Work starts to install air filter to reduce radiation at nuclear plant

TOKYO (Kyodo) - The operator of the crisis-hit Fukushima Daiichi nuclear plant on Monday commenced work to install an air filter in the building housing the No. 1 reactor to reduce the high radiation level and enable workers to enter and set up a system to cool the troubled reactor.
Tokyo Electric Power Co. said that workers are expected to enter the building as early as Thursday to start the ventilation device. It would be the first time for workers to step into the plant's reactor building since March 12, when a hydrogen explosion occurred at the No. 1 unit and led to the external release of radioactive substances.
Meanwhile, it was revealed the same day that Japan's system to predict the volume of emitted radioactive materials in the event of a nuclear accident failed to work when the March 11 quake and ensuing tsunami hit Fukushima because equipment to measure necessary data lost power, according to sources close to the matter.
The revelation shows that the so-called Emergency Response Support System and another key system for predicting the dispersal of radioactive materials have been of little use during the ongoing crisis, raising concern about how the quake-prone country would respond in the event of another nuclear disaster.
It remains unclear when the crisis will come to an end, with the utility known as TEPCO saying that it will take at least six months before the utility can stabilize the plant's troubled reactors that have lost their cooling functions since the magnitude 9.0 earthquake and tsunami.
TEPCO is currently trying to restore stable cooling functions to the reactors and spent nuclear fuel pools of the Nos. 1 to 4 units, and reducing the radiation level inside the No. 1 reactor building is seen as a key step toward that end as it would pave the way for workers to install equipment that would help create a cooling system.
''If we can find out how we can do things in the No. 1 reactor, I think we'll be able to apply a large part of the methods to the No. 3 reactor,'' Goshi Hosono, special adviser to Prime Minister Naoto Kan on the ongoing crisis at the plant, told a press conference jointly held with TEPCO and other government officials.
A TEPCO official said that running the ventilation system in the No. 1 reactor building for even one day is expected to ''reduce quite a large'' amount of radiation inside the building.
''We are expecting the radiation dose to become a twentieth,'' the official said.
While trying to improve the working environment inside the No. 1 reactor building, TEPCO is planning to fill the reactor's primary containment vessel with water to a level above the reactor fuel and possibly install an air-cooling device to take heat from the water that is expected to circulate around the reactor.
Reactor fuel is placed inside a pressure vessel, which is contained in a round-bottomed, flask-shaped primary containment vessel. Each reactor building houses these vessels.
So far, water has been injected into the pressure vessel from outside to keep the reactor cool, but TEPCO has decided that taking the unprecedented step of flooding the containment vessel with enough water to immerse the pressure vessel would cool the fuel more efficiently.
As for the No. 2 unit, TEPCO is planning to install a device to reduce the high humidity that has been detected at its reactor building before starting air ventilation.
TEPCO is aiming to restore stable cooling to the reactors and spent fuel pools of the Nos. 1 to 4 units in about three months, based on the restoration road map for the plant unveiled by the company on April 17.
Hosono said that the government and TEPCO have decided to hold press conference on May 17 to assess the progress made in line with the road map and update its content.