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We explicitly find the minima as well as the minimum points of the geodesic length functions for the family of filling (hence non-simple) closed curves, \(a^2b^n\) (\(n\ge 3\)), on a complete one-holed hyperbolic torus in its relative Teichmüller space, where a, b are simple closed curves on the one-holed torus which intersect exactly once transver...
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... Concrete structures are always associated with steel components, such as reinforcements, liners, post-tensioning systems, and anchorages. The list of possible degradation mechanisms for reinforced concrete include more than 30 different modes according to the Expended Materials Degradation Analysis (EMDA) report [1]. The EMDA report analyzed four factors: existing knowledge, likelihood of occurrence, significance for the LWR's component operation, and confidence of the expert's panel in their assessment. ...
... Two mechanisms emerged as research priorities: irradiation effects and alkali reactions. "Irradiation for containmentsconcrete component emerged as the most important degradation mechanism, mainly driven by the fact that insufficient data is available to improve the level of knowledge about the effects of irradiation on concrete mechanical properties" [1], and although "ASR is well documented by the operating experience (for bridges and dams in particular) and scientific literature, its high ranking in the EMDA analysis describes the need to assess its potential consequences on the structural integrity of the containment" [1]. These conclusions have defined the research activities of the US Department of Energy's Light Water Reactor Sustainability (LWRS) program until now. ...
... Two mechanisms emerged as research priorities: irradiation effects and alkali reactions. "Irradiation for containmentsconcrete component emerged as the most important degradation mechanism, mainly driven by the fact that insufficient data is available to improve the level of knowledge about the effects of irradiation on concrete mechanical properties" [1], and although "ASR is well documented by the operating experience (for bridges and dams in particular) and scientific literature, its high ranking in the EMDA analysis describes the need to assess its potential consequences on the structural integrity of the containment" [1]. These conclusions have defined the research activities of the US Department of Energy's Light Water Reactor Sustainability (LWRS) program until now. ...
Concrete structures in light water reactors (LWRs) are exposed to varied in-service environmental conditions (e.g., irradiation, moisture ingress, temperature). In conjunction with the specific chemical composition of the concrete constituents, several degradation modes can be triggered, including radiation-induced volumetric expansion, alkali-silica reaction (ASR), and corrosion. For about a decade, the US Department of Energy's Light Water Reactor Sustainability (LWRS) program has been comprehensively addressing research needs regarding the effects of concrete irradiation and the structural significance of ASR. Despite some remaining knowledge gaps (e.g., comparing possible rate effects caused by accelerated experimental conditions with in-service degradation that requires characterizing harvested materials), the existing corpus of knowledge favorably supports the second license renewal's application of operating LWRs. The possibility of operation beyond 80 years is governed by endogenous (e.g., aging management, operation costs) and exogenous (e.g., natural gas, deployment of advanced nuclear reactors) economic factors but also by technical issues associated © 2022 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (hxxp://energy.gov/downloads/doe-public-access-plan). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s). Paper No. 17261 2 with doubling the original 40-year license period. Over such an extended time, the possibility of degradation to mechanism synergies must be studied to ensure that concrete structures will satisfy their desired performance up to 100 years of operation. This article highlights the varied coupling mechanisms among irradiation, ASR, corrosion, and microcracking in concrete and discusses existing knowledge gaps.
... The latter aspect has been recently addressed as equivalent to that of concrete heating and drying [3]. Nevertheless, for long-term creep phenomena the mechanism requires a better understanding [3,23,24]. Creep may lead to potential relaxation of RIVE-induced stresses in the cement paste or be influenced by gamma irradiation [25], since creep is known to be related to a coupled moisture-heat transport process. ...
The need for long-term predictions of the performance of old nuclear power plants concrete shielding all around the world has recently relaunched the issue of predictive modeling of the deterioration mechanisms associated to irradiated concrete, both theoretically and numerically. A robust numerical model for describing concrete affected by prolonged nuclear irradiation, based on a coupled thermo-hydro-mechanical formulation, is proposed and the main features that are phenomenologically responsible for the degradation of concrete material at the mesoscale level are discussed. The study is conducted at the mesoscale to account for the antagonist action of the cement paste and aggregates when irradiated. Radiation-induced damage is assimilated to mechanical damage in the proposed formulation in that radiation-induced volumetric expansion of aggregates is conceived as the source of triggering of damage in the surrounding paste. The numerical results for plain concrete samples exposed to severe radiation fluences and high temperature are juxtaposed with experimental data, showing that the model agrees satisfactorily with the general tendency of the irradiated concrete stiffness evolution and dehydrated water mass of the sample. On the other hand, the model tends to underestimate its global radiation-induced volumetric expansion.
... Aging management of concrete structures in nuclear power plants is often planned based on knowledge of general structures. Many studies such as by Graves et al. (2014) have been conducted on the durability and maintenance of concrete structures in the general environment. However, the deterioration of concrete members in nuclear power plant facilities under neutron and gamma irradiation has not been fully investigated. ...
... Cracks formed through the containment building, with repair estimates exceeding 3 billion US dollars, which led to a permanent closure of the plant (Duke Energy 2013). Multiple time-dependent and degradation mechanisms are at play as concrete ages, including creep, damage, radiation-induced expansion, internal and external chemical attacks such as freeze-thaw, alkali-silica reaction (ASR), and delayed ettringite formation (DEF) (Graves et al. 2014). Hardened concrete is a heterogeneous composite composed of coarse aggregates, sand and hydrated cementitious materials forming a complex porous network. ...
Ten years after the Fukushima Daiichi Nuclear Power Plant accident, the nuclear industry is facing a pivotal moment. As we face growing public concerns in Japan and a highly competitive environment driven by the low cost of fossil energies in the United States, a gradual reduction of the nuclear power fleetʼs capacity may seem inevitable. Overcoming the challenges posed by nuclear plant aging management during decommissioning could add several decades to the service life of the concrete infrastructure. Nuclear energy provides sustainable, carbon-free electricity and the necessary base-load power generation that is indispensable to a safe, dependable, economically viable generation mix of energy sources, including renewable energies. Because replacement of existing concrete structures in reactor buildings is economically unrealistic, the sustained long-term operation of nuclear power plants requires that the structural performance of the concrete structures, systems and components (SSCs) is maintained during an extended service period, possibly for another 80+ years. Extending nuclear power plant operations requires sound, comprehensive, and reliable justifications of plant safety. Therefore, it is imperative that research be conducted to assess the condition, manage aging, and evaluate the performance of the materials, members, and structures currently in service. Furthermore, predictive approaches must be developed to assess future performance of materials, members, and structures. Based on these factors, a second special issue on the aging management of concrete structures in nuclear power plants was created. This issue provides a state-of-the-art review highlighting the current technical challenges for aging management of these structures, and it presents options to address these challenges. This special issue includes 12 pertinent manuscripts addressing the varied technical issues associated with the long-term operation of nuclear power plants. Five of these manuscripts (18-648, 18-618, 18-558, 19-555, 19-668) focus on the effects of gamma and neutron irradiation on concrete and its constituents, bridging the gap between the fundamental understanding of the effect of gamma irradiation (19-555, 18-558) and the advanced modeling techniques using lattice-based models that are applied at varied scales to provide predictive simulation of the physical and engineering properties of concrete-forming aggregates (19-668), concrete (18-648), and the concrete biological shield (18-618). Two papers complement this research by presenting (1) a novel automated petrographic x-ray‒based characterization method (19-395), and (2) a method to implement advanced characterization of the aggregate forming mineral phases into a fast Fourier transform (FFT-based simulation framework (19-149). These techniques may also be used to address other degradation modes, such as the alkali-silica reaction (ASR). Notably, this pathology is addressed in this issue in two original papers focused on the modeling and monitoring of the structural performance of ASR-affected shear walls (19-280, 19-477). The effects of chemical attacks caused either by sulfate ingress (19-796) or carbonation (19-382) are also presented in this special issue, with a focus on the effects of the actual operating conditions in nuclear power plants. A discussion of the structural performance of concrete structures that support vibrating equipment such as that found in a turbine building of a nuclear power plant is also included (19-414). These research works provide invaluable state-of-the-art overview of the knowledge, methodology, and simulation techniques necessary to reinforce public trust and to provide industry stakeholders and regulatory bodies with the guidance and approaches needed to address future nuclear power generation technologies.
... Cracks formed through the containment building, with repair estimates exceeding 3 billion US dollars, which led to a permanent closure of the plant (Duke Energy 2013). Multiple time-dependent and degradation mechanisms are at play as concrete ages, including creep, damage, radiation-induced expansion, internal and external chemical attacks such as freeze-thaw, alkali-silica reaction (ASR), and delayed ettringite formation (DEF) (Graves et al. 2014). Hardened concrete is a heterogeneous composite composed of coarse aggregates, sand and hydrated cementitious materials forming a complex porous network. ...
As the nuclear fleet in the United States ages and subsequent license renewal applications grow, the prediction of concrete durability at extended operation becomes more important. To address this issue, a Fast-Fourier Transform (FFT) method is utilized to simulate aging-related degradation of concrete within the Microstructure Oriented Scientific Analysis of Irradiated Concrete (MOSAIC) software. MOSAIC utilizes compositional phase maps to simulate damage from radiation-induced volumetric expansion (RIVE), applied force, creep, and thermal expansion. This compositional detail allows each mineral in the microstructure to be assigned specific material properties, allowing the simulation to be as accurate and representative as possible. The principal goal of MOSAIC is to simulate the effects of nonlinear aging mechanisms occurring in nuclear concrete on the macroscopic mechanical properties, using only the aggregate microstructure compositional information as a starting point. Several realistic example simulations are shown to demonstrate the utility and uniqueness of the MOSAIC software.
... As shown in Fig. 6, the compression ignition engines serve in steam stations to supply auxiliary power and in some industrial plants and institutional as emergency stand-by sources of energy in the event of main power-supply failure. In some smaller systems I.C engines work with steam units to supply the peakload demands on the plant [11]. IV. ...
... Diesel Engine and Compression Engine[11] ...
... As late as 2007, it was reported that to date, no incidences of ASR-related damage have been identified in U.S. nuclear power plants [3]. Nevertheless a report seeking to identify potential concrete issues affecting an NCC life extension from 60 to 80 years, identified ASR as a high risk problem [4]. Indeed, a first case of ASR in an NCC was reported by ADAMS Accession No. ML 12160A374 [5]. ...
The alkali silica reaction (ASR) is a complex multifaceted deleterious one with broad implications on the structural integrity of a nuclear concrete containment (NCC). When compounded with seismic excitation, the structural assessment is even more complex, specially when its intrinsic shear strength is not yet well understood. This paper will highlight 3 years of a holistic research on the pre-cited problem, highlighting the interaction of various tasks, while details can be found in referenced publications. The reported work is broken into four integrated parts: (a) Design of a reactive concrete mix representative of the one in an NCC and likely to expand sufficiently within 6 months; (b) Specimens expansion monitoring in terms of different dimensions and reinforcement ratios for a year; (c) Large-scale testing of shear specimens to evaluate both material (no reinforcement) and structural (with reinforcement) components to assess impact of ASR; and (d) 3D probabilistic nonlinear seismic analyses of an NCC subjected to 40 years of ASR expansion followed by multiple dynamic excitation. It will be shown that the true shear strength of concrete material is affected by ASR, and that this reduction will reduce the seismic resistance of an NCC.
... The morphology and microstructural arrangement of these minerals are critical in this degradation process. Thus, determining any specific concrete's tolerance/susceptibility against irradiation in order to inform potential nuclear power plant (NPP) license renewal (LR) [6] requires a detailed characterization of its microstructure, as well as advanced modeling. To this end, the US DOE Light Water Reactor Sustainability (LWRS) Program has been developing a holistic approach centered on a numerical platform combining the Microstructure-Oriented Scientific Analysis of Irradiated Concrete (MOSAIC) for image analysis and irradiation damage simulation with experimental data from the Irradiated Minerals Aggregates and Concrete (IMAC) database. ...
... Though potential concrete degradation (e.g. alkali silica reaction; ASR) in a nuclear containment vessel structure (NCVS) has long been recognized (Graves et al., 2013), there were no provisions to handle this situation. Hence, when ASR was found in an NCVS, industry and regulatory agencies entered into uncharted territory with (to the best of the authors' knowledge) practically no input from the research community. ...
... In anticipation for this requirement a joint NRC-DOE (Department of Energy) effort objectively ranked the safety significance of materials degradation issues, particularly as they relate to subsequent license renewal. Using a Phenomena Identification and Ranking Table (PIRT), ASR, acid attack and creep emerged as secondarily important mechanisms (following impact of irradiation) (Graves et al., 2013). ...
Alkali silica reaction (ASR) is a nefarious one that has been observed in many dams. Its recent discovery in a nuclear containment vessel structure (NCVS) in the U.S. has taken the industry by surprise, and has spurred much interest. Of particular concern is whether the degraded concrete will result in diminished resistance to seismic excitation of a NCVS. This three parts paper will first contextualize fragility analysis within the general framework of the Seismic Probabilistic Risk Assessment (SPRA) described by the Nuclear Regulatory Commission (NRC). Also reviewed are the challenges confronting the nuclear industry in the twenty first century. The second part is an extensive literature survey on published work related to seismic analysis of NCVS. Finally, the third part will develop a detailed seismic analysis of a fictitious NCVS suffering from ASR. Starting with the theoretical underpinning and concluding with the structure capacity and fragility curves. The study will show that ASR can reduce the structural capacity of a NCVS, and the impact will be much greater for high probability low intensity ground motions (such as the operating based one) than for the low probability high intensity ones.
... The minimum yield strength at room temperature of the steel reinforcement ranges from 280 to 520 MPa, with the 420 MPa strength material being most common and is available in bar size designations from #3 (diameter B9.5 mm) to #18 (diameter B 457 mm)". 126 Based on neutron transport simulation, the neutron flux in 3-loop PWR at energies 41 MeV is one order of magnitude lower than the flux at energies 40.1 MeV 73 (See Fig. 16). Hence, steel elements embedded in the CBS are expected to be exposed to relatively low neutron fluence o10 19 n cm À2 (i.e., 0.1 n pm À2 ) at E 4 1 MeV. ...
... Concrete in Nuclear Power Plants (NPPs) can be exposed to a wide range of degradation phenomena. In the past years, the Light Water Reactor Sustainability (LWRS) program has investigated Radiation-Induced Volumetric Expansion (RIVE) as a potential degradation mechanism for concrete biological shields [Graves et al., 2014, Rosseel et al., 2016. RIVE causes swelling and micro-mechanical damage in concrete due to the amorphization of mineral phases contained in the aggregates under neutron irradiation [Hilsdorf et al., 1978, Rosseel et al., 2016. ...
... Doing so requires the assessment of the durability of all components under long-term operating conditions. This includes the concrete used for the NPP structure, notably the Concrete Biological Shield (CBS), which is exposed to a particularly high neutron and gamma dose, and which may, for some LWRS, exceed the threshold at which degradation has been reported in the literature [Esselman and Bruck, 2013, Graves et al., 2014, Rosseel et al., 2016]. ...
