| 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. |
Measures for Tsunami Striking Nuclear Power Station in Japan
Planning and Consideration on SFR R&D Activities in China
