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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Simulating Fracture Sealing by Granular LCM Particles in Geothermal Drilling

Lost circulation occurs when the returned fluid is less than what is pumped into the well due to loss of fluid to pores or fractures. A lost-circulation event is a common occurrence in a geothermal well. Typical geothermal reservoirs are often under-pressured and have larger fracture apertures. A severe lost-circulation event is costly and may lead to stuck pipe, well instability, and well abandonment. One typical treatment is adding lost-circulation materials (LCMs) to seal fractures. Conventional LCMs fail to properly seal fractures because their mechanical limit is exceeded at elevated temperatures. In this paper, parametric studies in numerical simulations are conducted to better understand different thermal effects on the sealing mechanisms of LCMs. The computational fluid dynamics (CFDs) and the discrete element method (DEM) are coupled to accurately capture the true physics of sealing by granular materials. Due to computational limits, the traditional Eulerian–Eulerian approach treats solid particles as a group of continuum matter. With the advance of modern computational power, particle bridging is achievable with DEM to track individual particles by modeling their interactive forces between each other. Particle–fluid interactions can be modeled by coupling CFD algorithms. Fracture sealing capability is investigated by studying the effect of four individual properties including fluid viscosity, particle size, friction coefficient, and Young’s modulus. It is found that thermally degraded properties lead to inefficient fracture sealing.

15 GEOTHERMAL ENERGY↗
NASA NTRS2014

Implementation of Statistical Process Control: Evaluating the Mechanical Performance of a Candidate Silicone Elastomer Docking Seal

The National Aeronautics and Space Administration has been developing a novel docking system to meet the requirements of future exploration missions to low-Earth orbit and beyond. A dynamic gas pressure seal is located at the main interface between the active and passive mating components of the new docking system. This seal is designed to operate in the harsh space environment, but is also to perform within strict loading requirements while maintaining an acceptable level of leak rate. In this study, a candidate silicone elastomer seal was designed, and multiple subscale test articles were manufactured for evaluation purposes. The force required to fully compress each test article at room temperature was quantified and found to be below the maximum allowable load for the docking system. However, a significant amount of scatter was observed in the test results. Due to the stochastic nature of the mechanical performance of this candidate docking seal, a statistical process control technique was implemented to isolate unusual compression behavior from typical mechanical performance. The results of this statistical analysis indicated a lack of process control, suggesting a variation in the manufacturing phase of the process. Further investigation revealed that changes in the manufacturing molding process had occurred which may have influenced the mechanical performance of the seal. This knowledge improves the chance of this and future space seals to satisfy or exceed design specifications.

docking seal↗
DOE OSTI2013

Investigating Low Temperature Properties of Rubber Seals - 13020

To achieve the required tightness levels of containers for low and intermediate level radioactive wastes rubbers are widely applied as main sealing materials. The save encapsulation of the radioactive container contents has to be guaranteed according to legislation and appropriate guidelines for long storage periods as well as down to temperatures of -40 deg. C during transportation. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. It is known that the material properties of rubbers are strongly influenced by temperature. At low temperatures this is caused by the rubber-glass transition (abbr. glass transition). During continuous cooling the material changes from rubber-like entropy-elastic to stiff energy-elastic behaviour, that allows nearly no strain or retraction. Therefore, rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely, what can cause problems during application. The temperature range where full functionality is possible is strongly dependent on the application conditions and the material. For this investigation mainly ethylene propylene diene (EPDM) and fluorocarbon rubbers (FKM) were selected as they are often used for radioactive waste containers. Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) are typically used for the determination of the temperature range of the glass transition process. The standardized compression set measurement according to ISO 815 is common for investigation of rubber sealing materials as the test simulates the seal behaviour after release. To reduce the test time of the standard tests a faster technique giving the same information was developed. Additionally, the breakdown temperature of the sealing function of complete O-ring seals is measured in a component test setup to compare it with the results of the other tests. The experimental setup is capable of measuring the leakage rate at low temperatures by the pressure rise method. A model was developed that allows calculating the minimum working temperature limit of a seal by combining the results of the applied methods. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Sealed Source Security and Disposition: Progress and Prospects - 13515

Due to their high activity and portability, unsecured or abandoned sealed sources could cause significant health or environmental damage. Further, some of these sources could be used either individually or in aggregate in radiological dispersal devices commonly referred to as 'dirty bombs', resulting in significant social disruption and economic impacts in the billions of dollars. Disposal access for disused sealed sources, however, has been a serious challenge. From 2008 to 2012, sealed source disposal was available to only 14 states; additionally, waste acceptance criteria for sealed sources at the low-level waste disposal facilities in operation both prior to and after 2012 exclude some common yet potentially dangerous sealed sources. Recent developments, however, suggest that significant improvement in addressing this challenge is possible, although challenges remain. These developments include 1) the initiation of operations at the Waste Control Specialists (WCS) commercial low-level radioactive waste (LLRW) disposal facility in Andrews County, Texas; 2) the potential for significant revisions of the U.S. Nuclear Regulatory Commission's (NRC) 1995 'Final Branch Technical Position on Concentration Averaging and Encapsulation' (1995 BTP); and 3) the Utah Department of Environmental Quality's (UDEQ) approval of a license variance for sealed source disposal at the EnergySolutions LLRW disposal facility near Clive, Utah. (authors)

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

The Off-Site Source Recovery Program Capabilities in Recovering Transuranic Sealed Sources - 17599

Over the past 16 years, the mission of the Off-Site Source Recovery Program (OSRP) has been recovering disused radioactive sealed sources in the interest of national security, public health and safety. This program, which is sponsored by the National Nuclear Security Administration's Office of Global Material Security's Office of Radiological Security, is managed at Los Alamos National Laboratory and Idaho National Laboratory and has recovered sources worldwide. To date, OSRP has recovered more than 38,000 sources from over 1,300 locations worldwide. Since its inception, OSRP has grown from recovering only sealed sources containing one transuranic (TRU) isotope, Pu-239, in the early days of the program, to recovering sealed sources containing several other TRU and non-TRU isotopes. Primarily, OSRP's mission includes Pu-238, Pu-239, Am-241, Cf-252, Cm-244, Sr-90, Cs-137, Co-60, Ir-192 and Ra-226 sources that are US-origin, defense related and not commercially disposable. Over the lifetime of this program the types of recoveries performed have expanded from a single site to multi-site round-up recoveries. An additional approach, referred to as self-ship recoveries, is also used in cases where only a few sources may be present at a licensee's site. In these situations, the licensee ships their source(s) to an OSRP staging facility for ultimate consolidation and disposal. OSRP recovers sources from many types of licensees, with the majority of sources being removed from industry, universities and hospitals. These include sealed sources used in industrial radiological devices like moisture-density gauges and thickness gauges, medical devices such as blood irradiators and radiotherapy devices and sealed sources from nuclear power plants, among others. The recovery and management of sealed sources is a complex process covering multidisciplinary areas, including source construction, characteristics of the radioactive material, source packaging and transportation per DOT regulations, safe and secure storage, and final disposition per waste acceptance criteria of repository sites. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2018

International Implementation of IAEA's Borehole Disposal Concept for Sealed Radioactive Sources - 18545

With funding from the Government of Canada, and support from the U.S. Nuclear Regulatory Commission's (NRC's) Office of International Program and many others, the International Atomic Energy Agency (IAEA) is supporting the field deployment of the Borehole Disposal Concept (BDC) for secure disposal of radioactive sources in Ghana, the Philippines and Malaysia. This is a first-of-its-kind implementation. Though small in volume, disused sealed radioactive sources can be intensively radioactive and create a significant safety and security liability for the majority of the 168 Member States in the IAEA. Millions of sealed radioactive sources have been manufactured since 1901, and it is estimated that hundreds of thousands are now unwanted. The irony is that some of the countries with the smallest inventories have the greatest difficulties managing their radioactive wastes. The BDC was originally conceptualized in an IAEA-study undertaken by the South African Nuclear Energy Corporation (NECSA) for countries with small inventories of disused sealed radioactive sources. There are multiple, passive engineered and natural barriers in the BDC design, including an inner stainless-steel capsule (which holds the wastes), an inner cement containment barrier, an outer stainless steel container and outer backfill cement, as well as the surrounding geosphere. In common subsurface geochemical environments, these barriers will isolate the wastes from the biosphere, provide effective containment and ensure long-term safety. To greatly limit the likelihood of inadvertent human intrusion (safety), and deliberate human intrusion (security), these waste packages will be disposed of in a narrow diameter borehole (26 cm) at depths greater than 30 m. This type of borehole disposal creates an exceptionally small footprint, removes the wastes from normal human surficial activities, and isolates the waste packages from near-surface processes. Over the past 20 years, the IAEA, NECSA and many others have advanced the BDC on the shoulders of the IAEA's broader work supporting safe and secure disposal of radioactive wastes and management of sealed radioactive sources. With recent funding and support from many others, the IAEA has assisted Ghana, Malaysia and the Philippines in assessing their inventories and conditioning their disused sealed radioactive sources, in drilling investigation boreholes and characterizing their proposed sites, and in designing their disposal systems. These countries plan to place the uppermost waste package at depths greater than 100 m. While activities in the Philippines remain focused on-site characterization, Ghana is in the latter stages of developing their Safety Case for operational and 'post-closure' safety and Malaysia has completed their Safety Case and submitted a license application to construct and operate a BDC facility. Though this paper identifies the support provided to Member States by the IAEA, it is the Ghana Atomic Energy Commission and the Malaysian Nuclear Agency that are responsible for the safety and security of the disposals and that have been responsible for carrying-out their disposal programs. Once the BDC is licensed by the relevant national regulatory bodies, these first-of-a-kind disposal approaches will provide a template for other countries to safely dispose of their disused sealed radioactive sources - permanently eliminating their safety and security liabilities. (authors)

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

Radiological Risk From Disused Radioactive Sealed Sources in Egypt - 19083

Sealed sources are radioactive nuclear substances encased in a sealed capsule or in a cover to which the substance is bonded, and are used for a variety of activities, such as medical, industrial, academic and research, as well as commercial applications. While most sources are of relatively low activity, there are many of medium or very high activity. In use radioactive sealed sources after time become disused sources according to several reasons like, if the source activity became less than the desired activity (unfit for the intended application), if the model of the instrument became old fashion and no longer uses, if the source had been damaged, and if the user company was shut down and no longer in business. In developing countries, thousands of radium needles, teletherapy sources, oil well logging neutron sources, and miscellaneous industrial radioactive gauges are annually collected as waste and stored in centralized waste facilities. Although these sources become disused, it still dangerous and the mismanagement of high activity sources is responsible for most of the radiological accidents that result in loss of life or disabling injuries. On the other hand, these sources may be a target for criminal acts in countries where final disposal options are unavailable. Egyptian Atomic Energy Authority (EAEA) represented in Hot Labs and Waste Management Center (HLWMC) is responsible by the national nuclear law (law No. 7 /2010) for management of all kinds of radioactive waste including disused radioactive sealed sources from all Egyptian territories. Categorization of disused sources is necessary to ensure that the controls and security measures that are applied to the sources are adequate with its radiological risk. The aim of this work is to use the international Atomic Energy Agency (IAEA) categorization system to provide a simple, logical system for grading disused radioactive sealed sources in Egypt as well as to update the inventory of such sources which already collected as waste in Egypt. The categorizations of radioactive sealed sources are based on their potential to cause harm to human health. This study revealed that nearly 980 sources have been defined in Egypt as disused sources with a total activity of 46100 Ci according to available data in July 2018. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2011

Binary, ternary and quaternary silicates of CaO, BaO and ZnO in high thermal expansion seals for solid oxide fuel cells studied by high-temperature X-ray diffraction (HT-XRD)

Highlights: Black-Right-Pointing-Pointer We examined the thermal expansion of various silicates of CaO, BaO and ZnO. Black-Right-Pointing-Pointer Thermal expansions were determined by dilatometry and high-temperature X-ray diffraction. Black-Right-Pointing-Pointer High-temperature X-ray diffraction enabled to determine anisotropic thermal expansion. Black-Right-Pointing-Pointer CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and BaCa{sub 2}Si{sub 3}O{sub 9} exhibit the highest thermal expansion. Black-Right-Pointing-Pointer CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and BaCa{sub 2}Si{sub 3}O{sub 9} are suitable as components in high temperature seals. -- Abstract: Gas-tight seals based on glasses suitable for joining of materials with high thermal expansion coefficients are for example required for solid-oxide fuel cells. If these seals are to be used at high temperatures, they can only be fabricated from glasses which enable the crystallization of phases with high thermal expansion coefficients. This paper reports on some components from systems suitable for high thermal expansion seals: binary calcium silicates, CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and Ca{sub 2}SiO{sub 4} zinc silicates, Zn{sub 2}SiO{sub 4}, ternary silicates of BaO, CaO and ZnO, BaCa{sub 2}Si{sub 3}O{sub 9}, Ca{sub 2}ZnSi{sub 2}O{sub 7}, and one quaternary silicate, Ba{sub 2}CaZn{sub 2}Si{sub 6}O{sub 17,} studied by high-temperature X-ray diffraction. Only CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and BaCa{sub 2}Si{sub 3}O{sub 9} exhibit thermal expansion coefficients in the range suitable for high thermal expansion seals of 11.2-11.8 Multiplication-Sign 10{sup -6} K{sup -1} (100-800 Degree-Sign C). The thermal expansions strongly depend on the respective crystallographic axis. The coefficient of thermal expansion of a sealing glass is not only affected by the thermal expansions of the crystalline phases, but also by that of the residual glassy phase as well as by the elastic properties. The phase formation should carefully be controlled also with respect to aging.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Sensitivity study of coupled chemical-CFD simulations for analyzing aluminum-clad spent nuclear fuel storage in sealed canisters

We report the United States Department of Energy (DOE) manages over 50 Metric Tons Heavy Metal (MTHM) of aluminum-clad spent nuclear fuel. One main source for DOE’s Aluminum-clad spent nuclear fuel (ASNF) inventory is the advanced test reactor (ATR) at the INL site, which makes this fuel of particular interest for storage scenarios. Road-ready and final disposition packaging configurations for the ATR fuel dictates storage within helium-backfilled, sealed DOE standard canisters. The conditions within these sealed canisters for extended (greater than50 year dry) storage is of interest. To further this goal, a three-dimensional (3D) multi-physics computational fluid dynamics (CFD) model is developed of the sealed DOE standard canisters. This 3D CFD model is one-way coupled with bulk gas radiolysis reactions considering sealed canisters with inert gas and possible trace amounts of air and water vapor. This study looks at the evolution of the thermal history of the canisters over a 50 year time period with a coupling to the chemical reactions occurring from radiolytic breakdown of residual water. A sensitivity study is then carried out over the parameters of the model including the fuel decay heat, residual water content, sealed pressure, canister external temperature, and canister emissivity. In pure helium, hydrogen generation rates are low, under 10 ppm, but hydrogen generation rates are affected greatly by the presence of even 1% residual air, increasing by 50-plus-fold, and nitric acid generation with residual air also occurs ranging from 500 to 4000 ppm after 50 years. The fuel decay heat and the residual water content show the most importance in the generation of hydrogen gas in pure air, and for nitric acid with a residual air condition. External temperature, canister emissivity and sealed pressure all show minor sensitivity effects to the generation of potentially harmful species.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Airtight metallic sealing at room temperature under small mechanical pressure

Metallic seals can be resistant to air leakage, resistant to degradation under heat, and capable of carrying mechanical loads. Various technologies – such as organic solar cells and organic light emitting diodes – need, at least benefit from, such metallic seals. However, these technologies involve polymeric materials and can tolerate neither the high-temperature nor the high-pressure processes of conventional metallic sealing. Recent progress in nanorod growth opens the door to metallic sealing for these technologies. Here, we report a process of metallic sealing using small well-separated Ag nanorods; the process is at room temperature, under a small mechanical pressure of 9.0 MPa, and also in ambient. The metallic seals have an air leak rate of 1.1 3 1023 cm3 atm/m2 /day, and a mechanical shear strength higher than 8.9 MPa. This leak rate meets the requirements of organic solar cells and organic light emitting diodes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Aluminization Coatings and Glass Seals for High Temperature System: CRADA 536 [Abstract Only]

The proposed work will demonstrate the suitability of PNNL Reactive Air Aluminization (RAA) coatings (US Patent Numbers 10,577,694, 10,378,094, and 9,481,923) for use in high-temperature systems. In particular, the Participant and Contractor will explore applicability of these coatings in Participant’s high-temperature hydrogen reactors where they would be used to prepare the sealing surfaces of the reactor technology. Utility Global will also instruct PNNL regarding their needs relating to the further development of glass seal technologies that are suitable for use in their systems. This effort will entail alkaline earth-based silicate glass development and characterization; evaluation and characterization of reliability and compatibility of the coatings with glass seals, working environments, and substrates; performance demonstrations of representative cells and intermediate cells sealed using the glass seals and/or coatings of interest; and incorporation of the aluminization coatings and glass seals into the reactor for full-scale testing.

08 HYDROGEN↗
DOE OSTI2022

Aluminization Coatings and Glass Seals for High Temperature Systems - CRADA 536 (Final Report)

The objective of this project was to demonstrate the suitability of PNNL’s Reactive Air Aluminization (RAA) coatings (US Patent Numbers 10,577,694, 10,378,094, and 9,481,923) for use in high-temperature systems. In particular, PNNL and Utility Global undertook a collaborative effort to explore the applicability of these coatings in Utility Global’s high-temperature hydrogen reactors where they would be used to prepare the sealing surfaces of the reactor technology. Utility Global instructed PNNL regarding their needs relating to further development of glass seal technologies suitable for use in their systems. This effort entailed alkaline earth-based silicate glass development and characterization; evaluation and characterization of reliability and compatibility of the coatings with glass seals, working environments, and substrates; performance demonstrations of representative cells and intermediate cells sealed using the glass seals and/or coatings of interest; and incorporation of the aluminization coatings and glass seals into Utility Global reactors for testing.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Spatial Seal Database for Prospective Storage Resources in the USA

The goal of the Spatial Seal Database for Prospective Storage Resources in the USA is to provide relevant information and spatial extents of caprock and seal rocks. A lack of aggregated information is readily available that focuses on the caprock and seal units within sedimentary basins. The EPA class VI permit requires an assessment of the confining zone as part of submitting a permit. The data catalog of seal unit names and relevant properties with the seal spatial extent database aims to help provided important data for carbon storage based assessments. The data catalog and database are designed to show what seal data is available in a sedimentary basin and guide stakeholders to the original data source for those datasets.

Pantaleone, Scott↗
NASA NTRS1972

Improved lip seal for rotating shafts

Sealing efficiency, service life, and seal loading limits of lip seal for rotating shafts are analyzed. Construction of seal and areas of application are described. Specific advantages of improved lip seal over conventional seals are listed.

Endicott, D. L.↗
NASA NTRS1973

Labyrinth seal testing for lift fan engines

An abradable buffered labyrinth seal for the control of turbine gas path leakage in a tip-turbine driven lift fan was designed, tested, and analyzed. The seal configuration was not designed to operate in any specific location but was sized to be evaluated in an existing test rig. The final sealing diameter selected was 28 inches. Results of testing indicate that the flow equations predicted seal air flows consistent with measured values. Excellent sealing characteristics of the abradable coating on the stator land were demonstrated when a substantial seal penetration of .030 inch into the land surface was encountered without appreciable wear on the labyrinth knife edges.

Dobek, L. J.↗
NASA NTRS1973

Self-acting and hydrodynamic shaft seals

Self-acting and hydrodynamic seals are described. The analytical procedures are outlined for obtaining a seal force balance and the operating film thickness. Particular attention is given to primary ring response (seal vibration) to rotating seat face runout. This response analysis revealed three different vibration modes. Proposed applications of self-acting seals in gas turbine engines and in rocket vehicle turbopumps are described. Also experimental data on self-acting face seals operating under simulated gas turbine conditions are given; these data show the feasibility of operating the seal at conditions of 345 newtons per square centimeter (500 psi) and 152 meters per second (500 ft/sec) sliding speed.

Ludwig, L. P.↗
NASA NTRS1973

Self-acting and hydrodynamic shaft seals.

Self-acting and hydrodynamic seals are described. The analytical procedures are outlined for obtaining a seal force balance and the operating film thickness. Particular attention is given to primary ring response (seal vibration) to rotating seat face runout. This response analysis revealed three different vibration modes. Proposed applications of self-acting seals in gas turbine engines and in rocket vehicle turbopumps are described. Also experimental data on self-acting face seals operating under simulated gas turbine conditions are given; these data show the feasibility of operating the seal at conditions of 345 newtons per square centimeter (500 psi) and 152 meters per second (500 ft/sec) sliding speed.

Ludwig, L. P.↗
NASA NTRS1974

Testing of improved polyimide actuator rod seals at high temperature and under vacuum conditions for use in advanced aircraft hydraulic systems

Polyimide second-stage rod seals were evaluated to determine their suitability for applications in space station environments. The 6.35-cm (2.5-in.)K-section seal was verified for thermal cycling operation between room temperature and 478 K (400 F) and for operation in a 133 micron PA(0.000001 mm Hg) vacuum environment. The test seal completed the scheduled 96 thermal cycles and 1438 hr in vacuum with external rod seal leakage well within the maximum allowable of two drops per 25 actuation cycles. At program completion, the seals showed no signs of structural degradation. Posttest inspection showed the seals retained a snug fit against the shaft and housing walls, indicating additional wear life capability. Evaluation of a molecular flow section during vacuum testing, to inhibit fluid loss through vaporization, showed it to be beneficial with MIL-H-5606, a petroleum-base fluid, in comparison with MIL-H-83282, a synthetic hydrocarbon-base fluid.

Sellereite, B. K.↗