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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Radiation damages the silicates present in polyphasic mineral aggregates causing concrete’s degradation

While many U.S. nuclear power plants have submitted Subsequent License Renewal Application to operate beyond 60 years, others are already considering Operations Beyond Eighty years. In such cases, concrete biological shields are exposed to neutron and gamma radiation exceeding prescribed thresholds. Radiation-induced volumetric expansion (RIVE), extensively studied in single crystals, may also contribute to the degradation of polycrystalline aggregates. Since minerals differ in atomic structure and chemistry, radiation can affect them in distinct ways. This study examines quartzite, marble, and limestone to evaluate how irradiation affects their physical attributes and chemical reactivity. Results show crystalline silicates experience significant RIVE damage and enhanced reactivity in alkaline solutions compared to non-irradiated phases. Enhanced intra- and inter-granular dissolution could compromise aggregate integrity. An empirical correlation links silicate dissolution rate to atomic constraints (density, rigidity) and radiation dose, providing a predictive framework for estimating changes in silicate aggregate properties within radiation-exposed concrete.

Bouissonnié, Arnaud [Univ. of California, Los Ange↗
DOE OSTI2023

Chemical composition, coordination, and stability of Ca–organic associations in the presence of dissolving calcite

Environmental biotic and abiotic factors and soil physical, mineralogical, and chemical properties control the chemical composition of soil organic matter (SOM). Particularly, soil mineralogy and the presence of multivalent cations affect SOM labile fraction composition, stability, and environmental persistence. The persistence of SOM in aridic or limestone deposit derived soils, i.e., calcareous soils, has been partially attributed to SOM stabilization through adsorption or inclusion into the calcite mineral structure. Recently, however, it was shown that Ca(aq) released during calcite dissolution formed aqueous Ca–organic associations with OM components, which were unbound to mineral surface sites. This study investigates the structure, composition, and coordination of these associations by characterizing lyophilized Ca–organic containing solutions with spectromicroscopy [Scanning Transmission X-ray Microscopy (STXM)] and with a nanoimaging chemical probe [Infrared scattering-Scanning Nearfield Optical Microscopy (IR s-SNOM)]. Chemical stability of Ca–organic associations is furthermore determined with pyrolysis mass spectrometry analysis. The results demonstrate that Ca–organic associations are formed in the presence of dissolving calcite and OM components relevant to soil chemistry, i.e., lignin and amino acids. This study further reveals a spatial homogeneity of solution-derived (bi) carbonate in Ca–organic associations indicating for the first time that an inorganic anion, such as (bi)carbonate, may be part of these associations. Most likely, Ca ions are bound to both the (bi)carbonate and the organic components. These Ca (bi)carbonate–organic associations seem to have greater chemical stability than the pristine organic mixtures and, possibly, a higher environmental stability and reduced mineralization rate.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Effects of Cement Changes and Aggregate System on Mechanical Properties of Concrete

In this paper, mechanical properties of concrete mixtures containing different cementitious combinations and two aggregate systems were investigated under plastic and drying conditions. Emphasis was laid on durability and shrinkage of concrete. Life Cycle Analysis was also conducted by using Green Concrete LCA Webtool. Results indicated that the presence of larger aggregate sizes tend to enhance durability of concrete. The presence of nanosilica also imparted superior mechanical properties to concrete. A cementitious combination containing Portland Limestone Cement and fly ash with larger aggregate sizes emerged as a better performing mixture in terms of mechanical properties and with minimum environmental impact.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Massive formation of early diagenetic dolomite in the Ediacaran ocean: Constraints on the “dolomite problem”

Paleozoic and Precambrian sedimentary successions frequently contain massive dolomicrite [CaMg(CO 3 ) 2 ] units despite kinetic inhibitions to nucleation and precipitation of dolomite at Earth surface temperatures (<60 °C). This paradoxical observation is known as the “dolomite problem.” Accordingly, the genesis of these dolostones is usually attributed to burial–hydrothermal dolomitization of primary limestones (CaCO 3 ) at temperatures of >100 °C, thus raising doubt about the validity of these deposits as archives of Earth surface environments. We present a high-resolution, >63-My-long clumped-isotope temperature (T Δ47 ) record of shallow-marine dolomicrites from two drillcores of the Ediacaran (635 to 541 Ma) Doushantuo Formation in South China. Our T ∆47 record indicates that a majority (87%) of these dolostones formed at temperatures of <100 °C. When considering the regional thermal history, modeling of the influence of solid-state reordering on our T Δ47 record further suggests that most of the studied dolostones formed at temperatures of <60 °C, providing direct evidence of a low-temperature origin of these dolostones. Furthermore, calculated δ 18 O values of diagenetic fluids, rare earth element plus yttrium compositions, and petrographic observations of these dolostones are consistent with an early diagenetic origin in a rock-buffered environment. We thus propose that a precursor precipitate from seawater was subsequently dolomitized during early diagenesis in a near-surface setting to produce the large volume of dolostones in the Doushantuo Formation. Our findings suggest that the preponderance of dolomite in Paleozoic and Precambrian deposits likely reflects oceanic conditions specific to those eras and that dolostones can be faithful recorders of environmental conditions in the early oceans.

58 GEOSCIENCES↗
DOE OSTI2022

A re-examination of the mechanism of whiting events: A new role for diatoms in Fayetteville Green Lake (New York, USA)

Whiting events—the episodic precipitation of fine-grained suspended calcium carbonates in the water column—have been documented across a variety of marine and lacustrine environments. Whitings likely are a major source of carbonate muds, a constituent of limestones, and important archives for geochemical proxies of Earth history. While several biological and physical mechanisms have been proposed to explain the onset of these precipitation events, no consensus has been reached thus far. Fayetteville Green Lake (New York, USA) is a meromictic lake that experiences annual whitings. Materials suspended in the water column collected through the whiting season were characterized using scanning electron microscopy and scanning transmission X-ray microscopy. Whitings in Fayetteville Green Lake are initiated in the spring within the top few meters of the water column, by precipitation of fine amorphous calcium carbonate (ACC) phases nucleating on microbial cells, as well as on abundant extracellular polymeric substances (EPS) frequently associated with centric diatoms. Whiting particles found in the summer consist of 5–7 μm calcite grains forming aggregates with diatoms and EPS. Simple calculations demonstrate that calcite particles continuously grow over several days, then sink quickly through the water column. In the late summer, partial calcium carbonate dissolution is observed deeper in the water column. Settling whiting particles, however, reach the bottom of the lake, where they form a major constituent of the sediment, along with diatom frustules. The role of diatoms and associated EPS acting as nucleation surfaces for calcium carbonates is described for the first time here as a potential mechanism participating in whitings at Fayetteville Green Lake. This mechanism may have been largely overlooked in other whiting events in modern and ancient environments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Optimal band selection for target detection with a LWIR multispectral imager

Multispectral imaging can offer many benefits in cost, complexity, resolution, size, weight, and power, relative to hyperspectral imaging. When designing a multispectral system, spectral bandpasses can be selected using optimization algorithms configured to maximally separate target detection scores between target and background regions. A hyperspectral image (HSI) can serve as the source of data from which band groupings can be tested for optimality. The output of an adaptive cosine estimator target detection algorithm is used in an objective function. Three optimization algorithms are compared: particle swarm, dual annealing, and differential evolution. A global optimum is also found using a brute force approach on the Livermore Computing Syrah supercomputer. Three materials are investigated: calcite, gypsum, and limestone. This is done for 3-, 4-, and 5-band systems. The data originate from a longwave infrared HSI of a material display board. The optimization algorithms were run 30 times for every scenario. Performance statistics (maximum, minimum, mean, standard deviation, and median) based on the separation values are given. Additional characterization was performed using receiver operator characteristic (ROC) curves and the area under the ROC curve. While good performance was obtained for the three optimization algorithms, the dual annealing algorithm produced the highest and most consistent detection separation scores on average.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Characterization of prokaryotic communities in Puerto Rican caves using 16S rDNA amplicon sequencing

The cave ecosystems host microbial communities adapted to extreme environments. This study utilized 16S rDNA to investigate the prokaryotic diversity across seven caves in Puerto Rico’s northern limestone karst belt. Microbial profiling revealed distinct subterranean communities, enhancing our understanding of cave microbiology and potential applications in environmental conservation and microbial research.

16S↗
DOE OSTI2020

Formation of wide-blocky calcite veins by extreme growth competition

Liassic limestones on the coast of Somerset in the UK contain dense arrays of calcite microveins with a common, but poorly understood microstructure, characterized by laterally wide crystals that form bridges across the vein. We investigated the mechanisms of formation and evolution of these ‘wide-blocky’ vein microstructures using a combination of high-resolution analytical methods, including virtual petrography, optical cathodoluminescence and scanning electron microscopy techniques (e.g. energy-dispersive X-ray spectrometry, back-scattered electron imaging, cathodoluminescence and electron back-scattered diffraction), laboratory experiments and multiphase field modelling. Our results indicate that the studied veins formed in open, fluid-filled fractures, each in a single opening and sealing episode. As shown by the optical and electron back-scattered diffraction images, the vein crystals grew epitaxially on grains of the wall rock and we hypothesize that their growth rates differed depending on whether the crystals were on a wall rock grain substrate that fractured intergranularly (slow growth rates) or transgranularly (rapid growth rates). Our multiphase field models support this hypothesis, showing that wide, blocky crystals only form where there are significant differences in the growth rate and are dependent on the type of seed grain. These results provide strong evidence for extreme growth competition, a process that we propose controls vein-filling in many micritic carbonate reservoirs, as well as demonstrate that the characteristics of the fracture wall can affect the filling processes in syntaxial veins. Supplementary material: The description and images of the studied thin sections are available at https://doi.org/10.6084/m9.figshare.c.5172371 . High-resolution optical microscopy mosaics (under plane-polarized- and crossed polarized light) of the thin section collection in PetroScan file format are available on request from the authors.

Geology↗
DOE OSTI2023

Numerical Simulations of Carbon Dioxide Storage Efficiency in Heterogeneous Reservoir Models

The U.S. Department of Energy’s National Energy Technology Laboratory (DOE-NETL) has been developing methods and tools (the online Carbon Dioxide Storage prospeCtive Resource Estimation Excel aNalysis (CO2-SCREEN) tool) to estimate carbon dioxide (CO2) storage potential in subsurface reservoirs. The CO2 storage efficiency terms are input in the tool to calculate storage potential in targeted reservoirs. In this effort, two CO2 storage efficiency terms were evaluated: volumetric displacement ( E V ) and microscopic displacement ( E d ). The first term deals with efficiency of CO2 propagation into an accessible reservoir volume, while the second term evaluates effectiveness of native fluid displacement with CO2. The interpreted well logs and core sample measurements were applied to create the heterogeneous reservoir models including geostatistical realizations of porosity and intrinsic permeability fields. Supercritical CO2 was injected over the course of 30 years into brine-saturated reservoir models for clastics, limestone, and dolomite lithologies and deltaic fluvial, aeolian, shallow marine, and reef depositional environments by means of varying reservoir parameters and injection scenarios. The reservoir models providing vertically heterogeneous petrophysical properties and designated as “layered reservoir models” (with homogeneous parameters along each layer of the model) were not determined to be a transition between the homogeneous and heterogeneous models in respect to storage efficiency. Another finding shows that high-efficiency factors do not necessarily mean increased CO2 storage; they rather indicate that the available volume and pore space are more fully utilized. The CO2 storage efficiency factors were evaluated dynamically at the select time points using P 10 ‐ P 50 ‐ P 90 percentiles. The results of this study show that the P 10 ‐ P 90 distribution for volumetric efficiency is wider when compared to the microscopic efficiency. It was found that where dominant buoyancy forces drive the plume to the top of a target formation, the volumetric efficiency is low. Tighter sandstone and carbonate formations show prevalence of capillary forces and better utilization of reservoir volume.

Myshakin, Evgeniy M.↗
DOE OSTI2025

STILGAR Seismic Array Data

Two three-component dense seismic arrays were deployed above an active limestone mine in Pleasant Gap, Pennsylvania; one in the fall and one in the spring of 2023. Each campaign lasted approximately four weeks and included 80 to 100 seismic stations with stations spaced between 100 and 400 meters apart. Each campaign also included several small dense seismic arrays. Two types of seismic stations were deployed including FairfieldNodal ZLand 3C All-in-One seismometers and Geospace 3C GS-ONE geophone paired with GSX3 and GSX4 dataloggers. This dataset includes ~ 4 TB of three-component continuously recorded seismic data in the miniseed format data from both campaigns as well as a readme file for the data structure.

58 GEOSCIENCES↗
DOE OSTI2021

AmeriFlux US-Jo1 Jornada Experimental Range Bajada Site

This is the AmeriFlux version of the carbon flux data for the site US-Jo1 Jornada Experimental Range Bajada Site. Site Description - The Jornada Basin Experimental Range (JER) covers 783 km2 in the La Jornada del Muerto Plain of the northern Chihuahuan Desert and is located 20km of Las Cruces, NM. Extensive livestock grazing at the JER and througout the US Southwest was coincident with large-scale grassland deterioration and transition to shrubland begining in the 1800s. The JER was established n 1912 to investigate these rangeland changes and has since become a central location for understanding dryland ecology. This flux tower monitors CO2 and H2O dynamics in a representative shrubland on the piedmont slope (bajada) of the San Andreas mountains. The dominant shrubs are evergreen Larrea tridentata (Creosote) and winter-deciduous Prosopis glandulosa (Honey Mesquite). Other cover types include Flourensia cernua (tarbush) and patchy occurences of the grasses Muhlenbergia porteri (Bush Muhly) and Dasyochloa pulchella (Fluff Grass). The site is occasionally visited by stray domestic cattle, free-ranging introduced Oryx, and other native herbivores (Jack Rabbits, Desert Pronghorn). Soils at the site are Ustic Calciargids and parent material consists of limestone, other sedimentary rock, and some igneous rock. Virtual Site Visit: https://youtu.be/v1uJCKuicqs​

Tweedie, Craig↗
DOE OSTI2022

AmeriFlux FLUXNET-1F US-Jo1 Jornada Experimental Range Bajada Site

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-Jo1 Jornada Experimental Range Bajada Site. This is the FLUXNET version of the carbon flux data for the site US-Jo1 Jornada Experimental Range Bajada Site produced by applying the standard ONEFlux (1F) software. Site Description - The Jornada Basin Experimental Range (JER) covers 783 km2 in the La Jornada del Muerto Plain of the northern Chihuahuan Desert and is located 20km of Las Cruces, NM. Extensive livestock grazing at the JER and througout the US Southwest was coincident with large-scale grassland deterioration and transition to shrubland begining in the 1800s. The JER was established n 1912 to investigate these rangeland changes and has since become a central location for understanding dryland ecology. This flux tower monitors CO2 and H2O dynamics in a representative shrubland on the piedmont slope (bajada) of the San Andreas mountains. The dominant shrubs are evergreen Larrea tridentata (Creosote) and winter-deciduous Prosopis glandulosa (Honey Mesquite). Other cover types include Flourensia cernua (tarbush) and patchy occurences of the grasses Muhlenbergia porteri (Bush Muhly) and Dasyochloa pulchella (Fluff Grass). The site is occasionally visited by stray domestic cattle, free-ranging introduced Oryx, and other native herbivores (Jack Rabbits, Desert Pronghorn). Soils at the site are Ustic Calciargids and parent material consists of limestone, other sedimentary rock, and some igneous rock. Virtual Site Visit: https://youtu.be/v1uJCKuicqs​

Tweedie, Craig↗
DOE OSTI2023

AmeriFlux US-CLF Cole Farm

This is the AmeriFlux version of the carbon flux data for the site US-CLF Cole Farm. Site Description - The Cole Farm catchment (0.65km2) is located ~ 4 km southwest of the Shale Hills site, draining orthogonally to a syncline axis of the Wills Creek Formation, a calcareous shale containing interbedded siltstone, sandstone, shaly limestone, and dolomite. Even though the farm adopted no-till practices in the 1970s, the axial channel of Cole Farm flows over a thick (>2.5 m) package of sediment in the valley floor. Soils range in texture from silty clay at the ridge top to sandy loam in the valley floor. Data was collected and funded by the Critical Zone Observatory Network.

Davis, Kenneth J.↗
DOE OSTI2026

AmeriFlux FLUXNET-1F US-CLF Cole Farm

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-CLF Cole Farm. This is the FLUXNET version of the carbon flux data for the site US-CLF Cole Farm produced by applying the standard ONEFlux (1F) software. Site Description - The Cole Farm catchment (0.65km2) is located ~ 4 km southwest of the Shale Hills site, draining orthogonally to a syncline axis of the Wills Creek Formation, a calcareous shale containing interbedded siltstone, sandstone, shaly limestone, and dolomite. Even though the farm adopted no-till practices in the 1970s, the axial channel of Cole Farm flows over a thick (>2.5 m) package of sediment in the valley floor. Soils range in texture from silty clay at the ridge top to sandy loam in the valley floor. Data was collected and funded by the Critical Zone Observatory Network.

Davis, Kenneth J. [Department of Meteorology, Eart↗
DOE OSTI2020

Experimentally Validated Computational Modeling of Creep and Creep-Cracking for Nuclear Concrete Structures

In a Nuclear Power Plant, one of the most important components is the concrete nuclear reactor cavity, which serves both a structural and protective function as the biological radiation shield. Given that creep has been identified as a major knowledge gap in the assessment of nuclear structures (NUREG/CR-7153), this work helps to further the understanding of creep behavior of massive concrete containment structures for decades to enable safe and long-term operation of these facilities. This project has developed a robust, experimentally validated model to predict creep in nuclear concrete structures for up 60 years using short-term creep data thereby enabling a longer service life of critical facilities and early detection of structural failure. The work presented in this report is a pairing of computational and experimental methods. For the first time, the time temperature superposition (TTS) principle was successfully used to generate a uniaxial creep compliance master curve to predict mortar creep response for up to 22,500 days (nearly 60 years) at a reference temperature of 20°C. These data were used as input into finite element analysis (FEA) codes that use highly realistic random, 3D concrete microstructures from reconstructed coarse limestone aggregates. Finite element analysis performed provides the ability to quickly upscale mortar viscoelastic behavior to long-term concrete creep/relaxation data. A master creep compliance curve, constructed from the TTS principle, spanning 27 years, was used to validate two and a half decades of simulated concrete creep. Concurrently, three different simulated wall specimens were designed to mimic the behavior of post-tensioned concrete nuclear containment facility vessel walls over time as a result of concrete creep. The specimens were designed with different thicknesses, transverse and longitudinal reinforcement ratios, and level of post-tensioning stress. Each specimen contained various instrumentation to measure internal concrete temperature, concrete strain, and post-tensioning strain hourly for over 3 years. The concrete creep model developed in this project, based on the FEA concrete simulations, was applied to simulate the structural-scale experiments of prestressed concrete walls conducted in this project using the Grizzly code. These models can represent the effects of reinforcing and prestressing. Although there are some discrepancies with the experimental data, the model can predict the overall trends of the creep response in these experiments. One of these experimental models was also applied to an extended time to demonstrate how the findings from this study can be used to predict the behavior of actual structures of interest that have been in service for extended periods of time.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Ordovician-Cambrian Units: Hierarchical Evaluation of Geologic Carbon Storage Resource Estimates

The Indiana Geological and Water Survey (IGWS) led subtask 1.1 to assess the regional distribution and estimate the storage capacity of Ordovician-Cambrian stratigraphic units located within the partnership region. A comprehensive data set of wireline logs and petrophysical information was used to generate these interpretations. These data include core analysis for porosity and permeability, mercury injection capillary pressure (MICP), and existing well data including location and stratigraphic information. This report includes storage resource estimates (SREs) for three potential storage reservoirs(limestone and dolostone from the Upper Ordovician Trenton Limestone/Black River Group and equivalent units, the Middle Ordovician St. Peter Sandstone, and primary target reservoir rocks of the Lower Ordovician and Upper Cambrian Knox Supergroup and equivalent units) calculated using six methodologies: (1) a fixed value of porosity of 10 percent in all units evaluated; (2) a unique average porosity (per well) from wireline-derived porosity (neutron, sonic, and/or density porosity for each unit); (3) porosity values from core analysis; (4) a depth-dependent porosity model (Knox Supergroup only); (5) porosity based on a model based on petrophysical facies; and (6) SREs using National Energy Technology Laboratory’s CO2 Storage prospeCtive Resource Estimation Excel aNalysis (CO2-SCREEN beta V2). All methods used the same values for thickness for each unit. However, the areal extent of each assessment was limited by the data available for each method. Estimated volumes were calculated in 1-by-1 kilometer grid cells and summarized as county and total stratigraphic unit volumes. The resultant SREs mass are displayed using boxplots, which allow for comparing data statistics (mean values and variability) between methods. Differences observed in SRE results from the six methods are mainly attributable to differences in the data and conceptual models used to interpret or estimate porosity in each method. Based on this systematic variability between methods, it is inferred that methods 1, 4, and 6 are best used for regional-scale reconnaissance estimates of storage capacity while methods 2, 3, and 5 are more appropriate for local scales where more data is required. All estimates are data-density dependent and different methods require different amounts of data for reasonable assessments. ArcMap 10.5.1 software was used to portray SREs to help visualize spatial variance of estimates for each methodology, and more importantly, to highlight those areas having the greatest total storage potential estimates.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2021

A Scalable Process for Upcycling Carbon Dioxide (CO 2 ) and Coal Combustion Residues into Construction Products

Anthropogenic sources of carbon dioxide are generated from a number of sources, but the key among these are ordinary Portland cement (OPC) production and combustion of fossil fuels. Cement production is the largest global CO 2 source from the mineral decomposition of carbonates. Combination of the limestone decomposition and thermal requirements of the clinkering process causes cement production to contribute 8-9% of annual global CO 2 emissions. Combustion of fossil fuels (coal, oil and gas) was shown to contribute a much larger portion of global CO 2 emissions. As of 2018, combustion of fossil fuels accounted for 65% of global CO 2 , where 41% was derived from stationary sources for electricity and heat generation and the other 24% was related to transport. To reduce these contributions, key steps forward in CO 2 utilization technologies are required. The purpose of this project is to demonstrate the feasibility of the Reversa process evolving from a TRL-3 technology at the bench-scale up to TRL-6 technology at the pilot-scale. The reliability of the Reversa technology was tested to prove the effective production of concrete masonry units (CMUs) at bench scale, where the units exceeded the required 13.8 MPa compressive strength requirements. The overall goal of this project was to accelerate the development of a CO 2 mineralization process that synergistically utilizes CO 2 in flue gas and coal combustion residues (CCRs) to synthesize carbonated concrete, a functional replacement for traditional concrete. The culmination of this work resulted in 12 successful production runs at the Integrated Test Center (ITC), Gillette, WY using coal flue gas as a CO 2 source. This was followed by 6 production runs which were completed at the National Carbon Capture Center (NCCC), Wilsonville, AL, using coal-fired and natural gas (NG) flue gas as the CO 2 source. Over the course of the production runs at NCCC and ITC, the CO 2 utilization as a function of time, 24-h CO 2 uptake, electricity usage, and 28-d net area compressive strength recorded for each run. The ITC and NCCC demonstrations achieved an average of 0.19 and 0.1 g CO 2 /g reactant, respectively. Both demonstrations exceeded the project’s target goals of uptake > 0.05 g CO 2 /g reactant. Average compressive strength of the ITC blocks was 18.24 MPa at 28-days. This exceeded the target strength of 13.8 MPa specified by ASTM C90. ITC and NCCC produced an average CO 2 utilization efficiency of 74.9 and 57.9%, respectively. Both demonstration averages were within the target range of 50 to 90% utilization efficiency. For some production runs the NCCC demo did exceeded the a CO 2 utilization efficiency of 75%. An LCA of the Reversa process compared to an industry standard product revealed a net CO 2 reduction of 39% to 42%. This exceeded the target requirement of >25% net CO 2 reduction. Collection of this data was used to determine that the project was successful as the demonstration goals were achieved: (1) achieving in excess of 75% CO 2 utilization efficiency, (2) utilizing greater than 250 kg of CO 2 per production batch/run, and (3) ensuring compliance of carbonated blocks with industry standard specifications (ASTM C90).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Development of a Reconstruction Methodology Based on X-Ray Computed Tomography to Generate Realistic 3D Concrete Microstructures in MOSAIC

Despite being passive components, concrete structures represent a major capital investment in nuclear power plants. However, some concrete components are critical for the safety and long-term operation of the reactors: the concrete containment building protects the reactors from external aggression. The concrete biological shield (CBS) contains the radiation exiting the reactor to protect equipment and personnel. Depending on the design, the CBS also has a function for supporting the reactor’s systems. This function needs to be ensured in-service and during accident scenarios. After several decades of use, the CBS is exposed to high-energy irradiation over an extended operation time, exceeding the fluence level currently considered detrimental for the concrete’s structural properties. Such conditions occur at different times depending on the reactor’s operation and design. Nevertheless, from the perspective of subsequent license application, it is mandatory to assess the potential effects of prolonged irradiation on concrete. Unlike steel components, concrete structures are built with local constituents (cement, sand, and coarse aggregates) to avoid prohibitive transportation costs. Thus, concrete performance is determined by the tolerance or the susceptibility of its constituents against any aging mechanism. The tolerance against irradiation of the CBSs may vary greatly among the 56 nuclear power plants and 93 nuclear power reactors that form the current US light-water reactor fleet. Irradiation-induced degradation is mainly a result of amorphization-induced expansions of the silicated minerals present in the aggregates. The neutron irradiation–induced expansion varies from one rock-forming mineral to another: well framework–structured silicates (e.g., quartz and feldspars) exhibit higher swelling than chained (e.g., pyroxene) or isolated silicates (e.g., garnet). Silicates make up nearly 90% of the Earth’s crust. Other common minerals present in construction aggregates are carbonates found, for example, in limestone. Irradiated carbonates exhibit only very minor expansions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗