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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Evaluation of Hydrogen Gettering Rates Correlated to Surface Composition and Texture of Nickel-Plated Zircaloy Getters of Different Heat Treatment Procedures

Coatings of metal specimens are known to have an impact on hydrogen gettering (hydrogen absorption). The coating can have one or more functions, such as enhancing gettering, preventing gettering and/or preventing oxidation of the metal substrate. It is known that contaminants and surface texture can impact hydrogen gettering/absorption performance, but has not previously been thoroughly explored. This study evaluated the role of different post-plating heat treatments of nickel-plated zircaloy-4 getters (NPGs) and the role of the heat treatments on gettering rates, surface composition and texture. Nickel plating is applied to prevent oxidation of the Zircaloy-4 surface and also enhances gettering. The nickel plating must be heat treated before desirable gettering can occur. Our NPG getters with historically known satisfying performance were pre-heat treated in air followed by activation heat treatment in a vacuum at a higher temperature. In this study, we were interested in finding out if both heat treatment steps were necessary to obtain a desirable gettering performance, or if one step could be omitted. XPS analysis showed that if the nickel surface is not heat treated before bonding the nickel to the zirconium in the activation step, there will be carbon contaminants on the surface, which significantly reduces gettering. We studied the texture of Zircaloy-4 using SEM/EBSD to compare NPGs with both heat treatment steps with NPGs that had no post-plating heat treatment to learn if the degree of cold work could be impacted by the heat treatment steps. We did not observe any differences in texture between them. We measured gettering rates of both pretreated and activated NPGs and NPGs that had been activated without first being pre-heat treated. We found that the NPGs without the first post-plating heating step had up to a seven times slower gettering rate and obtained higher plateau pressures due to the contaminated surface. Thus, the pre-heat treatment in air before activation is necessary to avoid slower gettering rates and higher plateau pressures.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Exceptional gettering response of epitaxially grown kerfless silicon

The bulk minority-carrier lifetime in p- and n-type kerfless epitaxial (epi) crystalline silicon wafers is shown to increase >500× during phosphorus gettering. We employ kinetic defect simulations and microstructural characterization techniques to elucidate the root cause of this exceptional gettering response. Simulations and deep-level transient spectroscopy (DLTS) indicate that a high concentration of point defects (likely Pt) is “locked in” during fast (60 °C/min) cooling during epi wafer growth. The fine dispersion of moderately fast-diffusing recombination-active point defects limits as-grown lifetime, but can also be removed during gettering, confirmed by DLTS measurements. Synchrotron-based X-ray fluorescence microscopy indicates metal agglomerates at structural defects, yet the structural defect density is sufficiently low to enable high lifetimes. Consequently, after phosphorus diffusion gettering, epi silicon exhibits a higher lifetime than materials with similar bulk impurity contents but higher densities of structural defects, including multicrystalline ingot and ribbon silicon materials. Device simulations suggest a solar-cell efficiency potential of this material >23%.

DLTS↗
DOE OSTI2014

Gettering of hydrogen and methane from a helium gas mixture

In this study, the authors developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. The authors performed a systematic study to examine how both H{sub 2} and CH{sub 4} can be removed simultaneously from the mixture using two SAES St 172{sup ®} getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. The optimum combination involved operating one getter at 650 °C to decompose the methane, and the second at 110 °C to remove the hydrogen. This approach eliminated the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1%. The authors anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements.

42 ENGINEERING↗
DOE OSTI2016

Low-cost, high-performance nonevaporable getter pumps using nonevaporable getter pills

Nonevaporable getter (NEG) pumps are widely used for maintaining a clean ultrahigh vacuum (UHV) of ≤10{sup −8 }Pa because of their high pumping speeds for hydrogen (H{sub 2}) and active gases in the UHV region. In addition, they are oil free, evaporation free, sputtering free, sublimation free, magnetic field free, vibration free, economical, compact, lightweight, and energy saving. In the present paper, the authors report a new NEG pump which is composed of commercial 60 NEG pills (ϕ10 × 3 mm; 70 wt. % Zr, 24.6 wt. % V, and 5.4 wt. % Fe), titanium parts, a DN 40 conflat flange, and a tantalum heater. The NEG pills are vertically and radially aligned around the heater to maximize the effective area for pumping. After activation at 400 °C for 30 min, the pumping speeds of the NEG pump were measured with the orifice method. Pumping speeds of 140–130, 200–140, 190–130, and 35–17 l/s were estimated for H{sub 2}, CO, CO{sub 2}, and N{sub 2} gasses, respectively, in a pumped-quantity range of 0.01–0.1 Pa l. Since the NEG pump is composed of a heating unit and a NEG module, the pumping speeds can be improved by increasing the number of NEG modules. These NEG pumps are favorable alternatives to sputtering ion pumps or titanium sublimation pumps.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Technetium and Iodine Getters to Improve Cast Stone Performance

To determine the effectiveness of the various getter materials prior to their solidification in Cast Stone, a series of batch sorption experiments was performed at Pacific Northwest National Laboratory. To quantify the effectiveness of the removal of Tc(VII) and I(I) from solution by getters, the distribution coefficient, Kd (mL/g), was calculated. Testing involved placing getter material in contact with spiked waste solutions at a 1:100 solid-to-solution ratio for periods up to 45 days with periodic solution sampling. One Tc getter was also tested at a 1:10 solid-to-solution ratio. Two different solution media, 18.2 MΩ deionized water (DI H2O) and a 7.8 M Na LAW simulant, were used in the batch sorption tests. Each test was conducted at room temperature in an anoxic chamber containing N2 with a small amount of H2 (0.7%) to maintain anoxic conditions. Each getter-solution combination was run in duplicate. Three Tc- and I-doping concentrations were used separately in aliquots of both the 18.2 MΩ DI H2O and a 7.8 M Na LAW waste simulant. The 1× concentration was developed based on Hanford Tank Waste Operations Simulator (HTWOS) model runs to support the River Protection Project System Plan Revision 6. The other two concentrations were 5× and 10× of the HTWOS values. The Tc and I tests were run separately (i.e., the solutions did not contain both solutes). Sampling of the solid-solution mixtures occurred nominally after 0.2, 1, 3, 6, 9, 12, 15 days and ~35 to 45 days. Seven getter materials were tested for Tc and five materials were tested for I. The seven Tc getters were blast furnace slag 1 (BFS1) (northwest source), BFS2 (southeast source), Sn(II)-treated apatite, Sn(II) chloride, nano tin phosphate, KMS (a potassium-metal-sulfide), and tin hydroxapatite. The five iodine getters were layered bismuth hydroxide (LBH), argentite mineral, synthetic argentite, silver-treated carbon, and silver-treated zeolite. The Tc Kd values measured from experiments conducted using the 7.8 M Na LAW simulant (the simulant selected to represent LAW) for the first 15 days for four Tc getters (BFS1, BFS2, Sn(II)-treated apatite, and Sn(II) chloride) show no, to a very small, capacity to remove Tc from the LAW simulant. For the Tc-getter experiments in the 7.8 M LAW simulant, the majority of the effluent samples show very small drops in Tc concentrations for the 35-day compared to the 15-day samplings. However, the Tc concentration in the simulant blanks also dropped slightly during this period, so the effect of the getter contacting LAW simulant at 35 days compared to 15 days is minimal; except that the BFS1 1:10 test shows a slow but steady decrease in Tc concentration in the LAW simulant supernatant from the beginning to the 35 day contact at which point about 20% of the original Tc has been removed from solution. Lastly, the KMS getter gives the highest Kd value for Tc at 35 days where Kd values have increased to 104 mL/g. When considering the different I getters reacting with the 7.8 M LAW simulant, two getters are much more effective than the others: Ag zeolite and Syn Arg. The other getters have calculated iodide distribution coefficients that show very limited effectiveness in the caustic conditions created by the LAW simulant. These are preliminary results that will need more detailed analyses including both pre- and post-batch sorption getter solid-phase characterization using state-of-the-art instrumentation such as synchrotron X ray absorption spectroscopy, which can delineate the oxidation state of the Tc and likely iodine species as well as some of the getters key major components, sulfur and iron in the BFS, and tin and sulfur in the tin-bearing and sulfur-bearing getters. This report also describes future experimental studies to be performed to better elucidate the mechanisms controlling the Tc and I sequestration processes in the various getters and leach tests of getter-bearing Cast Stone monoliths.

Tc getters, I getters, Cast Stone, Waste Forms↗
DOE OSTI2015

Technetium and Iodine Getters to Improve Cast Stone Performance

To determine the effectiveness of the various getter materials prior to their solidification in Cast Stone, a series of batch sorption experiments was performed at Pacific Northwest National Laboratory. To quantify the effectiveness of the removal of Tc(VII) and I(I) from solution by getters, the distribution coefficient, K d (mL/g), was calculated. Testing involved placing getter material in contact with spiked waste solutions at a 1:100 solid-to-solution ratio for periods up to 45 days with periodic solution sampling. One Tc getter was also tested at a 1:10 solid-to-solution ratio. Two different solution media, 18.2 MΩ deionized water (DI H 2 O) and a 7.8 M Na LAW simulant, were used in the batch sorption tests. Each test was conducted at room temperature in an anoxic chamber containing N2 with a small amount of H 2 (0.7%) to maintain anoxic conditions. Each getter-solution combination was run in duplicate. Three Tc- and I-doping concentrations were used separately in aliquots of both the 18.2 MΩ DI H2O and a 7.8 M Na LAW waste simulant. The 1× concentration was developed based on Hanford Tank Waste Operations Simulator (HTWOS) model runs to support the River Protection Project System Plan Revision 6. The other two concentrations were 5× and 10× of the HTWOS values. The Tc and I tests were run separately (i.e., the solutions did not contain both solutes). Sampling of the solid-solution mixtures occurred nominally after 0.2, 1, 3, 6, 9, 12, 15 days and ~35 to 45 days. Seven getter materials were tested for Tc and five materials were tested for I. The seven Tc getters were blast furnace slag 1 (BFS1) (northwest source), BFS2 (southeast source), Sn(II)-treated apatite, Sn(II) chloride, nano tin phosphate, KMS (a potassium-metal-sulfide), and tin hydroxapatite. The five iodine getters were layered bismuth hydroxide (LBH), argentite mineral, synthetic argentite, silver-treated carbon, and silver-treated zeolite. The Tc Kd values measured from experiments conducted using the 7.8 M Na LAW simulant (the simulant selected to represent LAW) for the first 15 days for four Tc getters (BFS1, BFS2, Sn(II)-treated apatite, and Sn(II) chloride) show no, to a very small, capacity to remove Tc from the LAW simulant. For the Tc-getter experiments in the 7.8 M LAW simulant, the majority of the effluent samples show very small drops in Tc concentrations for the 35-day compared to the 15-day samplings. However, the Tc concentration in the simulant blanks also dropped slightly during this period, so the effect of the getter contacting LAW simulant at 35 days compared to 15 days is minimal; except that the BFS1 1:10 test shows a slow but steady decrease in Tc concentration in the LAW simulant supernatant from the beginning to the 35 day contact at which point about 20% of the original Tc has been removed from solution. Lastly, the KMS getter gives the highest K d value for Tc at 35 days where K d values have increased to 104 mL/g. When considering the different I getters reacting with the 7.8 M LAW simulant, two getters are much more effective than the others: Ag zeolite and Syn Arg. The other getters have calculated iodide distribution coefficients that show very limited effectiveness in the caustic conditions created by the LAW simulant. These are preliminary results that will need more detailed analyses including both pre- and post-batch sorption getter solid-phase characterization using state-of-the-art instrumentation such as synchrotron X-ray absorption spectroscopy, which can delineate the oxidation state of the Tc and likely iodine species as well as some of the getters key major components, sulfur and iron in the BFS, and tin and sulfur in the tin-bearing and sulfur-bearing getters. This report also describes future experimental studies to be performed to better elucidate the mechanisms controlling the Tc and I sequestration processes in the various getters and leach tests of getter-bearing Cast Stone monoliths.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Industrialization of Hydrogen Getter for Nuclear Waste Transportation Application - 18189

The hydrogen risk generated by radiolysis of organic compounds during a nuclear waste transport is a major issue. The use of irreversible getters is considered to limit this risk. We previously worked on MnO{sub 2}/Ag{sub 2}O getter, in order to better understand the trapping phenomenon and to ensure its reliability. We demonstrated that chemisorption of hydrogen, which is required for its application, has been shown by using several characterization techniques. Proton insertion mechanism in MnO{sub 2} has been elucidated by pair distribution function analysis. Gamma irradiation up to 4 MGy has been performed on MnO{sub 2}/Ag{sub 2}O hydrogen getter and shown that chemical and crystallographic properties are not influenced under gamma irradiation. After those fundamentals studies, industrialization of MnO{sub 2}/Ag{sub 2}O getter preparation has been studied in order to have available getter materials for industrial applications with large amounts of MnO{sub 2}/Ag{sub 2}O powder. The preparation of hydrogen getter at laboratory scale consists of mixing commercial powders with various chemical treatments (grounding, moistening, sonication and drying). The industrialization strategy consists of preparing firstly on a laboratory scale and then increasing the getter preparation up to several kilograms. At each preparation step, hydrogen trapping experiments are performed to confirm the expected performance of getter materials. Several characterizations techniques have been performed (X-Ray Diffraction, Specific Surface Area...) to analyse the properties of the getter and have shown that no impact of upscale preparation is evidenced. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Tritium Pressure Enhancement on the TPBAR Cladding by Physical Processes at the Getter

Tritium for the U.S. nuclear weapon stockpile is produced in tritium producing burnable absorber rods (TPBARs) inserted into Tennessee Valley Authoritys (TVA) light-water nuclear reactors. The rods are stainless steel tubes with a permeation barrier coating and internal components that generate and contain the tritium. The TPBAR incorporates a Ni-plated Zircoloy getter tube to capture tritium and prevent it from reaching the rod cladding and permeating into the environment. Under the conventional view of getter behavior, the tritium pressure outside the getter tube is expected to be limited to the equilibrium vapor pressure of Zr hydride at the temperature of the rod as long as the total hydrogen concentration remains below the capacity of the hydride. Since the tritium pressure is higher within the rod core, this behavior relies on the thin getters ability to hold off a differential tritium pressure. The effective tritium pressure on the cladding can also be enhanced by isotope exchange. Hydrogen ingress through the cladding from the reactor coolant creates a hydrogen pressure on the outer surface of the getter that can exchange with tritium, allowing the tritium partial pressure to increase toward this hydrogen gettering pressure. The goal of this work was to use laboratory-scale experiments to examine these mechanisms and create a model of getter behavior that describes tritium transport within the TPBAR. A third mechanism wherein the concentration at the outer surface of the getter is increased by the temperature gradient within the getter tube wall (the Soret effect) is not experimentally tested but is captured in the model. While not conclusively demonstrated by the experiments due to low pressure, high temperature, and small gap volume conditions, the model shows that when combined, the three mechanisms can explain both the magnitude and time dependence of the tritium release observed for reactor fuel assemblies with TPBARs. The model also shows how various modifications of the TPBAR design can reduce this tritium release into the environment.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2017

Preparation, Performance and Mechanism of Tc and I Getters in Cementitious Waste Forms - 17124

Cementitious waste forms offer a low temperature, cost effective technology for the solidification of liquid wastes. At the Department of Energy Hanford Site, 99-Tc and 129-I are radionuclides contained within low activity waste (LAW) which contribute significantly to environmental impacts associated with clean-up of the site. Cast Stone, a cementitious waste form comprised of 47 wt% blast furnace slag, 45 wt% fly ash and 8 wt% ordinary Portland cement, has undergone investigation as a possible candidate technology for the solidification of LAW. In screening tests using EPA Method 1315 leach testing of various mixes of Cast Stone with simulated LAW, Tc observed effective diffusivities (Dobs) had an average of 5.3 x 10-11 cm{sup 2}/s and I Dobs had an average of 5.7 x 10-9 cm{sup 2}/s. From these measurements, an opportunity exists to improve retention of Tc and I by Cast Stone. One approach to accomplish this is through the incorporation of Tc and I getters to selectively sequester Tc and I in the waste stream and eventual waste form. Initial testing conducted at PNNL identified potassium metal sulfide (KMS-2) and Sn(II)-apatite (Sn-A) as the strongest performing Tc getters and silver exchanged zeolite (Ag-Z) as the top performing I getter. This research also demonstrated that the Tc and I getters, when added to solution simultaneously, can have deleterious interactions with one another and lower the Tc and I removal levels. However, these interactions can be overcome through sequential treatment of solution with the getters. Cast Stone samples were fabricated using a 6.5 M Na average LAW simulant spiked with Tc and I with the addition of various combinations of Tc and I getters. Through EPA Method 1315 and Method 1313 testing it was found that the KMS-2 Tc getter was most successful at lowering Tc Dobs. The I getters were not effective, as apparent interference from sulfide components of the waste form may have led to dissociation of the AgI formed by the Ag-Z getter in sequestering the I from solution. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Evaluation of different getter substrates using two-dimensional gas chromatography with time of flight mass spectrometry

We report while understanding hydrogen uptake by organic based getters such as 1,4-bis(phenylethynyl)benzene (DEB) combined with a palladium(0)bis(dibenzylideneacetone) (Pd(dba) 2 ) catalyst is essential, another crucial element to understand is the decomposition of the DEB, Pd(dba) 2 , and/or substrate material. The breakdown of these materials may create unwanted volatiles, which may interact with and lead to deterioration of sensitive materials. Moreover, it is critical to understand if different substrates cause the getter and/or catalyst to degrade in different manners. Utilizing comprehensive two-dimensional gas chromatography (GC×GC) with time-of-flight mass spectrometry (TOFMS), the presence of volatiles located in the headspace of various DEB/Pd(dba) 2 getter substrates is examined. These samples include a getter infused silicone foam, a hydrogenated getter infused silicone foam, an activated carbon getter pellet, and a hydrogenated activated carbon getter pellet. Application of Fisher ratio (F-ratio) analyses lead to the identification of several compounds that are generated or consumed through the hydrogenation process. These include benzene derivatives such as bibenzyl, benzaldehyde, and vinyl benzoate in the activated carbon pellets and 1,5-diphenyl-3-pentanone, toluene, styrene, and 1–1'(2-pentene 1,5-diyl)bis benzene in the silicone foams, and alkane/alkene derivatives such undecane, 4-tridecene, and decane in the activated carbon pellets and 2,6-dimethyl undecane in the silicone foams. Further comparison of the different hydrogenated getter substrates (e.g. activated carbon pellet and silicone foam) indicates that the different substrates alter the decomposition products created from the degradation of the DEB and Pd(dba) 2 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Getter Incorporation into Cast Stone and Solid State Characterizations

Washington River Protection Solutions (WRPS) is collecting relevant available data on waste forms for use as a supplemental immobilization technology, to provide the additional capacity needed to treat low-activity waste (LAW) in Hanford Site tanks and complete the tank waste cleanup mission in a timely and cost-effective manner. One candidate supplemental waste form, fabricated using a low-temperature process, is a cementitious grout called Cast Stone. Cast Stone has been under investigation for this application at Pacific Northwest National Laboratory (PNNL) since initial screening tests in FY13. This report is the culmination of work to lower the diffusivities of Tc and I from Cast Stone using getters. Getters are compounds added to a system designed to selectively sequester a species of interest to provide increased stability to the species. The work contained within this report is related to waste form development and testing, and does not directly support the 2017 integrated disposal facility (IDF) performance assessment. However, this work contains valuable information which may be used in performance assessment maintenance past FY17, and in future waste form development. This report on performance characterization of Tc and I getters in Cast Stone fabricated with simulated LAW covers several areas of interest and major findings to WRPS: investigating performance of potassium metal sulfide (KMS-2-SS) and tin (II) apatite (Sn-A) as Tc getters when incorporated into Cast Stone; investigating performance of silver exchanged zeolite (Ag-Z) and argentite (Arg) as I getters when incorporated into Cast Stone; utilizing sequential addition of Tc and I getters to overcome any deleterious interactions between the getters in solution; determining, for the first time, Tc distribution within the cured Cast Stone and its evolution during leaching; and performing solid state characterization of getters and Cast Stone samples to support leach test findings and develop a mechanistic understanding of the processes that control Tc and I release into solution.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Strontium Manganese Oxide Getter for Capturing Airborne Cr and S Contaminants in High-Temperature Electrochemical Systems

Traces (ppm to ppb level) of airborne contaminants such as CrO 2 (OH) 2 and SO 2 irreversibly degrade the electrochemical activity of air electrodes in high-temperature electrochemical devices such as solid oxide fuel cells by retarding oxygen reduction reactions. The use of getter has been proposed as a cost-effective strategy to mitigate the electrode poisoning. However, owing to the harsh operating conditions (i.e., exposure to heat and moisture), the long-term durability of getter materials remains a considerable challenge. In this study, we report our findings on strontium manganese oxide (SMO) as a robust getter material for cocapture of airborne Cr and S contaminants. The SMO getter with a 3D honeycomb architecture, fabricated via slurry dip-coating, successfully maintains the electrochemical activity of solid oxide cells under the flow of gaseous Cr and S species, validating the getter's capability of capturing traces of Cr and S contaminants. Investigations found that both Sr and Mn cations contribute to the absorption reaction and that the reaction processes are accompanied by morphological elongation in the form of SrSO 4 nanorods and SrCrO 4 whiskers, which favors continued absorption and reaction of incoming S and Cr contaminants. The SMO getter also displays robust stability at high temperatures and in humid environments without phase transformation and hydrolysis. These results demonstrate the feasibility of the use of SMO getter under severe operating conditions representative of high-temperature electrochemical systems.

36 MATERIALS SCIENCE↗
DOE OSTI2011

EVALUATION AND SELECTION OF 99TC GETTERS FOR SEQUESTRATION OF LIQUID SECONDARY WASTE RESULTING FROM VITRIFICATION OF RADIOACTIVE WASTE FROM HANFORD

Getters are most commonly inorganic materials that selectively adsorb radionuclide and metallic contaminants. Typically, these materials have been deployed in two different modes to immobilize and retard contaminant release from monolithic waste forms. One mode is to first use getters to selectively scavenge the radionuclide of interest from a liquid waste stream, and then incorporate the radionuclide-loaded getters in cementitious or other monolithic waste forms. The other mode consists of mixing getters and liquid waste together during formulation of monolithic waste forms. Desirable characteristics for a getter material include, (1) specific adsorption of radionuclide of interest and very high selectivity toward radionuclides of concern in concentrations that would be several orders of magnitude less than the concentrations of competing anions and cations, (2) adsorption capacity that should be sufficient for the mass and volume of the material that will be deployed to be within practicable limits, (3) long-term adsorption and retention of radionuclide, (4) sufficient physical and chemical stability that its radionuclide retention performance will not degrade significantly during the designed life span of the waste form, (5) chemical stability under the range of Eh, pH, and solution conditions that exist in the waste form environment, and (6) should not adversely affect chemical and physical integrity of waste forms. We conducted a literature review to identify getters that are suitable for effectively sequestering 99Tc in monolithic waste forms that are being evaluated for stabilizing secondary liquid waste streams resulting from treatment and vitrification of radioactive tank wastes at Hanford. As a result of this review, we identified a set of getters that warrant further evaluation for this specific application.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Performance and Microstructure of a Novel Cr-Getter Material with LSCF-based Cells in a Generic Stack Test Fixture

In addition to developing passive means for Cr mitigation via coatings, Pacific Northwest National Laboratory has teamed up with the University of Connecticut to adopt an active approach by employing a novel Cr-getter material in the system. In this work, validation of the novel Cr-getter was conducted using cells in a generic stack test condition with humidified air and coated metallic interconnect. Two Cr-getter locations were investigated: one upstream and one “on cell.” Pre-oxidized AISI 441 metal stripes were used as Cr source. Three single cell tests were conducted at 800oC in constant current mode for 1000h with periodic stops for measurement of impedance and IV: a baseline cell, a cell with Cr source and getter, and a cell with Cr source but no getter. Results showed that the cell with Cr-getter degraded much slower (11.5% kh-1) than the baseline (15.3% kh-1) and the cell without the getter (56% kh-1).

Chou, Yeong-Shyung↗
DOE OSTI2025

Investigating the Impact of Absorbed Surface Impurities (CO, CO 2 , CH 4 , and H 2 O) on Getter Rate Performance

This report provides an overview of engineering and experimental efforts to establish a new capability for measuring H2 uptake rates for Tritium Producing Abosrber Rod (TPBAR) getter materials. This new system was used to gain a better understanding of the impact of contaminant species (CO 2 , CO, CH 4 , and H 2 O) on getter performance under relevant hydrogen uptake conditions (350 °C, 20 torr). Herein, we successfully established a high-resolution gravimetric sorption (HRGS) system in a flow through configuration that can measure sample mass changes with high resolution (1 µg or 10 µg) over long experiment times (days), high temperature, and varying pressures. We coupled this capability with an in-line universal gas analyzer (UGA) system to characterize potential surface chemistry side reactions occurring after contaminant gas exposure. The major findings of this study suggest that methane and CO have the most detrimental effects on getter H 2 uptake performance showing large changes in rate after exposure compared to CO 2 and water. The effect of these contaminant species did not influence getter sample capacity (~ 1.8 wt% H 2 ). After CO and methane exposure, changes in getter rate were accompanied by observable Ni-surface defects and pinholes via SEM imaging suggesting possible Ni- layer corrosion. Additionally, the increase in C and O signal in the zircaloy layer, observed via EDX, point to C and O species transport through the getter sample resulting in the formation of carbides and oxide species. Thus, co-exposure studies where mixed gases or water vapor are introduced together will be important to further understand what mechanisms are contributing to Ni-layer corrosion and changes in getter performance.

36 MATERIALS SCIENCE↗
DOE OSTI2018

3D-Printable Silicone Materials with Hydrogen Getter Capability

Organic getters are used to reduce the amount of reactive hydrogen in applications such as nuclear plants and transuranic waste. Here, the present study examines the performance of getter loaded silicone elastomers in reducing reactive hydrogen gas from the gas phase and their capability of being 3D printed using direct ink writing techniques. The samples are placed in closed vessels and exposed to hydrogen atmosphere at pressures of 580 torr and 750 mtorr and at a temperature of 25 °C. The hydrogen consumption is measured as a function of time and normalized to getter concentration in the polymer. The performance of the getter-loaded silicone elastomer containing 1,4-bis[phenylethynyl]benzene (DEB) as the organic getter and Pd/C catalyst (ratio of 3:1 DEB to catalyst) decreases with increasing the resin's curing temperature. Chemical analysis suggests that DEB reacts with the silicone resin at high temperatures. In addition, it is demonstrated that the increased surface area of 3D printed composites results in improved getter performance.

36 MATERIALS SCIENCE↗