Workers entered the No. 1 reactor building at the crippled Fukushima No. 1 nuclear power plant on May 10 to begin the process of cooling the reactor.
Workers entered the No. 1 reactor building at the crippled Fukushima No. 1 nuclear power plant on May 10 to begin the process of cooling the reactor.
The workers' first task was repairing monitoring equipment within the reactor to give officials of Tokyo Electric Power Co., the plant's operator, a more accurate picture of the situation inside the building.
In order to cool the reactor core to below 100 degrees, workers have been pumping water into the pressure container itself as well as trying to submerge the containment vessel surrounding the pressure container.
A total of 9,911 tons of water had been pumped into the No. 1 reactor as of midnight May 9, but TEPCO officials said they did not know how much water had actually entered the pressure container or the surrounding containment vessel because gauges had been damaged in the crisis following the March 11 quake.
The workers in the No. 1 reactor building on May 10 started by fixing the water gauge on the pressure container. A display was installed to allow workers in the building to confirm measurements.
A TEPCO official said: "In order to confirm whether work is being carried out under safe conditions, having the water and pressure gauges operating properly and accurately knowing the condition of the core, is indispensable."
TEPCO officials also began inspecting piping that will be connected to the cooling mechanism.
A major problem for personnel working within the reactor building is the high level of radiation.
Some parts of the reactor building have levels of radiation between 600 and 700 millisieverts per hour, much higher than the maximum limit of 250 millisieverts of radiation that workers can be exposed to.
Before allowing workers within the reactor building, ventilation equipment was used to reduce the radiation levels. While there were some areas with radiation levels of 280 millisieverts per hour, most other areas within the reactor building had radiation levels between 10 to 100 millisieverts.
Workers had also found rubble within the reactor building, likely the result of hydrogen explosions. The building itself and the main equipment did not appear to be greatly damaged. No water leaks were found.
The ventilation equipment removed some of the dust within the building, but rubble, surfaces, pipes and equipment have been contaminated with radiation.
TEPCO officials had hoped to reduce radiation levels to 1 millisievert per hour.
After sources of radiation are determined, TEPCO officials are considering using lead mats or sheets to contain the radiation. Consideration is also being given to removing the rubble or wiping away radiation.
A TEPCO official said they were not planning to push back the timetable for cooling the reactors, but the company may change where piping is installed and reconsider the number of workers needed to do the work depending on the progress made.
(This article was written by Takashi Sugimoto and Eisuke Sasaki.)