KAGOSHIMA – Kyushu Electric Power Co. said Friday it will delay planned increases in electrical output from the No. 1 reactor at its Sendai nuclear power plant in Kagoshima Prefecture as seawater is believed to have entered into a reactor cooling system.
The company planned to bring the recently reactivated reactor up to full capacity on Tuesday. But this will now be delayed as it will take about a week to fix the problem, officials from the utility said.
A small amount of seawater is believed to have flowed into one of the three condensers in the reactor’s secondary cooling system, the officials said. Condensers turn steam into water by cooling it, after the steam runs power generation turbines.
But there should be no problem in continuing the reactor’s operations as the salt can be removed with the aid of desalination equipment, the officials added.
The level of electric conductivity, which is monitored to check water conditions, rose Thursday afternoon at an outlet of a condensate pump used to circulate secondary coolant water.
Kyushu Electric checked the water quality and confirmed an increase in salt content.
Each condenser has some 26,000 tubes inside that are used to pipe seawater around for cooling. Kyushu Electric suspects that holes have opened on such tubes, causing seawater to enter into the condenser.
The company will seal any tubes found to have holes, the officials said.
In Japan, similar problems have occurred about 50 times in the past, but the latest case was the first at the Sendai power plant. In the past, Kyushu Electric experienced two cases at the No. 1 reactor at its Genkai plant in Saga Prefecture in 1997 and 1999.
The output at the Sendai plant’s No. 1 reactor, restarted on Aug. 11, reached 50 percent of capacity last Sunday and 75 percent on Wednesday. The company had planned to raise output to 95 percent Friday.
The reactor is the first in Japan to run under strict new safety standards introduced in July 2013 following the meltdown accident at Tokyo Electric Power Co.’s Fukushima No. 1 plant, which was wrecked in the March 2011 earthquake and tsunami.
The reactor’s restart also brought to an end the total absence of active reactors in Japan that had become a feature since September 2013, when Kansai Electric Power Co.’s Oi plant in Fukui Prefecture suspended operations for routine safety checks.
Some nuclear experts have said reactors could face severe safety problems because they have been mothballed for such a long period of time.