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Occasional Topics
OT5 (09-10-01)
 
New Maintenance Strategy and Effective Ageing Management
in TEPCO
 
Hiroshi ABE and Takeyuki INAGAKI (Tokyo Electric Power Company)
 
KEYWORDS:
Ageing Management, Nuclear Power Plant (NPP), maintenance, Ageing Management Technical Evaluation (AMTE), PDCA cycle, degradation, As-Found Data
 

Full Download( PDF)
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  1. New Maintenance Strategy and Effective Ageing Management in TEPCO
Hiroshi ABE and Takeyuki INAGAKI
September 2009
Tokyo Electric Power Company
  2. Fukushima Dai-ichi Nuclear Power Plant (1F NPP)
  3. Conventional Ageing Management Activities at 1F NPP
  Different levels of activities to manage ageing have been performed.
  - Continuous implementation of normal maintenance (preventive and corrective) activities
- Replacement/refurbishment of degraded or obsolescent structures/components (SCs)
- Implementation of long-term maintenance plans based on ageing management reviews (After 30 years of operation),
- Re-evaluation of the long-term maintenance plans (every 10 years after 30 years of operation)
- R&D programs related to ageing management
  4. Repairs, Replacements and Refurbishments of SCs at 1F NPP Unit 1 (Examples)
  - Repair and replacement based on condition assessment of SCs
- Repair and replacement as a preventive (proactive) action
  5. Ageing Management Review (Ageing Management Technical Evaluation : AMTE)
  6. Examples of Long-term Maintenance Plans
- UT inspection of some components susceptible to SCC, such as the Off-Gas System re-combiner;
- Inspection of buried piping;
- Inspection of sea water systems against corrosion (both internal and external surfaces);
- Inspection of the flammability control system components;
- UT inspection for connections between the turbine rotors and blades;
- Sampling inspection of RPV stud bolts;
- Re-evaluation of cable insulation degradation using recent R&D findings.
  7. Challenges for Effective Maintenance, Ageing Management and Safe Long-term Operation
- The conventional maintenance programs have not been sufficiently effective for managing ageing degradations of SSCs.
- Systematic ageing management programs should be introduced in the early stage of plant operation.
↓↓
- Need to improve normal maintenance programs to be focused on possible ageing degradations.
- More interactions among normal maintenance programs, ageing management reviews and replacement/ refurbishment projects.
  8. New Regulatory Approach for Ageing Management
  - Ageing management through improved normal maintenance programs from the early stage of NPP operation.
- Ageing management every 10 years within the framework of Periodic Safety Review.
     * Low cycle fatigue, Neutron irradiation embrittlement, Irradiation assisted stress corrosion cracking (IASCC).
- Ageing management through AMTEs performed before the 30th year of operation and subsequent every 10 years
     * Neutron irradiation embrittlement of the RPV, IASCC, Low cycle fatigue, Thermal ageing, Insulation degradation of electrical cables, Degradation of concrete properties for strength and shielding
  9. New Maintenance Strategies of TEPCO and 1F NPP
  - TEPCO Strategies
     * New maintenance plans based on the strategic reliability centered maintenance (SRCM) approach;
     * Evaluation of effectiveness of maintenance programs from ageing management point of view using “As Found” data sheets.
- Additional 1F NPP Strategies
     * Improvement of the feed back system of internal/external operational experience information through:
          ・analysis of past non-conformance issues in the plant related to ageing;
          ・acquisition of information on practices of similar NPPs (similar NPPs in Japan, similar NPPs in other countries, e.g. Santa Maria de Garona NPP);
     * Proactive and integrated component/equipment refurbishment program using “refreshing outages”;
     * Standardizing AMTE evaluations using AMTE knowledgebase.
10. PDCA Cycle to Improve Maintenance Programs
11. PDCA of Maintenance Programs which takes into account ageing degradations
12. Summary Sheet of Ageing Mechanisms
13. Example of As-Found Data Sheet
14. Evaluation of As-Found Data
15. As-Found Data Handbook
16. Analysis and Feed-back of Past Nonconformity Issues (Corrective Action Program)
17. Conclusions
- TEPCO headquarters and the 1F NPP are setting-up new maintenance strategies which enable the NPP to improve maintenance activities and to systematically and effectively manage ageing degradations of SSCs.
- Actual programs for the new strategy are being established in the plant. It is expected that ageing management of SSCs at the plant would be considerably improved through these programs.
- To fully accomplish the objective of the new strategy and activities, it must be a crucial factor to strengthen engineering capability of the plant staff members and to have a suitable organizational structure in the maintenance department.
EJAM OT5: "New Maintenance Strategy and Effective Ageing Management in TEPCO " by Hiroshi ABE and Takeyuki INAGAKI (Tokyo Electric Power Company)