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© Swedish Qualification Centre AB, 17-07-11--14 Page 1
Effectiveness Evolution of DMW Inspection Techniques and Crack Simulations
Assessed Through the International PARENT Project
Tommy Zettervall, SQC
IAEA TM-55108 in Vienna
Background and Objectives of PARENT
Results and conclusions from the blind trials and reference to NUREC reports
Crack simulation and signal response
Conclusions from cracks simulation project
© Swedish Qualification Centre AB, 17-07-11--14 Page 2 IAEA TM-55108 in Vienna
Presentation outline
In the outage of year 2000 a number of surface breaking transverse defects were detected during the in-service inspection (ISI) of dissimilar connection welds (Alloy 182) in the RC-loops
The cracks were, with one exception, oriented across the weld at an angle close to 90°
IDSCC appeared in the weld metal, primarily consisting of Alloy 182
The cracks occurred as a result of internal welding repairs
Crack opening displacement COD decreases at the intersection of the crack with the component surface
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ISI experience from Sweden
In the USA there have been a number of events related to PWSCC in DMWs There have been 17 events reported for butt weld PWSCC from 1993 through 2012 Nearly one-half of these events involved PWSCC that had circumferential flaw orientation Axial flaws were typically deeper in through wall extent than the circumferential flaws This was one of the driving forces for the PINC and the PARENT programs
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ISI experience from USA
Program to Assess the Reliability of Emerging Non-destructive Techniques PARENT (2010-2017) was a continuation of the work begun in PINC (2006-2010) and applies the lessons learned to a series of open and blind international round-robin tests (PISC, PINC, PARENT)
The objectives were:
To pool International expertise and resources
To identify and quantitatively assess NDE methods for accurately detecting, characterizing, and sizing PWSCC/IDSCC cracks
To investigate and document field locations and crack morphologies for PWSCC/IDSCCin an electronic database “ATLAS”
To utilize lessons learned from PINC to employ techniques to manufacture representative NDE mock-ups containing realistic PWSCC/IDSCC
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Background and Objectives of PARENT
The following organizations were part of PARENT: USA (NRC, PNNL) Japan (NRA, JAPEIC, MHI, NPP’s) Korea (KINS, KHNP) Europe (SSM, ENSI, VTT, SQC, SVTI)
A total number of 29 laboratories participate and contribute with NDE-data
19 open test assemblies and 13 blind test assemblies were used, representing small-bore piping, large-bore piping and BMIs
The test blocks contained laboratory-grown stress corrosion cracks, weld solidification cracks and repairs
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PARENT organizations
SBDMW (BWR Safe-End nozzle)
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LBDMW (PWR Safe-End nozzle)
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BMI
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Conclusions from PARENT
I.D. procedures show better performance over O.D. procedures
Circumferential flaws exhibiting a greater likelihood of detection than axial flaws, as a function of depth
I.D. procedures that include ECT performed better at length sizing
Flaw orientation did not show an influence on depth sizing performance based on RMSE results
PAUT procedures show better performance than conventional UT procedures on O.D
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Conclusions from PARENT
PARENT results indicate substantial improvement in PAUT performance compared with PINC
One of the conventional UT procedures exhibiting the poorest performance for examinations of SBDMWs using only one angle for inspection
One of five procedures applied for length sizing on LBDMW test blocks on O.D. did not meet the intent of ASME Code
One of nine procedures applied for length sizing on SBDMW test blocks on O.D. did not meet the intent of ASME Code
Two of three procedures applied for depth sizing on LBDMW test blocks by I.D. surface access meet the intent of the ASME Code Section XI requirement of RSME within 3.12 mm
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Conclusions from PARENT
Two of nine procedures applied for depth sizing on SBDMW test blocks by O.D. surface access meet the intent of the ASME Code, Section XI requirement of RSME within 3.12 mm
Insufficient data was collected on BMI test blocks to draw firm conclusions regarding detection and length sizing performance, due to the flaws implant technique
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© Swedish Qualification Centre AB, 17-07-11--14
One of the significant differences with PARENT versus PINC was that many more procedures combined a variety of techniques In PARENT
Nevertheless, the majority of the results from PINC were confirmed by the PARENT RRT results
Multiple techniques tended to perform a higher POD and smaller sizing RMSE values in PARENT
Page 13 IAEA TM-55108 in Vienna
Procedure families POD for Flaw depth of
False call rate 5 mm 10 mm 15 mm
Eddy Current 0,22 0,72 0,96 0,03
UT 0,15 0,31 0,67 0,07
PAUT 0,23 0,58 0,87 0,06
UT + ECT 0,15 0,30 0,50 0,07
UT + PAUT 0,55 0,98 1,00 0,03
UT + TOFD 0,37 0,90 0,99 0,04
UT + TOFD + ECT 0,21 0,46 0,74 0,08
Brief comparison between PINC and PARENT
The POD results for the DMW round robin show significant variability in detection performance based upon the technique, procedure and inspection team None of the NDE techniques in PISC and PINC demonstrated the capability to accurately depth size flaws to the requirements specified in ASME Section XI, and tended to slightly undersize the flaws The use of a diversity of NDE techniques tended to improve performance for detection, depth sizing and length sizing The advances in the use of PAUT is significant and procedures including this technology tended to perform better than those relying on conventional UT
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Lessons learned
Having access to the surface from which IDSCC/PWSCC initiates is preferred All three studies recommend the need for procedure, equipment and personnel qualification All three RRTs support only using correct flaw simulation techniques to obtain NDE responses realistic of service degradation in test assemblies
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Lessons learned, cont.
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© Swedish Qualification Centre AB, 17-07-11--14 Page 17
PARENT – Flaw simulation and implant of real flaws
The main objective of this project was to developed a technique to cut out real cracks and weld them into a new test block with correct geometry
Another objective was to verify that solidification cracks SC, that are used in qualification specimens, give a realistic signal response
An idea that emerged was to cut out real cracks and weld them into a new INCONEL-block with a NPP realistic geometry
Phase1 – Defect free coupon’s
Phase 2 – EDM-notches in Inconel 182
Phase 3 – Solidification cracks in Inconel 182 + one fatigue crack from
Phase 4 – Implant of real cracks into a new weld/pipe
IAEA TM-55108 in Vienna
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Example of a field IDSCC with ECT
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TOFD on the same field IDSCC
Part 3 – Solidification + fatigue cracks, ECT
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Part 3 – Solidification + fatigue cracks, UT ID
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Part 3 – Solidification crack No. 2, P-A OD
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Part 4 – Coupon from P32
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Part 4 – ENSI cracks, ECT
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P28 P29 P31 P32
Part 4 – SC and ENSI cracks, UT ID
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SC
ENSI
The height measurements
gave small different
values depending on
probe and scan direction,
and therefore we took the
average values from the
different probes and
directions.
Several tip signals in
depth of a crack depends
on the tightness and
“bridges” between crack
surfaces in depth, and it
will cause a problem to
find the deepest tip
signal.
Part 4 – SC and ENSI crack, TOFD ID
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SC
ENSI
Conclusions from crack simulation project
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The project developed a technique to cut out real cracks and weld them into a
new test block with correct geometry
Detection
The SC simulations were more conservative compared to the real cracks with
ECT, in the sense that the defects were more closed in the surface
Sizing
The signal pattern for UT is typical for what is considered characteristic for
IDSCC/PWSCC, i.e. multiple and more or less weak signals in depth, which
have an impact on the through wall sizing
Height measurement of IDSCC/PWSCC is a challenging process and should
be a part for future work and projects
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