A Demonstration of Concrete Structural Health Monitoring Framework for Degradation due to Alkali-Silica Reaction

Abstract

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 a health diagnosis and prognosis of aging concrete structures in a nuclear power plant that is subjected to physical, chemical, environmental, and mechanical degradation. The proposed framework consists of four elements: monitoring, data analytics, uncertainty quantification, and prognosis. This report focuses on degradation caused by alkali-silica reaction (ASR). Controlled specimens were prepared to develop accelerated ASR degradation. Different monitoring techniques (i.e., thermography, digital image correlation, mechanical deformation measurements, nonlinear impact resonance acoustic spectroscopy, and vibro-acoustic modulation) were used to detect the damage caused by ASR. Heterogeneous data from multiple techniques were used for damage diagnosis and prognosis and quantification of the associated uncertainty using a Bayesian network approach. Additionally, the MapReduce technique has been demonstrated with synthetic data. This technique can be used in the future to handle large amounts of observation data obtained from online monitoring of realistic structures. vi vii EXECUTIVE SUMMARYOne challenge for the current fleet of light water reactors in the United States is age-related degradation of their passive assets that include concrete, cables, piping, and the reactor pressure vessel. As the current fleet of nuclear power plants (NPPs) continues to operate up to 60 years or beyond, it is important to understand the current and the future health condition of passive assets under different operating conditions that would support operational and maintenance decisions. To ensure long-term safe and reliable operation of the current fleet, the U.S. Department of Energy's Office of Nuclear Energy funds the Light Water Reactor Sustainability Program to develop the scientific basis for extending operation of commercial light water reactors beyond the current license extension period.Among the different passive assets of interest in NPPs, concrete structures are investigated in this research project. Reinforced concrete structures found in NPPs can be grouped into four categories: (1) primary containment, (2) containment internal structures, (3) secondary containments/reactor buildings, and (4) spent fuel pool and cooling towers. These concrete structures are affected by a variety of degradation mechanisms that are related to chemical, physical, and mechanical causes and to irradiation. Age-related degradation of concrete results in gradual microstructural changes (e.g., slow hydration, crys...

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

“…The standard test methods for determining the potential alkali-silica reactivity and for determination of the amount of time needed for concrete to change due to ASR are documented in ASTM C1567-13 and ASTM C1293-08b, respectively. Earlier reports by Mahadevan et al (2016Mahadevan et al ( , 2017 have studied various techniques and found them to be useful in damage detection. The VAM technique, investigated in detail in this report, shows particular promise in damage localization.…”

“…cast on December 21, 2015 and cured at Vanderbilt University. The details on casting and curing process of this concrete sample is discussed in detail the report by Mahadevan et al (2016). Figure 3 shows an image of the slab immediately after the mold was removed.…”

“…The framework will help plant operators to make risk-informed decisions on structural integrity, remaining useful life, and concrete structure performance. The demonstration performed at Vanderbilt University using various techniques to assess ASR degradation in controlled concrete specimens was reported in Mahadevan et al (2016Mahadevan et al ( , 2017.…”

“…The objective of this report is to examine the use of vibro-acoustic modulation (VAM) in informing the PHM framework. A series of experiments were conducted at the Vanderbilt University to provide sufficient degradation data in support of the PHM framework (Mahadevan et al 2014;Mahadevan et al 2016) used to examine and forecast the condition of aging concrete structures in NPPs. Within this experimental campaign, multiple concrete slab samples are exposed to different accelerated aging conditions in a laboratory to ensure formation of ASR gel within an observable time frame.…”

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

“…The framework will enable plant operators to make risk-informed decisions on structural integrity, remaining useful life, and performance of the concrete structure. The demonstration examples performed at Vanderbilt University using various techniques to assess the ASR degradation in controlled concrete specimens were reported in Mahadevan et al (2016).…”