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Multistage metal hydride compressor

Description: Metal hydride compressors can compress hydrogen to high pressures without using mechanical moving parts. They are particularly suited for tritium applications because they require minimal maintenance. A three-stage metal hydride compressor which can compress hydrogen from 14.7 to 20,000 psia has been demonstrated. The design principle and experimental results are presented.
Date: January 1, 1986
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

Using Metal Hydride to Store Hydrogen

Description: Hydrogen is the lightest element. At ambient conditions on a volume basis it stores the least amount of energy compared to other fuel carriers such as natural gas and gasoline. For hydrogen to become a practical fuel carrier, a way must be found to increase its volumetric energy density to a practical level. Present techniques being developed include compressed gas, cryogenic liquid and absorbed solid. Each of these techniques has its advantages and disadvantages. And none of them appears to be satisfactory for use in a hydrogen economy. In the interim all of them are used for demonstration purposes. Metal hydrides store hydrogen in a solid form under moderate temperature and pressure that gives them a safety advantage. They require the least amount of energy to operate. Their stored hydrogen density is nearing that of liquid hydrogen. But they are heavy and the weight is their main disadvantage. Current usable metal hydrides can hold no more than about 1.8 percent hydrogen by weight. However much effort is underway to find lighter materials. These include other solid materials other than the traditional metal hydrides. Their operation is expected to be similar to that of metal hydride and can use the technology developed for metal hydrides.
Date: March 12, 2003
Creator: Heung, L. K.
Partner: UNT Libraries Government Documents Department

Tritium transport vessel using depleted uranium

Description: A tritium transport vessel using depleted uranium was tested in the laboratory using deuterium and protium. The vessel contains 0.5 kg of depleted uranium and can hold up to 18 grams of tritium. The conditions for activation, tritium loading and tritium unloading were defined. The safety aspects that included air-ingress, tritium diffusion, temperature and pressure potentials were evaluated.
Date: January 1995
Creator: Heung, L. K.
Partner: UNT Libraries Government Documents Department

Stripper system performance in the replacement tritium facility

Description: The Replacement Tritium Facility (RTF) at the Savannah River Site in the United States was designed and built to handle kilogram levels of tritium. The RTF was started up in January 1994. All the design objectives were achieved. To minimize tritium release to the environment, the tritium handling process is installed inside nitrogen-atmosphere gloveboxes. Any tritium that might leak from the process to the gloveboxes is recovered by stripper systems. The tritium concentration in the gloveboxes is normally maintained at below 0.1 Ci/m{sup 3}. During a large tritium leak from the process to the glovebox, the stripper system lowered the tritium concentration in the glovebox from about 8,000 Ci/m{sup 3} to about 100 Ci/m{sup 3} in one hour. After that the tritium concentration decreased very slowly. It required 5 days of stripping before the concentration was down to about 10 Ci/m{sup 3}.
Date: January 1, 1995
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

On-board hydrogen storage system using metal hydride

Description: A hydrogen powered hybrid electric bus has been developed for demonstration in normal city bus service in the City of Augusta, Georgia, USA. The development team, called H2Fuel Bus Team, consists of representatives from government, industry and research institutions. The bus uses hydrogen to fuel an internal combustion engine which drives an electric generator. The generator charges a set of batteries which runs the electric bus. The hydrogen fuel and the hybrid concept combine to achieve the goal of near-zero emission and high fuel efficiency. The hydrogen fuel is stored in a solid form using an on-board metal hydride storage system. The system was designed for a hydrogen capacity of 25 kg. It uses the engine coolant for heat to generate a discharge pressure higher than 6 atm. The operation conditions are temperature from ambient to 70 degrees C, hydrogen discharge rate to 6 kg/hr, and refueling time 1.5 hours. Preliminary tests showed that the performance of the on-board storage system exceeded the design requirements. Long term tests have been planned to begin in 2 months. This paper discusses the design and performance of the on-board hydrogen storage system.
Date: July 1, 1997
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

Design of Metal Hydride Vessels for Processing Tritium

Description: Metal hydrides offer safe, compact and efficient ways to process tritium in areas including storage, pumping, compression, transportation and purification. Westinghouse at Savannah River Site in USA has developed and implemented metal hydride based technology for various tritium applications over the past 20 years. This paper presents our experience in designing different types of metal hydride vessels for tritium processing.
Date: October 2, 2001
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

Hydrogen Storage Development for Utility Vehicles

Description: Hydrogen storage for mobile applications is still a challenge. Savannah River Technology Center (SRTC) and its partners have identified industrial utility vehicles and mining vehicles as potential early niche markets for the use of metal hydride to store hydrogen. The weight of metal hydride is not a problem for these vehicles. The low pressure of metal hydride gives a safety advantage. SRTC has developed onboard hydrogen storage containers using metal hydrides for the demonstration of two generations of fuel cell powered utility vehicles. Another storage container is being developed for a mining vehicle. This paper provides a brief overview of the utility vehicle project and a detail discussion of the hydrogen storage system.
Date: July 18, 2001
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

Hydrogen Absorption Property of Encapsulated Lani4.25A10.75

Description: For hydrogen economy to become a reality, hydrogen production will have to be greatly increased from what it is today. Hydrogen will have to be recovered from a variety of gas streams including low concentration streams with efficient methods. Efficient process for recovering hydrogen in low concentration streams is not available today. Powder of LaNi4.25Al0.75 was encapsulated in a porous silica matrix to produce a stable composite material. The material was packed in a column and tested for hydrogen absorption from streams containing nitrogen, methane or carbon monoxide. The composite material removed hydrogen from nitrogen containing methane very well, but suffered decrease in capacity and rate when carbon monoxide was present. Using fluorinated metal hydride powder improved the kinetics but not the tolerance to carbon monoxide.
Date: July 21, 2003
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

Separation Membrane Development (Separation Using Encapsulated Metal Hydride)

Description: The goal of this work is to develop an efficient hydrogen separation process based on a new type of composite material. There are two main objectives: The first is to produce a sol-gel encapsulated metal hydride packing material that will (a) absorbs hydrogen selectively and reversibly, (b) not break down to fines, and (c) be resistant to reactive impurities. The second objective is to evaluate the hydrogen separation properties of these composite samples in a laboratory scale separation column.
Date: June 13, 2002
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

Titanium for long-term tritium storage

Description: Due to the reduction of nuclear weapon stockpile, there will be an excess of tritium returned from the field. The excess tritium needs to be stored for future use, which might be several years away. A safe and cost effective means for long term storage of tritium is needed. Storing tritium in a solid metal tritide is preferred to storing tritium as a gas, because a metal tritide can store tritium in a compact form and the stored tritium will not be released until heat is applied to increase its temperature to several hundred degrees centigrade. Storing tritium as a tritide is safer and more cost effective than as a gas. Several candidate metal hydride materials have been evaluated for long term tritium storage. They include uranium, La-Ni-Al alloys, zirconium and titanium. The criteria used include material cost, radioactivity, stability to air, storage capacity, storage pressure, loading and unloading conditions, and helium retention. Titanium has the best combination of properties and is recommended for long term tritium storage.
Date: December 1, 1994
Creator: Heung, L. K.
Partner: UNT Libraries Government Documents Department

Tritiated ammonia formation

Description: A rate equation that closely simulates experimental data has been developed. this rate equation can be used to calculate the formation of tritiated ammonia from different concentrations of tritium and nitrogen. The reaction of T{sub 2} and N{sub 2} to form NT{sub 3} is a slow process, particularly when the tritium concentration is low. The reaction requires weeks or months to reach equilibrium dependent on the concentrations of the reactants.
Date: March 1, 1994
Creator: Heung, L. K.
Partner: UNT Libraries Government Documents Department

Hydrogen storage composition and method

Description: A hydrogen storage composition based on a metal hydride dispersed in an aerogel prepared by a sol-gel process. The starting material for the aerogel is an organometallic compound, including the alkoxysilanes, organometals of the form M(OR){sub X} where R is an organic ligand of the form C{sub n}H{sub 2n+1}, and organometals of the form MO{sub x}Ry where R is an alkyl group, where M is an oxide-forming metal, n, x and y are integers and y is two less than the valence of M. A sol is prepared by combining the starting material, alcohol, water, and an acid. The sol is conditioned to the proper viscosity and a hydride in the form of a fine powder is added. The mixture is polymerized and dried under supercritical conditions. The final product is a composition having a hydride uniformly dispersed throughout an inert, stable and highly porous matrix. It is capable of absorbing up to 30 motes of hydrogen per kilogram at room temperature and pressure, rapidly and reversibly. Hydrogen absorbed by the composition can be readily be recovered by heat or evacuation.
Date: January 1, 1994
Creator: Wicks, G.G. & Heung, L.K.
Partner: UNT Libraries Government Documents Department

Silica Embedded Metal Hydrides

Description: A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.
Date: August 1, 1998
Creator: Heung, L.K. & Wicks, G.G.
Partner: UNT Libraries Government Documents Department

Confinement and Tritium Stripping Systems for APT Tritium Processing

Description: This report identifies functions and requirements for the tritium process confinement and clean-up system (PCCS) and provides supporting technical information for the selection and design of tritium confinement, clean-up (stripping) and recovery technologies for new tritium processing facilities in the Accelerator for the Production of Tritium (APT). The results of a survey of tritium confinement and clean-up systems for large-scale tritium handling facilities and recommendations for the APT are also presented.
Date: October 20, 1997
Creator: Hsu, R.H. & Heung, L.K.
Partner: UNT Libraries Government Documents Department

Cryogenic Adsorption of Hydrogen Isotopes Over Nano-Structured Materials

Description: Porous materials such as zeolites, activated carbon, silica gels, alumina and a number of industrial catalysts are compared and ranked for hydrogen and deuterium adsorption at liquid nitrogen temperature. All samples show higher D{sub 2} adsorption than that of H{sub 2}, in which a HY sample has the greatest isotopic effect while 13X has the highest hydrogen uptake capacity. Material's moisture content has significant impact to its hydrogen uptake. A material without adequate drying could result in complete loss of its adsorption capacity. Even though some materials present higher H{sub 2} adsorption capacity at full pressure, their adsorption at low vapor pressure may not be as good as others. Adsorption capacity in a dynamic system is much less than in a static system. A sharp desorption is also expected in case of temperature upset.
Date: October 7, 2010
Creator: Xiao, S. & Heung, L.
Partner: UNT Libraries Government Documents Department

Tcap Hydrogen Isotope Separation Using Palladium and Inverse Columns

Description: The Thermal Cycling Absorption Process (TCAP) was further studied with a new configuration. Previous configuration used a palladium packed column and a plug flow reverser (PFR). This new configuration uses an inverse column to replace the PFR. The goal was to further improve performance. Both configurations were experimentally tested. The results showed that the new configuration increased the throughput by a factor of more than 2.
Date: August 31, 2010
Creator: Heung, L.; Sessions, H. & Xiao, S.
Partner: UNT Libraries Government Documents Department


Description: The isotopic effect of palladium has been applied in different ways to separate hydrogen isotopes for many years. At Savannah River Site palladium deposited on kieselguhr (Pd/k) is used in a thermal cycling absorption process (TCAP) to purify tritium for over ten years. The need to design columns for different throughputs and the desire to advance the performance of TCAP created the need to evaluate different column designs and packing materials for their separation efficiency. In this work, columns with variations in length, diameter and metal foam use, were tested using an isotope displacement method. A simple computer model was also developed to calculate the number of theoretical separation stages using the test results. The effects of column diameter, metal foam and gas flow rate were identified.
Date: June 27, 2007
Creator: Heung, L; Gregory Staack, G; James Klein, J & William Jacobs, W
Partner: UNT Libraries Government Documents Department


Description: An external gelation process was developed to produce spherical granules that contain metal hydride particles in a sol-gel matrix. Dimensionally stable granules containing metal hydrides are needed for applications such as hydrogen separation and hydrogen purification that require columns containing metal hydrides. Gases must readily flow through the metal hydride beds in the columns. Metal hydrides reversibly absorb and desorb hydrogen and hydrogen isotopes. This is accompanied by significant volume changes that cause the metal hydride to break apart or decrepitate. Repeated cycling results in very fine metal hydride particles that are difficult to handle and contain. Fine particles tend to settle and pack making it more difficult to flow gases through a metal hydride bed. Furthermore, the metal hydrides can exert a significant force on the containment vessel as they expand. These problems associated with metal hydrides can be eliminated with the granulation process described in this report. Small agglomerates of metal hydride particles and abietic acid (a pore former) were produced and dispersed in a colloidal silica/water suspension to form the feed slurry. Fumed silica was added to increase the viscosity of the feed slurry which helped to keep the agglomerates in suspension. Drops of the feed slurry were injected into a 27-foot tall column of hot ({approx}70 C), medium viscosity ({approx}3000 centistokes) silicone oil. Water was slowly evaporated from the drops as they settled. The drops gelled and eventually solidified to form spherical granules. This process is referred to as external gelation. Testing was completed to optimize the design of the column, the feed system, the feed slurry composition, and the operating parameters of the column. The critical process parameters can be controlled resulting in a reproducible fabrication technique. The residual silicone oil on the surface of the granules was removed by washing in mineral spirits. The ...
Date: February 23, 2004
Creator: Hansen, E; Eric Frickey, E & Leung Heung, L
Partner: UNT Libraries Government Documents Department


Description: 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 LaNi{sub 4.25}Al{sub 0.75} 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 LaNi{sub 4.15}Al{sub 0.85} material was procured and processed to obtain the desired pressure-composition-temperature (PCT) properties. Other bed design improvements are also presented.
Date: February 23, 2011
Creator: Klein, J.; Estochen, E.; Shanahan, K. & Heung, L.
Partner: UNT Libraries Government Documents Department


Description: The Savannah River National Laboratory (SRNL) has developed a new medium for storage of hydrogen and other gases. This involves fabrication of thin, Porous Walled, Hollow Glass Microspheres (PW-HGMs), with diameters generally in the range of 1 to several hundred microns. What is unique about the glass microballons is that porosity has been induced and controlled within the thin, one micron thick walls, on the scale of 10 to several thousand Angstroms. This porosity results in interesting properties including the ability to use these channels to fill the microballons with special absorbents and other materials, thus providing a contained environment even for reactive species. Gases can now enter the microspheres and be retained on the absorbents, resulting in solid-state and contained storage of even reactive species. Also, the porosity can be altered and controlled in various ways, and even used to filter mixed gas streams within a system. SRNL is involved in about a half dozen different programs involving these PW-HGMs and an overview of some of these activities and results emerging are presented.
Date: April 15, 2008
Creator: Wicks, G; Leung Heung, L & Ray Schumacher, R
Partner: UNT Libraries Government Documents Department


Description: A new encapsulation method was investigated in an attempt to develop an improved palladium packing material for hydrogen isotope separation. Porous wall hollow glass microspheres (PWHGMs) were produced by using a flame former, heat treating and acid leaching. The PWHGMs were then filled with palladium salt using a soak-and-dry process. The palladium salt was reduced at high temperature to leave palladium inside the microspheres.
Date: April 9, 2008
Creator: Heung, L.; George Wicks, G. & Ray Schumacher, R.
Partner: UNT Libraries Government Documents Department


Description: 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.
Date: January 9, 2009
Creator: Heung, L; Henry Sessions, H; Steve Xiao, S & Heather Mentzer, H
Partner: UNT Libraries Government Documents Department

On-Board Hydrogen Storage for a City Transit Bus

Description: An electric bus was modified to use hydrogen fuel for demonstration in the city of Augusta, Georgia, USA. The hydrogen fuel is stored in a solid form using an on-board metal hydride storage system. The storage system performs better than expected.
Date: March 1, 1998
Creator: Heung, L.K.
Partner: UNT Libraries Government Documents Department

HyTech - The Hydrogen Technology Laboratory at Savannah River

Description: SRS recently announced the formation of the Hydrogen Technology Laboratory (HyTech) to work with industry and government in developing technologies based on the site`s four decades of experience with tritium and other forms of H. HyTech will continue to sustain the site`s ongoing role in H technology applications for defense programs. In addition, the laboratory will work with the chemical, transportation, power, medical, and other industries to develop and test related technologies. HyTech, which is located in the Savannah River Technology Center, will make use of its facilities and staff, as well as the infrastructure within the site`s Tritium Facilities. More than 80 SRS scientists, engineers, and technical professionals with backgrounds in chemistry, engineering, materials science, metallurgy, physics, and computer science will work with the laboratory. This paper describes some of HyTech`s current initiatives in the area of H storage, transportation, and energy applications.
Date: December 31, 1995
Creator: Motyka, T.; Knight, J.R.; Heung, L.K. & Lee, M.W.
Partner: UNT Libraries Government Documents Department