TEPCO prepares massive cover for reactor building

TEPCO began assembling a cover on Aug. 10 to be installed over the No. 1 reactor building at its Fukushima No. 1 nuclear power plant to contain leakage of radioactive materials. A hydrogen explosion blew off the roof at the No. 1 reactor building on March 12 during the early phase of the crisis. Tokyo Electric Power Co. hopes to complete the installation of the cover toward the end of September. The cover, which will be 47 meters long, 42 meters wide and 54 meters high, consists of polyester fiber panels coated with nonflammable resin that are to be set in a steel frame. It will be assembled remotely using a crane to minimize worker exposure to radiation. On Aug. 10, a crane with a 140 m arm began assembling a post that will support the cover from the southeast side of the building. The structure will be built without screws and bolts, drawing upon construction methods used in Japanese architecture. The radiation levels near the No. 1 reactor stand between 1 and 20 millisieverts per hour. Six ventilators, with filters capable of absorbing radioactive substances, will be installed on the cover. Upon completion, the ventilators are expected to purify and replace 40,000 cubic meters of air per hour. Although there is anxiety about damage from typhoons and other causes, the cover is designed to withstand winds of up to 90 kph. "The maximum 10-minute average wind velocity observed in the neighborhood during the past 35 years is 61 kph," a TEPCO official said. TEPCO said the air inside the cover will tend to retain heat. The interior air temperature is expected to rise to a maximum 39 degrees when the exterior air temperature is 28.5 degrees, so TEPCO is preparing to install air conditioners. Similar to what occurred at the No. 1 reactor building, explosions destroyed the roofs at the No. 3 and No. 4 reactor buildings. Cover installation over these buildings will begin after spent fuel has been taken out of the storage pools. All reactor buildings will be encased inside concrete buildings in about three years, according to TEPCO.