Non-destructive evaluation of concrete damages of containment walls in nuclear power plants (original) (raw)
Related papers
2018
The reinforced concrete structures in nuclear power plants (NPP) are deteriorated due to aging and environmental stressors during the lifetime of the power plant. To assess construction quality and the long-term performance of reinforced concrete structures, different non-destructive testing (NDT) and evaluation (NDE) methods are used. Some of the challenges for assessing the performance of these structures are that (i) the assessment could be performed only during the annual overhauls when testing is timelimited, (ii) the accuracy and reliability of the available NDT testing devices, (iii) uncertainty of the international uniformity of the methods used for NDT tests, and (iv) the creditability of results and analyses. To increase the reliability of condition evaluation, a mock-up wall representing a NPP containment concrete wall is constructed for the critical investigation of NDT&E methods and techniques. The mock-up wall contains simulated defects, which are representing typical ...
Radiation damage evaluation on concrete shielding for nuclear physics experiments
Annals of Solid and Structural Mechanics, 2011
Concrete is commonly used as a biological shield against nuclear radiation. As long as, in the design of nuclear facility, its load carrying capacity is required together with its shielding properties, changes in the mechanical properties due to nuclear radiation are of particular significance and may have to be taken into account in such circumstances. The study presented here allows for reaching first evidences on the behavior of concrete when exposed to nuclear radiation in order to evaluate the consequent effect on the mechanical field, by means of a proper definition of the radiation damage, strictly connected with the strength properties of the building material. Experimental evidences on the decay of the elastic modulus of concrete have allowed for implementing the required damage law within a 3D F.E. research code which accounts for the coupling among moisture, heat transfer and the mechanical field in concrete treated as a fully coupled porous medium. The upgrade of the numerical model allows for assessing the durability of concrete under the effects of a radioactive environment; considerations on the ultimate strength resource in the lifetime of a nuclear structure can finally lead to its restoration in the damaged parts of the concrete slabs to preserve their load bearing capacity. The development of the damage front in a concrete shielding wall is analyzed under neutron radiation and results within the wall thickness are reported for long-term radiation spans and several concrete mixtures in order to discuss the resulting shielding properties.
Journal of Hazardous Materials, 2011
Concrete is commonly used as a biological shield against nuclear radiation. As long as, in the design of nuclear facilities, its load carrying capacity is required together with its shielding properties, changes in the mechanical properties due to nuclear radiation are of particular significance and may have to be taken into account in such circumstances. The study presented here allows for reaching first evidences on the behavior of concrete when exposed to nuclear radiation in order to evaluate the consequent effect on the mechanical field, by means of a proper definition of the radiation damage, strictly connected with the strength properties of the building material. Experimental evidences on the decay of the mechanical modulus of concrete have allowed for implementing the required damage law within a 3D F.E. research code which accounts for the coupling among moisture, heat transfer and the mechanical field in concrete treated as a fully coupled porous medium. The development of the damage front in a concrete shielding wall is analyzed under neutron radiation and results within the wall thickness are reported for long-term radiation spans and several concrete mixtures in order to discuss the resulting shielding properties.
Concrete is commonly used as a biological shield against nuclear radiation. As long as, in the design of nuclear facility, its load carrying capacity is required together with its shielding properties, changes in the mechanical properties due to nuclear radiation are of particular significance and may have to be taken into account in such circumstances. Experimental evidences on the decay of the mechanical modulus of concrete have allowed for implementing the required damage law within a 3D F.E. research code which accounts for the coupling among moisture, heat transfer and the mechanical field in concrete treated as a porous medium. The development of the damage front in a concrete shielding wall is analyzed under neutron radiation and results within the wall thickness are reported for long-term radiation spans and several concrete mixtures in order to discuss the resulting shielding properties.
Use of Non-Destructive Tests to Avert the Risk of Building Collapse
2018
Structural integrity assessment involves the determination of reliability and soundness of a structures over time and has evolved greatly over the years. The use of destructive testing is not acceptable in integrity assessment of structures since it leads to partial or wholesome destruction of the structure. This makes the use of nondestructive tests as the most viable option. As the need for structural assessment continue to acquire a high level of significance in relation to the great economic and social importance of safety and minimization of structural failures, the use of nondestructive tests (NDTs) methods continue to acquire more relevance in structural health monitoring. Due to a high rate of structural failures in Nigeria, caused by internal defects that cannot be easily detected by visual inspection, it has become necessary to adopt modern structural health monitoring tool such as NDT to assess the integrity of structures. This study assesses the integrity of a concrete c...
Journal of Advanced Concrete Technology, 2017
In 2008, Nuclear and Industrial Safety Agency (NISA) (currently integrated to the Nuclear Regulatory Authority) launched a project to develop a soundness assessment method for concrete members subject to a radiation environment. Presently, the soundness of concrete members subject to radiation is evaluated based on whether the predicted fast neutron fluence and gamma-ray dose values are lower than specific reference values in Japan, which are 1×10 20 n/cm 2 and 2×10 5 kGy, respectively. These reference values were determined based on report by Hilsdorf et al. This project begins by reviewing Hilsdorf et al.'s report, and we find that the scientific evidence for the current reference values is weak. We thus conclude that new experimental research is required to assess the current reference values and to propose a new alternative soundness assessment procedure if needed. We quantitatively evaluated the influence of neutrons, gammarays, and the resultant heating and drying processes on the strength of concrete as well as their underlying mechanisms. The irradiation experiments confirmed the degradation mechanism of concrete due to neutron irradiation. The main reason for this degradation is the metamictization of rock-forming minerals, which, in turn, leads to aggregate expansion. Due to aggregate expansion, cracks around aggregates form, which reduce the compressive strength and Young's modulus of concrete. Among the rock-forming minerals, α-quartz is the most sensitive to neutron radiation. 60 Co gamma-ray irradiation experiments demonstrated that concrete strength increased as the gamma-ray dose and gammaray flux does not have a dose-rate impact on the first radiolysis of evaporable water in cement paste within the present study. The effect of gamma-ray irradiation on the properties of concrete is equivalent to that of heating and drying. Concrete strength alteration due to heating and drying is attributed to the colloidal and porous nature of hardened cement paste and crack formation around the aggregate due to a mismatch in the volume changes of the mortar and aggregate. In addition, a numerical analysis code called DEVICE (Damage EValuation for Irradiated ConcretE) is developed to harness knowledge obtained from concrete samples to predict the distribution of the physical properties in concrete members and their changes over time. From these fundamental studies, we propose a new soundness assessment procedure for concrete members subject to radiation. We also recommend a new radiation-induced strength-degradation reference value of 1×10 19 n/cm 2 for fast neutron.
Journal of Advanced Concrete Technology, 2022
The Fukushima Daiichi Nuclear Power Plant lost its core cooling function due to the massive tsunami generated by the 2011 off the Pacific coast of Tohoku Earthquake, which caused core meltdown, resulting in high temperature inside the containment vessel and exposing the RPV pedestal, a reinforced concrete structure, to an abnormally high temperature environment. In order to cool the molten core, water was poured into the containment vessel, and the concrete structure was gradually cooled in the process. Since it will take at least 40 years from the earthquake to remove the fuel from the core, the long-term integrity of the RPV pedestal is a major concern for the decommissioning of Fukushima Daiichi. In this study, the effects of high temperature exposure and subsequent wetting conditions on concrete properties were experimentally investigated. As a result, it was confirmed that the strength of concrete decreased by heating at high temperature, but recovered under subsequent wetting conditions.
Nondestructive Test Methods for Evaluation of Concrete in Structures
A review is presented of nondestructive test methods for evaluating the condition of concrete and steel reinforcement in structures. The methods discussed include visual inspection, stress-wave methods, nuclear methods, penetrability methods, magnetic and electrical methods, infrared thermography and ground-penetrating radar. The principle of each method is discussed and the typical instrumentation is described. The testing procedures are summarized and the data analysis methods are explained. The advantages and limitations of the methods are highlighted. The report concludes with a discussion of the planning of a nondestructive testing program. The report provides general information to individuals who are faced with the task of evaluating the condition of a concrete structure and are considering the applicability of nondestructive test methods to aid in that evaluation.
Brief Overview and Comparison between Destructive and Non-Destructive Concrete testing
The Introduction to Engineering (NGN 110 ) course walks freshman engineering students at AUS through the various engineering fields and demonstrations of some applications of each field. This lab report illustrates the two of the prominent methods of concrete testing: Destructive using hydraulic compression, and Non-Destructive using the Schmidt hammer, to which students were introduced in their Civil Engineering Lab.