Improved VT Techniques
35th Annual EPRI Steam Generator NDE and Tube Integrity workshop Clearwater Beach, FL, USA July 18~20, 2016
New and Improved Inspection Techniques for Steam Generator Tubes to Further Enhance the Safety and Reliability of Nuclear Power Plants in Japan K.Namba, T. Hasebe, T.Kinoshita, T. Matsuura, I.Seki and T. Tsuruta
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
1
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
2
Timeline after Fukushima accident After the Fukushima Daiichi Nuclear Accident caused by the Tohoku Earthquake and Tsunami in March 2011, the nuclear regulatory system in Japan was reorganized. Shown below is a timeline summary of events and actions relative to the resumption of NPP operations in Japan. *Nuclear Regulation Authority (NRA)
2011 Overall/ Plant operation
2012
2013
2014
2015
2016
Fukushima accident NRA established
Plant operation stopped one after another
NRA assessment
New regulations ordered 12 PWR plants applied to resume operation
NRA review Sendai-1/2 resumed operation injunction Takahama-3 resumed operation (Takahama-4 postponed to resume operation) Pre-operation inspection for Ikata-3
MHI activity
• • •
Safety analysis Mid- and long- term preventative measures Plant design and construction enhancements to prevent severe accidents
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
3
Plant situation as of July, 2016 PWR plants with applications to resume operation Plant
Utility
Reactor
Status of NRA review/inspection
Sendai-1/2
Kyusyu
PWR
Review of design enhancements and Pre-operation inspection completed. Operation resumed.
Takahama-3
Kansai
PWR
Review of design enhancements and Pre-operation inspection completed. Operation resumed but stopped again by District Court order.
Takahama-4
Kansai
PWR
Review of design enhancements and Pre-operation inspection completed. Operation is postponed by District Court order.
Ikata-3
Shikoku
PWR
Review of design enhancements and Pre-operation inspection completed. Operation will be resumed in end of July.
Takahama-1/2
Kansai
PWR
Review of construction plan completed.
Ohi-3/4
Kansai
PWR
Mihama-3
Kansai
PWR
Genkai-3/4
Kyusyu
PWR
Tomari-1/2/3
Hokkaido
PWR
Review of application for installment license in progress.
Genkai-1,Ikata-1 and Mihama-1/2 were decided to be decommissioned. License renewal over 40 years operation were applied for Takahama-1/2 and Mihama-3. Takahama-1/2 were already approved. © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
4
Plant situation as of July, 2016 (cont’) BWR plants with applications to resume operation Plant
Utility
Reactor
Kashiwazaki-6/7
Tokyo
BWR
Shimane-2
Chugoku
BWR
Onagawa-2
Tohoku
BWR
Higashidori-1
Tohoku
BWR
Hamaoka-3/4
Chubu
BWR
Tokai-2
JAPC
BWR
Shiga-2
Hokuriku
BWR
Oma
J-power
BWR
Status of NRA review/inspection
Review of plant design, construction, safety and reliability for the application of a renewed operations license, in progress.
Hamaoka-1/2, Tsuruga-1, and Fukushimadaiichi-1/2/3/4/5/6 are to be decommissioned.
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
5
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
6
Continuous improvement of Inspection Techniques As a preventative measure against the potential negative effects of service induced tube degradation (flaws), and to enhance the safety and reliability of steam generators, it is necessary to develop, and continuously improve, the applied NDE techniques. The goal is to achieve the earliest detection and characterization possible in support of root cause analysis and mitigation. Moreover, it is important to continuously analyze and assess the results from improved NDE techniques
and to apply that knowledge to inform each aspect of plant operations from design, to construction, to specific operating parameters. To achieve improvements in detection and characterization the various flaw types, MHI has developed highly advanced and effective NDE techniques. Examples of specifically targeted flaws are PWSCC in the tube sheet region or at the TTS, and wall thinning either in the free span or near/under tube support plates. The, methods, technologies, and specific techniques that MHI has developed/improved are:
• Multi-functional UT system
• PWSCC depth-sizing using UT techniques • Improved VT techniques © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
7
Continuous improvement of Inspection Techniques Summary table of UT and VT
Purpose
Wear depth sizing SCC detection
Method
Multi-functional UT
Feature
• Detectability: 20%t depth • Sizing accuracy (wear): 5%t
SCC depth sizing
PWSCC depth-sizing UT
• Detectability: 20%t • Sizing accuracy: approximately 10%t (more than 30%t)
Surface observation of SCC
VT
• Detectability: 5 to 10μm width SCC can be detected
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
8
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
9
Multi-functional UT System Outline of multi-functional UT
ECT sensor for probe positioning
Sensor for Axial flaw
Sensor for Circ. flaw
Straight UT sensor for wear
Feature • Detection of outside/inside cracks and wear in straight section locations. • Simultaneous implementation of straight beam and angle beams techniques. • Sizing accuracy is enhanced through an algorithm which automatically compensates for the varying distance of UT sensor to the tube surface as it is scanned • Accurate Probe positioning is provided by an accurately controlled probe driver and built-in ECT coil which identifies landmarks such as tube supports or the TTS. © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
10
Multi-functional UT System Detectability and Characterization Accuracy • Detectability (For SCC and wear): 20%t depth for 7/8in. tube • Sizing accuracy (For wear): 5%t for 7/8in. tube Corrected C scope
B scope
Line No Tube
Tip of defect
Outer surface
Flaw Thickness
Wall loss Evaluation : 22%t
Axial distance[mm]
ID
OD
Line 1
Line 3X
Evaluation result of 20% depth EDM notch © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
Circ distance[°]
11
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
12
PWSCC depth-sizing UT Technique Outline of PWSCC depth-sizing UT
Sensor for Circ. flaw
Sensor for Axial flaw
Feature • High S/N ratio is achieved by “point focusing” the ultrasonic beam and by reduction of the echo from tube inner surface. • Angle beam technique with single element probe is applied and the echo from tip of defect is used so as to enhance PWSCC detectability from multi functional UT.
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
13
PWSCC depth-sizing UT Technique Detectability and Characterization Accuracy • Detectability: 20%t for 7/8in. tube • Sizing accuracy: approximately RMSE 0.13mm (more than 30%t) for 7/8in. tube
B scope
D scope
A scope
Tip echo
Evaluated depth by UT（ %t)
C scope
100
80
60
40 Axial SCC (CCW) Axial SCC（ CW）
20
Circ. SCC (DOWN) Circ. SCC（ UP）
0 0
Axial SCC data within 22%t © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
20
Fig.5
40 60 Actual depth (%t)
80
100
Results of UT sizing 14
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
15
Improved VT Techniques Description of VT
Camera head with Lens unit for side viewing
Camera head with Lens unit for viewing ahead
Feature • Camera for both ahead and side viewing • 360 degree articulation • Accurate probe positioning with well controlled probe driver and ECT coil © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
16
Improved VT Techniques Detectability and Characterization Accuracy • Detectability: 5 to 10μm width SCC can be detected for 7/8in. Tube • Comparison with previous methods (replica and sketch of it): approximately equal to previous methods Superior SCC
3.0mm
亀裂欠陥多数
3.0mm
4.0mm
4.0mm
Camera image
Sketch
VT
Replica
Previous methods
Advantage of VT • ECT pushers and remote controlled positioning robots can be used to apply the VT probe greatly reducing radiation exposure. •
(The alternative, replicating flaws, requires inspectors much higher radiation exposure) © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
17
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
18
Conclusions • Improved UT technologies and techniques were developed to achieve more accurate characterization and depth sizing of wear and SCC type flaws. • Improved VT technologies and techniques were developed to achieve far more efficient and effective surface inspections with superior detection and characterization of SCC, and it greatly reduces radiation exposure as compared to the alternative. • These more highly enhanced NDE techniques have now proven to provide increased sensitivity for early detection while vastly improving flaw characterization accuracy (i.e. flaw orientation as well as geometric and depth sizing). • Enhanced NDE techniques like these further contribute to NPP safety and reliability by providing higher value input to continuous condition monitoring and operational assessment programs (CMOA). © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
19
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
20
New and Improved Inspection Techniques for Steam Generator Tubes to Further Enhance the Safety and Reliability of Nuclear Power Plants in Japan K.Namba, T. Hasebe, T.Kinoshita, T. Matsuura, I.Seki and T. Tsuruta
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
1
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
2
Timeline after Fukushima accident After the Fukushima Daiichi Nuclear Accident caused by the Tohoku Earthquake and Tsunami in March 2011, the nuclear regulatory system in Japan was reorganized. Shown below is a timeline summary of events and actions relative to the resumption of NPP operations in Japan. *Nuclear Regulation Authority (NRA)
2011 Overall/ Plant operation
2012
2013
2014
2015
2016
Fukushima accident NRA established
Plant operation stopped one after another
NRA assessment
New regulations ordered 12 PWR plants applied to resume operation
NRA review Sendai-1/2 resumed operation injunction Takahama-3 resumed operation (Takahama-4 postponed to resume operation) Pre-operation inspection for Ikata-3
MHI activity
• • •
Safety analysis Mid- and long- term preventative measures Plant design and construction enhancements to prevent severe accidents
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
3
Plant situation as of July, 2016 PWR plants with applications to resume operation Plant
Utility
Reactor
Status of NRA review/inspection
Sendai-1/2
Kyusyu
PWR
Review of design enhancements and Pre-operation inspection completed. Operation resumed.
Takahama-3
Kansai
PWR
Review of design enhancements and Pre-operation inspection completed. Operation resumed but stopped again by District Court order.
Takahama-4
Kansai
PWR
Review of design enhancements and Pre-operation inspection completed. Operation is postponed by District Court order.
Ikata-3
Shikoku
PWR
Review of design enhancements and Pre-operation inspection completed. Operation will be resumed in end of July.
Takahama-1/2
Kansai
PWR
Review of construction plan completed.
Ohi-3/4
Kansai
PWR
Mihama-3
Kansai
PWR
Genkai-3/4
Kyusyu
PWR
Tomari-1/2/3
Hokkaido
PWR
Review of application for installment license in progress.
Genkai-1,Ikata-1 and Mihama-1/2 were decided to be decommissioned. License renewal over 40 years operation were applied for Takahama-1/2 and Mihama-3. Takahama-1/2 were already approved. © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
4
Plant situation as of July, 2016 (cont’) BWR plants with applications to resume operation Plant
Utility
Reactor
Kashiwazaki-6/7
Tokyo
BWR
Shimane-2
Chugoku
BWR
Onagawa-2
Tohoku
BWR
Higashidori-1
Tohoku
BWR
Hamaoka-3/4
Chubu
BWR
Tokai-2
JAPC
BWR
Shiga-2
Hokuriku
BWR
Oma
J-power
BWR
Status of NRA review/inspection
Review of plant design, construction, safety and reliability for the application of a renewed operations license, in progress.
Hamaoka-1/2, Tsuruga-1, and Fukushimadaiichi-1/2/3/4/5/6 are to be decommissioned.
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
5
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
6
Continuous improvement of Inspection Techniques As a preventative measure against the potential negative effects of service induced tube degradation (flaws), and to enhance the safety and reliability of steam generators, it is necessary to develop, and continuously improve, the applied NDE techniques. The goal is to achieve the earliest detection and characterization possible in support of root cause analysis and mitigation. Moreover, it is important to continuously analyze and assess the results from improved NDE techniques
and to apply that knowledge to inform each aspect of plant operations from design, to construction, to specific operating parameters. To achieve improvements in detection and characterization the various flaw types, MHI has developed highly advanced and effective NDE techniques. Examples of specifically targeted flaws are PWSCC in the tube sheet region or at the TTS, and wall thinning either in the free span or near/under tube support plates. The, methods, technologies, and specific techniques that MHI has developed/improved are:
• Multi-functional UT system
• PWSCC depth-sizing using UT techniques • Improved VT techniques © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
7
Continuous improvement of Inspection Techniques Summary table of UT and VT
Purpose
Wear depth sizing SCC detection
Method
Multi-functional UT
Feature
• Detectability: 20%t depth • Sizing accuracy (wear): 5%t
SCC depth sizing
PWSCC depth-sizing UT
• Detectability: 20%t • Sizing accuracy: approximately 10%t (more than 30%t)
Surface observation of SCC
VT
• Detectability: 5 to 10μm width SCC can be detected
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
8
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
9
Multi-functional UT System Outline of multi-functional UT
ECT sensor for probe positioning
Sensor for Axial flaw
Sensor for Circ. flaw
Straight UT sensor for wear
Feature • Detection of outside/inside cracks and wear in straight section locations. • Simultaneous implementation of straight beam and angle beams techniques. • Sizing accuracy is enhanced through an algorithm which automatically compensates for the varying distance of UT sensor to the tube surface as it is scanned • Accurate Probe positioning is provided by an accurately controlled probe driver and built-in ECT coil which identifies landmarks such as tube supports or the TTS. © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
10
Multi-functional UT System Detectability and Characterization Accuracy • Detectability (For SCC and wear): 20%t depth for 7/8in. tube • Sizing accuracy (For wear): 5%t for 7/8in. tube Corrected C scope
B scope
Line No Tube
Tip of defect
Outer surface
Flaw Thickness
Wall loss Evaluation : 22%t
Axial distance[mm]
ID
OD
Line 1
Line 3X
Evaluation result of 20% depth EDM notch © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
Circ distance[°]
11
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
12
PWSCC depth-sizing UT Technique Outline of PWSCC depth-sizing UT
Sensor for Circ. flaw
Sensor for Axial flaw
Feature • High S/N ratio is achieved by “point focusing” the ultrasonic beam and by reduction of the echo from tube inner surface. • Angle beam technique with single element probe is applied and the echo from tip of defect is used so as to enhance PWSCC detectability from multi functional UT.
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
13
PWSCC depth-sizing UT Technique Detectability and Characterization Accuracy • Detectability: 20%t for 7/8in. tube • Sizing accuracy: approximately RMSE 0.13mm (more than 30%t) for 7/8in. tube
B scope
D scope
A scope
Tip echo
Evaluated depth by UT（ %t)
C scope
100
80
60
40 Axial SCC (CCW) Axial SCC（ CW）
20
Circ. SCC (DOWN) Circ. SCC（ UP）
0 0
Axial SCC data within 22%t © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
20
Fig.5
40 60 Actual depth (%t)
80
100
Results of UT sizing 14
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
15
Improved VT Techniques Description of VT
Camera head with Lens unit for side viewing
Camera head with Lens unit for viewing ahead
Feature • Camera for both ahead and side viewing • 360 degree articulation • Accurate probe positioning with well controlled probe driver and ECT coil © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
16
Improved VT Techniques Detectability and Characterization Accuracy • Detectability: 5 to 10μm width SCC can be detected for 7/8in. Tube • Comparison with previous methods (replica and sketch of it): approximately equal to previous methods Superior SCC
3.0mm
亀裂欠陥多数
3.0mm
4.0mm
4.0mm
Camera image
Sketch
VT
Replica
Previous methods
Advantage of VT • ECT pushers and remote controlled positioning robots can be used to apply the VT probe greatly reducing radiation exposure. •
(The alternative, replicating flaws, requires inspectors much higher radiation exposure) © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
17
Contents Current situation of nuclear power plants in Japan Continuous development and improvement of inspection techniques to enhance safety and reliability • Multi-functional UT system • PWSCC depth-sizing using UT techniques • Improved VT techniques Conclusions
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
18
Conclusions • Improved UT technologies and techniques were developed to achieve more accurate characterization and depth sizing of wear and SCC type flaws. • Improved VT technologies and techniques were developed to achieve far more efficient and effective surface inspections with superior detection and characterization of SCC, and it greatly reduces radiation exposure as compared to the alternative. • These more highly enhanced NDE techniques have now proven to provide increased sensitivity for early detection while vastly improving flaw characterization accuracy (i.e. flaw orientation as well as geometric and depth sizing). • Enhanced NDE techniques like these further contribute to NPP safety and reliability by providing higher value input to continuous condition monitoring and operational assessment programs (CMOA). © 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
19
© 2016 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.
20
