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Saturday, March 26, 2011
Injuries point to fuel rod damage in No. 3
Radiation in basement water 10,000 times above normal
The fuel rods in the Fukushima No. 1 nuclear plant's No. 3 reactor, including MOX, may be damaged, based on the highly radioactive water that injured two workers and exposed a third the previous day, the nuclear safety agency said Friday.
Although nothing is definite, "it is highly likely that some fuel rods have been damaged" and that radioactive material leaked into the water, Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency said. MOX is mixed oxide fuel made from uranium and plutonium.
The radiation level of the water was 3.9 million becquerels per cu. centimeter, or 10,000 times stronger than water from a healthy reactor would be, Nishiyama said.
The three workers were setting up cables in the basement of the No. 3 reactor's turbine building Thursday when they stepped into about 15 cm of contaminated water.
Two of them got soaked because they were not wearing high boots and received beta ray burns from the water. They were sent to the National Institute of Radiological Sciences in Chiba for further examination, according to Tokyo Power Electric Co., operator of the troubled plant.
The other worker was sent along as well because he was exposed to high radiation.
Altogether, the three received 170 to 180 millisieverts of radiation; the amount measured at the surface of the water was more than double at 400 millisieverts.
Although exposed to radioactive materials to some extent, Nishiyama said water inside a healthy reactor normally doesn't have high radiation levels because the fuel rods are encased in zirconium.
The maximum allowable dose for a nuclear plant worker is now 250 millisieverts. The previous threshold of 100 millisieverts was raised after the crisis worsened.
The radioactive water is driving speculation that reactor 3 was damaged. Nishiyama said that was unlikely because it still has pressure.
Puddles of contaminated water were also seen in the turbine buildings of reactors 1 and 2.
There are now indications that the government will raise the crisis level for the event, now at 5, to level 6, putting it above the Three Mile Island incident. The 1986 Chernobyl disaster tops the international scale at level 7.
Nishiyama said that NISA, which is under the Ministry of Economy, Trade and Industry, verbally reprimanded Tepco and told it to take better care of its employees.
Tepco was told to give workers detailed instructions about how to act and what to wear in the deadly environment. Measuring radiation levels before starting work is also vital, Tepco was told, as only one of the three workers was wearing tall boots in the flooded basement.
Despite Thursday's accident, efforts to contain the crisis continued Friday as workers checked the cooling systems for the reactors and for the storage pools containing spent fuel rods.
Nishiyama said reactors No. 1 and No. 2 are being injected with seawater but that efforts are under way to use fresh water to minimize corrosion and other damage that saltwater can cause. The No. 1 and No. 3 reactors were switched to fresh water later in the day.