Measures to Prevent Reoccurrence of Problems in relation to Check Plans for Equipment Past Its Check Period and the Results of Investigation of Check Records at Hamaoka Nuclear Power Station
November 30, 2010
Chubu Electric Power Co.,Inc.
Chubu Electric Power has discovered that the check period for some equipment in Hamaoka Nuclear Power Station Reactors No. 3 and 4 subject to periodic licensee's inspections has been exceeded due to mistakes in input to the Check Plan Control Table, and that unclear points exist in regard to procedures for the extension of the check date and the evaluation of equipment. Based on "Responses in Relation to Equipment for which the Check Date has been Exceeded and Results of Investigation of Check Records for Hamaoka Nuclear Power Station," issued by the Nuclear and Industrial Safety Agency (NISA No.1 issued October 08, 2010), among other responses Chubu Electric Power has formulated measures to prevent a reoccurrence of the problem, and has today reported these measures to the agency.
1. Check plans for equipment not subject to periodic licensee's inspections and results of investigation of check records
Periodic licensee's inspections involve disassembly inspection, etc., of equipment that performs safety functions in order to determine whether those functions are operating correctly. In addition to periodic licensee's inspections, voluntary inspections are also conducted, including adjustment and visual inspection of equipment subject to the periodic licensee's inspection and disassembly inspection of equipment that does not perform any safety functions.
As a result of an examination of the check plans for equipment in Hamaoka Nuclear Power Station Reactors No. 3, 4 and 5 and an investigation of check records, Chubu Electric Power has discovered that the check period has been exceeded for some equipment for the same reasons as previously reported in another case*. We have evaluated the soundness of this equipment, and have concluded that the equipment can continue to be employed without inspection until the upcoming periodic inspection.
In addition, it was also discovered that the check period had been exceeded for some equipment in Reactors No. 1 and 2, which are presently being decommissioned, and inspections of this equipment will be conducted as soon as possible.
* The previous case involved check plans for equipment subject to periodic licensee's inspections in which the equipment check date had been exceeded in Hamaoka Nuclear Power Station Reactors No. 3, 4 and 5, and an investigation of the check records. (Reported to the Nuclear and Industrial Safety Agency on October 12, 2010, and made the subject of a press release on the same day).
2. Measures to prevent reoccurrence of errors in input to the Check Plan Control Table, etc.
The input errors, etc., included input omissions and errors concerning check dates using Chubu Electric Power's standard forms and general-purpose software program, etc., and the recording of incorrect data during data transfer into a plant management system to which we are transferring these functions. These errors concerned equipment that does not directly perform safety functions, mainly valves, electric meters and other pieces of equipment that are used in large numbers and for which changes are frequently input to the Check Plan Control Table. Because our new plant management system possesses a function that checks for input errors, further errors have not occurred to the data whose transition to the system was complete. The following measures have been formulated in order to prevent these input errors from reoccurring.
- We will rapidly complete the transfer of inspection management functions to our plant management system, to enable integrated management. Until the transition to the plant management system is completed, and while the system is still managed using general-purpose software, we will make every effort to prevent input errors, having third parties not involved in the duties verify any changes that are input.
- We have added a function that blocks mistaken inputs and a reminder function to our plant management system in order to improve checks when transitioning to different systems or changing check dates.
3.Improvement of procedures related to the extension of check dates and equipment evaluation
Chubu Electric Power has established company rules based on safety regulations, stipulating precise methods for equipment maintenance management. These rules allow the required check date to be exceeded when checks are planned, based on an evaluation of the soundness of the equipment for the purpose of extension of the check date. The following problems existed in relation to the relevant procedures, and measures for their improvement have been formulated.
(1)Problems related to establishment of check dates and evaluation of soundness of equipment for extension of check dates
- The treatment of check dates as a requirement was unclear, for example in the case of the use of check dates for valves as criteria for judgment, and staff displayed insufficient awareness regarding check periods as a requirement.
- The company rules for procedures related to the extension of check dates and the evaluation of the soundness of equipment, in addition to the preservation of the evaluation records, contained unclear points.
(2)Measures for improvement of problem points
- In order to clarify the treatment of check periods as a requirement, criteria for the establishment of check dates have been improved.
- In future, ensuring that check periods are observed will be set as a maintenance management target, and the level of achievement of this target will be periodically verified.
In addition, checks will be planned in shorter check periods than specified by the check plans, in order to provide a greater margin of safety.
- When it proves absolutely impossible to conduct an inspection within the check period, the equipment will be regarded as not conforming to requirements, and its soundness will be evaluated. In addition, precise methods for these evaluations have been clarified (procedures, items for evaluation, preservation of evaluation records, etc.).
Chubu Electric Power will continue, based on our quality management system, to improve maintenance management through the continuous optimization of check plans (details of equipment inspections and check periods), and to educate our employees in this area.
In addition, a thorough analysis of root causes will be undertaken in order to determine how the problems indicated above were able to continue to the present without being corrected by the system. Based on this analysis, further improvement measures will be formulated and appropriately implemented.