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Occasional Topics
OT9 (2010-2-10)
 
Japanese Nuclear Industry's Efforts
for PWR's Plant Life Management
 
Takayuki AOKI*
Kouji DOZAKI*
Takehiro KUSUNOKI*
*The Japan Atomic Power Co.
 
KEYWORDS:
Plant Life Management, Ageing Management, R&D, Proactive Maintenance, PWSCC, IASCC, RCC GT Wear, Turbine Disc SCC
 

Full Download( PDF)
slide
 
  1. Japanese Nuclear Industry’s Efforts for PWR's Plant Life Management
The Japan Atomic Power Co.
November, 2009
  2. Contents
  1. History of R&D on Plant Life Management
2. R&D for Plant Life Management/Ageing M.
3. Next generation LWR Development using PLM R&D results
4. Field Applications of R&D Results
  (1) PWSCC
  (2) IASCC in core internal bolts
  (3) RCC Guide Tube Wear
  (4) SCC in turbine discs
5. Conclusion
  3. History of Japan’s PWR
  WH 2-loop Design
・Fuel: 10ft→12ft
・New RV Material
・New SG Tube
・New RCP
WH 3-loop Design
・Fuel: 14X14→15X15
・System Improvement
・CV Enclosure
WH 4-loop Design
・Larger Output: 1,170MW
・Ice Condenser CV
・Higher System Efficiency
The first Design Standardization (3-loop plant)
・870MW
・Standardized Domestic Design
・Partially Mono-Block Turbine
The Second Design Standardization (4-loop plant)
・Integration of Domestic Tech.
・Pre-stressed Concrete CV
The third Design Standardization (APWR: Tsuruga-3,4)
・ 1,530MW
・Higher Capacity Factor
・Improvement of Operability & Economic Efficiency
  4. History of PLM/AM at Japanese NPPs
  1996 [PART-1]
Basic Policy & Concept of PLM
- Assessed SSC not to be easily replaced
- Policies for long-term & safe operation
1998 [PART-2]
Utilities’ evaluation
- SSC which are important to plant safety and operation
- Reviewed by the regulatory body, NISA
2005
Preparation of the Regulatory Guidance Documents by the Regulatory Body, NISA
- Ageing Management Implementation Guideline for Nuclear Power Plants
- Standard Review Plan for Ageing Management Technical Evaluation of Nuclear Power Plants
- Technical Documents for Ageing Management Implementation of Nuclear Power Plants
2008
Introduction of PLM/AM into the New Regulatory System
  5. Organization in Japan to Promote PLM-related R&D Activities
  - Technical Information Sharing Committee (JNES)
- PLM Research Promotion Council Board (Secretariat : JANTI)
- PLM Research General Review Committee (Secretariat :CRIEPI)
- PLM Research 10 Specific Review Committees
[The Federation of Electric Power Companies of Japan]
- Nuclear Energy Development Committee
- Task Force
- Plant Maintenance Committee
  6. PLM related R&D Items
Specific Issues
1. SCC
2. Irradiation Embrittlement
3. Fatigue
4. Seismic Safety
5. Concrete Degradation
6. Cable Insulation Degradation
7. Pipe Wall Thinning
8. Inspection/Monitoring Technologies
9. Preventive Maintenance & Repair Techniques
10. Enhancement of Maintenance Activities
R&D focus
1. Fundamental Research Projects
  - Clarify ageing mechanisms, identify potential consequences, and develop new materials
2. Develop. of Advanced Technologies
  - Technologies required for evaluation, inspection and repair
3. Application of Technologies in field
  - Technical approaches, demonstration tests, making standards and their approval by the government
4. Construction of Database Required for PLM Technical Evaluations
5. Development of Alternative inspection/monitoring methods instead of ones by the conventional overhaul
6. Proposals for Improving the Current Regulatory system and Rules
7. Securing of human resources by establishing the system to promote it
  7. Next Generation LWR Development
By utilizing the results of the PLM related R&D
Project based on the Japan’s Nuclear Energy National Plan
Objective:
(1) Develop the next generation LWRs which could be recognized as the world standard (1,700~1,800MW-class BWR and PWR)
(2) The government and electric power companies should promote the R&D projects with the help of the plant vendors.
Project Term: 2008~2015 (8 years)
Development Targets of The Project (6 Core Items)
- Achieve significant reduction of spent fuels and the highest availability in the world by developing NSSS utilizing 5% or higher enrichment fuel.
- Realize the standardized plant design regardless of site conditions by adopting the seismic isolation technology.
- Introduce new materials and improved water chemistry aiming at 80 years plant design life and significant reduction of radiation exposure received during maintenance work.
- Reduce the construction schedule significantly by introducing the radial construction technologies.
- Achieve both the highest safety and economic efficiency in the world by optimized combination of passive and active systems.
- Adopt the most advanced digital technology to improve the availability and safety simultaneously.
  8. PWSCC in RV Head Penetration
Sketch of Leakage Trace in the Case of a Japanese Plant
  9. PWSCC in RV Head Penetration
  Replacement of Material from Alloy 600 to Alloy 690
10. PWSCC in RV Nozzle Welds (1/2)
  Leakage from the Main Loop in V.C.SUMMER(Oct. 2000)
<Root Cause>
- PWSCC in Alloy 600 Weld
- High Tensile Residual Stress Generated by Weld Repair
11. PWSCC in RV Nozzle Welds (2/2)
  Improved Inspection Method
Repair Technique
12. PWSCC on DMW of SG Nozzle
- PWSCC cracks were found on DMW of SG inlet nozzle at some PWR plants in Japan since September 2007.
- Mihama-2, Tsuruga-2 etc.: Cracks were found by ECT as the check prior to shot peening.
13. Repair Process Overview - For Deep Cracks
1. Remove the existing elbow
2. Decontamination
3. Crack removal
 ● All around shallow cutting
 ● Local deep cutting
4. Inlay welding
 ● Local cladding weld using alloy 600
 ● All around inlay weld using alloy 690
5. Install new elbow
14. Repair Process Overview - For Shallow Cracks
1. Install the cutting machine
2. Crack removal
3. Inspection by ECT
4. Wall thickness measurement
5. Perform ultrasonic shot peening
15. ECT System for PWSCC in SG Tubes
16. IASCC in Baffle Former Bolts
17. IASCC in Baffle Former Bolts
Identification of IASCC Susceptible Components
Understanding of Degradation Mode & Fracture Mode
Establishment of Criteria to maintain Component Function
Evaluation of Acceptable Crack Size & Inspection Interval
18. RCC Guide Tube Wear
19. Guide Tube Wear Growth
20. SCC in LP Turbine Discs
21. SCC in LP Turbine Discs
  1. Mono-Block Rotor
2. 3D Fluid Dynamic Design Blade
3. Modification of Coupling
4. Long Blade
22. Conclusion
It is very important to perform proactive maintenance for a long-term safe operation
Understanding the actual condition of plant components and R&D are essential for performing the proactive maintenance in aged plants
EJAM OT9: "Japanese Nuclear Industry's Efforts for PWR's Plant Life Management" by Takayuki AOKI, Kouji DOZAKI and Takehiro KUSUNOKI (The Japan Atomic Power Co.)