Situation of Inspection related to Seawater Infiltration Event at Hamaoka Nuclear Power Station Unit 5
October 03, 2014
Chubu Electric Power Co.,Inc.
Chubu Electric Power Co., Inc. (hereafter Chubu Electric) is assessing the equipment and fuel infiltrated by seawater and checking its soundness, as seawater infiltrated systems due to the main condenser tube damage which occurred on May 14, 2011 at Hamaoka Nuclear Power Station Unit 5.
Regarding the inspection planned to conclude in September of this year, we would like to announce an extension of the inspection period due to the addition of inspection items for some equipment, such as the lining material of the reactor pressure vessel, as well as announce the inspection results thus far.
1 Inspection Results
1. Reactor Pressure Vessels and Core Structures
Corrosion has been confirmed on some of the lining material of the reactor pressure vessel and core structures as a result of the visual inspection.
Although corrosion has been confirmed in the lining material for the reactor pressure vessel, it has been assessed that the corrosion does not have an impact on functions of the vessel. This is a result of measurement tests of the corrosion depth using ultrasound, as well as visual inspections of the size of the corrosion leading to the estimation that the vessel maintained the required thickness. We will additionally conduct investigations in the future to further grasp the details of the depth and shape of the corrosion in the lining material.
On the other hand, core structures such as steam dryers, etc., have been assessed to be capable of maintaining functions by performing repairs and replacements for the corroded areas. As a means to assess in detail, we will additionally carry out measurements on the depth of the corrosion.
2. Other Reactor and Turbine Equipment
Corrosion was confirmed in some equipment as a result of disassembly and open inspections on pumps, valves, and pipes, etc., in systems infiltrated by seawater. Additional inspections are being conducted for equipment confirmed to have an abnormality that may impact its functions. For either inspection, all equipment was assessed to be capable of maintaining its functions by performing repairs and replacements.
Chubu Electric will continue to steadily implement the remaining additional inspections in the future.
As a result of the fuel investigations and material tests, no impact due to seawater infiltration was confirmed on the soundness of the fuel. From results of analytical investigations, foreign matters and attached substances discovered in the course of fuel investigations were confirmed to not pose an impact on the soundness of the fuel.
2 Extension of the Inspection Period
Chubu Electric originally planned to conclude inspections by September of this year, and summarize the assessments of equipment, etc., from those results. As additional investigation and inspections are to be conducted from the inspection situation thus far, the inspection period for reactor pressure vessels and core structures will be changed to during the first half of FY2015, and the inspection period for other nuclear and turbine equipment will be changed to within FY2014.
Chubu Electric will continue to carefully check and assess Unit 5.