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[en] Deuterium-Tritium (D-T) solid fuel layers must meet stringent roughness specifications for both the ICF and IFE laser fusion programs and native beta-layering alone is unable to provide sufficient solid layer smoothing to meet these specifications at 18.3 K or below. Consequently, several supplemental smoothing options have been proposed to resolve this issue, including a technique called 'Thermal Breathing'. This technique consists of oscillating the temperature of the solid D-T layer about its equilibration temperature for a period of one to several hours. Recently, thermal oscillations have been used to successfully smooth rough solid D2 in spherical targets. In order to study this particular smoothing technique, we examined the effects of thermal oscillations on equilibrated D-T solid layers, using both ICF and IFE scale layering cells and layer thicknesses. The D-T solid layers that were Subjected to thermal breathing in these studies were equilibrated at temperatures ranging from 16.0 K to 19.25 K, followed by 1.5 to 2 hours of temperature oscillations. During the HAPL scale experiments the amplitude and period of the oscillations were both varied to examine parametric effects of these variables on final layer roughness. In both sets of experiments, once the oscillations completed we allowed the layers to 'relax' at their initial equilibration temperature for another 1 to 2 hours, to observe any 'rebounding' or re-roughening that might occur. The rCF scale experiments were performed using a 2 mm beryllium torus, for which the layer was free from optical distortions that were observed in our IFE scale cell (a 4 mm dia. sapphire sphere-cylinder). Our results showed a temperature dependent smoothing effect ofthe DT solid layer ranging from 20% to 35% over the temperature range of 17.3 K to 19.0 K for the rCF-scale, 2-mm celL The final RMS roughness for layers grown in this 2-mm Be torus was on average less than 1 /lm for modes 7 and above. Results for the rFE scale cell showed a temperature dependent smoothing effect that varied from 5% to more than 30% over a 16.0 K to 18.3 K temperature span, and which resulted in an average overall RMS roughness of3.8 /lm at 17.3 K and 3.2 /lm at 18.3 K. We discuss the configuration ofboth of these DT layering cells, the equilibration and oscillation parameters were used, and results that show thermal oscillations can make significant contributions to the smoothing of normally equilibrated beta-layered surfaces, as well as potentially reducing the time required to produce smooth solid DT surfaces.
[en] Samples of ethylene propylene diene monomer (EPDM) elastomer were exposed to tritium gas in closed containers initially at 101 kPa (1 atmosphere) pressure and ambient temperature for about one week. Tritium exposure effects on the samples were characterized by dynamic mechanical analysis (DMA) and radiolysis products were characterized by measuring the total final pressure and composition in the exposure containers at the end of exposure period. There was no effect of one week tritium exposure on the glass transition temperature, Tg, of the samples tested. Impurity gases produced in the closed containers included HT and lesser amounts of H2, DTO, and CT4. The total pressure remained the same during exposure
[en] The Savannah River Site (SRS) tritium facilities have used 1st generation (Gen1) metal hydride storage bed assemblies with process vessels (PVs) fabricated from 3 inch nominal pipe size (NPS) pipe to hold up to 12.6 kg of LaNi4.25Al0.75 metal hydride for tritium gas absorption, storage, and desorption for over 15 years. The 2nd generation (Gen2) of the bed design used the same NPS for the PV, but the added internal components produced a bed nominally 1.2 m long, and presented a significant challenge for heater cartridge replacement in a footprint limited glove-box. A prototype 3rd generation (Gen3) metal hydride storage bed has been designed and fabricated as a replacement candidate for the Gen2 storage bed. The prototype Gen3 bed uses a PV pipe diameter of 4 inch NPS so the bed length can be reduced below 0.7 m to facilitate heater cartridge replacement. For the Gen3 prototype bed, modeling results show increased absorption rates when using hydrides with lower absorption pressures. To improve absorption performance compared to the Gen2 beds, a LaNi4.15Al0.85 material was procured and processed to obtain the desired pressure-composition-temperature (PCT) properties. Other bed design improvements are also presented.
[en] The first generation of TCAP hydrogen isotope separation process has been in service for tritium separation at the Savannah River Site since 1994. To prepare for replacement, a next-generation TCAP process has been developed. This new process simplifies the column design and reduces the equipment requirements of the thermal cycling system. An experimental twelve-meter column was fabricated and installed in the laboratory to demonstrate its performance. This new design and its initial test results were presented at the 8th International Conference on Tritium Science and Technology and published in the proceedings. We have since completed the startup and demonstration the separation of protium and deuterium in the experimental unit. The unit has been operated for more than 200 cycles. A feed of 25% deuterium in protium was separated into two streams each better than 99.7% purity
[en] A diffuser/permeator commercially fabricated by Johnson-Matthey was purchased for characterization testing at the Savannah River National Laboratory (SRNL). A test system was fabricated to not only feed and bleed flows and pressures, but also permeate pressure for flows up to 20 SLPM
[en] In this paper, the High Energy Density Physics program at Los Alamos National Laboratory (LANL) has had a multiyear campaign to verify the predictive capability of the interface evolution of shock propagation through different profiles machined into the face of a plastic package with an iodine-doped plastic center region. These experiments varied the machined surface from a simple sine wave to a double sine wave and finally to a multitude of different profiles with power spectrum ranges and shapes to verify LANL’s simulation capability. The MultiMode-A profiles had a band-pass flat region of the power spectrum, while the MultiMode-B profile had two band-pass flat regions. Another profile of interest was the 1-Peak profile, a band-pass concept with a spike to one side of the power spectrum. All these profiles were machined in flat and tilted orientations of 30 and 60 deg. Tailor-made machining profiles, supplied by experimental physicists, were compared to actual machined surfaces, and Fourier power spectra were compared to see the reproducibility of the machining process over the frequency ranges that physicists require.
[en] Specialized machining processes and programming have been developed to deliver thin tin and copper Richtmyer-Meshkov instability targets that have different amplitude perturbations across the face of one 4-in.-diameter target. Typical targets have anywhere from two to five different regions of sine waves that have different amplitudes varying from 4 to 200 μm across the face of the target. The puck is composed of multiple rings that are zero press fit together and diamond turned to create a flat platform with a tolerance of 2 μm for the shock experiment. A custom software program was written in Labview to write the point-to-point program for the diamond-turning profiler through the X-Y-Z movements to cut the pure planar straight sine wave geometry. As a result, the software is optimized to push the profile of the whole part into the face while eliminating any unneeded passes that do not cut any material.
[en] Metal hydrides, specifically Pd deposited on kieselguhr (Pd/k) and LaNi4.25Al0.75 (LANA.75), have been used at the Savannah River Site for almost twenty years for hydrogen isotope separation and storage. Radiolytic decay of tritium to helium-3 in the metal matrix causes three classic changes in the performance of the hydride: the plateau pressure decreases, the plateau slope increases, and a heel forms, reducing the reversible capacity of the hydride. Deuterium and tritium isotherms were collected on the virgin materials, only tritium isotherms were collected at approximately 2 years, and both deuterium and tritium isotherms were collected at approximately 3.5 years of quiescent aging. Points of interest include those mentioned above as well as the effects of cycling the materials. The methods and results are presented
[en] Increased requirements for tighter tolerances on assembled target components in complex three-dimensional geometries with only days to assemble complete campaigns require the implementation of a computer-controlled high-precision assembly station. Over the last year, an 11-axis computer-controlled assembly station has been designed and built with custom software to handle the multiple coordinate systems and automatically calculate all relational positions. Preliminary development efforts have also been done to explore the benefit of a machine vision feedback module with a dual-camera viewing system to automate certain basic features like crosshair calibration, component leveling, and component centering.
[en] A large number of inertial fusion energy (IFE) chamber concepts have been proposed and analyzed to various levels of detail [1, 2]. A smaller number of detailed power plant design studies (i.e., studies considering self-consistent integration of targets, drivers and chambers) have also been completed for both direct-drive and indirect-drive, central ignition (CI) targets [3-5]. There have not been any comparable studies of fusion chambers or integrated power plants for fast-ignition (FI) based IFE. Some specific aspects (advantages and issues) have been previously describe [6, 7], but not to the level of detail of the large integrated design studies. In this paper, we review current understanding of chamber design and power plant features for fast-ignition. We approach this topic by asking what chamber and power plant issues and features will be different for fast ignition compared to central ignition. In this article, we consider first wall and final optics design issues for various chamber concepts with direct and indirect drive FI targets, while target manufacture and injection issues are considered in another paper in this special issue . If it is found that the ignitor beams can efficiently penetrate the plasma that is blown off the fuel capsule surface during the compression phase, the FI targets may look much like CI targets. In this case the fusion chamber and final optics issues are likely to be very similar to those for CI targets, except for the final optics of the ignitor beams. It is more likely that the efficiency of transferring ignitor beam energy through the blow-off plasma to the ignition spot fuel will be so low that whatever advantage fast ignition has in reducing required compression driver energy will be more than offset by the size and, therefore, cost of the ignitor lasers themselves. Therefore, it has been proposed to use a cone of high-Z material  to shield the ignitor beam line-of-sight from the blow-off plasma and possibly help focus the short pulse ignitor beams onto the dense fuel. Figure 1 illustrates what these cone focus targets might look like for laser direct-drive, laser indirect-drive and heavy ion indirect-drive concepts. The Tabak article in this special issue describes the operation and performance of these targets . The cones must be relatively heavy and thick to avoid breaking up during the implosion of the fuel. In the direct-drive case, the cone must also be long enough that ablated material from the fuel capsule does not go around the end and into the ignitor beam line of sight. It has been suggested that the cone length may have to be up to four times the initial radius of the fuel capsule . For hohlraum targets, the cones need not be as long because the hohlraum wall itself retards the expanding plasma. The presence of the massive high-Z cone in close proximity to the high density fuel will affect the energy partition of the burning capsule output and its x-ray and debris spectra. It can also affect the aerodynamics of the target during injection. Finally, if the capsule fails to ignite, the consequences of the dud may be different for cone targets than for central ignition targets. All these potential differences will be examined in this article. In Section 2, we discuss the power plant benefits of FI cone-focus targets with emphasis on the economic advantages of high target gain at low driver energy. Section 3 shows how the energy partition and spectra of cone focus targets compares with central ignition targets. Section 4 covers possible chamber concepts that are compatible with indirect-drive fast ignition. Section 5 reviews two special issues for FI power plants: Section 5.1 describes the survival of final optics, especially for the extremely intense ignitor beams, while Section 5.2 discusses the consequences of duds, which may occur more frequently for FI targets. Section 6 lists recommended near-term future work for FI power plant issues discussed in this article, and Section 7 gives our conclusions