Kansai Electric Power Co. and other utilities will install filter-equipped venting systems for their pressurized light-water reactors to release vapor and prevent damage to containment vessels in the event of a crisis, according to sources.
The utilities had maintained that such venting systems were unnecessary for pressurized water reactors and are making the about-face amid heightened public fear brought on by the Fukushima crisis and the hard sell they face in gaining the OK to restart reactors idled for safety checks, the sources said Monday.
Following the Chernobyl nuclear meltdown calamity in 1986, Japanese electric utilities voluntarily began to install venting systems in boiling-water reactors, including those at Tokyo Electric Power Co.'s Fukushima No. 1 plant, in the 1990s.
But they concluded such vents were unnecessary for pressurized reactors as their containment vessels are larger and prevent pressure from rising when an accident occurs, compared with those of boiling-water reactors.
Although specific designs for a venting system for pressurized water reactors have yet to be finalized, they are expected to include a mechanism to release vapor through a filter of sand and water to absorb radioactive substances, the sources said.
In the Fukushima No. 1 crisis, reactors 1, 2 and 3 used a vent system for the first time in Japan.
The system caused serious problems, particularly massive radioactive fallout in the absence of filters in the piping.
Of the nation's 54 commercially operated reactors, including those at Fukushima No. 1, pressurized water runs 24 of them located in five prefectures.