Labeling tags were not attached to 1,500 valves controlling the flow of radioactive water in piping and other equipment at the Fukushima No. 1 nuclear power plant in the aftermath of the March 2011 disaster, sources said.
The revelation shows that plant operator Tokyo Electric Power Co.'s measures to deal with the accident are still lagging three years after the triple meltdown triggered by the Great East Japan Earthquake and tsunami.
Tags are used to indicate where pipes and other equipment are connected to prevent workers from operating the wrong valves and releasing radioactive water to the wrong places. The pipes connect contaminated water storage tanks, pumps and other equipment.
In principle, valves are accompanied with tags at nuclear power plants across the country, sources said. At the Fukushima plant, each tag is usually numbered to prevent radioactive water from leaking due to erroneous operation of the valves.
Even though the use of tags is not legally mandated, their use is regarded as “essential to prevent operational errors,” according to a central government official who is in charge of radioactive water measures.
According to TEPCO and other sources, there are about 5,000 valves at the Fukushima plant that should be tagged, such as those on piping for radioactive water accumulated inside turbine buildings and those at contaminated water processing facilities.
The utility started attaching tags on Oct. 21 last year. A total of 3,500 tags have been attached, but work is still outstanding on 1,500 more, or 30 percent.
The work is not expected to be completed until June 27.
A TEPCO spokesperson, commenting on the lack of tags, said the utility “was able to identify valves that have to be operated based on piping drawings.”
The official said the utility started fitting tags last autumn “because it took time to identify valves (that have to be operated) and there was a need to lower the risk of erroneous operations.”
The Democratic Party of Japan said TEPCO’s failure to attach tags could be behind the string of leakages of contaminated water at the plant.
DPJ member Yuichiro Tamaki raised the issue at a session of the Lower House Committee on Economy, Trade and Industry on March 26.
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