Integrated Extraction System Research Articles

Surface area and particle size distribution of plutonium oxides derived from the direct oxidation of Pu metal

The intent of this paper is to interrogate the physical characteristics of PuO2 powders and aggregates produced by direct metal oxidation to examine possible relationships between process parameters and the physical characteristics of the product. The majority of the PuO2 samples considered were generated during the pre-production and production phases of the Advanced Recovery and Integrated Extraction System (ARIES) program at Los Alamos National Laboratory (LANL). Oxide formed passively on Pu metal surfaces at ambient atmospheric conditions is also characterized. Plutonium oxide powders from the ARIES Direct Metal Oxidation (DMO) furnace and muffle furnace process lines are very consistent in terms of their bulk and tapped density, specific surface area (SSA) and particle size distribution (PSD). The SSAs of calcined PuO2 generated in the ARIES DMO-2 and muffle furnaces are between 0.1 and 0.5 m2/g. Oxides from both the DMO-2 and muffle furnaces also had similar tri-modal PSDs with maxima at 0.73–3.16 μm, 10.9–18.5 μm, and 41.3–63.0 μm. The PSDs of the oxide formed passively on Pu metal surfaces at ambient conditions were unimodal, with near-Gaussian distributions and D50 close to 1 μm. The oxide formed passively at ambient conditions also had significantly higher SSAs (6–8 m2/g).A documented process upset that originated from a heater element failure in DMO-2 resulted in significantly lower oxidation temperatures, and produced oxide having a slightly greater SSA, and lower bulk and tapped densities. Macroscopic (by quantitative sieving) and microscopic (by laser diffraction of aqueous suspensions) PSDs of the oxide produced during this interval are characterized by depleted large-diameter particle populations. We speculate that the lack of large particles in the aggregate emerging from DMO-2 during the temperature anomaly reflects a change in the thermal regime during oxidation which favors the generation of finer-grained aggregate.

Theory and practice of integrated coal production and gas extraction

The integrated extraction of coal and gas combines coal mining with gas capture. Taking into account the gas deposition and flow conditions in the Chinese coal basins, this paper describes the status of the theory and key technologies of this integrated extraction system, and presents its application and practice in the Shaqu, Zhongxing, Fenghuangshan and Pingmei mines. Areas for further improvements in future studies are discussed, focusing in particular on the fundamentals of the extraction system to make it greener, more scientific, and more advanced in both the exploitation and utilization of coal and the gas in coal.

Multicenter Evaluation of the BD Max GBS Assay for Detection of Group B Streptococci in Prenatal Vaginal and Rectal Screening Swab Specimens from Pregnant Women

A new integrated extraction and real-time PCR-based system for the detection of group B streptococci in antepartum screening samples enriched in Lim broth was compared to the CDC-recommended culture method. The BD Max GBS assay exhibited acceptable sensitivity (95%) and specificity (96.7%) compared to those of the culture method in this multisite evaluation.

Process Modeling of Plutonium Conversion and Mixed-Oxide Fuel Fabrication for Plutonium Disposition

In an effort to reduce the global stockpile of nuclear explosive devices, ~50 tonnes of weapons-grade plutonium have been declared surplus to national security needs by the United States. This surplus, located at six sites within the U.S. Department of Energy complex (the Hanford Site, Idaho National Engineering and Environmental Laboratory, Los Alamos National Laboratory, the Pantex Plant, the Rocky Flats Environmental Technology Site, and the Savannah River Site) must now be rendered unattractive for use in nuclear weapons. The goal is that this drive will be concurrent with similar activities in Russia. One method currently under investigation is the conversion of the plutonium metal into mixed-oxide (MOX) reactor fuel. Approximately 35 tonnes of the surplus plutonium is in a form suitable for fabrication into MOX fuel. This fuel would be used in currently operating reactors for power production.Two processes are currently under consideration for the disposition of the 35 tonnes of surplus plutonium through its conversion into fuel for power production. These processes are the Advanced Recovery and Integrated Extraction System (ARIES) process, by which plutonium metal is converted into a powdered oxide form, and MOX fuel fabrication, where the oxide powder is combined with uranium oxide powder to form ceramic fuel. Because it is envisioned that plutonium disposition will occur concurrently in the United States and Russia, the timely disposition of the plutonium is deemed important to national security. However, the need for quick disposition must be tempered by cost considerations and constraints on the reactors that will ultimately use the fuel. This study was undertaken to determine the optimal size for both the pit conversion and MOX fabrication facilities, whereby the 35 tonnes of plutonium metal will be converted into fuel and burned for power. Proper sizing of the facilities will help avoid unnecessary delays and excessive costs and thus is important in the success of the disposition mission.The bounding conditions used were a plutonium concentration of 3 to 7%, a burnup of 20,000 to 40,000 MWd/tonnes HM, a core fraction of 0.1 to 0.4, and the number of reactors ranging from 2 to 6. Using these boundary conditions, the optimal plutonium concentration was found to be 7%. This resulted in an optimal throughput ranging from 2000 to 5000 kg/yr of plutonium. The data showed minimal costs (based solely on facility size and required manpower) resulting from throughputs in this range, at 3840, 2779, and 3497 kg/yr of plutonium, which resulted in a facility lifetime of 9.1, 12.6, and 10.0 yr, respectively.