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Phosgenation procedure for synthesis of carbon-14 labeled isocyanates, noting isotope distribution in compounds
During operations at the U.S. Department of Energy Hanford Site, releases of chemical and radioactive waste resulted in contamination of the soil and groundwater beneath portions of the site, including inadvertent releases of carbon-14 in the 100-K Area. Ongoing environmental cleanup efforts in the 100-K Area are focused on hexavalent chromium [Cr(VI)] and thus have not yet addressed the two carbon-14 groundwater plumes.
Dry catalytic combustion at high temperatures is used for assaying biological materials labeled carbon-14 and tritium, or double-labeled. A modified oxygen-flask technique is combined with standard vacuum-line techniques and includes convenience of direct in-vial collection of final combustion products, giving quantitative recovery of tritium and carbon-14.
Rapid technique for liquid scintillation counting of carbon-14-labelled barium carbonate
Liquid scintillation counting technique is applied to the direct measurement of carbon-14 in carbon dioxide. This method has high counting efficiency and eliminates many of the basic problems encountered with previous techniques. The technique can be used to achieve a percent substitution reaction and is of interest as an analytical technique.
Liquid scintillation counting method with sonic oscillations, noting decreased preparation time and increased counting efficiency
Dissolution of biological materials combines the simplicity of oxygen-flask combustion with the reproducibility and purity of the final product, and convenience of direct in-vial collection of the sample by the sealed-tube method. It assures quantitative and reproducible recoveries.
Carbon 14 radiation detection system for life detection experiments
Detector consists of plastic, cylindrical double-wall scintillation cell, which is filled with gas to be analyzed. Thin, inner cell wall is isolated optically from outer (guard) scintillator wall by evaporated-aluminum coating. Bonding technique provides mechanical support to cell wall when device is exposed to high temperatures.
The carbon-assimilation experiment detects life in soils by measuring the incorporation of carbon from carbon-14 monoxide and carbon-14 dioxide into organic matter. It is based on the premise that Martian life, if it exists, is carbonaceous and exchanges carbon with the atmosphere, as do all terrestrial organisms. It is especially sensitive for photosynthesizing cells, but it detects heterotrophs also. The experiment has the particular advantage that it can be carried out under essentially Martian conditions of temperature, pressure, atmospheric composition, and water abundance.
The results of two of the three biology experiments carried out on the Viking Mars landers have been simulated. The mixture of organic compounds labeled with carbon-14 used on Mars released carbon dioxide containing carbon-14 when reacted with a simulated Martian surface and atmosphere exposed to ultraviolet light (labeled release experiment). Oxygen was released when metal peroxides or superoxides were treated with water (gas exchange experiment). The simulations suggest that the results of these two Viking experiments can be explained on the basis of reactions of the Martian surface and atmosphere.
Biological accelerator mass spectrometry (AMS) provides ultrasensitive carbon-14 isotopic analysis enabling a deeper understanding of human health concerns by enabling quantification of pharmacokinetics and other molecular endpoints directly in humans. It enables environmentally and human relevant studies of metabolic pathways through the use of very low concentrations of labeled metabolic substrates in cells and organisms. Here, we discuss why AMS is an important tool for the biosciences, the development and evolution of biological AMS at Livermore and discuss technical refinements that will improve the efficiency of operation for the measurement of ultra-trace levels of 14 C, which, long term, will enable greater ease of use and sample throughput.
Conventional ethylene production heavily depends on fossil-derived feedstocks via steam cracking, a very energy- and emission-intensive process. Researchers have been exploring alternatives to reduce CO 2 emissions including producing ethylene from biobased feedstocks. This paper evaluates the cradle-to-gate greenhouse gas (GHG) emissions of bioethylene produced from U.S. corn ethanol. The analysis includes different pathways for the dehydration of corn ethanol to ethylene and co-processing routes via fluid catalytic cracking (FCC) processes. For the FCC co-processing route carbon-14 analysis is used to determine bioethanol yields. A 127% reduction in life cycle GHG emissions of bioethylene is estimated compared to fossil-derived ethylene for the base case. Additional case studies are also discussed to understand the reduction of GHG emissions due to sustainable corn farming and renewable power use, biogenic carbon capture, and fuel switch with biofuels at the ethanol plant, and its impact on bioethylene GHG emissions.
Mountain glaciers are sensitive climate indicators. Glaciers in the western United States are projected to disappear by 2100 CE, but whether they were previously absent in the current interglacial (past 11,700 years) remains debated. Here, we present evidence that two of the largest glaciers in California’s Sierra Nevada near Yosemite National Park persisted throughout the Holocene. Cosmogenic in situ carbon-14 and beryllium-10 exposure dating in newly exposed proglacial bedrock indicates continuous Holocene cover, likely by ice. At a nearby smaller glacier, bedrock exposure-burial ages suggest glacier expansion at ~7 thousand years ago, earlier than previously recognized. Moraine exposure ages at these sites and the Sierra Nevada’s largest glacier are distributed across the past several thousand years, suggesting that glaciers were near their preindustrial extent for much of the late Holocene. These findings imply that a glacier-free Sierra Nevada is unprecedented since before the Holocene. Future alpine glacial environments in California are thereby likely a no-analog scenario within the current interglacial.
Trenches 31 and 34 located in the 200 West Area Low-Level Burial Ground (LLBG) are authorized for disposal of low-level and mixed low-level radioactive waste under DOE Order 435.1, Radioactive Waste Management. A revised Disposal Authorization Statement was issued in October 2023 following approval of the performance assessment (PA) and supporting technical basis documents. To be consistent with approved PA calculations, the waste acceptance criteria (WAC) needs to be updated to include concentration limits for Category 1 (CAT1) and Category 3 (CAT3) waste along with the inventory limits. This environmental calculation file (ECF) provides the inventory limits for Category 1 and Category 3 waste disposal of radionuclides at Trench 31 and 34 based on the PA calculations. The concentration limits are not calculated as they are provided in the PA itself. The inventory thresholds (or limits) are calculated for only those radionuclides that are identified in the PA as the primary dose contributors. The primary dose contributors for the groundwater pathway are technetium-99, iodine-129, niobium-94, chlorine-36, molybdenum-93, and niobium-93m while those for the air pathway are tritium and carbon-14.
Catalytic fast pyrolysis (CFP) provides a versatile platform for producing fuels to combat climate change and meet decarbonizing targets. In this contribution, we will discuss the hydroprocessing of CFP oils to a variety of fuels, including sustainable aviation fuel (SAF), diesel, and marine fuel. Both standalone and co-hydroprocessing with petroleum streams will be covered. Hydrotreating CFP oil at temperatures around 400 Degrees Celsius can produce a highly deoxygenated product with oxygen contents below the detection limit. However, the quality of fuel fractions produced has been a problem, manifesting as low octane numbers for the gasoline-range fraction and low cetane numbers for the diesel-range fraction. Incorporating an initial transition zone for hydrogenation during hydrotreating was shown to dramatically increase the diesel fraction cetane number from 24 to 45. A similar approach enabled the production of a cycloalkane-rich SAF fraction meeting key ASTM 4054 guidelines with respect to density, viscosity, heating value, volatility, freeze and flash point. Over 400 hours of hydrotreating for SAF was demonstrated with no signs of catalyst bed fouling, measured by pressure drop over the catalyst bed. Compared to other fuels, marine fuel is unique in that it does not require complete deoxygenation. We investigated the minimum hydrotreating requirements to produce fuel compatible with very low sulfur fuel oil, and the results suggested 30% reduction in hydrotreating costs for this approach. Co-hydroprocessing offers an opportunity to take advantage of refinery infrastructure and economies of scale although the operation is less flexible with respect to operating conditions. Co-hydroprocessing CFP oil with petroleum streams gave efficient deoxygenation at milder conditions (e.g. at temperatures of 320 Degrees Celsius) than required for standalone hydrotreating. Over 90% incorporation of biogenic carbon in the CFP oil was confirmed by carbon-14 analysis. Hydrotreating of CFP oil, whether by standalone or co-processing, can produce a variety of fuel cuts, whose quality can be tailored by changing process conditions. Challenges remain, including long-term catalyst performance and determining CFP oil quality requirements.
System monitors expired breath patterns simultaneously from four small animals after they have been injected with carbon-14 substrates. It has revealed significant quantitative differences in oxidation patterns of glucose following such mild treatments of rats as a change in diet or environment.
This investigation was made to adapt wet-process autoradiography to metallurgical samples to obtain high resolution of segregated radioactive elements in microstructures. Results are confined to development of the technique, which was perfected to a resolution of less than 10 microns. The radioactive samples included carbon-14 carburized iron and steel, nickel-63 electroplated samples, a powder product containing nickel-63, and tungsten-185 in N-155 alloy.