Activities in Support of Continuing the Service of Nuclear Power Plant Safety Related Concrete Structures

Miele

Karve

et al. 2018

The objectives of this ongoing research project focus on health monitoring and data analytics of concrete slabs with alkali-silica reaction (ASR) degradation. Researchers at Vanderbilt University cast a controlled concrete slab with four pockets of reactive aggregates (pure silica, wells, placitas, and spratt) and cured in representative conditions to accelerate degradation due to ASR. A set of four concrete samples were also cast and cured at the University of Alabama for ASR testing. Of these four samples, two slabs contained reactive aggregates while the other two had the non-reactive aggregate counterparts mixed throughout the samples. Vibro-acoustic testing was used on these slabs to locate ASR damage within the reactive samples. Vibro-acoustic modulation (VAM) is a vibration-based nondestructive examination (NDE) method that utilizes signatures of nonlinear dynamic interactions on contact surfaces of crack or delamination damage to detect and localize the damage. VAM analysis was conducted on both the Vanderbilt and Alabama samples using multiple variables for damage detection and localization. This report discusses in detail the results from the data analysis of the vibroacoustic testing on concrete slabs cured at Vanderbilt University and the University of Alabama. Results for damage localization are dependent on multiple variables used in the vibro-acoustic modulation experiments. A major focus of this report is to quantify the uncertainty in the diagnosis due to multiple factors and uncertainty sources. Researchers applied the uncertainty quantification methodology presented in this report to VAM-based diagnosis and prognosis. However, the methodology is general, and is capable of being applied to multiple techniques that collect spatially distributed data. Future work needs to investigate the incorporation of uncertainty quantification in developing a robust Prognostics and Health Management framework. Digital image correlation is a three-dimensional, full-field, optical NDE technique to measure contour, deformation, vibration, and strain. This report also discusses the application of the digital image correlation technique to study ASRrelated degradation on a large concrete specimen at the University of Tennessee. Research observations are collected and presented in this report. v

Section: Introductionmentioning

confidence: 99%

Uncertainty Quantification in Vibro-Acoustics Diagnosis of Alkali-Silica Reaction Degradation in Medium-Sized Concrete Samples

Miele

Karve

et al. 2018

“…The concrete structures are grouped into the following four categories: (1) primary containment, (2) containment internal structures, (3) secondary containment/reactor buildings, and (4) other structures such as used fuel pools, dry storage casks, and cooling towers. These concrete structures are affected by a variety of chemical, physical, and mechanical degradation mechanisms, such as a alkali-silica reaction (ASR), chloride penetration, sulfate attack, carbonation, freeze-thaw cycles, shrinkage, and mechanical loading (Naus 2007). The age-related deterioration of concrete results in continuing microstructural changes (e.g., slow hydration, crystallization of amorphous constituents, and reactions between cement paste and aggregates).…”

Section: Introductionmentioning

confidence: 99%

Digital Image Correlation of Concrete Slab at University of Tennessee, Knoxville

Agarwal

Pham

et al. 2016

Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Some degradation mechanisms of concrete manifest themselves via swelling or by other shape deformation of the concrete. Specifically, degradation of concrete structures damaged by the alkali-silica reaction (ASR) is viewed as one of the dominant factors impacting the structural integrity of aging nuclear power plants. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. Numerous nondestructive examination techniques (i.e., thermography, digital image correlation, mechanical deformation measurements, nonlinear impact resonance [DIC] acoustic spectroscopy, and vibro-acoustic modulation) are used to detect the damage caused by the ASR. DIC techniques have been increasing in popularity, especially in micro-and nano-scale mechanical testing applications due to its relative ease of implementation and use. Advances in computer technology and digital cameras help this method moving forward. To ensure the best outcome of the DIC system, important factors in the experiment are identified. They include standoff distance, speckle size, speckle pattern, and durable paint. These optimal experimental options are selected basing on a thorough investigation. The resulting DIC deformation map indicates that this technique can be used to generate data related to the degradation assessment of concrete structure damaged by the impact of the ASR.

“…The concrete structures are grouped into four categories: primary containment, containment internal structures, secondary containment/reactor buildings, and other structures such as used fuel pools, dry storage casks, and cooling towers. These concrete structures are affected by a variety of chemical, physical, and mechanical degradation mechanisms such as alkali-silica reaction (ASR), chloride penetration, sulfate attack, carbonation, freeze-thaw cycles, shrinkage, and mechanical loading (Naus, 2007). The age-related deterioration of concrete results in continuing microstructural changes (slow hydration, crystallization of amorphous constituents, reactions between cement paste and aggregates, etc.).…”

Section: Introductionmentioning

confidence: 99%

A Simple Demonstration of Concrete Structural Health Monitoring Framework

Agarwal

Cai

et al. 2015

Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This ongoing research project is seeking to develop a probabilistic framework for health diagnosis and prognosis of aging concrete structures in a nuclear power plant that is subjected to physical, chemical, environment, and mechanical degradation. The proposed framework consists of four elements: damage modeling, monitoring, data analytics, and uncertainty quantification. This report describes a proof-of-concept example on a small concrete slab subjected to a freeze-thaw experiment that explores techniques in each of the four elements of the framework and their integration. An experimental setup at