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Posts tagged ‘radiation’

Cesium spikes in Tokyo Bay samples; Contamination linked to Fukushima plant; no immediate threat to health

Sludge samples taken at the mouths of two major rivers emptying into Tokyo Bay showed radioactive cesium contamination linked to the Fukushima No. 1 nuclear plant crisis grew by 1.5 to 13 times since August, a researcher at Kinki University said Monday.

The contamination poses no immediate health risk since no seafood from Tokyo Bay has seen contamination levels exceed the government-set threshold. But close, long-term monitoring of the seabed mud is needed, said Hideo Yamazaki, professor at Kinki University’s Research Institute for Science and Technology.

“Contamination is flowing into the bay from rivers, including the Edogawa River, where cities with high radiation levels like Kashiwa (in Chiba Prefecture) are located upstream,” Yamazaki told The Japan Times.

“Contaminated sludge appears to be . . . accumulating on the bottom at the mouth of the rivers,” he added.

Yamazaki, an expert on how radiation and chemical substances impact the environment, and his team took the samples at three locations at the mouths of the Arakawa and Edogawa rivers on April 2 following studies carried out in August.

Samples of mud pulled from 1 meter below the seabed at the sites turned up cesium contamination ranging from 7,305 to 27,213 becquerels per square meter. The August readings were between 578 and 18,242 becquerels per square meter.

Yamazaki noted a thirteenfold rise was detected in a spot where the August readings were relatively low. He said, however, the contamination does not pose a health threat, even if a child were to play in the water.

Although radioactive mud will continue to flow into the bay, the peak contamination concentrations should be within the next couple of years, considering that the half-life of cesium-134 is about two years, Yamazaki said.

“If the contamination were to spread to fish, it is possible that radioactive isotopes could accumulate when bigger fish feed on smaller ones,” he said. “We’re scheduled to continue our monitoring in the following years” to study such cases.


‘Hot spots’ detected at 20 schools


FUKUSHIMA — More than 20 schools in Koriyama, Fukushima Prefecture, have radiative “hot spots” on their premises, a civic group said Sunday.

The finding was based on city board of education documents obtained through an information disclosure request, it said.

The board instructed elementary and junior high schools as well as nursery schools in January to check air radiation levels in side ditches, hedges and drains on their premises. Schoolyards and classrooms were excluded as the levels there have been regularly examined.

Reports submitted by each school in April showed at least 14 elementary and seven junior high as well as five nursery schools have hot spots where the cumulative annual radiation dose could reach 20 millisieverts, or more than 3.8 microsieverts per hour.

At the start of the new academic year in April, the board of education lifted a restriction that had limited students to playing in schoolyards for less than three hours per day due to the Fukushima No. 1 nuclear plant disaster that started last year.


Fukushima air to stay radioactive in 2022

FUKUSHIMA — A decade from now, airborne radiation levels in some parts of Fukushima Prefecture are still expected to be dangerous at above 50 millisieverts a year, a government report says.

The report, which contains projections through March 2032, was presented by trade minister Yukio Edano Sunday to leaders of Futaba, one of the towns that host the crippled Fukushima No. 1 power plant.

The report includes radiation forecasts for 2012 to 2014, and for 2017, 2022 and 2032, based on the results of monitoring in November last year. It was compiled to help municipalities draw up recovery and repopulation programs for the nuclear disaster.

The forecasts do not take into account experimental decontamination efforts.

Earlier this month, the government designated areas where annual radiation dosage exceeds 50 millisieverts as those likely to remain off-limits to evacuees in the near term.

The report said that annual radiation levels in March 2022 will probably exceed 50 millisieverts in some of the areas, including Futaba and Okuma, the other town that hosts the radiation-leaking plant.

In another meeting between the central and local governments, Reconstruction Minister Tatsuo Hirano presented a draft policy for reviving Fukushima that is based on a special reconstruction law that took force in March.

The draft said the central government will provide fiscal support to improve living conditions and revive the regional economy and communities.

The government plans to give Cabinet approval to the policy as early as May.


High radiation means delays in decommissioning crippled Fukushima reactors

The decommissioning process at the Fukushima No. 1 nuclear power plant faces a further obstacle after Tokyo Electric Power Co. said radiation readings in the containment vessel of the No. 2 reactor were at fatal levels on March 27.

It said readings were detected as high as 72.9 sieverts per hour, which would be fatal to humans in the event of a leak.

That is also enough to affect electronics in robots or other remote-controlled equipment used to probe the reactor ahead of final decommissioning.

Junichi Matsumoto, acting general director of TEPCO’s Nuclear Power and Plant Siting Division, said, “We believe it is the effect from the fuel (that melted) and leaked into the containment vessel. For the decommissioning operation, we will need to develop equipment that can withstand high radiation levels.”

The March 27 announcement marked the first time TEPCO directly measured radiation levels within the containment vessel of the No. 1 to No. 3 reactors where reactor meltdowns occurred a year ago.

TEPCO workers inserted an industrial endoscope into the containment vessel of the No. 2 reactor and measured radiation levels at eight locations. The highest reading of 72.9 sieverts was recorded about 4.2 meters from the bottom of the vessel.

After the Fukushima nuclear disaster flared, the highest radiation level recorded was about 10 sieverts per hour last August around piping near the main exhaust duct of the No. 1 and No. 2 reactors.

At that time, the high radiation was considered the result of fuel leaking during the venting process. The latest reading is not only much higher but reinforces the possibility that the decommissioning process will be prolonged.

High radiation levels can cause electronic parts to malfunction. The latest measurement throws another spanner in the works: Much more work will need to be done to decontaminate the area to reduce radiation levels.

Decommissioning of the No. 1 to No. 3 reactors will involve the unprecedented process of collecting nuclear fuel that has melted into the containment vessel.

Decommissioning was initially expected to take around 30 years, but that estimate will likely now have to be revised.


Survey finds soaring cesium level in soil in Iitate

Tuesday, March 20, 2012


The Environment Ministry said Monday that a soaring cesium reading of 154,000 becquerels per kilogram has been logged in soil from the village of Iitate, Fukushima Prefecture, the highest level yet.

According to the results of a January survey, the cesium reading came from soil taken from the banks of the Niida River in Iitate, which lies in the hot zone around the disaster-hit Fukushima No. 1 power plant, the ministry said.

The figure put the soil’s radiation above the level that requires incinerated ash to be buried in sites with ferroconcrete partitions, which is 100,000 becquerels.

The ministry survey, its third, was conducted from Jan. 5 to Jan. 27 to measure the density of cesium in water and soil at 179 points across the prefecture.

In the water portion of the survey, 8 becquerels of cesium per liter were detected in the Hirose River in the city of Date, but no cesium was detected at most points surveyed, the ministry said.

High level of radioactive cesium found in Okinawa noodles

High level of radioactive cesium found in Okinawa noodles

Air radiation drops after snowfall / But decontamination necessary, levels will rise once snow melts, experts say

The Fukushima prefectural government has received many inquiries because air radiation levels across the prefecture following the crisis at the Fukushima No. 1 nuclear power plant declined considerably late January and have since remained constant, perhaps due to fallen snow blocking radiation above the ground.

According to monitoring by the Education, Culture, Sports, Science and Technology Ministry and others, the rate of decline was particularly large in the Akougi district in Namie and the Nagadoro district in Iitate, located in the expanded evacuation zone around the nuclear plant.

Radiation measuring found that the Akougi district had a reading of 19.7 microsieverts per hour in the morning of Jan. 25, down from 30 microsieverts per hour recorded in the morning of Jan. 18.

Air radiation levels also decreased to 5.9 microsieverts per hour from 10 microsieverts per hour over the same period in the Nagadoro district.

It is believed there were no major changes in air radiation levels before Jan. 18 and after Jan. 25.

According to the ministry’s Nuclear Emergency Response Headquarters, the decline can be attributed only to snowfall since decontamination operations were not conducted in the areas at the time.

The Fukushima Meteorological Observatory said snow accumulation is not monitored in Namie and Iitate, but temperatures and other factors suggest the town and the village had snow from Jan. 20 to 22.

The prefectural emergency response headquarters said radiation levels also declined in the city of Fukushima. While such levels measured 0.84 microsievert per hour at 6 p.m. on Jan. 21 when snow began to fall, at 9 p.m. on Jan. 22, after snowfall, radiation levels in the air measured 0.62 microsievert per hour.

Farmer Masuo Kaneko, 63, who evacuated to the city from Nagadoro district, said after reading the newspapers he thought the radiation levels were dropping rapidly. But he was disappointed to hear the decline was due to snowfall.

“I expected radiation levels to halve in about two years time,” he said.

Tokyo Institute of Technology Associate Professor Keiji Saneyoshi said air radiation levels may halve if about 20 centimeters of snow falls in certain areas. “Yet decontamination work needs to continue since the levels will rise again once the snow melts,” Saneyoshi said.

Fukushima update – As temperature in pressure vessel rises, boric acid added to coolant to prevent chain reaction

Water rate increased for reactor 2

As temperature in pressure vessel rises, boric acid added to coolant to prevent chain reaction

Workers at the Fukushima No. 1 nuclear plant increased the amount of water injected into reactor 2 on Tuesday to the highest level since the plant achieved cold shutdown in December as concerns grew over rising temperatures at the bottom of the pressure vessel.

Following the move, the temperature in the vessel eased to 68.5 degrees by 5 p.m. from 73.3 degrees logged at 7 a.m. Monday, Junichi Matsumoto, a spokesman for Tokyo Electric Power Co., told a news conference.

“The temperature has apparently hit its peak and believed to be on the decline. We will continue to monitor the situation,” he said.

Tepco said it increased the amount of injected water, some of which contained boric acid, at 4:24 a.m. Tuesday. Reactor 2 is now being cooled with 13.5 tons of water per hour, up from 10.5 tons. The boric acid is being used to prevent a sustained nuclear chain reaction, or recriticality.

Nuclear disaster minister Goshi Hosono told reporters that Tepco is making every effort to lower the temperature.

Touching on last month’s change in the amount of coolant water for reactor 2 after pipes were replaced, a move that apparently affected the temperature, Hosono said, “This was a process to enhance stability, but it has become clear that there is a possibility (the replacement work created) an unstable situation temporarily. We have to consider matters in an even more careful way.”

Tepco changed pipes and the amount of coolant water in reactor 2 last month, and suspects the water did not sufficiently cover some parts of the pressure vessel, as only a small amount was injected through a pipe designed to take in large amounts.

Tepco’s Matsumoto said he believes reactor 2 remains in cold shutdown because the temperature is not rising continuously. Readings on two other thermometers at the bottom of the pressure vessel were around 40 degrees as of 10 a.m.

Tepco said it also believes recriticality probably did not occur because it did not detect radioactive xenon, which is generated as a result of nuclear fission.

The utility said it injected water containing boric acid, which works to suppress criticality, and will increase the amount of coolant water further.

Radioactive water leak “somewhat” higher than originally thought?

From the Japan Times – a masterpiece of understatement:

Pipe leaks water from reactor 4 fuel pool

Tepco discovers that 8.5 tons of radioactive coolant water leaked in reactor 4 at the Fukushima No. 1 nuclear plant, somewhat higher than its initial estimate of 6 liters, but says none flowed outside the building.

Cabinet kept alarming nuke report secret

Fearful of scaring public, existence of document was denied for months

The government buried a worst-case scenario for the Fukushima nuclear crisis that was drafted last March and kept it under wraps until the end of last year, sources in the administration said Saturday.

 After the document was shown to a small, select group of senior government officials at the prime minister’s office in late March, the administration of then Prime Minister Naoto Kan decided to quietly bury it, the sources said.

“When the document was presented (in March), a discussion ensued about keeping its existence secret,” a government source said.

In order to deny its existence, the government treated it as a personal document of Japan Atomic Energy Commission Chairman Shunsuke Kondo, who authored it, until the end of December, the sources said.

It was only then that it was actually recognized as an official government document, they said.

“The content was so shocking that we decided to treat it as if it didn’t exist,” a senior government official said.

A private-sector panel investigating the disaster at the Fukushima No. 1 nuclear plant intends to examine whether the government tried to manipulate information during its handling of the crisis.

The panel plans to interview Kan and Goshi Hosono, minister in charge of the nuclear crisis and Kan’s former adviser, among others.

Kondo drew up the document at Kan’s request and is dated March 25, 2011. The document forecast that in a worst-case scenario the plant’s crippled reactors would intermittently release massive quantities of radioactive materials for about a year.

The projection was based on a scenario in which a hydrogen explosion would tear through the No. 1 reactor’s containment vessel, forcing all workers at the plant to evacuate because of the ensuing lethal radiation levels.

The document said that in such an event, residents within a radius of 170 km of the power station, and possibly even further away, would be forced to evacuate. Those living within a radius of between 170 km and 250 km of the plant, including Tokyo, could chose to evacuate voluntarily. The wrecked power station is about 220 km northeast of the capital.

Kan admitted in September that a worst-case scenario for the disaster had been drawn up. After parts of it were leaked in December, his successor, Prime Minister Yoshihiko Noda, decided to start treating it as a Cabinet Office document.

“Because we were told there would be enough time to evacuate residents (even in a worst-case scenario), we refrained from disclosing the document due to fear it would cause unnecessary anxiety (among the public),” Hosono, the nuclear crisis minister, said at a Jan. 6 news conference.

The health ministry has not been keeping track of radiation that workers at the Fukushima No. 1 nuclear plant are exposed to while off-site or off duty, ministry officials said Saturday, prompting concerns that current systems to check exposure may be inadequate.

The health ministry also doesn’t check radiation doses that workers are exposed to during decontamination efforts around the wrecked No. 1 plant.

The ministry currently only keeps track of radiation exposure for the plant’s employees when they are engaged in work around the facility.

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