431 research outputs found
Geology of the Northwestern Krania Basin
The Greveniotiki Pindos Mountains of Greece showcases the tectonics
affecting the Central Mediterranean; however no detailed geological
maps have been produced of the region. In this study we present a
1:10000 geological map of Mount Orliakas and its surrounding areas,
including westernmost parts of the Pindos Ophiolite complex and the
Mesohellenic basin. We also provide new lithological, structural, and
palaeontological discussions of the region and give new evidence for
the provenance of the Kranea Formation
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Integrated Electrorefining Efficiency Test for Pyrochemical Fuel Cycle
Pyrochemical processing plays an important role in the development of next generation nuclear reactors and closed nuclear fuel cycle technology. The Idaho National Laboratory (INL) has implemented a pyrochemical process for the treatment of sodium-bonded spent fuel from the Experimental Breeder Reactor-II (EBR-II). A successful demonstration of the technology was performed from 1996 to 1999 for the Department of Energy (DOE) [1]. Processing of the spent fuel and associated research and development activities have been integrated into DOE’s Advanced Fuel Cycle Initiatives (AFCI) program since 2003. Electrorefining can be considered to be the signature or central technology for pyrochemical processing. In order to assess the efficiencies involved in the electrorefining process, an integrated electrorefining efficiency test was performed in the Mk-IV electrorefiner. This paper summarizes the observations and results obtained from the test. EXPERIMENT AND RESULTS The primary goal of the integrated processing efficiency test is to demonstrate the integrated actinide dissolution and recovery efficiencies typical for the fixed operating parameters that have been applied to Mk-IV electrorefiner (ER) and cathode processor (CP) to treat spent EBR-II driver fuel during the last three years. The findings are of importance for scaling-up the pyroprocess to recover and recycle valuable actinides from spent nuclear fuel. The test was performed in the Mk-IV electrorefiner. The ER is located in the hot cell of the Fuel Conditioning Facility at the Materials and Fuels Complex. Descriptions of the major components of the ER and the process in general have been provided elsewhere [2]. Salt and cadmium levels were measured, and multiple samples were obtained prior to performing the integrated test to establish an ER baseline for assessing the test results. The test consisted of four electrorefining batches of spent driver fuel with approximately 50 kg heavy metal. Typically, three to four ER runs are required to complete a batch. Fig. 1 shows pictures of the cathodes produced by three electrorefining runs during the second batch. The cathode No.3 in the figure has clearly different morphology than that of the first two. The cathodes produced by the other three batches have the similar morphology as those pictured. The first and second cathodes are ordinary uranium dendrite, and the third and fourth cathode show typically high Zr content morphology [3]. The end-point for each batch was determined by weighing each anode basket and assuring a net residue mass being equal or less than 3.0 kg. The 3.0 kg residue included any un-dissolved fuel constituents and adhering salt. Previous operating experience has shown that uranium dissolution in excess of 99.7 wt% was achieved when using this established end-point. Cladding hull samples were taken from each basket after it was removed from the ER. The actinide dissolution efficiency will be evaluated when the analytical results become available. Cathode No. 1 Cathode No. 2 Cathode No. 3 Fig.1 Three cathodes produced through electrorefining the second batch of spent EBR-II driver fuel As a part of the integrated efficiency test, the ca
Cyclotech - contribution to solve the Technetium shortage by using low energy medical cyclotrons
This paper presents work in progress, to develop an efficient and economic way to directly produce Technetium 99metastable (99mTc) using low-energy cyclotrons. Its importance is well established and relates with the increased global trouble in delivering 99mTc to Nuclear Medicine Departments relying on this radioisotope. Since the present delivery strategy has clearly demonstrated its intrinsic limits, our group decided to follow a distinct approach that uses the broad distribution of the low energy cyclotrons and the accessibility of Molybdenum 100 (100Mo) as the Target material. This is indeed an important issue to consider, since the system here presented, named CYCLOTECH, it is not based on the use of Highly Enriched (or even Low Enriched) Uranium 235 (235U), so entirely complying with the actual international trends and directives concerning the use of this potential highly critical material. The production technique is based on the nuclear reaction 100Mo (p,2n) 99mTc whose production yields have already been documented.
Until this moment two Patent requests have already been submitted (the first at the INPI, in Portugal, and the second at the USPTO, in the USA); others are being prepared for submission on a near future.
The object of the CYCLOTECH system is to present 99mTc to Nuclear Medicine radiopharmacists in a routine, reliable and efficient manner that, remaining always flexible, entirely blends with established protocols.
To facilitate workflow and Radiation Protection measures, it has been developed a Target Station that can be installed on most of the existing PET cyclotrons and that will tolerate up to 400 μA of beam by allowing the beam to strike the Target material at an adequately oblique angle. The Target Station permits the remote and automatic loading and discharge of the Targets from a carriage of 10 Target bodies.
On other hand, several methods of Target material deposition and Target substrates are presented. The object was to create a cost effective means of depositing and intermediate the target material thickness (25 - 100μm) with a minimum of loss on a substrate that is able to easily transport the heat associated with high beam currents.
Finally, the separation techniques presented are a combination of both physical and column chemistry. The object was to extract and deliver 99mTc in the identical form now in use in radiopharmacies worldwide. In addition, the Target material is recovered and can be recycled
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Electrorefining Experience For Pyrochemical Reprocessing of Spent EBR-II Driver Fuel
Pyrochemical processing has been implemented for the treatment of spent fuel from the Experimental Breeder Reactor-II (EBR-II) at Idaho National Laboratory since 1996. This report summarizes technical advancements made in electrorefining of spent EBR-II driver fuel in the Mk-IV electrorefiner since the pyrochemical processing was integrated into the AFCI program in 2002. The significant advancements include improving uranium dissolution and noble metal retention from chopped fuel segments, increasing cathode current efficiency, and achieving co-collection of zirconium along with uranium from the cadmium pool
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Integrated Efficiency Test for Pyrochemical Fuel Cycles
An integrated efficiency test was conducted with sodium bonded, spent EBR-II drive fuel elements. The major equipment involved in the test were the element chopper, Mk-IV electrorefiner, cathode processor, and casting furnace. Four electrorefining batches (containing 54.4 kg heavy metal) were processes under the fixed operating parameters that have been developed for this equipment based on over a decade’s worth of processing experience. A mass balance across this equipment was performed. Actinide dissolution and recovery efficiencies were established based on the mass balance and chemical analytical results of various samples taken from process streams during the integrated efficiency test
Beyond nudges: Tools of a choice architecture
The way a choice is presented influences what a decision-maker chooses. This paper outlines the tools available to choice architects, that is anyone who present people with choices. We divide these tools into two categories: those used in structuring the choice task and those used in describing the choice options. Tools for structuring the choice task address the idea of what to present to decision-makers, and tools for describing the choice options address the idea of how to present it. We discuss implementation issues in using choice architecture tools, including individual differences and errors in evaluation of choice outcomes. Finally, this paper presents a few applications that illustrate the positive effect choice architecture can have on real- world decisions
Precise Doppler Monitoring of Barnard's Star
We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the
second nearest star system to Earth, obtained from Lick and Keck Observatories
during 25 years between 1987 and 2012. The early precision was 20 \ms{} but was
2 \ms{} during the last 8 years, constituting the most extensive and sensitive
search for Doppler signatures of planets around this stellar neighbor. We
carefully analyze the 136 Keck radial velocities spanning 8 years by first
applying a periodogram analysis to search for nearly circular orbits. We find
no significant periodic Doppler signals with amplitudes above 2 \ms{},
setting firm upper limits on the minimum mass (\msini) of any planets with
orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for
circular orbits, we determine that planetary companions to Barnard's Star with
masses above 2 \mearth{} and periods below 10 days would have been detected.
Planets with periods up to 2 years and masses above 10 \mearth{} (0.03 \mjup)
are also ruled out. A similar analysis allowing for eccentric orbits yields
comparable mass limits. The habitable zone of Barnard's Star appears to be
devoid of roughly Earth-mass planets or larger, save for face-on orbits.
Previous claims of planets around the star by van de Kamp are strongly refuted.
The radial velocity of Barnard's Star increases with time at
\msy{}, consistent with the predicted geometrical effect, secular acceleration,
that exchanges transverse for radial components of velocity.Comment: 21 pages & 11 figures; accepted to ApJ for publication; revision
comments: the conclusions and results remain unchanged, removed the last
paragraph in section 4.2, a few minor changes to the text, replaced figure 7
with figures 7 and 8, corrected typos in the rv data tables (tables 2 and 3,
data downloadable from ApJ
Scintigraphic detection of regional disruption of adrenergic neurons in the heart
Experiments were designed to detect regional disruptions of adrenergic neurons in the hearts of living dogs. The neuron disruption was achieved by the application of phenol to the epicardium of the left ventricle. Evidence for denervation was the reduction in endogenous norepinephrine (NE) concentrations in the myocardium beneath the region of phenol treatment and toward the apex. Radiolabeled meta-iodobenzylguanidine (MIBG) acts as an analog of NE and as such is concentrated in adrenergic nerve terminals. Following phenol application, MIBG labeled with 125I was found, 20 hours after injection, to be distributed within myocardium in patterns comparable to those of NE. However, left stellectomy did not alter the distributions of NE or 125I-MIBG in the myocardium and apparently did not disrupt adrenergic innervation. MIBG labeled with 123I enabled scintigraphic images of heart neurons in the living dog 3 and 20 hours after injection; these images portrayed the regions of adrenergic neuron disruption caused by phenol treatment. Concentrations of thallium-201 depicted on scintigraphic image and of triphenyltetrazolium observed on in vitro staining demonstrated no myocardial injury. Thus scintigraphy with 123I-MIBG will display regional adrenergic denervations in the heart.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27464/1/0000505.pd
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