Out of vacuum electron beam welding
Explore the source record for details and available documents.
ELECTRON BEAM WELDING↗
SEARCH · Engineering Papers
Results for “WELDING, GAS”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Tough strong iron alloys for cryogenic service
Series of alloys with minor additions of reactive metals possesses outstanding strength and toughness at cryogenic temperatures. Effective metal additons include aluminum, niobium, titanium, and vanadium. Strengthening of series is achieved by thermomechanical processing and by precipitate strengthening while maintaining high level of toughness. Possible applications include liquefied natural-gas storage and transmission, structural members in superconducting machinery, and welding rod for other alloys such as nine nickel steels.
Stephens, J. R.↗
Remote Neural Pendants In A Welding-Control System
Neural network integrated circuits enhance functionalities of both remote terminals (called "pendants") and communication links, without necessitating installation of additional wires in links. Makes possible to incorporate many features into pendant, including real-time display of critical welding parameters and other process information, capability for communication between technician at pendant and host computer or technician elsewhere in system, and switches and potentiometers through which technician at pendant exerts remote control over such critical aspects of welding process as current, voltage, rate of travel, flow of gas, starting, and stopping. Other potential manufacturing applications include control of spray coating and of curing of composite materials. Potential nonmanufacturing uses include remote control of heating, air conditioning, and lighting in electrically noisy and otherwise hostile environments.
Venable, Richard A.↗
Quality status display for a vibration welding process
A method includes receiving, during a vibration welding process, a set of sensory signals from a collection of sensors positioned with respect to a work piece during formation of a weld on or within the work piece. The method also includes receiving control signals from a welding controller during the process, with the control signals causing the welding horn to vibrate at a calibrated frequency, and processing the received sensory and control signals using a host machine. Additionally, the method includes displaying a predicted weld quality status on a surface of the work piece using a status projector. The method may include identifying and display a quality status of a suspect weld. The laser projector may project a laser beam directly onto or immediately adjacent to the suspect welds, e.g., as a red, green, blue laser or a gas laser having a switched color filter.
36 MATERIALS SCIENCE↗
Identifying Challenges in Safeguards for Metallic Fuel Fabrication Facilities
As new advanced reactors gain popularity, there is an increasing interest in metallic fuel fabrication for fast reactors. While metallic fuels themselves are not a new idea, as many of the first reactors employed metallic fuels, new designs, compositions, and fabrication methods are appearing throughout the nuclear community. As the interest grows and facilities are constructed, both domestic and international safeguards will need to be heavily involved to support safeguards-by-design (SBD) measures from the start. This work compiles a review of historical and modern fuel types and fabrication methods, fabrication processes, safeguards gaps, and potential safeguards solutions. Metallic nuclear fuel types have been around for many decades and were included in some of the first reactors including the Experimental Breeder Reactor (EBR)-I and -II, the Fermi 1 reactor, the Integral Fast Reactor (IFR), and the Dounreay Fast Reactor (DFR). These reactors used various compositions including pure uranium (U) metal, U-zirconium (Zr) alloys, plutonium (Pu)-aluminum (Al) alloys, U-fissium (Fs) alloys, U-Pu-Zr alloys, and U-molybdenum (Mo) alloys [1, 2, 3, 4, 5]. These small alloying additions are included to improve the material properties of the pure U metal. The alpha-phase U (stable below 661C) suffers elongation in one direction causing grain boundary cracking and increasing creep rate due to irradiation growth, thermal cycling, and preferential crystal orientation. It is ideal to utilize the gamma-phase U (typically stable above 769C) by adding small amounts of alloying elements such as Zr or Mo to stabilize this phase down to room temperature [3]. Additionally, some research has been focused on U with transuranic (TRU) elements present, typically coming from the used fuel recycling process. Including these elements in fast reactor fuel can aid in the reduction of nuclear waste by burning minor long-lived actinides. However, the additions of TRU elements can cause concerns to arise when trying to fabrication or safeguard metallic fuels. A typical metallic fuel element is shown in Figure 1. Sodium is added into the cladding to create a thermal bond between the fuel slug and cladding wall. The fuel slug is then inserted and the end plug is welded on to the top of the fuel element. A gas plenum is left to create a headspace for gaseous fission products to escape rather than continue to build in the fuel itself [1, 5]. Other fuel element geometries exist as well, such as the Lightbridge twisted cruciform geometry shown in Figure 2 [6]. This design allows for better cooling performance and provides room for fuel rod swelling without impacting the fuel rod diameter. There are many different fabrication methods for metallic fuels, which is one of the many benefits of these fuel types. Many of these fabrication methods are relatively easy and cost-efficient. The most popular fabrication method is injection casting, sometimes called vacuum induction melting (VIM), shown in Figure 3 [4, 8, 9, 7, 10]. This method was largely used for EBR-II fuel fabrication. The injection casting system is contained inside of a vessel consisting of a Y2O3-coated graphite crucible surrounded by an induction coil with ZrO2-coated quartz molds suspended above the crucible. The fuel feedstock is placed inside of the graphite crucible and melted using the induction furnace. The induction furnace utilizes a dual frequency with the high frequency melting the feedstock and the low frequency causing stirring of the melted feedstock to form a homogeneous mixture. The mixture is heated to approximately 1600C in an argon environment. The vessel is evacuated and then the quartz molds are lowered into the graphite crucible containing the molten metal and the vessel is repressurized to inject the metal fuel upwards into the molds. The molds are removed and then shattered to release the fuel slugs. This fabrication method was used to fabricate 39,000 metallic fuel pins for EBR-II. While injection casting has been the most common metallic fuel fabrication method throughout the decades, many other methods have been explored including low-pressure gravity casting, microwave casting, continuous casting, centrifugal casting, coextrusion, and many others [11, 12, 8, 13, 14, 15]. Some of these methods aim to mitigate challenges that arise with americium (Am) volatilization during the casting process for TRU-containing fuel feedstocks, an issue with injection casting. Coextrusion is one of the methods explored at the Idaho National Laboratory (INL) and has been utilized for the initial fabrication tests of Lightbridge's unique fuels, as well as other metallic fuels with cladding coextruded. In this process, large billets are formed and machined and then inserted into a molten salt bath for approximately 30 minutes. The billets are then loaded into the extrusion press and extruded. This process can be seen in Figure 4 [15].
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Welding of unique and advanced alloys for space and high-temperature applications: welding and weldability of iridium and platinum alloys
Advances have been made in developing alloys for space power systems for spacecraft that travel long distances to various planets. The spacecraft are powered by radioisotope thermoelectric generators (RTGs) and the fuel element in RTGs is plutonia. For safety and containment of the radioactive fuel element, the heat source is encapsulated in iridium or platinum alloys. Ir and Pt alloys are the alloys of choice for encapsulating radioisotope fuel pellets. Ir and Pt alloys were chosen because of their high-temperature properties and compatibility with the oxide fuel element and the graphite impact shells. This review addresses the alloy design and welding and weldability of Ir and Pt alloys for use in RTGs.
36 MATERIALS SCIENCE↗
A prototype backside purge control system
New light-weight aluminum-lithium alloys are considered for propellant tank and aerospace structural applications. These alloys require more precise control of the welding atmosphere. Atmospheric oxygen contamination must be eliminated by flooding both the front and back sides of the weldment with an inert gas. This gas must be maintained at a desired pressure and flow rate that does not effect the stability of the weld process. The objective of the prototype backside purge control system being developed by Nichols Research Corporation (NRC) is to monitor and regulate the backside purge process and to develop a purge chamber design that enhances process controllability. This project will be conducted in two phases. The objective of Phase 1 is to develop a purge technique concept based on an investigation into the backside purge process. Phase 2 is to evaluate the backside purge concept developed in Phase 1.
Morris, Timothy B.↗
Effect of oxygen on weld shape and crystallographic orientation of duplex stainless steel weld using advanced A-TIG (AA-TIG) welding method
The double-shielded advanced A-TIG (AA-TIG) welding method was adopted in this study for the welding of the SUS329J4L duplex stainless steel with the shielding gases of different oxygen content levels. The oxygen content in the shielding gas was controlled by altering the oxygen content in the outer layer gas, while the inner layer remained pure argon to suppress oxidation on the tungsten electrode. As a result, a deep weld penetration was obtained due to the dissolution of oxygen into the weld metals. Additionally, the microstructure of the weld metal was changed by the dissolution of oxygen. The austenite phase at the ferrite grain boundary followed a Kurdjumov–Sachs (K–S) orientation relationship with the ferrite matrix phase at any oxide content. On the other hand, the orientation relationship between the intragranular austenite phase and the ferrite matrix phase exhibited different patterns under different oxygen content levels. When there was little oxide in the fusion zone, only a limited part of the intragranular austenite phase and the ferrite matrix phase followed the K–S orientation relationship. With the increase of the oxide, the correspondence of the K–S relationship increased and fit very well in the 2.5% O{sub 2} shielded sample. The investigation of this phenomenon was carried out along with the nucleation mechanisms of the intragranular austenite phases. - Highlights: • Weld penetration increased with the increase of the oxygen content. • Average diameter and number density of oxide were changed by the oxygen content. • K-S relationship of Widmanstätten austenite/ferrite wasn’t varied by oxide. • Orientation relationship of intragranular austenite/ferrite was varied by oxide.
36 MATERIALS SCIENCE↗
Innovative power conversion system for the French SFR prototype, ASTRID
In the framework of the French Act of 28 June 2006 about nuclear materials and waste management, the prototype ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration), foreseen in operation by the 20's, will have to demonstrate not only the minor actinide transmutation capability, but also the progress made in Sodium Fast Reactor (SFR) technology on an industrial scale, by qualifying innovative options. Some of these options still require improvements, especially in the field of operability and safety. In fact, one of the main issues with the standard steam/water Power Conversion System (PCS) of SFR is the fast and energetic chemical reaction between water and sodium, which could occur in steam generators in case of tube failure. To manage the sodium/water reaction, one way consists in minimizing the impact of such event: hence studies are carried out on steam generator design, improvement of the physical knowledge of this phenomenon, development of numerical simulation to predict the reaction onset and consequences, and associated detection improvement. On the other hand, the other way consists in eliminating sodium/water reaction. In this frame, the CEA contribution to the feasibility evaluation of an alternative innovative PCS (replacing steam/water by 180 bar pressurised nitrogen) is focused on the following main topics: - The parametric study leading to nitrogen selection: the thermodynamic cycle efficiency optimisation on Brayton cycles is performed with several gases at different pressures. - The design of innovative compact heat exchangers for the gas loop: here the key points are the nuclear codification associated with inspection capability, the innovative welding process and the thermal-hydraulic and thermal-mechanic optimisations. After a general introduction of the ASTRID project, this paper presents in detail these different feasibility studies being led on the innovative gas PCS for an SFR. (authors)
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
Additive Manufacturing of Fuel Injectors
Additive manufacturing (AM), also known as 3D-printing, has been shifting from a novelty prototyping paradigm to a legitimate manufacturing tool capable of creating components for highly complex engineered products. An emerging AM technology for producing metal parts is the laser powder bed fusion (L-PBF) process; however, industry manufacturing specifications and component design practices for L-PBF have not yet been established. Solar Turbines Incorporated (Solar), an industrial gas turbine manufacturer, has been evaluating AM technology for development and production applications with the desire to enable accelerated product development cycle times, overall turbine efficiency improvements, and supply chain flexibility relative to conventional manufacturing processes (casting, brazing, welding). Accordingly, Solar teamed with EWI on a joint two-and-a-half-year project with the goal of developing a production L-PBF AM process capable of consistently producing high-nickel alloy material suitable for high temperature gas turbine engine fuel injector components. The project plan tasks were designed to understand the interaction of the process variables and their combined impact on the resultant AM material quality. The composition of the high-nickel alloy powders selected for this program met the conventional cast Hastelloy X compositional limits and were commercially available in different particle size distributions (PSD) from two suppliers. Solar produced all the test articles and both EWI and Solar shared responsibility for analyzing them. The effects of powder metal input stock, laser parameters, heat treatments, and post-finishing methods were evaluated. This process knowledge was then used to generate tensile, fatigue, and creep material properties data curves suitable for component design activities. The key process controls for ensuring consistent material properties were documented in AM powder and process specifications. The basic components of the project were: • Powder metal input stock: Powder characterization, dimensional accuracy, metallurgical characterization, and mechanical properties evaluation. • Process parameters: Laser parameter effects, post-printing heat-treatment development, mechanical properties evaluation, and post-finishing technique. • Material design curves: Room and elevated temperature tensiles, low cycle fatigue, and creep rupture properties curves generated. • AM specifications: Key metal powder characteristics, laser parameters, and heat-treatment controls identified.
36 MATERIALS SCIENCE↗
Weld Quality Assessment in Fiber Laser Weldments of Ti-6Al-4V Alloy
Laser welding experiments are performed on Ti-6Al-4V alloy sheets by adopting fiber laser. A special kind of workpiece fixture is designed and fabricated for providing shielding gas. After experiments, penetration depth, fusion zone width and heat-affected zone size at different locations within weld bead are measured and discussed in detail. Influence of line energies on the formation of non-uniform microstructure within weld bead is explored by conducting microstructural analysis. Various kinds of microstructural morphology of martensitic structure such as α′ martensite, blocky α, massive α and basket-weave microstructure are found in fusion zone. Experimentally, it is found that beam power is the key parameter for controlling penetration depth. Higher hardness is noticed within fusion zone due to the existence of large volume of α′ martensite. Tensile strength and hardness of welded specimens are increased with decreasing line energy. Small amount of micropores are also found in solidified weld bead. However, its sizes are in acceptable range as per BSEN:4678 standard. Most favorable welding condition is identified as a combination of beam power of 800 W and welding speed of 1000 mm/min which yields full penetration, narrower bead width, small heat-affected zone, minimal defects and acceptable mechanical properties.
36 MATERIALS SCIENCE↗
Flow distribution analysis on the cooling tube network of ITER thermal shield
Thermal shield (TS) is to be installed between the vacuum vessel or the cryostat and the magnets in ITER tokamak to reduce the thermal radiation load to the magnets operating at 4.2K. The TS is cooled by pressurized helium gas at the inlet temperature of 80K. The cooling tube is welded on the TS panel surface and the composed flow network of the TS cooling tubes is complex. The flow rate in each panel should be matched to the thermal design value for effective radiation shielding. This paper presents one dimensional analysis on the flow distribution of cooling tube network for the ITER TS. The hydraulic cooling tube network is modeled by an electrical analogy. Only the cooling tube on the TS surface and its connecting pipe from the manifold are considered in the analysis model. Considering the frictional factor and the local loss in the cooling tube, the hydraulic resistance is expressed as a linear function with respect to mass flow rate. Sub-circuits in the TS are analyzed separately because each circuit is controlled by its own control valve independently. It is found that flow rates in some panels are insufficient compared with the design values. In order to improve the flow distribution, two kinds of design modifications are proposed. The first one is to connect the tubes of the adjacent panels. This will increase the resistance of the tube on the panel where the flow rate is excessive. The other design suggestion is that an orifice is installed at the exit of tube routing where the flow rate is to be reduced. The analysis for the design suggestions shows that the flow mal-distribution is improved significantly.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Effects of surface preparation on quality of aluminum alloy weldments
Study of surface preparations and surface contamination effects on the welding of 2014 aluminum involves several methods of surface analysis to identify surface properties conducive to weld defects. These methods are radioactive evaporation, spectral reflectance mass spectroscopy, gas chromatography and spark emission spectroscopy.
Kizer, D.↗
Plasma electron beam development for welding applications.
Plasma electron beam for welding, deriving beam current from secondary emission by ion bombardment, discussing gas pressure, equipment and applications
Boring, K. L.↗
Manufacturing process applications team (MATeam)
The objectives and activities of an aerospace technology transfer group are outlined and programs in various stages of progress are described including the orbital tube flaring device, infrared proximity sensor for robot positioning, laser stripping magnet wire, infrared imaging as welding process tracking system, carbide coating of cutting tools, nondestructive fracture toughness testing of titanium welds, portable solar system for agricultural applications, and an anerobic methane gas generator.
Bangs, E. R.↗
Vacuum Deposition From A Welding Torch
Process derived from arc welding produces films of high quality. Modified gas/tungsten-arc welding process developed for use in outer space. Welding apparatus in process includes hollow tungsten electrode through which inert gas flows so arc struck between electrode and workpiece in vacuum of space. Offers advantages of fast deposition, possibility of applying directional impetus to flow of materials, very low pressure at surface being coated, and inert environment.
Poorman, R. M.↗
Measuring Weld Parameters By Spectroscopy
Optical-emission spectrometric apparatus used to monitor variable-polarity plasma arc welding of aluminum alloys. Spectrometer incorporated into control system to ensure quality of weld because in keyhole, arc fully penetrates weld joint and impurities flushed out. Apparatus helps ensure high quality of weld by monitoring such contaminants as oxygen and hydrogen in shield gas, detecting inadequate flow of shield gas, and sensing changes in temperature of arc with changes in arc current and voltage.
Nunes, Arthur↗
Optimizing Transmission of Acoustic Signals to Monitor Internal Conditions of Canisters for Dry Storage of Commercial Spent Nuclear Fuel
Safe storage of spent nuclear fuel (SNF) is critical to the nuclear fuel cycle and the future of nuclear energy. In the United States, SNF is stored primarily via two methods regulated by the U.S. Nuclear Regulatory Commission: wet storage in SNF pools and dry storage in dry cask storage systems (DCSSs). After about five years of cooling in spent fuel pools, the fuel assemblies are transferred into DCSSs, and the systems are filled with helium and sealed by welding. Deterioration of conditions inside of a DCSS is reflected in changes in the internal gas properties; this motivates the development of acoustic techniques to monitor internal gas properties, over extended storage periods, using sensors mounted on the exterior of the storage packages. However, a major challenge in collecting acoustic signals is the impedance mismatch between the steel canister shell and the gas. Only a small fraction of the ultrasonic signal can be transmitted through the gas medium. This paper documents experimental studies conducted on a full-scale canister mock-up to capture the gas-borne signals. Damping materials were pasted on the outside, and blocking and unblocking tests were conducted to identify the gas-borne signal. The results show that the excitation frequency plays an important role in maximizing the gas-borne signals. The gas-borne signal was successfully detected at around the theoretical time-of-flight. A high signal-to-noise ratio was achieved in the measurements. Next, the acoustic impedance matching layers were introduced, and the gas signal was drastically improved compared with that using no AIM layers.
Spent nuclear fuel (SNF), Canisters, Internal cond↗