Xenon 400,000 times normal found in Chiba air immediately after Fukushima nuke accident(Mainichi, Dec 2, 2011)
CHIBA — Radioactive xenon-133 some 400,000 times normal levels was detected in the atmosphere here immediately after the outbreak of the crisis at the Fukushima No. 1 Nuclear Power Plant, a radiation survey organization said.
It took three months before the volume of radioactive substances returned to normal levels.
The Chiba-based Japan Chemical Analysis Center made the announcement during a radiation research session in Tokyo on Dec. 1, organized by the Education, Culture, Sports, Science and Technology Ministry.
Keisuke Isogai from the center denied that the high concentration of radioactive substance posed a health hazard.
“I think xenon-133 drifted from the Fukushima No. 1 nuclear plant to Chiba in the form of a plume. Since the detected amount translates into a cumulative external exposure to radiation of only 1.3 microsieverts over the three-month period, it won’t cause a health hazard,” he said.
The average amount of xenon-133 in the atmosphere was 1,300 becquerels per cubic meter of air in Chiba between March 14 and 22, as compared with zero to 3.4 millibecquerels before the crisis. The volume reached 400,000 times normal levels shortly after the nuclear crisis was triggered by the March 11 tsunami, according to the center.
Xenon-133 is generated in the process of nuclear fission of uranium and plutonium used as fuel at nuclear power stations. Since xenon-133 hardly reacts to any other substance, there is no fear of internal exposure to radiation even if inhaled, experts say.
Cesium-137 deposits 50 times more than previous record (Asahi, Dec 3)
TSUKUBA, Ibaraki Prefecture–Nearly 30,000 becquerels per square meter of cesium-137 fell on Tsukuba in March as a result of the accident at the Fukushima No. 1 nuclear power plant, the government’s Meteorological Research Institute said Dec. 1.
The amount was 50 times higher than the previous record level of 550 becquerels, which was measured in Tokyo in 1963 and was the result of deposits from atmospheric nuclear tests.
The MRI, affiliated with the Japan Meteorological Agency, said the cesium-137 deposits in Tsukuba in April fell to less than one-tenth the March level, and by summer fell further to several tens of becquerels per square meter, approximately the same levels found in the aftermath of the 1986 Chernobyl accident, researchers said.
“It may take decades for the figures to come down to levels before the Fukushima accident,” said Yasuhito Igarashi, a laboratory head at the MRI’s Atmospheric Environment and Applied Meteorology Research Department.
Meanwhile, analysis of seawater collected in April and May found that radioactive substances spewed by the stricken Fukushima No. 1 plant fell over broad areas in the North Pacific. Fallout was also detected near the West Coast of the United States.
The research institute estimated that the Fukushima plant discharged at least 3,500 trillion becquerels each of cesium-137 and cesium-134 into the ocean. It forecast that the radioactive material will spread east across the North Pacific on surface ocean current before drifting southwest on deeper ocean currents. Part of the radioactive materials carried by mid-depth ocean currents will return to seas near Japan’s coast in 20-30 years, the scientists said.
“Continual surveys are necessary across all areas of the North Pacific,” said Michio Aoyama, a laboratory head at the MRI’s Geochemical Research Department.
The MRI has been engaged in radioactivity measurements since 1954.
On March 31, the budget for fiscal 2011, which was to start the next day, was abruptly frozen, and the researchers were told to suspend the measurements. The latest findings are a fruit of efforts by scientists who ignored that order and continued with the measurements.
Tepco study shows water for spent fuel was critically low (Japan Times, Dec. 3, 2011)
A study by Tokyo Electric Power Co. indicates that water in the Fukushima No. 1 power plant’s reactor 4 spent fuel pool fell at one point to a level close to exposing the stored nuclear rods, according to sources.
After the reactor 4 unit lost its key cooling functions along with the plant’s other reactors in the wake of the March 11 quake and tsunami, the water level in its spent fuel pool fell at one point to only 1.5 meters above the top of the fuel assemblies, as heat from the fuel had caused the coolant to evaporate.
The water level is usually around 7 meters above the assemblies.
The water level remained low for more than a month, until at least April 20. Workers injected around 930 tons of water into the pool between April 22 and 27, filling it up, but a graph compiled by Tepco shows that the fuel would have been exposed in early May if the extra water had not been poured in.
While fuel inside a reactor is enclosed by multiple barriers so that radioactive substances don’t escape, a spent fuel pool is only separated from the external environment by the walls of the reactor building.
Exposure of nuclear fuel is dangerous because it could eventually melt and release radioactive substances into the outside world. Because the walls of the reactor 4 building were damaged in a hydrogen explosion, an extremely dangerous situation could have occurred.
The study also showed that the water levels in the spent fuel pools for reactors 1, 2 and 3 also dropped, but not significantly.
Heat from the fuel in reactor 4’s pool was greater than the other units because all of the fuel from the reactor, which was halted for a regular inspection before the quake, was stored there. The temperature of the water, usually kept at around 30 degrees, rose to about 90 after the crisis erupted.
TEPCO issues interim report on Fukushima accident (NHK, Friday, Dec 2, 2011)
The Tokyo Electric Power Company has released an interim report on its in-house probe into the nuclear disaster at the firm’s Fukushima Daiichi power plant.
But the report issued on Friday fails to clarify how or why a huge amount of radioactive materials leaked outside the facility.
Based on data and interviews of more than 250 workers since June, the report describes how the giant tsunami on March 11th knocked out almost all of the plant’s power sources and all of its fail-safe mechanisms. The report also details how meltdowns occurred at some of the plant’s reactors after the accident.
The report says the firm had worked with the government and obtained its endorsement in taking measures to guard the plant from severe accidents before March 11th.
The report also defends as reasonable the utility’s effort to contain the damage from the accident.
The report says that the plant lost all of its safety mechanisms because the tsunami was much larger than expected, that workers could not keep up with developments, and that core meltdowns occurred.
The report calls for thorough steps to protect the cooling and power systems of power plants from tsunamis and for installation of an emergency power source in a safe place.
The report calls on the utility to ensure that it has ways to cool reactors in case of further accidents.
The report does not contain an in-depth examination of the utility’s failure to immediately submit to the government the firm’s 2008 estimate that a tsunami higher than 10 meters could hit the plant. The utility has said it did not submit the estimate immediately because it was based on a groundless hypothesis. The firm eventually submitted the estimate only 4 days before the March 11th disaster.
Much remains unknown about how workers tried to cool the plant’s Number 1 reactor — where a meltdown occurred — or why the Number 2 reactor ended up releasing a large amount of radioactive materials.
Kawauchi Village mayor reports on Chernobyl visit (NHK, Dec 2, 2011)
The mayor of a village near the crippled Fukushima Daiichi nuclear power plant has called on villagers to do their part to recover from radioactive contamination.
Mayor Yuko Endo of Kawauchi Village was speaking on Friday at a meeting to report on his recent visit to areas of former Soviet republics that were heavily contaminated in the 1986 Chernobyl nuclear accident.
About 60 people, including Kawauchi villagers, attended the meeting in Koriyama City, more than 30 kilometers away from the village.
Endo said that children in the areas affected by the Chernobyl accident are measuring radiation levels in food and that villagers are working on farms using a contamination map produced by the local administration.
The mayor said people he met had advised that residents of the affected areas should do whatever they can for themselves, no matter how seemingly trivial.
Endo called on the villagers to voluntarily do what they can, so they can return home as early as possible.
Most of the Kawauchi villagers are currently living outside of the village to avoid radioactive contamination. The village is aiming to see all evacuees return to the affected areas by March next year.
A man in the audience said the mayor’s report was very useful, adding he will carefully do his best.
Exposure didn’t sicken plant boss: doc (Japan Times, Dec 3, 2011)
A radiation medicine expert has concluded the former head of the Fukushima No. 1 nuclear plant did not become ill as a result of radiation exposure, Tokyo Electric Power Co. said Friday.
Makoto Akashi, executive director of the National Institute of Radiological Science, reviewed the cumulative amount of radiation Masao Yoshida, 56, was exposed to since the nuclear crisis started in March and informed Tepco of his view Thursday night, the utility said. Yoshida was relieved of his post Thursday to undergo medical treatment. He was hospitalized Nov. 24.
There has been much speculation that his illness was caused by excessive radiation exposure, as he had led efforts to contain the disaster at the Fukushima No. 1 plant after the March 11 earthquake and tsunami knocked out three reactors.
But the utility again declined to disclose further details on Yoshida’s illness or his cumulative radiation exposure since the nuclear crisis started, citing privacy reasons.
After Fukushima, Now More Than Ever (NY Times, Dec 2, 2011)
After the accidents at the Fukushima Daiichi nuclear power plant in Japan, the role of nuclear energy is again at a turning point — the third since the birth of the industry in the 1950s. Views about its future are pulled between the fear of nuclear destruction and the need for energy. Memories of Hiroshima and the Cold War, while fading, can still induce anxiety. The accident at Fukushima also brought the Soviet-era disaster of Chernobyl back to mind. .. Read more here.
High radiation at Japan nuke plant (SIASAT Daily, Dec 2)
“The operator of Japan’s damaged Fukushima nuclear power plant has detected high levels of radioactive caesium in the seabed of the port where the plant is located.
The Tokyo Electric Power Co (TEPCO) recorded the highest concentration of radioactive caesium in an area just south of the water intakes for reactors, Kyodo News Agency reported.
The utility attributed the deposits to the leak of highly radioactive water into the sea in April, following the nuclear emergency at the plant.” …