[ RadSafe ] Workers find ultra-high radiation levels at Fukushima Daiichi plant

Michael LaFontaine, P. Phys. physics at execulink.com
Wed Aug 3 08:47:59 CDT 2011

    * By Tsuyoshi Inajima and Kari Lundgren
    * Tue Aug 2 2011

Note - the 10 Sv/h dose rate was the upper limit 
of the GM meters used for the measurements.

Second deadly radiation leak reported at Japanese reactor

TOKYO ­ Tokyo Electric Power Co. reported its 
second deadly radiation reading in as many days 
Tuesday at its wrecked Fukushima nuclear plant north of Tokyo.

Tepco said Tuesday it detected 5 sieverts of 
radiation per hour in the No. 1 reactor building. 
On Monday in another area it recorded radiation 
of 10 sieverts per hour, enough to kill a person 
“within a few weeks” after a single exposure, 
according to the World Nuclear Association.

Radiation has impeded attempts to replace cooling 
systems to bring three melted reactors and four 
damaged spent fuel ponds under control after a 
tsunami on March 11 crippled the plant. The 
latest reading was taken on the second floor of 
the No. 1 reactor building and will stop workers entering the area.

“This does emphasize what care has to be taken,” 
Richard Wakeford, a visiting professor of 
epidemiology at the University of Manchester’s 
Dalton Nuclear Institute in England, said in a 
telephone interview. “They have to put robots 
into those areas where they might expect high 
radiation levels. It’s no real substitute for human access.”

The 10 sieverts of radiation detected on Monday 
outside reactor buildings was the highest the 
Geiger counters used were capable of reading, 
indicating the level could have been higher, 
Junichi Matsumoto, a general manager at the utility, said at a news conference.

“In the area surrounding the breach of 
containment you’d expect high levels of 
contamination and those high levels would be 
difficult to predict,” Wakeford said. “You can 
dig them up if they’re on the soil and contain it 
or wash it down if it’s on the side of a building.”

Tepco was forced to pump water into the three 
reactors after the March 11 earthquake and 
tsunami disabled cooling systems. The company in 
May estimated there would be 200,000 tons of 
radiated water in basements and other areas of 
the Fukushima Dai-ichi plant by December.

“If nuclear fuels melted through containment 
chambers, Tepco will find even higher radiation 
readings after water in building basements is 
removed,” said Tetsuo Ito, the head of the Atomic 
Energy Research Institute at Kinki University.

Tepco has been criticized by the government for 
withholding radiation data and other missteps 
that have compounded the crisis, which led to 
160,000 people being evacuated from near the plant.

Radiation leaks from the Fukushima reactors have 
spread over 600 square kilometres, Tomio Kawata, 
a fellow at the Nuclear Waste Management 
Organization of Japan, said in a research report 
published on May 24 and given to the government.

Radioactive soil in pockets of areas outside the 
exclusion zone around the plant have reached the 
same level as in Chornobyl following a reactor 
explosion in the former Soviet Union territory 25 years ago, the report said.

The threats to Japan’s food chain are also 
multiplying as radioactive cesium emissions from 
the Fukushima plant spread. Contaminated beef has 
been found on supermarket shelves around the 
country, forcing the government to ban cattle 
shipments from areas in northern Japan.

The latest high radiation readings are probably 
coming from materials released during early 
failed attempts to release pressure in 
containment vessels and vent hydrogen gas to 
prevent explosions that damaged reactor 
buildings, Matsumoto said. There were about 2,760 
workers at the plant on Aug 1.

Tepco on April 17 set out a so-called road map to 
end the crisis by January, aiming to bring down 
radiation levels at the plant within three months 
and then achieve a so-called cold shutdown where 
reactor temperatures fall below 100 degrees Celsius.

Bloomberg News

At 01:57 PM 02/08/2011, you wrote:
>Workers find ultra-high radiation levels at Fukushima Daiichi plant
>Tokyo (CNN) -- The operator of Japan's crippled 
>Fukushima Daiichi nuclear plant has detected the 
>highest radiation levels at the facility since 
>the initial earthquake and tsunami five months 
>ago, a company spokesman said Tuesday.
>The ultra-high levels of radiation were measured 
>Monday afternoon on the grounds of the facility, 
>between reactors No. 1 and 2, Tokyo Electric 
>Power Company spokesman Naoki Tsunoda. The 
>lethal radiation was found at the bottom of a ventilation tower.
>The power company immediately cordoned off the 
>area and is currently investigating the cause of 
>the high radiation and how it will affect the 
>recovery work at the plant, Tsunoda said.
>The radiation levels -- 10,000 millisieverts per 
>hour -- are high enough that a single 60-minute 
>dose would be fatal to humans within weeks.
>The Fukushima Daiichi disaster occurred when a 
>15-meter (48-foot) tsunami inundated the coastal 
>plant after northern Japan's historic March 11 earthquake.
>The flooding knocked out the cooling systems for 
>the three operating reactors and their 
>associated spent fuel pools, causing the 
>reactors to overheat and hydrogen gas explosions 
>that blew apart the building housing reactors No. 1 and 3.
>Another hydrogen blast is believed to have 
>damaged the inside of the No. 2 reactor, while 
>engineers are struggling to manage an estimated 
>100,000 tons of highly contaminated water that 
>was used to cool the reactors during the emergency.
>Tokyo Electric Power Company projects the 
>situation won't be fully over until sometime 
>between October and January. The disaster has 
>caused Japan to rethink its commitment to 
>nuclear energy, and Germany has since announced 
>plans to abandon atomic power entirely by 2022.
>Sander C. Perle
>Mirion Technologies
>Dosimetry Services Division
>2652 McGaw Avenue
>Irvine, CA 92614
>+1 (949) 296-2306 (Office)
>+1 (949) 296-1130 (Fax)
>Mirion Technologies: http://www.mirion.com/
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Michael LaFontaine, P. Phys.  

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