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Nonlinear Ultrasonic Evaluation for Corrosion Assessment of Steel Plates Embedded in Concrete

Nilsson, Markus LU (2024)
Abstract
The growing demand for sustainable electricity production, coupled with global uncertainties, highlights the need for nations to achieve self-sufficiency in producing electricity. Nuclear power, which provides around 30% of Sweden's electricity, plays a critical role in delivering fossil-free electricity. As many nuclear plants are near the end of their designated lifespans, extending their operational periods is crucial to meeting current and future demands.
Ensuring safe nuclear operations is vital. To address this, the Swedish Energy Research Centre, along with the Swedish Radiation Safety Authority and other industry partners, runs a research program focusing on concrete-related challenges in nuclear power. A significant issue... (More)
The growing demand for sustainable electricity production, coupled with global uncertainties, highlights the need for nations to achieve self-sufficiency in producing electricity. Nuclear power, which provides around 30% of Sweden's electricity, plays a critical role in delivering fossil-free electricity. As many nuclear plants are near the end of their designated lifespans, extending their operational periods is crucial to meeting current and future demands.
Ensuring safe nuclear operations is vital. To address this, the Swedish Energy Research Centre, along with the Swedish Radiation Safety Authority and other industry partners, runs a research program focusing on concrete-related challenges in nuclear power. A significant issue within this program is detecting corrosion in containment liners – welded plate constructions that serve as gas-tight barriers to prevent the release of radioactive particles. These liners, sometimes embedded in thick concrete walls of reactor containment buildings, are difficult to inspect. Corrosion can compromise their structural integrity long before visible damage appears, making early detection essential for planning preventive measures.
This thesis evaluates nonlinear ultrasonic methods for detecting and assessing corrosion in embedded containment liners. Ultrasonic testing uses sound waves above the human audible range to image internal structures. However, in concrete, high-frequency sound waves are quickly absorbed, necessitating the use of low-frequency waves, which reduces the ability to resolve small defects. Nonlinear ultrasonic evaluation offers a solution. Defects like cracks cause elastic nonlinearity, leading to waveform distortion. This distortion creates new frequency components in the sound wave, allowing for the detection of defects regardless of the wave's frequency. The strength of these new components relative to the original frequency provides a measure of damage in the material.
The research, conducted on small-scale laboratory specimens, primarily focused on pre-corroded steel plates. The results demonstrate that nonlinear evaluation can locate and assess corrosion in embedded plates, with more severe corrosion yielding stronger nonlinear indications. Additionally, the method shows potential for detecting embedded foreign objects, such as wood, and separations between the plate and concrete. The findings suggest that combining conventional and nonlinear ultrasonic imaging techniques can provide a better understanding of a structure's damage state. However, further experiments on more realistic specimens are necessary to fully evaluate the methods' detection capabilities. These experiments should consider the challenges posed by intrinsic concrete micro-cracking, coarse aggregates, reinforcement, and large dimensions typical in nuclear power plants. 
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Abstract (Swedish)
Den växande efterfrågan på hållbar och miljövänlig elproduktion, tillsammans med globala osäkerheter, understryker behovet för nationer att uppnå självförsörjande produktion av el. Kärnkraft, som står för cirka 30% av Sveriges elproduktion, spelar en avgörande roll i att leverera fossilfri el. Eftersom många kärnkraftverk närmar sig slutet av sin planerade livslängd är det avgörande att förlänga deras driftsperioder för att möta nuvarande och framtida behov.
Att säkerställa säker drift av kärnkraftverk är av yttersta vikt. För att hantera detta driver Energiforsk AB, tillsammans med Strålsäkerhetsmyndigheten och andra branschpartners, ett forskningsprogram som fokuserar på betongtekniska utmaningar inom kärnkraft. En viktig fråga inom... (More)
Den växande efterfrågan på hållbar och miljövänlig elproduktion, tillsammans med globala osäkerheter, understryker behovet för nationer att uppnå självförsörjande produktion av el. Kärnkraft, som står för cirka 30% av Sveriges elproduktion, spelar en avgörande roll i att leverera fossilfri el. Eftersom många kärnkraftverk närmar sig slutet av sin planerade livslängd är det avgörande att förlänga deras driftsperioder för att möta nuvarande och framtida behov.
Att säkerställa säker drift av kärnkraftverk är av yttersta vikt. För att hantera detta driver Energiforsk AB, tillsammans med Strålsäkerhetsmyndigheten och andra branschpartners, ett forskningsprogram som fokuserar på betongtekniska utmaningar inom kärnkraft. En viktig fråga inom detta program är att upptäcka korrosion i tätplåtar – svetsade plåtkonstruktioner som fungerar som gastäta barriärer för att förhindra utsläpp av radioaktiva partiklar. Dessa tätplåtar, som ofta är ingjutna i tjocka betongväggar i reaktorinneslutningarna, är svåra att inspektera. Korrosion kan äventyra deras täthet långt innan synliga skador uppstår, vilket gör tidig upptäckt avgörande för att planera förebyggande åtgärder.
Denna avhandling utvärderar icke-linjära ultraljudsmetoder för att upptäcka och utvärdera korrosion i ingjutna tätplåtar. Ultraljudsprovning använder ljudvågor över det mänskliga hörbara området för att avbilda inre strukturer. I betong dämpas dock högfrekventa ljudvågor effektivt, vilket nödvändiggör användning av förhållandevis lågfrekventa vågor, vilket minskar förmågan att upptäcka små defekter. Icke-linjär utvärdering erbjuder en lösning. Defekter som sprickor orsakar elastisk icke-linjäritet, vilket leder till vågformsförvrängning. Denna distorsion skapar nya frekvenskomponenter i ljudvågen, vilket möjliggör detektering av defekter oavsett vågens frekvens. Styrkan hos dessa nya komponenter i förhållande till den ursprungliga frekvensen ger ett mått på skadeläget i materialet.
Forskningen, som genomfördes på småskaliga laboratorieprover, fokuserade främst på förkorroderade stålplåtar. Resultaten visar att icke-linjär utvärdering kan lokalisera och utvärdera korrosion i ingjutna plåtar, där allvarligare korrosion ger starkare icke-linjära indikationer. Dessutom visar metoden potential för att upptäcka ingjutna främmande föremål, såsom trä, och separationer mellan plåten och betongen.
Resultaten tyder på att en kombination av konventionell och icke-linjär utvärdering vid avbildning kan ge en god förståelse för en strukturs skadeläge. Ytterligare experiment på mer realistiska prover är dock nödvändiga för att fullt ut utvärdera metodernas detektionsförmåga. Dessa experiment bör beakta de utmaningar som ställs av naturliga mikrosprickor i betong, grova ballastmaterial, rikhaltig armering och stora dimensioner typiska för faktiska kärnkraftverk.
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Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr. Abraham, Odile, Gustave Eiffel University, France.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Nuclear, NDT, Ultrasound, Nonlinearity
publisher
Engineering Geology, Lund University
defense location
Lecture Hall V:D, building V, Klas Anshelms väg 14, Faculty of Engineering LTH, Lund University, Lund.
defense date
2024-12-06 09:00:00
ISBN
978-91-8104-206-1
978-91-89919-22-8
978-91-8104-205-4
project
Detection of concrete-emdedded steel liner corrosion using nonlinear ultrasound
language
English
LU publication?
yes
id
089e978e-bfc3-47da-a9f7-b2020bcc9b0b
date added to LUP
2024-11-05 14:45:52
date last changed
2024-11-13 09:32:40
@phdthesis{089e978e-bfc3-47da-a9f7-b2020bcc9b0b,
  abstract     = {{The growing demand for sustainable electricity production, coupled with global uncertainties, highlights the need for nations to achieve self-sufficiency in producing electricity. Nuclear power, which provides around 30% of Sweden's electricity, plays a critical role in delivering fossil-free electricity. As many nuclear plants are near the end of their designated lifespans, extending their operational periods is crucial to meeting current and future demands.<br/>Ensuring safe nuclear operations is vital. To address this, the Swedish Energy Research Centre, along with the Swedish Radiation Safety Authority and other industry partners, runs a research program focusing on concrete-related challenges in nuclear power. A significant issue within this program is detecting corrosion in containment liners – welded plate constructions that serve as gas-tight barriers to prevent the release of radioactive particles. These liners, sometimes embedded in thick concrete walls of reactor containment buildings, are difficult to inspect. Corrosion can compromise their structural integrity long before visible damage appears, making early detection essential for planning preventive measures.<br/>This thesis evaluates nonlinear ultrasonic methods for detecting and assessing corrosion in embedded containment liners. Ultrasonic testing uses sound waves above the human audible range to image internal structures. However, in concrete, high-frequency sound waves are quickly absorbed, necessitating the use of low-frequency waves, which reduces the ability to resolve small defects. Nonlinear ultrasonic evaluation offers a solution. Defects like cracks cause elastic nonlinearity, leading to waveform distortion. This distortion creates new frequency components in the sound wave, allowing for the detection of defects regardless of the wave's frequency. The strength of these new components relative to the original frequency provides a measure of damage in the material.<br/>The research, conducted on small-scale laboratory specimens, primarily focused on pre-corroded steel plates. The results demonstrate that nonlinear evaluation can locate and assess corrosion in embedded plates, with more severe corrosion yielding stronger nonlinear indications. Additionally, the method shows potential for detecting embedded foreign objects, such as wood, and separations between the plate and concrete. The findings suggest that combining conventional and nonlinear ultrasonic imaging techniques can provide a better understanding of a structure's damage state. However, further experiments on more realistic specimens are necessary to fully evaluate the methods' detection capabilities. These experiments should consider the challenges posed by intrinsic concrete micro-cracking, coarse aggregates, reinforcement, and large dimensions typical in nuclear power plants. <br/>}},
  author       = {{Nilsson, Markus}},
  isbn         = {{978-91-8104-206-1}},
  keywords     = {{Nuclear; NDT; Ultrasound; Nonlinearity}},
  language     = {{eng}},
  publisher    = {{Engineering Geology, Lund University}},
  school       = {{Lund University}},
  title        = {{Nonlinear Ultrasonic Evaluation for Corrosion Assessment of Steel Plates Embedded in Concrete}},
  url          = {{https://lup.lub.lu.se/search/files/199092213/Thesis_MN_FinalVer.pdf}},
  year         = {{2024}},
}