Survey of Effects of Damage to Main Condenser Tubes in Hamaoka Nuclear Power Station Reactor No. 5
April 25, 2012
Chubu Electric Power Co.,Inc.
Inspection of the lining of the condensate tank of Hamaoka Nuclear Power Station Reactor No. 5 (currently undergoing periodic inspection) commenced in October 2011, and 40 holes have been discovered in and around the welded sections of the lining. A detailed inspection of these holes showed that they had penetrated the lining in some areas, and this fact was reported to the Nuclear and Industrial Safety Agency (NISA) on March 30, 2012.
On the same day, based on its supposition that this penetration of the lining of the condensate tank was the result of infiltration of seawater into the reactor facility on May 14, 2011 due to damage to the main condenser tubes, NISA issued a directive* calling for Chubu Electric to survey the effects of seawater infiltration on the entire Reactor No. 5 facility, and to report the results of this survey.
Based on this directive, Chubu Electric has compiled a report including the results of a survey of the effects of seawater on the Reactor No. 5 facility and a summary of future plans, and has today submitted this report to NISA.
1. Survey of effects
The extent of the infiltration of seawater into the reactor facilities following damage to the main condenser tubes was estimated from the operating status of the reactor at the time of the incident and changes in electrical conductivity. Salt removal procedures have been conducted in order to limit the effect of salt on the equipment.
In order to assess the status of corrosion in actual equipment prior to the inspections and evaluations to be conducted in order to verify equipment soundness, equipment selected with consideration of structure and other factors was subjected to examination by opening and disassembly, and materials tests that reproduced or simulated the environment produced by seawater infiltration were conducted in order to increase knowledge regarding corrosion.
2. Future plans
In the future, we will open and disassemble the equipment exposed to seawater, and evaluate its soundness based on the results of these inspections. These inspections and soundness evaluations will be conducted on the basis of the results of the examinations of actual equipment and the materials tests.
* This directive was "Concerning a Survey of the Effects of Damage to Condenser Tubes in Hamaoka Nuclear Power Station Unit No. 5 (Directive)" (03.30.2012 Nisa No. 10), issued by the Nuclear and Industrial Safety Agency on March 30, 2012.