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DOE OSTI2015

Influence of Microstructure and Surface Activation of Dual-Phase Membrane Ce 0.8 Gd 0.2 O 2-δ -FeCo 2 O 4 on Oxygen Permeation

In dual-phase oxygen transport membranes we noticed that there is fast-growing interest in research for oxyfuel combustion process application. One such potential candidate is CGO-FCO (60wt% Ce 0.8 Gd 0.2 O 2-δ -40wt% FeCo 2 O4) identified to provide good oxygen permeation flux with substantial stability in harsh atmosphere. Dense CGO-FCO membranes of 1mm thickness were fabricated by sintering dry pellets pressed from powders synthesized by one-pot method (modified Pechini process) at 1200 degrees C for 10h. Microstructure analysis indicates presence of a third orthorhombic perovskite phase in the sintered composite. We also identified that the spinel phase tends to form an oxygen deficient phase at the grain boundary of spinel and CGO phases. Surface exchange limitation of the membranes was overcome by La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) porous layer coating over the composite. Moreover, the oxygen permeation flux of the CGO-FCO screen printed with a porous layer of 10mthick LSCF is 0.11mL/cm 2 per minute at 850 degrees C with argon as sweep and air as feed gas at the rates of 50 and 250mL/min.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Performance and Emissions Control of Commercial-Scale Biochar Production Unit

Abstract. Two commercial biochar production machines – a single-auger unit and a larger dual-auger version – were operated to evaluate feedstock specifications, biochar quality, throughput rates, and emissions profiles. Biochar was produced from woody biomass feedstocks of various species, contamination levels, comminution methods, and moisture contents. Feedstocks with ash content exceeding 15% dry basis or moisture content exceeding 25% wet basis were observed to decrease fixed carbon content of biochar and to increase the labor effort required to operate the machine. The dual-auger version of the machine was able to process 380 kg h -1 of biomass feedstock (dry basis) to produce 63 kg h -1 of biochar with a mean electricity demand of 4.5 kW. Average CO, propane, NO x , and SO 2 emission rates from the flare of this machine were measured to be 160, 120, 51, and 43 g h -1 , respectively, with total particulate matter (PM), PM 10 , and PM 2.5 emission rates of 380, 40, and 4.5 g h -1 , respectively. Results from these experiments indicate that high-quality biochar can be produced from a variety of feedstocks, including forest residuals, as long as the ash and moisture content are within the specifications. Future research and development should focus on increasing the throughput of the machine, implementing an automated control system to reduce the operational effort, and improving safety and product consistency. Keywords: Biochar, Biomass, Biomass conversion technology, Carbon sequestration, Forest residuals, Gasification, Pyrolysis.

Agriculture↗

DOE OSTI2012

Deliverable for FαST project: Ln Resin based PLE

This memo describes the fabrication of a polymer ligand extractant based on Eichrom's LN-1 resin. This work has been in support of the Fast Alpha Spectrometry Tool (FαST) project. The first part of LANL's role in this project is to evaluate new extractants for use in polymer ligand extractants (PLEs). The first new extractant evaluated is Di(2-ethyl hexyl) phosphoric acid (HDEHP), which is an effective metal extractant. It has very efficient chelating properties for a wide variety of metal ions. HDEHP is an amphiphillic molecule with two long hydrocarbon chains and a polar end with a phosphoryl oxygen (P=O) and an acidic -OH group as shown in Figure 1. HDEHP has shown effectiveness in extracting lanthanides, selective actinides, and other trivalent elements. Several authors have reported that lanthanides and elements with +3 oxidation state have similar extraction behavior in nitric acid. The distribution ratio for lanthanides rapidly decreases at lower nitric concentration then start to increase at higher concentration as shown in. The trivalent americium, curium, and yttrium exhibit similar trend as trivalent lanthanides. This extraction trend can be also observed from hydrogen chloride solution. This work describes the use of this ligand in a PLE to extract plutonium from solution. Polymer ligand films were prepared by dissolving HDEHP ligands and polystyrene beads in THF. The solution was directly deposited onto a 40 mm diameter stainless steel substrate using an automated pipette. HDEHP based PLEs with direct stippling method are shown in Figure 2. The solution was air dried at room temperature overnight to ensure complete evaporation of THF. The plutonium tracer solution was prepared in 0.01, 0.1, 1, and 8M nitric solutions to study the effect of nitric concentration in plutonium extraction. 0.1667 Bq 239 Pu tracer solution was directly stippled on each PLE and was allowed to equilibrate for 3 hours before removing the solution. The plutonium activity of each sample was measured by direct alpha counting to quantify the plutonium recovery by HDEHP PLE. The alpha spectra from alpha spectroscopy are shown in Figure 3. 1:5, 1:10, and 1:20 PLEs had sharp peak with low tailing. 1:2 had an extremely long tail, which is a possible indication that a large amount of ligands caused the film to not form a smooth surface. Also, it can be noted that 1:2 ratio PLE surface was not as rigid as the other ratio PLEs and it was prone to scratching during sample handing. The resolution of alpha spectra was quantified by measuring Full Width at Half of the Maximum (FWHM) using Bortels equation. The tailing component of the peak was also measured along with FWHM. The peak resolutions and tailing measurements for 0.1M nitric solution samples are given in Table 1. The best resolution was achieved with 1:5 PLE and worst was given by 1:2 PLE. The plutonium recovery by HDEHP PLE was dependent on both nitric concentration and ligand to polymer ratio. 1:2 PLE consistently had the highest recovery followed by 1:5 as shown in Figure 4. It should be noted that 1:2 ratio PLEs consistently had long tailing and the ROI of the spectrum had to be increased to encompass total counts from the tracer. 1:10 and 1:20 PLEs had close to zero percent recovery in all nitric concentration except for 0.01M. The highest plutonium recovery was observed for 0.1M nitric acid. 1:5 PLE gave the best combination of alpha spectroscopy resolution and plutonium recovery. Radiography image of samples were generated to study the plutonium distribution on the PLE surface. Samples were placed on an imaging plate (Fujifilm BAS-TR 2025) for 24 hours and the plate was scanned using GE Typhoon FLA 7000 system. The radiography image in Figure 5 shows uneven distribution with hot spots along the edge and in the center of the samples. These hot spots may be the result of highly localized concentration of ligands or surface defects that were observed in SEM. This unevenness in distribution may cause inaccurate activity measurement by alpha spectroscopy due to a bias in the energy calibration. PLEs based on HDEHP have been evaluated. The concentration of ligand in polystyrene is critical in the performance of the PLE; both for extraction efficiency as well as for alpha spectrometry results. The optimal PLE using this ligand has a concentration of 1:5 ligand to polystyrene. Under laboratory conditions, this configuration can produce similar results to those obtained for DIPEX based PLEs from previous studies. The concentration is very important to the results obtained for this ligand. This PLE is a good candidate for use in later field studies. Our next report will detail the evaluation of PLEs utilizing crown ether ligands.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Reducing Thermal Losses and Gains With Buried and Encapsulated Ducts in Hot-Humid Climates

The Consortium for Advanced Residential Buildings (CARB) monitored three houses in Jacksonville, FL, to investigate the effectiveness of encapsulated and encapsulated/buried ducts in reducing thermal losses and gains from ductwork in unconditioned attics. Burying ductwork beneath loose-fill insulation has been identified as an effective method of reducing thermal losses and gains from ductwork in dry climates, but it is not applicable in humid climates where condensation may occur on the outside of the duct jacket. By encapsulating the ductwork in closed cell polyurethane foam (ccSPF) before burial beneath loose-fill mineral fiber insulation, the condensation potential may be reduced while increasing the R-value of the ductwork.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2024

Thermally Insulating Transparent Barrier (THINNER) coatings on single pane windows

Conventional silica aerogel monoliths can provide remarkable thermal insulation but the presence of large pores (> 30 nm) tends to scatter visible light and render the material opaque or translucent instead of transparent. In addition, they are prone to cracking during synthesis and handling which makes them difficult to integrate in products and in particular in window solutions. This project developed two new solgel synthesis methods using silica precursors or preformed silica nanoparticles and ambient drying to produce mesoporous organo-silica monoliths. The monoliths were (i) thermally insulating, (ii) optically transparent, (iii) flexible, and (iv) hydrophobic. They feature porosity ranging from 50% to 90% with narrow pore size distribution with pore less than 20 nm resulting in excellent optical clarity (haze < 2%) and very low thermal conductivity (< 30 mW/mK). Interestingly, not only porosity but also pore size and mass fractal dimension were found to affect the thermal conductivity of the mesoporous silica. The superior transparency of the monoliths was shown to be attributed to dependent scattering among silica nanoparticles. Flexibility was achieved through trimethylchlorosilane surface modification. Furthermore, process scale-up and integration of the ambigel monoliths into window solutions using optically clear adhesives were also demonstrated in 6”x6” double-pane windows. The aerogel and the window solution were shown to be durable to accelerated aging under UV, moisture, and/or temperature gradient and thermal cycling. Overall, the window solution achieved the technical performance and the cost target of $10/sqft set for the SHIELD program. However, scaling to industry relevant scale (> 10’x10’) remains a challenge due to requirements on the drying process and fume hood size and to the propensity of large aerogel slab to crack during drying.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2023

Cosmogenic 10 Be in pyroxene: laboratory progress, production rate systematics, and application of the 10 Be– 3 He nuclide pair in the Antarctic Dry Valleys

Here, we present cosmogenic- 10 Be and cosmogenic- 3 He data from Ferrar dolerite pyroxenes in surficial rock samples and a bedrock core from the McMurdo Dry Valleys, Antarctica, with the goal of refining the laboratory methods for extracting beryllium from pyroxene, further estimating the 10 Be production rate in pyroxene and demonstrating the applicability of 10 Be– 3 He in mafic rock. The ability to routinely measure cosmogenic 10 Be in pyroxene will open new opportunities for quantifying exposure durations and Earth surface processes in mafic rocks. We describe scalable laboratory methods for isolating beryllium from pyroxene, which include a simple hydrofluoric acid leaching procedure for removing meteoric 10 Be and the addition of a pH 8 precipitation step to reduce the cation load prior to ion exchange chromatography. 10 Be measurements in pyroxene from the surface samples have apparent 3 He exposure ages of 1–6 Myr. We estimate a spallation production rate for 10 Be in pyroxene, referenced to 3 He, of 3.6 ± 0.2 atoms g –1 yr –1 . 10 Be and 3 He measurements in the bedrock core yield initial estimates for parameters associated with 10 Be and 3 He production by negative-muon capture ($f_{10}^{*}$ = 0.00183 and $f_{3}^{*}f_{C}f_{D}$ = 0.00337). Next, we demonstrate that the 10 Be– 3 He pair in pyroxene can be used to simultaneously resolve erosion rates and exposure ages, finding that the measured cosmogenic-nuclide concentrations in our surface samples are best explained by 2–8 Myr of exposure at erosion rates of 0–35 cm Myr –1 . Finally, given the low 10 Be in our laboratory blanks (average of 5.7 × 10 3 atoms), the reported measurement precision, and our estimated production rate, it should be possible to measure 2 g samples with 10 Be concentrations of 6 × 10 4 and 1.5 × 10 4 atoms g –1 with 5 % and 15 % uncertainty, respectively. With this level of precision, Last Glacial Maximum to Late Holocene surfaces can now be dated with 10 Be in pyroxene. Application of 10 Be in pyroxene, alone or in combination with 3 He, will expand possibilities for investigating glacial histories and landscape change in mafic rock.

58 GEOSCIENCES↗

NASA NTRS1972

Planetary Quarantine Activities

The activities of the Planetary Quarantine Department at Sandia Laboratories during the period April 1965 through June 1972 are summarized. Included are the rationale, the methods, and the results of modeling and experimentation used in dry heat, radiation, thermoradiation, and chemical sterilization studies. Publications describing these activities and accounts of closely related research are also furnished.

Source record↗

NASA NTRS1985

Practical aspects of laser holographic interferometry in wind tunnels

Practical aspects of using laser holographic interferometry in some NASA Ames wind tunnels are presented. These aspects include the development of techniques for dual-plate interferometry, optics alignment, and laser alignment. In addition, methods to alleviate problems associated with vibration, photographic processing, photographic drying, and photographic reconstruction are discussed.

Licursi, J.↗

NASA NTRS1985

Practical aspects of laser holographic interferometry in wind tunnels

Licursi, J. P.↗

NASA NTRS1988

Frequency domain solutions to multi-degree-of-freedom, dry friction damped systems

Dry friction damping has been considered as a means of increasing the passive damping of a variety of systems including large space structures and turbomachinery blades. However, dry friction is highly nonlinear, and hence, analytical investigations are difficult to perform. Here, a multiharmonic, frequency domain solution technique is developed and applied to a multi-degree-of-freedom, dry friction damped system. It is seen that the multiharmonic method is more accurate than traditional, one-harmonic solution methods. The method also compares favorably with time integration. Finally, comparisons are made with experimental results.

Ferri, A. A.↗

NASA NTRS1997

[Tail Plane Icing]

The Aviation Safety Program initiated by NASA in 1997 has put greater emphasis in safety related research activities. Ice-contaminated-tailplane stall (ICTS) has been identified by the NASA Lewis Icing Technology Branch as an important activity for aircraft safety related research. The ICTS phenomenon is characterized as a sudden, often uncontrollable aircraft nose- down pitching moment, which occurs due to increased angle-of-attack of the horizontal tailplane resulting in tailplane stall. Typically, this phenomenon occurs when lowering the flaps during final approach while operating in or recently departing from icing conditions. Ice formation on the tailplane leading edge can reduce tailplane angle-of-attack range and cause flow separation resulting in a significant reduction or complete loss of aircraft pitch control. In 1993, the Federal Aviation Authority (FAA) and NASA embarked upon a four-year research program to address the problem of tailplane stall and to quantify the effect of tailplane ice accretion on aircraft performance and handling characteristics. The goals of this program, which was completed in March 1998, were to collect aerodynamic data for an aircraft tail with and without ice contamination and to develop analytical methods for predicting the effects of tailplane ice contamination. Extensive dry air and icing tunnel tests which resulted in a database of the aerodynamic effects associated with tailplane ice contamination. Although the FAA/NASA tailplane icing program generated some answers regarding ice-contaminated-tailplane stall (ICTS) phenomena, NASA researchers have found many open questions that warrant further investigation into ICTS. In addition, several aircraft manufacturers have expressed interest in a second research program to expand the database to other tail configurations and to develop experimental and computational methodologies for evaluating the ICTS phenomenon. In 1998, the icing branch at NASA Lewis initiated a second multi-phase research program for tailplane icing (TIP II) to develop test methodologies and tailplane performance and handling qualities evaluation tools. The main objectives of this new NASA/Industry/Academia collaborative research programs were: (1) define and evaluate a sub-scale wind tunnel test methodology for determining tailplane performance degradation due to icing. (2) develop an experimental database of tailplane aerodynamic performance with and without ice contamination for a range of tailplane configurations. Wind tunnel tests were planned with representative general aviation aircraft, i.e., the Learjet 45, and a twin engine low speed aircraft. This report summarizes the research performed during the first year of the study, and outlines the work tasks for the second year.

Source record↗

NASA NTRS2003

Comparison of Ground-Penetrating Radar and Low-Frequency Electromagnetic Sounding for Detection and Characterization of Groundwater on Mars

Two orbital, ground-penetrating radars, MARSIS and SHARAD, are scheduled for Mars flight, with detection of groundwater a high priority. While these radars will doubtlessly provide significant new information on the subsurface of Mars, thin films of adsorbed water in the cryosphere will strongly attenuate radar signals and prevent characterization of any true aquifers, if present. Scattering from 10-m scale layering or wavelength-size regolith heterogeneities will also degrade radar performance. Dielectric contrasts are sufficiently small for low-porosity, deep aquifers that groundwater cannot be reliably identified. In contrast, low-frequency (mHz-kHz) soundings are ideally suited to groundwater detection due to their great depths of penetration and the high electrical conductivity (compared to cold, dry rock) of groundwater. A variety of low-frequency methods span likely ranges of mass, volume, and power resources, but all require acquisition at or near the planetary surface. Therefore the current generation of orbital radars will provide useful global reconnaissance for subsequent targeted exploration at low frequency. Introduction: Electromagnetic (EM) methods

R E Grimm↗

DOE OSTI2019

Probability of Pinching Failure in PWR SNF after Long-Term Storage

A probabilistic assessment was performed on pinching failure of PWR SNF rod cladding under accidental SNF cask transport conditions. a set of 3,000 rod pinching scenarios was analyzed, with different geometrical, material, and loading parameters, using a Latin Hypercube Sampling (LHS). The investigated accidents include train derailments leading to cask collisions or cask drops. Pinching failure was related to cladding offset strain, defined as the plastic deformation interval in radial cladding direction normalized with respect to the outer cladding diameter. Finite element (FE) models were used to compute SNF rod deformations and the offset strain demand OSD in each of the assessed pinching scenarios. The numerical models account for the contribution of the degraded fuel pellets to rod pinching stiffness. The offset strain capacity OSC was computed using regression and interpolation models based on ring compression (RCT) test results, and account for hydride-related effects on cladding ductility. The results show a low probability of pinching failure. Hydride-related cladding embrittlement affects the structural integrity of PWR SNF rods after long-term dry storage of up to 300 years. Radial hydride patterns or large amounts of circumferentially oriented hydrides reduce the cladding ductile deformation capability when pinched at low material temperatures. The probability of hydride-related pinching failure of PWR cladding is estimated after long-term dry storage to address: How do PWR SNF rod conditions like hydrogen content, vacuum drying peak cladding hoop stress σ{sub θ}, and cladding material temperature affect cladding ductility? Is hydride-related cladding embrittlement a material degradation mechanism that affects the structural integrity of PWR SNF rods under pinching loading? What are the controlling parameters for deformation demands in PWR SNF rods under pinching loading? Is the pinching load amplitude an important parameter that controls the probability of pinching failure? How do parameters like pellet-cladding gap or fuel pellet degradation affect the pinching loading capacity of PWR SNF rods? Statistical modelling of PWR SNF rod conditions in U.S. inventory: A pseudo rod database was generated based on EIA database. Analysis of train accident scenarios: a probability density function (pdf) of a pinching load distribution P{sub 9m} of a 9-m cask drop is linearly scaled to generate a more representative: distribution P{sub AS}. The new distribution considers train collision velocities, cask drops for on- and off-bridge accidents, and cask impact orientation. LHS generates 3,000 rod pinching scenarios based on nine independent geometrical, material, and loading parameters. Probabilistic FE Analysis: The LHS realizations are used to generate 3,000 FE models. The FE analysis is conducted for P{sub 9m}, and P{sub AS}. The workflow is automatized. The OSC is computed with regression and interpolation models, as a function of the hydrogen content C{sub H}, vacuum drying peak σ{sub θ}, and SNF temperature T{sub FR}: The regression data was obtained in RCTs on PWR cladding. The OSD is derived from the cladding deformations in the FE models. Cladding failure was identified via a comparison of OSC and OSD. A 300 and a 30 years-of-dry-storage duration is investigated: The dry-storage period affects the expected SNF temperature and consequently, the OSC and the OSD. The material temperature LHS population is adapted to account for a SNF temperature variation. The probability of hydride-related, ductile cladding failure during a severe transportation accident is not significantly affected by the pinching load amplitude: The probability is slightly reduced from a range of less than 0.0333% to 0.1667% for P{sub 9m}, to a range of less than 0.0333% to 0.1333% for P{sub AS}, depending on the vacuum drying peak cladding hoop stress modelling assumptions. Further, the SNF dry-storage duration does not significantly affect the probability of ductile pinching failure. Based on available train accidents data, the pinching failure probability for a 5,000 km long transportation route ranges from less than 1.62 E-7 to a value of 6.47 E-7, depending on the vacuum drying peak cladding hoop stress modelling assumptions. The pinching load amplitude is not a controlling parameter for the probability of ductile cladding pinching failure, and does not control the cladding deformations once pellet-cladding contact is established, The pellet-cladding gap width, however, plays a key role. Fuel pellet degradation only affects the deformation capacity, if the pellet stiffness is significantly reduced (more than 90%). Only highly embrittled cladding is likely to fail. The deformation demands on the cladding under pinching loading are small.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2015

Optimization of a dry, mixed nuclear fuel storage array for nuclear criticality safety - 14339

A dry storage array of used nuclear fuel at the Idaho National Laboratory contains a mixture of more than twenty different types of research and test reactor fuels. Significant neutronic interaction occurs between fuel canisters within this large storage arrangement of 636 fuel storage canisters. Nuclear criticality safety is maintained primarily by moderation control and through control of neutron interaction and leakage provided by the credited geometry. Over the nearly forty years of operation the collected fuels are now arranged in a configuration that does not minimize the system neutron multiplication factor (k{sub eff}). This creates a concern since the entire remaining facility storage capacity cannot be utilized without exceeding the system minimum subcritical state (k{sub safe}) for ensuring nuclear criticality safety. This work determines a more optimal arrangement for the stored fuels with a goal to minimize the system k{sub eff}, but also with a minimum of potential fuel canister relocation movements. The ultimate goal is to establish a solution for this multiple-objective optimization problem by finding the Pareto Front for maximum k{sub eff} reduction versus the number of canister relocations. The process first required additional analysis of the array by Monte-Carlo neutron transport codes (specifically, MCNP) to gain a greater understanding of the interaction characteristics of the disparate fuel types. Some stored fuels are composed of primarily metallic and oxide components that provide very little inherent moderation, while other fuel types contain graphite or zirconium-hydride which can contribute a significant amount of moderation. These factors cause a complex relationship within a fuel arrangement with respect to thermal utilization and axial leakage probability. The new MCNP analysis was utilized to develop a simplified spreadsheet-based empirical model which simulates the array k{sub eff} result. This empirical model was benchmarked against additional MCNP calculations for various arrangements and then employed in the optimization analysis. A Tabu metaheuristic and stochastic approximation optimization was applied to the empirical model with the optimization function to minimize the array k{sub eff}. The optimization algorithm interrogated the empirical model to determine the optimal rearrangement for up to sixty canister movements. The Pareto Front was found, which shows that a limited number of canister relocation movements could allow the existing thirty-one empty array positions to be filled with common research reactor fuels while also yielding a reduction in the overall array k{sub eff} relative to the current arrangement. This will impart an improvement in the facility utilization while also offering an enhancement in the safety margin. The reduction in array reactivity has been confirmed by a final set of MCNP calculations with the proposed new arrangements. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2014

Electrochemical Measurement of Gold Oxide Reduction and Methods for Acid Neutralization and Minimization of Water in Wet Ionic Liquid

The formation and reduction of gold oxide in wet ionic liquid (IL), N-trimethyl-N-butylammonium bis(trifluoromethanesulfonyl)imide, ([Me 3 N n Bu][TFSI]) is examined. The water concentration is determined using both the charge and peak current from the reduction of gold oxide and compared directly with Karl Fischer data. The quantitative determination of water in the IL is demonstrated for concentrations between 0.09 and 0.74 by weight (w%). The treatment of wet IL with dry nitrogen or molecular sieves reduces the water below background levels. Finally, methods for acid neutralization and the reduction of water with molecular sieves are conducted to minimize their impact on subsequent electrochemical measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Carbon nanotube fiber spun from wetted ribbon

A fiber of carbon nanotubes was prepared by a wet-spinning method involving drawing carbon nanotubes away from a substantially aligned, supported array of carbon nanotubes to form a ribbon, wetting the ribbon with a liquid, and spinning a fiber from the wetted ribbon. The liquid can be a polymer solution and after forming the fiber, the polymer can be cured. The resulting fiber has a higher tensile strength and higher conductivity compared to dry-spun fibers and to wet-spun fibers prepared by other methods.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2017

Review of Soil Organic Carbon Measurement Protocols: A US and Brazil Comparison and Recommendation

Soil organic carbon (SOC) change influences the life-cycle assessment (LCA) calculations for globally traded bio-based products. Broad agreement on the importance of SOC measurement stands in contrast with inconsistent measurement methods. This paper focuses on published SOC research on lands managed for maize ( Zea mays L.) in the U.S. and sugarcane ( Saccharum officinarum L.) in Brazil. A literature review found that reported SOC measurement protocols reflect different sampling strategies, measurement techniques, and laboratory analysis methods. Variability in sampling techniques (pits versus core samples), depths, increments for analysis, and analytical procedures (wet oxidation versus dry combustion) can influence reported SOC values. To improve consistency and comparability in future SOC studies, the authors recommend that: (a) the methods applied for each step in SOC studies be documented; (b) a defined protocol for soil pits or coring be applied; (c) samples be analyzed at 10 cm intervals for the full rooting depth and at 20 cm intervals below rooting until reaching 100 cm; (d) stratified sampling schemes be applied where possible to reflect variability across study sites; (e) standard laboratory techniques be used to differentiate among labile and stable SOC fractions; and (f) more long-term, diachronic approaches be used to assess SOC change. Here, we conclude with suggestions for future research to further improve the comparability of SOC measurements across sites and nations.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2021

Preliminary Analysis of Source Physics Experiment Explosion-Triggered Microseismicity Using the Back-Projection Method

A series of four chemical explosions were detonated in a deep borehole within the Yucca Flat Dry Alluvium Geology (DAG) at the Nevada National Security Site between 2018 and 2019. The two larger chemical explosions of 50 tons (DAG-2) and 10 tons (DAG-4) TNT equivalent yield triggered energetic aftershock sequences numbering 1392 and 347 microearthquakes, respectively, within the first 10 days. No significant aftershock activity was observed for the two smaller 1-ton explosions (DAG-1 and DAG-3). Here, we used a back-projection method based on travel-time migration and stacking of signal-to-noise ratio traces to detect, associate and locate aftershocks from a subset of 22-geophones within a larger 2 urn:x-wiley:21699313:media:jgrb54910:jgrb54910-math-0001 2 km seismic array surrounding the borehole. The aftershocks located within 300 m of the borehole and the depths were above the working points of 300 and 50 m depths of DAG-2 and DAG-4, respectively, ruling out triggering slip on geologic faults or disturbances beneath neighboring collapse craters. DAG-2 and DAG-4 aftershocks decayed at similar rates, with power-law exponents of p = 1.48 and p = 1.49, respectively. These decay rates are comparable to aftershocks sequences triggered by earthquakes and historical nuclear explosions at Yucca Flat. A smooth power-law aftershock decay within the first 10 days suggests a triggering mechanism from explosion generated stress relaxation due to the diffusion of high gas pressures in the cavity and radial fractures. A more random and episodic aftershock rate would be expected due to cavity collapse or falling rubble in chimney formation.

58 GEOSCIENCES↗