Female worker at nuke plant suffers radiation dose exceeding limit+

TOKYO, April 28 Kyodo -
Tokyo Electric Power Co. said Wednesday that one of its female employees was exposed to radiation doses far above the legal limit at the crisis-hit Fukushima Daiichi nuclear power plant -- the latest revelation of lax radiation management by the plant operator since the crisis erupted last month.
As a key step to bringing an end to the ongoing crisis, the utility said, meanwhile, it will seek to start in June decontamination of highly radioactive water accumulating in the plant's premises, which has prevented restoration work as a side effect of the emergency water injection into troubled reactors from outside in place of their lost cooling functions.
TEPCO as the firm is known also started to increase the amount of water injected into the damaged No. 1 reactor core in preparation to flood the reactor's primary containment vessel to cool the fuel inside in a stable manner.
The utility is trying to contain the country's worst nuclear disaster in line with a recently unveiled roadmap, which seeks to restore stable cooling of the reactors and spent fuel pools of the Nos. 1 to 4 units in about three months.
But in the latest sign of tough working conditions at the radiation-leaking plant, the firm said it found earlier in the day that one of its 19 female employees working at the plant when the March 11 quake and tsunami crippled it had been exposed to 17.55 millisieverts of radiation by March 23, against the legal limit of 5 millisieverts over a three-month period.
The woman, who is in her 50s, has no health problems, but two more female workers may also have been exposed to radiation in excess of the limit before all the female employees left the plant on March 23, the utility and the government's nuclear safety agency said.
Hidehiko Nishiyama, a spokesman for the Nuclear and Industrial Safety Agency, said at a press conference that the situation was ''extremely deplorable,'' and urged the utility to investigate the reason and take measures to prevent a recurrence.
The woman concerned was found to have suffered more internal than external radiation exposure, with the internal exposure reaching 13.6 millisieverts. She was involved in work to refuel fire trucks and worked inside a building on-site, which is used as an operation center to deal with the crisis, according to TEPCO and the agency.
TEPCO official Junichi Matsumoto said that the woman may have inhaled radioactive substances that have entered the building in the early days of the crisis. ''For some time after the accident, people were not wearing masks inside the building,'' he added.
Matsumoto acknowledged that radiation-dose management was not sufficient after hydrogen explosions occurred in some reactor buildings and spewed massive radioactive materials. The company is currently taking measures to prevent radioactive substances from entering the building, he added.
Under Japanese law, radiation workers cannot be exposed to more than 100 millisieverts over five years and more than 50 millisieverts in one year, but the limit for female workers comes to 5 millisieverts in a three-month period, considering chances of pregnancy.
For the general public, the limit is 1 millisievert per year, excluding exposure from medical procedures.
As for efforts to restore the plant, TEPCO started in the morning to gradually increase the amount of water injected into the most damaged No. 1 reactor core from 6 tons per hour.
By temporarily increasing the rate, possibly up to 14 tons per hour, TEPCO hopes to discover how far the reactor's primary containment vessel has filled up with water, which is currently not clear, according to Nishiyama.
''After looking at the outcome of the attempt, it will be decided whether TEPCO should take the action to fill water inside the vessel to the level above the reactor fuel,'' he said.
To prevent the release of radioactive substances in the event of an accident, reactor fuel is placed inside a pressure vessel, which is contained in a round-bottom flask-shaped primary containment vessel. A reactor building houses these vessels.
The agency, however, has earlier said that the water injected into the No. 1 reactor's pressure vessel is believed to be leaking out into the primary containment vessel.
The reactors and spent nuclear fuel pools of the Nos. 1 to 4 units need to be periodically injected with water from outside because they lost their cooling functions after the March 11 disaster. The units also suffered hydrogen explosions and fires.
Matsumoto told a press conference that a total of 87,500 tons of highly radioactive water is believed to exist in the Nos. 1 to 4 reactor turbine buildings and nearby underground trenches, and that the firm will process it with a new decontamination system.
The system, to be created by Hitachi-GE Nuclear Energy Ltd., Toshiba Corp. and foreign companies such as Kurion Inc. from the United States and Areva SA from France, is expected to treat some 1,200 tons per day and the decontaminated liquid will be used as water to cool the reactor fuel, it said.
==Kyodo