Plan Changes to Countermeasures against the Fracture of Moving Vane Mounting Assembly in the Hamaoka Nuclear Power Station Unit 4 Low-Pressure Turbine
October 03, 2014
Chubu Electric Power Co.,Inc.
As regards the fracture confirmed at Hamaoka Nuclear Power Station Unit 4 (rated electrical output 1.137MW, undergoing its 13th periodic facility inspection), presumably due to stress corrosion cracking, Chubu Electric Power Co., Inc. (hereafter Chubu Electric) decided to replace the shaft in low-pressure turbines (A) to (C) with those designed based on measures for suppressing stress corrosion cracking. We would like to announce that the notification of a construction plan was filed today with the Minister of Economy, Trade and Industry, as well as the Nuclear Regulation Authority.
For the restoration of the Unit 4 low-pressure turbine, along with the replacement of the low-pressure turbine (C) shaft with a new part, the pressure plates on the 12th stage of low-pressure turbines (A) to (C) were planned to be installed and replaced. As the generator output decreases due to the installation of pressure plates, it was decided that the shafts for both low-pressure turbines (A) and (B) shall be replaced as well, as a long-term countermeasure. We have been moving forward with restoration with plans to finish by the end of fiscal year 2014. (Reported June 21,2014)
As a result of considerations for the shaft replacement, we concluded that replacement of the shafts can be carried out at an early stage for low-pressure turbines (A) and (B) as well. Thus the installation of the pressure plates that was originally planned was suspended, and we decided to replace the shafts for low-pressure turbines (A) to (C). Along with the replacement of the shafts, a full-scale new replacement of all moving vane blades will be conducted upon taking measures to prevent high cycle fatigue cracking, which is presumed to be the cause of fracture and breaking.
The restoration of the Unit 4 low-pressure turbines is scheduled to take place by the end of September 2015.