, since it has yet to incorporate other important risk factors such as the strength of tsunami barriers and the availability of emergency-operation facilities.
The rating should also take into account plant layout and what’s around the facilities, argues Ikuko Tanioka, an upper house member of the ruling Democratic Party of Japan. “Many of them have no open space around them to host large Self-Defense Force contingents,” she said. “Many also stand in snowy regions, with access easily blocked in winter.”
The Self-Defense Forces, Japan’s equivalent to a military, played a big role in helping control last year’s accident at Fukushima Daiichi, and evacuate residents in the surrounding areas.
Another possible hazard is multiple reactors at the same location, says Masaru Kaneko, a Keio University professor and expert on the economics of nuclear power, who was invited by the lawmakers to comment on the rankings. Most Japanese plants have three, four, or even up to seven reactors in one place. That means an accident at one reactor could easily affect the operations of other units, as happened at Fukushima Daiichi. “No more than two reactors should be allowed to restart at any one plant,” Mr. Kaneko said.
But scrapping reactors is costly. According to the Ministry of Economy, Trade and Industry, if Japan abandons nuclear power now, utilities would need to register ¥4.4 trillion in one-off costs for decommissioning and asset write-offs. They will also face ¥3.1 trillion in additional fossil-fuel costs every year.
As of the end of March, the nation’s 10 utilities had a combined net worth of only ¥5.7 trillion. An immediate exit from nuclear power would leave four of them insolvent — Tepco, Tohoku Electric Power Co., Hokkaido Electric and Japan Atomic Power, METI said.
The government said that the areas around the tsunami-crippled Fukushima Daiichi nuclear power plant no longer posed any danger to human health.Japan has allowed food supplies from the Fukushima prefecture.
Until now, only sea snails and octopuses from Fukushima have been on the market as they are less affected by radiation than other species.
Fukushima sea products are sold at below market prices.
Last spring, a devastating earthquake and tsunami hit Japan, damaging the Fukushima nuclear power plant and causing radiation leaks.
TOKYO (AFP) —
TEPCO, the operator of Japan’s crippled Fukushima nuclear plant, said Wednesday record amounts of radiation had been detected in the basement of reactor number 1, further hampering clean-up operations.
TEPCO took samples from the basement after lowering a camera and surveying instruments through a drain hole in the basement ceiling.
Radiation levels above radioactive water in the basement reached up to 10,300 millisievert an hour, a dose that will kill humans within a short time after making them sick within minutes.
The annual allowed dose for workers at the stricken site is reached in only 20 seconds.
“Workers cannot enter the site and we must use robots for the demolition,” said TEPCO.
The Fukushima operator said that radiation levels were 10 times higher than those recorded at the plant’s two other crippled reactors, number two and three.
This was due to the poor state of the nuclear fuel in the reactor compared to that in the two others.
The meltdown at the core of three of Fukushima’s six reactors occurred after the March 11, 2011 earthquake and ensuing massive tsunami shut off the power supply and cooling system.
Demolition of the three reactors as well as the plant’s number 4 unit is expected to take 40 years and will need the use of new technologies.
© 2012 AFP
TOKYO — About 20,000 people gathered in front of Japanese Prime Minister Yoshihiko Noda’s residence in Tokyo late Friday to protest his decision to restart two nuclear reactors.
“No to the restart!” shouted the protestors, who were led by investigative journalist Satoshi Kamata and Nobel Prize-winning author Kenzaburo Oe, who started an anti-nuclear petition that has so far gathered more than 7.5 million signatures.
Last Saturday, Noda gave the green light to start work to put back online two reactors at the Oi plant in western Japan, despite public distrust in the technology since last year’s meltdowns at Fukushima.
(Reuters) – Two prominent seismologists said on Tuesday that Japan is ignoring the safety lessons of last year’s Fukushima crisis and warned against restarting two reactors next month.
Japan has approved the restart of the two reactors at the Kansai Electric Power Ohi nuclear plant, northwest of Tokyo, despite mass public opposition.
They will be the first to come back on line after all reactors were shut following a massive earthquake and tsunami last March that caused the worst nuclear crisis since Chernobyl at Tokyo Electric Power’s Daiichi Fukushima plant.
Seismic modelling by Japan’s nuclear regulator did not properly take into account active fault lines near the Ohi plant, Katsuhiko Ishibashi, a seismologist at Kobe University, told reporters.
« The stress tests and new safety guidelines for restarting nuclear power plants both allow for accidents at plants to occur, » Ishibashi told reporters. « Instead of making standards more strict, they both represent a severe setback in safety standards. »
Experts advising Japan’s nuclear industry had underestimated the seismic threat, Mitsuhisa Watanabe, a tectonic geomorphology professor at Tokyo University, said at the same news conference.
« The expertise and neutrality of experts advising Japan’s Nuclear Industrial Safety Agency are highly questionable, » Watanabe said.
After an earthquake in 2007 caused radiation leaks at reactors north of Tokyo, Ishibashi said Japan was at risk of a nuclear disaster following a large earthquake, a warning that proved prescient after Fukushima.
While it is impossible to predict when earthquakes will happen, Ishibashi said on Tuesday the magnitude 9 quake last year made it more likely « devastating » earthquakes would follow. (Reporting by Aaron Sheldrick; Editing by Ed Lane)