Corrosion Holes in the Hamaoka Nuclear Power Station Reactor No. 5 Condensate Tank Lining
March 30, 2012
Chubu Electric Power Co.,Inc.
In Hamaoka Nuclear Power Station Reactor No. 5 (advanced boiling water reactor; rated output 1,380 MW; currently under periodic inspection), inspection*2 of the lining of the condensate tank*1 has been carried out since October 2011, and 40 holes have been confirmed at and around the interior welded part until the present.(Reported on March 21, 2012)
A detailed inspection was then carried out on the 40 holes (35 in the floor and 5 in the wall). The 35 holes in the floor were divided into 26 spots. Upon removal of the corrosion holes for repair welding and conducting of foam tests to check for leakage,*3 foam was today confirmed to be present in 11 of the 26 spots, which were therefore judged to be eaten through.
It was also confirmed that the 5 holes in the wall were not eaten through.
The leakage detector installed in the condensate tank floor did not detect a water leak going outside the tank.
This incident has not caused any leakage of radioactivity to the exterior of the reactor.
From now, investigation into the cause of the corrosion holes and repair of the holes will be carried out. Inspection results will be reported once collected.
This incident is a reportable incident to the nation according to Article 19, Paragraph 17 of the Regulations for Installation and Operation of Practical Reactors.*4 It also requires notification according to the Safety Agreement.
*1 The condensate tank stores water essential for plant operation. This water is slightly radioactive. The tank is also used as a water source for the emergency core cooling system.
*2 Inspection of the condensate tank was conducted as an inspection concerning desalting that accompanies seawater inflow incidents and checking of the soundness of facilities and fuel.
*3 The foam test to check for leakage is a test that detects leakage spots by checking for the presence of foam from foam spray applied to the test surface.
*4 The formal name of the Regulations for Installation and Operation of Practical Reactors is the Rules Governing Installation and Operation of Nuclear Reactors for Practical Power Generation. These regulations are based on the stipulations of laws and regulations concerning nuclear reactors in relation to the establishment, operation, etc. of nuclear reactors for power generation.