Plutonium detected in soil outside Fukushima nuke plant

TOKYO (Kyodo) — A small amount of plutonium believed to have been
emitted from the crippled Fukushima No. 1 nuclear plant has been
detected in soil outside the plant, a researcher at a university said
Sunday.

It is the first time that plutonium believed to have been spewed from
the Fukushima plant damaged by the March 11 mega earthquake and tsunami
has been detected in soil outside the plant.

Masayoshi Yamamoto, professor at Kanazawa University, said, however, the
level of the plutonium detected in samples of soil collected in the town
of Okuma in Fukushima Prefecture, about 1.7 kilometers from the front
gate of the nuclear plant, is lower than the average level of plutonium
observed in Japan following past bomb nuclear tests abroad.

The Ministry of Education, Culture, Sports, Science and Technology found
a small amount of plutonium in soil outside the plant in an earlier
survey but the substance was believed to have been emitted in such
nuclear bomb tests elsewhere.

But by analyzing the proportion of three types of isotopes in the
plutonium, Yamamoto determined that the substance was emitted from the
crippled Fukushima plant and was not from past nuclear bomb tests elsewhere.

The soil samples were collected by a team of researchers of Hokkaido
University before April 22. The government designated the town within
the 20-kilometer radius from the plant as a “no-go” zone where residents are barred from entry, Yamamoto said.

Kyodo, June 6, 2011
http://mdn.mainichi.jp/mdnnews/national/news/20110606p2g00m0dm011000c.html

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 Radioactivity of materials released in Fukushima nuclear crisis revised upward

The Nuclear and Industrial Safety Agency (NISA) on June 6 revised the
level of radioactivity of materials emitted from the crisis hit
Fukushima No. 1 Nuclear Power Plant from 370,000 terabecquerels to
850,000 terabecquerels.

The Cabinet Office’s Nuclear Safety Commission of Japan (NSC) had
estimated that the total level of radioactivity stood at around 630,000
terabecquerels, but this figure was criticized as an underestimation.
NISA officials plan to present the new figure at a ministerial meeting
of the International Atomic Energy Agency (IAEA) after reporting it to
the NSC.

The NSC and NISA, which operates under the Ministry of Economy, Trade
and Industry, announced a figure for the total amount of radioactivity
on April 12, when the severity of the Fukushima nuclear crisis on the
International Nuclear Events Scale was raised to level 7, matching that
of the Chernobyl nuclear accident. In the Chernobyl accident, the total
amount of radioactivity reached 5.2 million terabecquerels.

The NSC calculated the amount of radioactive materials released into the
air between the outset of the crisis and April 5, based on the amount of
radiation from measurements taken near the plant. NISA based its
calculations on the state of the plant’s reactors.

The latest figure takes into consideration the release of radioactive
materials during explosions at the plant’s No. 2 and 3 reactors. The
INES scale designates leaks of tens of thousands of terabecquerels as
level 7 events, and the seriousness of the disaster on the scale will
not change as a result of NISA’s revision of the amount.

Mainichi Shimbun , June 6, 2011
http://mdn.mainichi.jp/mdnnews/national/news/20110606p2a00m0na009000c.html

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 Japan mulls evacuating radiation ’hot spots’

TOKYO (Kyodo) — The government is considering expanding the scope of its evacuation order to include people from certain spots that are emitting high levels of radiation as a result of the nuclear accident at the Fukushima No. 1 power plant in March, government officials said.

The government will be discussing with municipalities these so-called “hot spots”’ suffering from radiation exposure that would exceed the yardstick of 20 millisieverts during the course of a year.

A hot spot refers to an area that has a high level of radiation following rain or as a result of landscape or wind conditions that affect the direction in which radioactive materials travel after being released into the air.

Normally, radiation spreads concentrically but under such conditions, radioactive materials spread randomly to various spots.

Top government spokesman Yukio Edano said at a news conference there are certain spots, other than the government-designated evacuation areas, where radiation levels are high depending on atmospheric and other conditions, and the government will boost monitoring at these locations.

“Based on the outcome of (radiation) monitoring, we will consider taking appropriate action,” the chief Cabinet secretary told a news conference, hinting at the possible evacuation of these areas.

Separately, Deputy Chief Cabinet Secretary Tetsuro Fukuyama told an opposition lawmaker that some parts of Minamisoma city in Fukushima have registered high levels of radiation, and the government will consult with the mayor and other officials on whether or not to evacuate the residents there.

Following the devastating March 11 earthquake and tsunami that triggered a nuclear emergency, the government ordered the evacuation of people living within 30 kilometers of the Fukushima Daiichi plant, which lost its key cooling functions and continues to spew radiation.

The government has since prohibited people from entering areas within a 20-kilometer radius of the crippled Fukushima plant and added some towns outside the limit to the list of areas covered by its evacuation directive due to concerns over high levels of radiation exposure.

Kyodo, June 7, 2011
http://mdn.mainichi.jp/mdnnews/news/20110607p2g00m0dm013000c.html

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 NISA doubles early fallout estimate

NISA on Monday more than doubled its estimate of the radioactive material ejected into the air in the early days of the Fukushima nuclear crisis to 770,000 terabecquerels.

The nuclear safety agency also issued its own assessment of the cores in reactors 1, 2 and 3 at the Fukushima No. 1 power plant, assuming that all of them melted, and said it was possible the meltdowns in units 1 and 2 happened faster than the time frame estimated by Tokyo Electric Power Co.

The assessment by the Nuclear and Industrial Safety Agency is expected to be reflected in Japan’s report on the accident at a ministerial meeting being hosted by the International Atomic Energy Agency later this month.

In April, Japan raised the severity level of the crisis to 7, the maximum on the International Nuclear Event Scale, putting it on par with the 1986 Chernobyl disaster.

At the time, NISA believed that 370,000 terabecquerels of radioactive material had been ejected from reactors 1, 2 and 3. That was revised Monday after NISA found that more material escaped from reactor 2 than thought.

Level 7 accidents correspond to the external release of material equal to tens of thousands of terabecquerels of radioactive iodine 131. One terabecquerel equals 1 trillion becquerels.

NISA said the melted fuel in reactor 1 fell to the bottom of the pressure vessel and damaged it at about 8 p.m. on March 11, about five hours after the quake. In reactor 2, a similar event took place at about 10:50 p.m. March 14, it said.

However, Tepco says the pressure vessel in reactor 1 was damaged on the morning of March 12, and the pressure vessel in reactor 2 in the early hours of March 16.

A NISA official said the assessments vary due to different water injection assumptions.

Kyodo, June 7, 2011
http://search.japantimes.co.jp/cgi-bin/nn20110607a2.html

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 Trace of Activities Found at Neglected Fault in Fukushima

Tokyo, June 6 (Jiji Press)—Japan’s nuclear safety agency said Monday that it has found a trace of activities at a fault long considered inactive near the crippled nuclear power station in Fukushima Prefecture.

The 13.5-kilometer-long Yunotake fault, about 50 kilometers southwest of Tokyo Electric Power Co.’s <9501> Fukushima No. 1 plant at the center of the country’s ongoing nuclear crisis, has emerged on the ground surface, the Nuclear and Industrial Safety Agency said.

The fault is seen to have moved in a major aftershock on April 11 of the 9.0-magnitude earthquake that ravaged northeastern Japan areas on March 11.

The plant’s operator has so far assessed that the fault is not active and can be neglected in designing a nuclear power plant and studying its seismic resistance, and the regulator has seen the assessment reasonable.

In the face of the massive earthquake and a spate of aftershocks, the nuclear safety agency ordered nuclear plant operators on April 28 to list faults that they have neglected.

Jiji Press, June 6, 2011
http://jen.jiji.com/jc/eng?g=eco&k=2011060600455

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