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Radiation Surges at Reactor as Tests for Plutonium Ordered

27/03/2011
The Fukushima 1 NPP

Image via Wikipedia

Radiation in water at Japan’s earthquake-damaged nuclear plant reached potentially lethal levels, hampering work to cool reactors.

As the worst atomic accident since Chernobyl entered its third week, the government said soil near the Fukushima plant would be tested for plutonium contamination. The radioactive metal was used in one of the reactors and its presence outside the plant would suggest the fuel rods were damaged.

Water in the Fukushima Dai-Ichi No. 2 reactor’s turbine building was measured at more than 1,000 millisieverts per hour, Japan’s nuclear safety agency said today. That’s higher than the dose that would cause vomiting, hair loss and diarrhoea, according to the World Nuclear Association. The radiation is 10 million times the plant’s normal level, broadcaster NHK said.

“They’re finding quite high levels of radiation fields, which is impeding their progress dealing with the situation,” said Richard Wakeford, an expert in radiation epidemiology at the U.K.’s Dalton Nuclear Institute in Manchester. At reactor 2, “you’d have a lot of difficulty putting anyone in there.”

Efforts to gain control over the damaged plant have been hampered by radiation leaks, forcing repair work to be suspended and engineers to rotate shifts. Two men who were exposed to radiation had “significant” skin contamination on their legs, the International Atomic Energy Agency said.

‘Won’t Immediately Improve’

“I’ve said the situation won’t immediately improve, and high radiation water is one of the unexpected things that I had said might occur,” Chief Cabinet Secretary Yukio Edano said at a briefing in Tokyo today. “We want to continue cooling, and establish a direction toward ending the situation.”

Soil samples have been taken and will be tested for plutonium, Edano told reporters.

Radiation leaks have contaminated vegetables in regions around the plant and sparked scares over tap water in Tokyo, 227 kilometers (140 miles) southwest of the Tokyo Electric Power Co. Dai-Ichi power station.

The number of dead and missing from the March 11 earthquake, tsunami and subsequent aftershocks reached 27,110 as of 10 a.m. Tokyo time. The government is struggling to relieve hundreds of thousands of people left homeless or without essential services and food and water.

Radiation in water was found in only one out of three Tokyo water purification plants based on samples taken today, the Tokyo metropolitan government said. Two out of three facilities detected radioactive levels yesterday.

Purification Plant

The only water purification plant that found radiation was the Asaka plant in Saitama, north of Tokyo, where the reading of radioactive iodine-131 fell for a second day to 27 becquerels per kilogram of water.

The levels of iodine-131 were within the 300 becquerels per kilogram limit set by the Nuclear Safety Commission of Japan for a fifth day. The levels have been below 100 becquerels per kilogram, a level that is safe for infants, for a fourth day.

The workers exposed to radiation at the Fukushima Dai-Ichi nuclear power plant are “walking and talking” as usual, Hiroko Imazeki, a spokeswoman for the institute, said today.

One of Dai-Ichi’s six reactors achieved “cold shutdown” status, where the temperature inside the core dropped below 100 degrees Celsius. One was shut for maintenance at the time of the quake, while the other four are at the center of the battle to contain leaks and overheating.

Fresh Water

“In the first eight days you were in a cycle where you’re trying to deal with the decay heat,” Robin Grimes, a professor of materials physics at Imperial College in London, said by phone. “Now, 90 percent of that energy has decayed away, so there is no longer a risk of something suddenly happening; things are going to change much more slowly.”

Tokyo Electric, or Tepco, is also starting to switch to fresh water for its cooling efforts of spent fuel rods and the reactor core to prevent further salt corrosion.

Tepco switched to using fresh water to cool the No. 2 reactor at 10:10 a.m. local time, and began draining excess water from the turbine building of the No. 1 unit, Tepco Vice President Sakae Muto said. The company, which is considering a similar operation on the No. 2 and No. 3 turbine houses, announced that it had to suspend the draining work because of high radiation levels.

“They clearly have not succeeded in re-establishing anything like a normal cooling function,” said Peter Bradford, a former member of the U.S. Nuclear Regulatory Commission. “It looks as though that’s still some time off, given the fact that they’ve had to slow down because of the high radiation levels on site.”

Radioactive Nuclides

Radioactive nuclides including cesium-136 and yttrium-91 were found in water at the turbine building of the No. 1 reactor, the Japanese nuclear agency said in a statement on its website. Three workers were exposed to radiation on March 24 after stepping in water at the No. 3 unit, which indicated a possible leakage from the reactor core, the agency said.

The nuclear agency said it doesn’t believe there is a physical crack in the pressure or containment vessels, which surround the core of the No. 3 reactor. Leakage may be coming from pipes connected to the reactor.

The March 11 quake left the plant without power needed to cool nuclear fuel rods. The government has advised more people living close to the nuclear site to evacuate because basic goods are in short supply, while assuring them that radiation levels hadn’t risen in the area.

Source: www.businessweek.com 

 

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