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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Electrostatic design and conditioning of a triple point junction shield for a –200 kV DC high voltage photogun [Electrostatic design of a triple point junction shield for a -200 kV DC high voltage photogun using COMSOL]

Nuclear physics experiments performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Lab require a DC high voltage photogun to generate polarized electron beams from GaAs photocathodes. The photogun uses a tapered ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. Increasing the operating voltage from nominal –130 kV to –200 kV will provide lower beam emittance, better transmission through injector apertures, and improved photocathode lifetime. This desire to increase the photogun operating voltage led to the design of a triple-point-junction shield electrode which minimizes the electric field at the delicate insulator-metal-vacuum interface and linearizes the potential across the insulator, thus reducing the risk of arcing along the ceramic insulator. Furthermore, this work describes the results obtained using COMSOL® electrostatic-field simulation software and presents the high voltage conditioning results of the upgraded –200 kV CEBAF photogun.

47 OTHER INSTRUMENTATION↗
NASA NTRS2005

Foam core shield (FCS) systems : a new dual - purpose technology for shielding against meteoroid strike damage and for thermal control of spacecrafts/satellite components

A new technology is being developed that can protect spacecraft and satellite components against damage from meteoroid strikes and control the thermal environment of the protected components. This technology, called Foam Core Shield (FCS) systems, has the potential to replace the multi-layer insulation blankets (MLI) that have been used on spacecraft for decades. In order to be an attractive candidate for replacing MLI, FCS systems should not only provide superior protection against meteoroid strikes but also provide an equal or superior ability to control the temperature of the protected component. Properly designed FCS systems can provide these principal functions, meteoroid strike protection and thermal control, with lower system mass and a smaller system envelope than ML.

thermal environment↗
DOE OSTI2019

Self-shielded, benchtop radio chemistry system with a plurality shielded carriers containing a disposable chip cassette

A self-shielded, bench-top radiochemistry system, including a radioactive isotope dispensing module configured to draw an isotope out of a vial and dispense one or more metered doses of the isotope to a concentration module that concentrates the metered dose into a droplet amount of isotope and a synthesizer module that delivers the droplet amount of isotope along with one or more reagents to an electrowetting on dielectrics (EWOD) chip to produce a radiolabeled molecule.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2014

Imaging Shielded Configurations Using Near-Horizontal and Near-Vertical Trajectory Cosmic-Ray Muons

This work will describe the proof-of-concept research applying muon tomography technologies based on drift tube systems to create images using near–horizontal trajectory muons. To date, the majority of imaging studies using cosmic-ray muons have used near–vertical trajectory muons. This work compares imaging results using near–vertical trajectory muons with results using near–horizontal trajectory muons. The muon flux is much lower for the near–horizontal trajectory muons, so requiring longer imaging times, but the average muon energy is higher, so the horizontal results are expected to better differentiate high-Z materials. The muon tracking system is easily configurable and can be oriented to capture near–vertical trajectory or near– horizontal trajectory cosmic-ray muons. The software can track each muon passing through the system, and generate 3-D images of the scene. The experimental design and preliminary results will be presented, including the comparisons of detection efficiency, image resolution, and integration times.

muon, passive, imaging, tomography, cosmic↗
DOE OSTI2018

Sodium and Lithium Hydride Shields At the Department of Energy's Oak Ridge Reservation - 18412

URS-CH2M Oak Ridge LLC (UCOR) is responsible for cleanup of the U.S. Department of Energy's (DOE) East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee. Formerly known as the K-25 site, the facility enriched uranium for major defense and energy programs for more than 40 years. DOE is seeking the safest, most environmentally protective and fiscally responsible treatment for its large inventory of radioactive-contaminated metals known as 'shields'. The 66 sodium and lithium shields were constructed for use in experiments at the Tower Shielding Facility (TSF), Oak Ridge National Laboratory (ORNL). The TSF operated from 1954 to 1992 and was designed and built for radiation-shielding studies. The shield containers are constructed of aluminum or stainless steel of varying sizes and shapes that were then filled with either sodium metal or lithium hydride material. The historical records indicate the sodium shields were constructed at the Molten Salt Reactor for use in experiments in the 1971 time frame, while the lithium shields were constructed at the Y-12 site and were used in experiments as early as 1961. A subset of the sodium and lithium shields contain depleted uranium. The sodium and lithium shields were initially used at the TSF to perform in-depth measurements of the neutron transport through the shield materials. Based on process knowledge, the shields are managed as radiologically contaminated containers. Efforts have been made over the last fifteen years to find recycle markets for both the sodium and lithium hydride shields. This includes an onsite operation that was initiated at the East Tennessee Technology Park (ETTP) in 2004. After an operational exothermic reaction incident occurred soon after startup, the onsite ETTP recycling action was discontinued and a search for offsite recycling facilities was initiated. In 2016, the Y-12 National Security Complex was contacted regarding recycle/repurpose of the lithium shields; however, the lithium was determined to not be acceptable for their current repurpose process. To date, no offsite recycling outlets have been identified. Recent progress on the waste disposal actions, a shipment of 22 small sodium shields have been shipped and treated offsite. Therefore, the current shield inventory consists of 29 sodium shields located at ETTP and 15 sodium and lithium hydride shields staged at ORNL. The time period needed to reasonably identify safe disposition or recycling outlets for the shields was expected to exceed the one-year Land Disposal Restrictions storage time limit; therefore, approval was received to add the shields to the Site Treatment Plan (STP) in March, 2017. Until a disposition path is found, the shields will continue to be stored in a safe configuration that is protective of human health and the environment. This engineering evaluation identifies and screens the alternatives for dispositioning the shields at the Oak Ridge(ORR). Four alternatives were evaluated including; (1) macro-encapsulation, (2) deactivation, (3) recycle and (4) leave-in-place. An initial screening was performed, and the alternative passing the initial screening are then evaluated in more detail. The evaluation criteria used included environmental risk, technical feasibility, administrative feasibility, worker safety, nuclear safety, transportation safety, and cost. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRSDate not supplied

Shielding Considerations for CubeSat Structures During Solar Maximum

The purpose of this lessons learned is to communicate the utility of shielding in small spacecraft planning for the support of mission assurance and reliability. Numerous SmallSats have been flying in polar low earth orbit for scientific, communications, technology demonstrations, and imaging with academic, commercial, and government interests. Shielding has been part of mission assurance and reliability from the advent of long duration spacecraft missions. The Shields-1 CubeSat has been operating in polar low earth orbit since 16 December 2018 with atomic number (Z)-grade radiation shielding and demonstrates shielding effectiveness. Shields-1 has collected a representative example of solar minimum data in 2019 with 8 Teledyne dosimeters over varying shielding effectiveness. It serves as current experimental data and has been compared with NOVICE Shielding estimates using the AP8 –AE8 trapped radiation model with the Shields-1 CAD and generic CubeSat 3 unit (U) models. Using NOVICE model radiation analysis coding, the shielding effectiveness's, based on a generic CubeSat 3U structure with 4 electronic boards, were estimated for aluminum wall thicknesses ranging from 0.204 cmto4.44 cm (0.550 g/cm2–12.0 g/cm2) thick aluminum. For modeled polar orbiting spacecraft, solar maximum total ionizing dose (TID)increases by nearly a magnitude for thin-walled aluminum 0.550g/cm2-0.686 g/cm2(0.204 cm –0.254 cm) typical CubeSat structures. The shielding effectiveness by NOVICE Sigma estimates, which is a shielding sphere approximation around a detector, showed a linear relationship with wall thickness, which increased over the wall thickness by a ratio of 1.43 determined by linear regression analysis. Using NOVICE Adjoint Monte-Carlo Modeling of solar minimum and solar maximum with the inclusion of a worst-case solar particle event over a one year mission without geomagnetic shielding, the TID for minimum and maximum conditions for a generic 3U with a wall thickness of 0.254 cm is 158 RAD and 1540 RAD, respectively. The modeled total solar maximum TID is over estimated, because at low orbital latitudes a spacecraft will have shielding from Earth's magnetic field. However, TID will still be significant at high latitudes over the poles, where a spacecraft is exposed in a solar particle event. In contrast, to a thin walled generic 3U CubeSat, Shields-1 electronics enclosure has a shielding effectiveness of 21.3 g/cm2from NOVICE Sigma modeling and is expected to show reduced total ionizing dose increases during the present active Solar Cycle 25 period. Because solar particle events during solar maximum increase TID on electronic parts with thin-walled shielding in short periods of time, it is a mission assurance and reliability consideration on the spacecraft’s mission value versus adding shielding for risk reduction of premature spacecraft or instrument payload loss. Since the volumes of many instruments and system electronics have reduced with small spacecraft, shielding material costs and weight penalties have diminished. A small spacecraft project budget and schedule may limit traditional radiation-hardened part use and radiation testing requirements, where shielding can contribute to mission assurance and reliability with reduced costs.

Shields-1↗
NASA NTRSDate not supplied

Shielding Considerations for CubeSat Structures During Solar Maximum

The purpose of this lessons learned paper is to communicate the utility of shielding in small spacecraft planning for the support of mission assurance and reliability. Numerous SmallSats have been flying in polar low Earth orbit for science, communications, technology demonstrations, and imaging with academic, commercial, and government interests. Shielding has been part of mission assurance and reliability from the advent of long duration spacecraft missions. The Shields-1 CubeSat has been operating in polar low Earth orbit since 16 December 2018 with atomic number (Z)-grade radiation shielding and demonstrates shielding effectiveness. Shields-1 has collected a representative example of solar minimum data in 2019 with eight Teledyne µDosimeters over varying shielding effectivenesses. It serves as current experimental data and has been compared with NOVICE Shielding estimates using the AP8 – AE8 trapped radiation model with the Shields-1 CAD and generic CubeSat three unit (3U) models. Using NOVICE model radiation analysis coding, the shielding effectivenesses, based on a generic CubeSat 3U structure with four electronic boards, were estimated for aluminum wall thicknesses ranging from 0.204 cm to 4.44 cm (0.550 g/cm 2 to 12.0 g/cm 2 ). For modeled polar orbiting spacecraft, solar maximum total ionizing dose (TID) increases by nearly a magnitude for thin-walled aluminum 0.550-g/cm 2 - 0.686-g/cm 2 (0.204-cm – 0.254-cm) typical CubeSat structures. The shielding effectiveness estimated by NOVICE Sigma, which is a shielding sphere approximation around a detector, showed a linear relationship with wall thickness, which increased over the wall thickness by a ratio of 1.43 determined by linear regression analysis. Using NOVICE Adjoint Monte-Carlo Modeling of solar minimum and solar maximum with the inclusion of a worst-case solar particle event over a one-year mission without geomagnetic shielding, the TID for minimum and maximum conditions for a generic 3U with a wall thickness of 0.254 cm is 158 RAD and 1540 RAD, respectively. The modeled total solar maximum TID is over estimated, because at low orbital latitudes a spacecraft will have shielding from the Earth’s magnetic field. However, TID will still be significant at high latitudes over the poles, where a spacecraft is exposed in a solar particle event. In contrast to a thin-walled generic 3U CubeSat, the Shields-1 electronics enclosure has a shielding effectiveness of 21.3 g/cm 2 from NOVICE Sigma modeling and is expected to show reduced total ionizing dose increases during the present active Solar Cycle 25 period. Because solar particle events during solar maximum increase TID on electronic parts with thin-walled shielding in short periods of time, it is a mission assurance and reliability consideration on the mission value of the spacecraft versus adding shielding for risk reduction of premature spacecraft or instrument payload loss. Since the volumes of many instruments and system electronics have reduced with small spacecraft, shielding material costs and weight penalties have diminished. A small spacecraft project budget and schedule may limit traditional radiation-hardened part use and radiation testing requirements, where shielding can contribute to mission assurance and reliability with reduced costs.

Shields-1↗
DOE OSTI2014

Optimization of the Shielding of a Canister Loading Machine with the deterministic Code Attila{sup R} - Paper 61

In general shielding components are designed with very conservative assumptions and boundary conditions to cover all possibly occurring situations. This often results in an overestimated shielding design in a lot of different fields of application; the shielding of components will be heavier and more expensive than needed. In most cases an initial shielding calculation in the design process shows an unbalanced shielding effect of the shielded radiation source. Sometimes the dose rate limits are slightly exceeded in several areas. From this arises a need for an optimization of the shielding structure. The goal is to decrease the radiation level in the accessible areas to keep the dose rate limits and to reduce the amount of the used shielding material if possible. Shielding material is moved from areas with higher shielding factors to which with lower ones. The optimization process is shown in an example of a loading machine for vitrified waste in canisters. The design review with an optimization of the shielding geometry was done with the deterministic code Attila{sup R} of the company Transpire, Inc. Attila{sup R} is a powerful tool to calculate and optimize the shielding effect of handling facilities for radioactive materials. It is easy to handle with its CAD integration module and an easy setup of the calculation cases. Areas with a low shielding effect which results in an exceeding of the dose rate limits can be found quickly with the illustration due to an Iso-Dose-Rate-Surface in the 3D Model. In these areas the shielding effect has to be improved. Otherwise there is material, which has no significant influence on the shielding effect and makes the handling facilities heavier and more expensive as needed. The optimization of the shielding design of the canister loading machine in the current case results in lower dose rates outside the facility to keep the dose rate limits. The demand of shielding material could be reduced and resulted in a cost reduction on the facility itself and furthermore in the caring facilities to transport this facility (cranes, etc.). (authors)

42 ENGINEERING↗