Thursday, August 25, 2011

Fukushima catastrophe - Disaster beyond imagining

Areas close to Japan’s Fukushima Dai Ichi nuclear facility are likely to remain off-limits for “several decades” due to high levels of radioactive contamination, even if the government lifts the 20-kilometer no-go zone currently in place.

Japan’s Fukushima Daiichi nuclear facility continues to impact the country’s citizenry, and new reports indicate the negative impact within 3 kilometers of the plant will likely last for decades, confirming what many had already believed: the disaster is far greater than government officials have previously indicated. Citing unnamed government sources, Japan’s Yomiuri Shimbun reports the no-entry zone will probably include parts of Okumamachi and Futabamachi, both located in Fukushima Prefecture and both lying within the new 3-kilometer no-entry zone initiated by the Japanese government on Monday. Japan’s Education, Culture, Sports, Science and Technology Ministry (MEXT) estimates cumulative radiation levels at the plant since the triple meltdown occurred will greatly exceed 20 millisieverts at 35 locations primarily in Okumamachi and Futabamachi. Designation of an expanded evacuation zone is based on the benchmark of 20 millisieverts. The ministry took radiation level measurements at 50 no-entry zone locations and found the Koirino district of Okumamachi, located three kilometers southwest of the plant, was estimated to reach 508.1 millisieverts. In Ottozawa, the calculation was 393.7 millisieverts. Prime Minister Nato Kan will be holding talks with local government leaders in the impacted areas and issue an apology for the prolonged evacuation. The Japanese government is contemplating using locations around the Daiichi facility as temporary storage areas for radioactive waste, including the sludge and debris remaining from the attempt at treating contaminated water. “I can't deny the possibility that it may be difficult for residents from some areas to return home for a long time. I deeply apologize for that,” said Chief Cabinet Secretary Yukio Edano, Agence France-Presse reports. The government declared a no-entry zone in April after the Daiichi plant suffered the nuclear meltdowns on March 11 from a deadly earthquake and ensuing tsunami. The plan at that time was to lift the no-entry zone next January, a time which the plant’s operator, Tokyo Electric Power Co. (TEPCO), said it would bring the facility to a cold shutdown, or stable condition. News of the decades-long no-go zone, however, means Japanese citizens who lived within three kilometers of the plant will now be forced to seek permanent living quarters elsewhere.

 The First Quantitative Estimate of Fukushima Radiation Leak

In an attempt to clear some confusion and understand exactly how much radiation actually leaked from the damaged nuclear reactor at the Fukushima Daiichi nuclear plant in Japan on March 11, atmospheric chemists at the University of California, San Diego, have produced the first quantitative estimate of how much radiation actually leaked from the reactor.

Mark Thiemens, study leader and Dean of the Division of Physical Sciences at UC San Diego, along with post-doctoral researcher Antra Priyadarshi, and a team of researchers, observed the amount of radioactive sulfur in the air soon after the earthquake in Japan and was able to report a quantitative measurement of the amount of radiation leaked.

When fuel rods melt, products like neutrons leak from the fuel rods. Seawater is used to cool the hot reactors, and absorbs the leaked neutrons. These neutrons "collide" with chloride ions in the seawater, which results in the loss of a proton out of the nucleus of a chloride atom and turns the atom into a radioactive form of sulfur. Most of this vaporizes into steam when the saltwater comes into contact with the hot reactors, and to avoid explosions due to the collection of hydrogen, operators vent the steam into the atmosphere. Once in the air, the sulfur reacts with oxygen to create sulfur dioxide gas and eventually sulfate particles.

On the other side of the Pacific Ocean in La Jolla, California on March 28, 2011, Thiemens and his team noticed an "unprecedented spike" in radioactive sulfur in the air. They used a model, which was based on the NOAA's observations of atmospheric conditions, to determine the path the air took to get to California over the previous 10 days, and found that it had come from Fukushima Daiichi.

The next step was to calculate how much radiation had leaked from the reactor based on the path over the Pacific Ocean. They took into account that some sulfate particles had fallen into the ocean or decayed along the way, and concluded that 400 billion neutrons were released per square meter surface of the cooling pools. They predicted that this occurred between March 13, 2011 and March 20, 2011. March 13 was when operators began flooding the reactor with seawater.

"You know how much seawater they used, how far neutrons will penetrate into the seawater and the size of the chloride ion," said Priyadarshi. "From that, you can calculate how many neutrons must have reacted with chlorine to make radioactive sulfur."

To achieve the levels observed in California, the team said the concentrations a kilometer above the ocean close to Fukushima must have been 365 times above normal levels. Over the four days that the team took measurements, which ended March 28, Thiemens measured 1501 atoms of radioactive sulfur in sulfate particles per cubic meter of air. They mentioned that this was the highest they had seen in two years of observations and recordings.

According to the researchers, the radioactive sulfur observed was produced by partially melted nuclear fuel in the storage ponds or reactors. While cosmic rays can produce radioactive sulfur, the team noted that these rays rarely mix into the layer of air right above the ocean.

Despite the high levels of radioactive sulfur recorded in California, Thiemens and his team said these levels were not dangerous to human health.

"Although the spike that we measured was very high compared to background levels of radioactive sulfur, the absolute amount of radiation that reached California was small," said Thiemens. "The levels we recorded aren't a concern for human health. In fact, it took sensitive instruments, measuring radioactive decay for hours after lengthy collection of the particles, to precisely measure the amount of radiation.

Sea water contamination 

The State Oceanic Administration's environmental protection department told that China will strengthen its monitoring for radioactive substances in the waters east of Fukushima, where the nuclear plant is, and in the East China Sea. By doing so, they hope to forecast what effect the radiation released by the plant will have on the marine environment and the safety of marine food.
The latest monitoring result released by the State Oceanic Administration on July 29 showed the first group of seawater samples collected from the area contained 300 times the amount of radioactive cesium that is found in nature and 100 times the amount of strontium.
The quality of the water and air in China haven't been affected so far by the radiation, the department said.
From June 16 to July 4, the administration sent a supervision team to look for radioactive materials in the waters east of Fukushima. They monitored an area encompassing 252,000 square kilometers, collecting large amounts of water, air and marine organisms during that time.
The test results will be gradually made public, according to the State Oceanic Administration.
In April, Tokyo Electric Power Co, the owner of the Fukushima Daiichi nuclear plant, announced plans to discharge about 11,500 tons of low-level radioactive water from the plant into the sea.
About 60,000 tons of water have been used to lower the temperature of the six reactors at the plant. The March earthquake and subsequent tsunami caused some of the plant's reactor cores to melt down after fuel rods there had become overheated, according to the Fukushima Nuclear Accident Update Log that was released by the International Atomic Energy Agency on April 11.
The State Oceanic Administration said the marine organisms in the places that are being monitored have been contaminated to different extents. Those that live near the surface are at a greater risk of being affected.
Cesium-137 and strontium-90 both have half-lives of about 30 years, making it more likely they will eventually enter the food chain and affect the health of consumers, the environmental protection department said.
Researchers will continue to try to protect public health by monitoring and gauging the effect of the radiation release on China's marine environment, according to the department.

Fukushima Japan Radiation Spreads Worldwide by Arnie Gundersen 8 22 11 

Crew from the Greenpeace ship, The Rainbow Warrior, collect sea water samples to monitor radiation contamination levels as the ship sails up the eastern coast of Japan, in the vicinity of Fukushima. © Jeremy Sutton-Hibbert / Greenpeace

Japan. Crew from the Rainbow Warrior collect sea water samples and monitor radiation contamination levels as the ship sails up the eastern coast of Japan, in the vicinity of the Fukushima nuclear disaster.

Fukushima Daiichi Sea Water Purification Equipment

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