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Radiation & Restoration Update

3 exposed to radiation:

http://english.kyodonews.jp/news/2011/03/80849.html

Kyodo News: March 25, 2011

Japan pushed ahead with work to restore power and key cooling functions at the crisis-hit Fukushima Daiichi nuclear plant Thursday despite three workers' exposure to radiation and black smoke observed from the No. 3 reactor causing some disruptions in the activities.

The government's nuclear safety agency said the work should go further ''with the least delay,'' while radioactive leaks from the crippled plant overshadowed various aspects of daily life in wider areas, most recently resulting in temporary warnings not to give tap water to infants in Tokyo some 220 kilometers away and the vicinity due to radioactive contamination.

With the black smoke found to be subsiding early in the morning, plant operator Tokyo Electric Power Co. resumed the restoration work, which was suspended from Wednesday afternoon, and succeeded in turning on the lights in the control room for the No. 1 reactor.

All six reactors at the plant, which was cut off from electricity after the March 11 earthquake and ensuing tsunami, had been reconnected to external power as of Tuesday night and workers are seeking to activate such equipment as data measuring tools. The No. 3 reactor control room saw lighting restored on Tuesday.

But part of the restoration work was suspended after three workers who were laying cable at the No. 3 reactor's turbine building were exposed to radiation amounting to 173 to 180 millisieverts. Two of them were hospitalized due to possible burns to their feet, the Nuclear and Industrial Safety Agency and Tokyo Electric officials said.

Given that the two had their feet in highly contaminated water, agency spokesman Hidehiko Nishiyama said that the incident has shown that workers should pay special attention to water in proceeding with their work, but added, ''We would like to find a delicate balance of keeping delay to the minimum and ensuring the safety of the people working there.''

With the three, a total of 17 workers have been exposed to radiation exceeding 100 millisieverts in the country's worst nuclear crisis. The 100 millisieverts is the limit workers are usually allowed to be exposed to in an emergency mission. The limit, however, has been raised to 250 millisieverts for the ongoing crisis.

The radiation level at the plant's entrance gate, which is about 1 km away from the No. 2 reactor, stayed around 200 microsieverts per hour throughout the day.

Efforts to cool down spent fuel pools of the No. 3 and No. 4 units also continued by pumping seawater through inner pipes, or by spraying water from outside the damaged part of the reactor building's outer shell. If water is not replenished, there is the risk of a massive release of radioactive substances.

Following the quake-tsunami disaster, the cooling functions failed at the No. 1, No. 2 and No. 3 reactors and their reactor cores partially melted, requiring seawater to be pumped in to prevent the fuel from being exposed.

The cooling functions of the pools storing spent nuclear fuel at the three units as well as at the No. 4 unit were also lost. The No. 4 reactor, halted for maintenance before the quake, has had all of its fuel rods stored in the pool for the maintenance work.

As a step to put the reactors under control, authorities are eager to replace seawater with fresh water in cooling the reactor cores, as crystallized salt could form a crust on the fuel rods and prevent smooth water circulation, thus diminishing the cooling effect.

''We used seawater to deal with the emergency situation...but basically fresh water should be put (in the reactor cores),'' Nishiyama said.

While the fight to regain control of the nuclear reactors continues, radiation contamination has been confirmed in vegetables, raw milk and tap water in areas near the plant and eastern Japan.

A day after the Tokyo metropolitan government warned that infants should not drink tap water in many parts of Tokyo, five cities in Saitama, Chiba and Ibaraki prefectures were also found to have had water contaminated with radioactive iodine at levels considered to be unsafe for infants to drink.

The iodine levels of 120 to 220 becquerels per 1 kilogram of water fell, however, below the limit of 100 becquerels for infants in water extracted Thursday as for the cases of Tokyo and Saitama, officials said.

The government said, meanwhile, it detected 2.54 million becquerels of iodine and 2.65 million becquerels of cesium, another radioactive substance, from weed leaves in the village of Iitate in Fukushima Prefecture about 40 km northwest from the nuclear plant, far above the provisional limits for food of 2,000 becquerels for iodine and 500 becquerels for cesium.

Abnormally high levels of these materials were also detected again in the sea near the plant, TEPCO said, warning the radiation levels in seawater may keep rising.

Chief Cabinet Secretary Yukio Edano suggested that the government may consider the possibility of moving people beyond the 30 km radius as the crisis prolonged.

The government has set the exclusion zone covering areas within a 20 kilometer radius of the plant, and urged people within 20 km to 30 km to stay indoors, but Edano said he has heard that people ordered to stay indoors are feeling that they are ''out of reach of supplies.''