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Investigation of Thermal-Hydraulic Effects of Dry Storage Canister Helium Backfill Loss Using the Horizontal Dry Cask Simulator
A previous investigation produced data sets that can be used to benchmark the codes and best practices presently used to determine cladding temperatures and induced cooling air flows in modern horizontal dry storage systems. The horizontal dry cask simulator (HDCS) was designed to generate this benchmark data and add to the existing knowledge base. The objective of the previous HDCS investigation was to capture the dominant physics of a commercial dry storage system in a well-characterized test apparatus for a wide range of operational parameters. The close coupling between the thermal response of the canister system and the resulting induced cooling air flow rate was of particular importance. The previous investigation explored these parameters using helium backfill at 100 kPa and 800 kPa pressure as well as air backfill with a series of simulated decay heats. The helium tests simulated a horizontal dry cask storage system at normal storage conditions with either atmospheric or elevated backfill pressure, while the air tests simulated horizontal storage canisters following a complete loss of helium backfill, in which case the helium would be replaced by air. The present HDCS investigation adds to the previous investigation by exploring steady-state conditions at various stages of the loss of helium backfill from a horizontal dry cask storage system. This is achieved by using helium/air blends as a backfill in the HDCS and running a series of tests using various simulated decay heats to explore the effects of relative helium/air molar concentration on the thermal response of a simulated horizontal dry cask storage system. A total of twenty tests were conducted where the HDCS achieved steady state for various assembly powers, representative of decay heat. The power levels tested were 0.50, 1.00, 2.50, and 5.00 kW. All tests were run at 100 kPa vessel pressure. The backfill gases used in these tests are given in this report as a function of mole fraction of helium (He), balanced by air: 1.0, 0.9, 0.5, 0.1, and 0.0 He. Steady-state conditions (where the steady-state start condition is defined as where the change in temperature with respect to time for the majority of HDCS components is less than or equal to 0.3 K/h) were achieved for all test cases.
Lianas and Trees From a Seasonally Dry and a Wet Tropical Forest Did Not Differ in Embolism Resistance but Did Differ in Xylem Anatomical Traits in the Dry Forest
One of the most prominent changes in neotropical forests has been the increase in abundance and size of lianas. Studies suggest that lianas have more acquisitive strategies than trees, which could allow them to take advantage of water more effectively when it is available in water-limited forests, but few studies compared across growth form (i.e., lianas vs. trees) and forest type (i.e., wet vs. seasonally dry). We measured hydraulic and anatomical traits of co-occurring lianas and trees that convey drought resistance (xylem embolism resistance and intervessel pit membranes) and water transport capacity (xylem vessel diameter and density) in a seasonally dry and a wet evergreen tropical forest to address: (1) Are there differences between vulnerability to embolisms (P 50 —water potential at 50% loss of hydraulic conductivity) and hydraulic safety margins (HSM) across growth form and forest type? (2) How do vessel diameter and density vary across growth form and forest type? (3) Are there differences in xylem intervessel pit membrane thickness across growth form and forest type and does it predict xylem embolism vulnerability in trees and lianas? We examined hydraulic and xylem anatomical traits of 32 species—eight lianas and eight trees in each forest type. We found no difference in P 50 and HSMs between lianas and trees and between the wetter and drier forest. Dry forest lianas had 81% greater maximum vessel diameter and 125% greater range in vessel diameter sizes than dry forest trees but, there was no significant difference between life forms in the wet forest. Dry forest species had 50% greater vessel density and 30% greater maximum pit membrane thickness than wet forest ones. Maximum pit membrane thickness was correlated to P 50 and HSMs. The main difference between lianas and trees occurred in the dry forest, where lianas had larger maximum xylem vessel size than trees, implying that they have proportionally greater hydraulic conductive capacity than the trees in seasonal forests.
Soil biogeochemistry across Central and South American tropical dry forests
Not provided.
SNL Contribution: Consequence Analysis for Moisture Remaining in Dry Storage Canisters After Drying
This report discusses several possible sources of water that could persist in SNF dry storage canisters through the drying cycle. In some cases, the water is trapped in occluded geometries in the cask such as dashpots or damaged fuel. Persistence of water or ice in such locations seems unlikely, given the high heat load of the canistered fuel; this is especially true in the case of vacuum drying, where a strong driver exists to remove water vapor from the headspace of such occluded geometries. Water retention in Boral® core material is a known problem, that has in the past resulted in the need for much extended drying times. Since the shift to slightly higher porosity "blister resistant" Boral®, water drainage appears to be less of a problem. However, high surface areas for the Boral® core material will provide a trap for significant amounts of adsorbed water, at least some of which is certain to survive the drying process. Moreover, if corrosion within the cores produces hydrous aluminum corrosion products, these may also survive.
A numerical simulation of a dry-out process for CO 2 sequestration in heterogeneous deep saline aquifers: Original Research Article: Dry-out problem: Multifactorial numerical simulation
Salt precipitation can be generated near the injection well when dry supercritical CO 2 (scCO 2 ) is injected into deep saline aquifers. Traditional laboratory experiments and numerical simulations focus on the generation of salt precipitation and its impact on core permeability. Current laboratory experimental studies have shown that the heterogeneity of the core and water content on the surface of the particles plays an important role in the formation of salt precipitation. The aim of this study is to explore the effects of brine back-flow, heterogeneity, and low water content on salt precipitation. Numerical simulations were performed using core-scale and site-scale models. Simulation results showed the following: 1. Back-flow plays an important role in the salt accumulation near the well – an homogeneous laboratory experiment used with a small core may not provide a full picture of the back-flow phenomenon. 2. The continuous dry-out process reduces the water content near the injection well to zero. As a result, the full range of saturation flow equations should be used to simulate the dry-out process accurately. 3. The heterogeneity of the matrix not only affects the distribution of salt precipitation but also increases the amount of salt precipitation near the well. Homogeneous simulation underestimates the amount of salt precipitation. 4. The reduction in porosity due to salt precipitation could extend the dry-out process in the low permeability zone, further expanding the salt precipitation area.
Economizing on Precious Metals in Three-Way Catalysts: Thermally Stable and Highly Active Single-Atom Rhodium on Cera for NO Abatement under Dry and Industrially Relevant Conditions
We show for the first time that atomically dispersed Rh cations on ceria, prepared via high-temperature atom trapping synthesis, are the active species for (CO+NO) reaction. This provides a direct link with the organometallic homogeneous Rh(I) complexes capable of catalyzing dry (CO+NO) reaction but without the stability concern. In particular, thermally stable Rh cations in 0.1wt% Rh1/CeO2 achieve full NO conversion with a TOF of ~ 330 hr-1 per Rh atom at 120 °C. Under dry conditions, the main product above 100 °C is N2 with N2O being the minor product. The presence of water promotes low-temperature activity of 0.1wt% Rh1/CeO2 starting at 50 °C with full NO conversion at ~120 °C. In the case with the wet stream, however, ammonia and nitrogen are the main products with only minor N2O amounts. NH3 formation at such low temperatures is attractive because of the potential to use this as a passive SCR system. Because of the uniformity of Rh ions on the support, we are able to observe the intermediates of (CO+NO) reaction via infrared measurements on Rh cations on zeolite and ceria. Furthermore, we show that ammonia formation correlates with the WGS activity of the material and thus, rhodium hydride Rh-H species are involved in this reaction: we detect Rh(CO)Hx species on ceria using isotopic IR measurements. These findings provide new mechanistic understanding for the catalytically active species in TWC catalysis and open up a new avenue for the synthesis of novel emissions control catalysts with 100% atom economy of ultra-expensive precious metals such as Rh.
Optimizing Transmission of Acoustic Signals to Monitor Internal Conditions of Canisters for Dry Storage of Commercial Spent Nuclear Fuel
Safe storage of spent nuclear fuel (SNF) is critical to the nuclear fuel cycle and the future of nuclear energy. In the United States, SNF is stored primarily via two methods regulated by the U.S. Nuclear Regulatory Commission: wet storage in SNF pools and dry storage in dry cask storage systems (DCSSs). After about five years of cooling in spent fuel pools, the fuel assemblies are transferred into DCSSs, and the systems are filled with helium and sealed by welding. Deterioration of conditions inside of a DCSS is reflected in changes in the internal gas properties; this motivates the development of acoustic techniques to monitor internal gas properties, over extended storage periods, using sensors mounted on the exterior of the storage packages. However, a major challenge in collecting acoustic signals is the impedance mismatch between the steel canister shell and the gas. Only a small fraction of the ultrasonic signal can be transmitted through the gas medium. This paper documents experimental studies conducted on a full-scale canister mock-up to capture the gas-borne signals. Damping materials were pasted on the outside, and blocking and unblocking tests were conducted to identify the gas-borne signal. The results show that the excitation frequency plays an important role in maximizing the gas-borne signals. The gas-borne signal was successfully detected at around the theoretical time-of-flight. A high signal-to-noise ratio was achieved in the measurements. Next, the acoustic impedance matching layers were introduced, and the gas signal was drastically improved compared with that using no AIM layers.
Experimental Determination and Modeling of Used Fuel Drying by Vacuum and Gas Circulation for Dry Cask Storage
More than 120 drying tests were conducted using a mock fuel assembly with depleted uranium rods and heater rods to simulate decay heat. These tests followed standard industry practice for vacuum and forced helium drying (FHD). Both single effect tests evaluating a single fuel assembly or cask feature and combined effect tests were conducted. Single effect tests evaluated drying of a specific, known amount of water in a feature. Combined effect tests evaluated specific features and followed the flooding of the chamber, dewatering, and blowdown procedures before beginning the drying procedure. Specific simulated fuel assembly and canister features evaluated included PWR dashpot, BWR water rod, failed fuel rod, spacer disc, and Boral sheet. Ceria pellets were fabricated and used in the failed fuel rod to avoid issues of uranium contamination. A method of monitoring water content in the canister gas and gas stream was developed using optical emission spectroscopy (OES) in addition to monitoring of relative humidity in the chamber and in the vacuum lines.
Carnot Analysis of Heat Pump Drying: Ideal Efficiency and Dry Time
Drying processes are important in appliances and in industry, and clothes drying accounts for approximately 3% of residential primary energy consumption in the US. Globally, heat pump tumble dryers (HPD) are increasing their market share against the ubiquitous electric resistance tumble dryer (ERD). In this work, efficiency and dry time limits are defined for ideal HPDs, for both closed air cycle (unvented) and open air cycle (vented). These limits are compared with the limits for ERD. The traditional Carnot efficiency limit for an ideal heat pump, operating between a hot and a cold thermal reservoir, does not apply directly to clothes dryers. One reason dryers require a novel analysis is the presence of additional degrees of freedom, since the hot and cold temperatures are floating, unfixed by ambient conditions. Furthermore, dryers can operate in a closed or open air cycle, and each requires a different analysis. In the closed (unvented) case, the hot and cold temperatures are coupled to each other; while in the open (vented) case, the hot and cold temperatures are both independent free variables. This paper provides an analysis of the fundamental efficiency limits of ERDs and HPDs, which can inform the design and performance limits of evaporative drying technology.
Engineering Graphene-Ceramic 3D Composite Foams by Freeze Drying
A 3D graphene foam produced by the chemical vapor deposition (CVD) technique is recognized as an effective nanofiller material, as it does not agglomerate in the matrix. Though CVD facilitates pristine graphene foam production, the method poses limitations in developing large-scale 3D graphene composite foams as advanced engineering materials. In this paper, a freeze-drying (FD) process is used to produce a composite 3D foam, which is a mixture of graphene nanoplatelet (GNP) and a low-temperature co-fired ceramic (LTCC). The freeze-dried GNP-LTCC reticulated 3D composite foam has an average pore size ranging from 70 to 100 μm. Pore size is varied by regulating the heat transfer rate during the freezing process using a thermally conductive aluminum (Al) mold and a thermally insulating acrylonitrile butadiene styrene (ABS) mold. Computational thermal modeling is used to visualize the heat transfer and its effect on foam pore size. Subsequently, a freeze-dried GNP-LTCC composite foam is embedded into the LTCC matrix to form a hierarchical assembly by a spark plasma technique without compromising the 3D structure of the FD foam. This study established that a simple, eco-friendly, and scalable processing methodology can produce advanced graphene-based 3D composite foams as the future tailorable nanofillers for designing multimatrix materials.
Plant community responses to stand-level nutrient fertilization in a secondary tropical dry forest
Not provided.
The effect of variety and maturity on the quality of freeze-dried carrots. The effect of microwave blanching on the nutritional and textural quality of freeze-dried spinach
Using carrots, the quality of freeze-dried products was studied to determine the optimum varieties and maturation stages for quality attributes such as appearance, flavor, texture, and nutritive value. The quality of freeze-dried carrots is discussed in terms of Gardner color, alcohol insoluble solids, viscosity, and core/cortex ratio. Also, microwave blanching of freeze-dried spinach was studied to determine vitamin interrelationships, anatomical changes, and oxidative deteriorations in terms of preprocessing microwave treatments. Statistical methods were employed in the gathering of data and interpretation of results in both studies.
The effects of bimetallic interactions for CO[subscript 2];#8208;assisted oxidative dehydrogenation and dry reforming of propane
Abstract not provided
Dry Sliding Wear Resistance of Cobalt Boride Coatings Formed on ASTM F1537 Alloy
New results about the wear resistance of CoB-Co{sub 2}B coatings under dry sliding conditions were estimated in this work. The cobalt boride coatings were developed at the surface of the ASTM F1537 alloy by means of the powder-pack boriding process using two experimental conditions: 1223 K with 6 h of exposure and 1273 K with 10 h of exposure. Before the sliding wear tests, Vickers depth-sensing microindentation tests were conducted on the cross section of the cobalt boride coatings to estimate the distribution of hardness, Young’s modulus, and residual stresses. Otherwise, the sliding wear tests were performed on both boriding conditions and on the untreated material, using a ball-on-flat configuration comprised of an alumina ball as a counterpart with applied loads between 5 and 20 N. The wear rates of the borided ASTM F1537 alloy were ranged between 4.02 and 8.91 × 10{sup −6} mm{sup 3} N{sup −1} m{sup −1} compared with the values of the untreated material (13.90 and 15.78 × 10{sup −6} mm{sup 3} N{sup −1} m{sup −1}) for the overall set of experimental conditions; nevertheless, the influence of boriding conditions (1273 K with 10 h of exposure) tended to increase the CoB coating thickness, developing a more brittle layer that decreased the sliding wear resistance at the surface of the borided ASTM F1537 alloy. Finally, the presence of failure mechanisms on the surface of the wear tracks was analyzed for both borided ASTM F1537 alloy and untreated material.
Demonstration of Selective Single-Barium Ion Detection with Dry Diazacrown Ether Naphthalimide Turn-on Chemosensors
Single-molecule fluorescence imaging (SMFI) of gas-phase ions has been proposed for “barium tagging,” a burgeoning area of research in particle physics to detect individual barium daughter ions. This has potential to significantly enhance the sensitivity of searches for neutrinoless double-beta decay (0νββ) that is obscured by background radiation events. The chemistry required to make such sensitive detection of Ba 2+ by SMFI in dry Xe gas at solid interfaces has implications for solid-phase detection methods but has not been demonstrated. Here, we synthesized simple, robust, and effective Ba 2+ -selective chemosensors capable of function within ultrapure high-pressure 136 Xe gas. Turn-on fluorescent naphthalimide-(di)azacrown ether chemosensors were Ba 2+ -selective and achieved SMFI in a polyacrylamide matrix. Here, fluorescence and NMR experiments supported a photoinduced electron transfer mechanism for turn-on sensing. Ba 2+ selectivity was achieved with computational calculations correctly predicting the fluorescence responses of sensors to barium, mercury, and potassium ions. With these molecules, dry-phase single-Ba 2+ ion imaging with turn-on fluorescence was realized using an oil-free microscopy technique for the first time—a significant advance toward single-Ba 2+ ion detection within large volumes of 136 Xe, plausibly enabling a background-independent technique to search for the hypothetical process of 0νββ.
Development of a Freeze-Dried CRISPR-Cas12 Sensor for Detecting Wolbachia in the Secondary Science Classroom
Training the future synthetic biology workforce requires the opportunity for students to be exposed to biotechnology concepts and activities in secondary education. Detecting Wolbachia bacteria in arthropods using polymerase chain reaction (PCR) has become a common way for secondary students to investigate and apply recombinant DNA technology in the science classroom. Despite this important activity, cutting-edge biotechnologies such as clustered regularly interspaced short palindromic repeat (CRISPR)-based diagnostics have yet to be widely implemented in the classroom. To address this gap, we present a freeze-dried CRISPR-Cas12 sensing reaction to complement traditional recombinant DNA technology education and teach synthetic biology concepts. The reactions accurately detect Wolbachia from arthropod-derived PCR samples in under 2 h and can be stored at room temperature for over a month without appreciable degradation. Here, the reactions are easy-to-use and cost less than $40 to implement for a classroom of 22 students including the cost of reusable equipment. We see these freeze-dried CRISPR-Cas12 reactions as an accessible way to incorporate synthetic biology education into the existing biology curriculum, which will expand biology educational opportunities in science, technology, engineering, and mathematics.