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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Development of Stirling Convertors for Radioisotope and Fission Power Systems

NASA has been developing free-piston Stirling-cycle power convertors over the past 22 years for use in nuclear power systems that would provide electricity for space science missions to dark, dusty, or distant destinations where solar power is not practical. These nuclear power systems would generate heat from either the radioactive decay of isotopes or fission nuclear reactors. That heat would be converted to usable electricity using highly efficient Stirling convertors for a wide range of power needs needing 10s of watts to 50 kWe. NASA’s Radioisotope Power Systems (RPS) Program is maturing advanced thermoelectric and dynamic conversion technologies that would increase the system efficiency beyond what is currently possible using heritage systems to enable a larger number of robotic missions or higher power missions to solar system bodies of interest. The Dynamic Radioisotope Power Systems (DRPS) Project has matured prototype Stirling convertors to sufficiently increase the technology readiness level for infusion into flight development. Flexure and gas-bearing free-piston Stirling convertors were developed under contract by commercial partners and delivered to enable government evaluation. Gas-bearing designs have met performance and robustness requirements and were selected for flight development. This paper provides the status of SRSC test campaign and maturity level.

Dynamic↗
NASA NTRSDate not supplied

Status of Dynamic Radioisotope Power System Development for NASA Missions

Under the Radioisotope Power Systems Program, NASA and the Department of Energy have been advancing a novel Radioisotope Power System (RPS) based on dynamic energy conversion. This approach will manifest a dynamic RPS (DRPS) option with a conversion efficiency at least three times greater than thermoelectric based RPS. Significant progress has recently been made towards this end. A one-year system design phase has been completed by industry partner Aerojet Rocketdyne which resulted in a 300-We DRPS with convertor-level redundancy. In-house technology development at NASA Glenn Research Center has demonstrated the conversion devices in relevant environments and shown all requirements can be met. Progress has also been made on the control electronics necessary for dynamic energy conversion. Flight-like controllers were recently upgraded and achieved an 11-percentage-point increase in efficiency. Control architectures have been developed to handle the multi-convertor arrangements in the latest DRPS design. A system-level DRPS Testbed is being assembled now that will experimentally demonstrate the DRPS concept being pursued.

Stirling↗
NASA NTRS2023

Development of Stirling Convertors for Radioisotope and Fission Power Systems

NASA has been developing free-piston Stirling-cycle power convertors over the past 22 years for use in nuclear power systems that would provide electricity for space science missions to dark, dusty, or distant destinations where solar power is not practical. These nuclear power systems would generate heat from either the radioactive decay of isotopes or fission nuclear reactors. That heat would be converted to usable electricity using highly efficient Stirling convertors for a wide range of power needs needing 10s of watts to 50 kWe. NASA’s Radioisotope Power Systems (RPS) Program is maturing advanced thermoelectric and dynamic conversion technologies that would increase the system efficiency beyond what is currently possible using heritage systems to enable a larger number of robotic missions or higher power missions to solar system bodies of interest. The Dynamic Radioisotope Power Systems (DRPS) Project has matured prototype Stirling convertors to sufficiently increase the technology readiness level for infusion into flight development. Flexure and gas-bearing free-piston Stirling convertors were developed under contract by commercial partners and delivered to enable government evaluation. Gas-bearing designs have met performance and robustness requirements and were selected for flight development. This paper provides the status of SRSC test campaign and maturity level.

Dynamic↗
NASA NTRSDate not supplied

Surviving Night at the Lunar South Pole: Exploring Viability of Radioisotope Power Systems for a Crewed Rover

Spacecraft thermal environments tend to be extreme, and the lunar surface is no exception. Future lunar missions aim to explore the lunar south pole region, focusing on permanently shadowed region (PSRs) that may act as cold traps for volatile elements such as hydrogen. By careful selection of landing sites, the longest continuous period devoid of insolation near these PSRs can be reduced significantly from the maximum of 354 hours. Future NASA missions aim to allow exploration of PSRs with a crewed lunar rover. Program architectures may impose a requirement that the vehicle be able to survive repeated lunar nights. Surface temperatures at southern latitudes can be lower than 100K during night, causing significant energy demands heating components above keep-alive temperatures. This adversely affects lunar programs which are heavily mass-constrained. A technical exploration of various radioisotope power systems and their viability, benefits, and drawbacks was completed. An analysis was also performed examining potential vehicular mass reduction and increased lunar night survivability due to the inclusion of radioisotope power sources. The results of this analysis were compared to a baseline non-nuclear vehicle utilizing only batteries and solar arrays for energy storage.

radioisotope↗
NASA NTRSDate not supplied

The European Radioisotope Power Systems Program: Updates & Synergies

Radioisotope power systems (RPS) are an essential building block of the space exploration strategies of a number of countries around the world. The UK, US and the European Space Agency (ESA) view RPS technologies as enabling for a range of scientific space missions targeting the most challenging, distant, and cold environments in the solar system over the coming decades. However, RPS interest and associated capabilities are growing across the globe, where drivers include the increasing importance of space to address defense and commercial interests. Most missions have utilized 238 Pu as the radioisotope of choice to generate electrical power and to produce heat for the operation and thermal management of spacecraft systems. In Europe, since 2009, 241 Am in ceramic form has been selected for the ESA RPS development program. The ESA program has evolved in the past few years into a cross directorate program. This paper provides an update on this RPS technology program with a focus on technology updates, missions and partnerships.

Americium↗
NASA NTRSDate not supplied

NASA’s Radioisotope Power Systems Program Enabling the Power to Explore

Radioisotope power systems (RPS) have been safely providing the power to explore space by the United States for over 60 years. RPS-enabled NASA missions have utilized this space nuclear power to explore planets, moons, and interstellar space, enabling missions to some of the deepest, darkest, and dustiest regions in the solar system and beyond. This extreme exploration has deepened our understanding of the solar system and our role within it. NASA established the RPS Program in 2010 to support these specialized science missions and potential future opportunities more effectively and efficiently. The RPS Program ensures the availability of RPS for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible. The RPS Program, in partnership with the Department of Energy (DOE) Office of Nuclear Energy, continues interagency collaboration to provide robust radioisotope power system solutions to spacecraft that conduct extreme missions for science and exploration. This Program invests in systems and technologies to ensure that NASA maintains this capability well into the future and it manages processes that ensure the safe use and launch of these systems. This paper provides a synopsis of current activities of the RPS Program, which demonstrates a record of successful formal interagency partnering with the DOE.

radioisotope power systems↗
NASA NTRSDate not supplied

NASA’s Radioisotope Power Systems Program: Status Update

Radioisotope power systems (RPS) have safely been in use in the United States for over 60 years. RPS-enabled NASA missions have utilized space nuclear power to explore planets, moons, and interstellar space. This exploration resulted in changes to our understanding of our Solar System and our place within it. In 2010, NASA HQ established a NASA program to invest in RPS technologies and systems that could enable future missions. The RPS Program ensures the availability of RPS for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible. The RPS Program, in partnership with the Department of Energy (DOE) Office of Nuclear Energy continues to operate as an interagency partnership to provide robust power system solutions to spacecrafts that conduct missions for exploration and science that otherwise would not be feasible. This paper provides a synopsis of current activities after well over a decade of formal interagency partnering.

Radioisotope↗
DOE OSTI2025

A virtual Frisch-grid geometry-based CZT gamma detector for in-field radioisotope identification

Here, we present a Virtual Frisch-Grid geometry-based CZT gamma detector developed for identifying different radioisotopes over an energy range from a few keV up to 2 MeV, and useful for efficient characterization of CZT crystals. The detector is built with a 3 x 3 matrix of CZT crystals, each measuring approximately 6 mm x 6 mm x 15 mm. The charge generated within the sensor’s active volume is read out via an anode connected directly to the AVG3_Dev integrated circuit. A current signal induced by charge drift is collected on side pads of the crystals, enabling reconstruction of a 3D interaction position. This paper discusses the design, development, and performance of the standalone, mobile detector system, which integrates the AVG3_Dev readout IC developed at Brookhaven National Laboratory, a high-speed FPGA-based with per-channel digital signal processing, and embedded system capabilities. The device is compact, battery-powered, and supports wireless data streaming, making it suitable for field operations for radioisotope identification.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

Unsupervised domain adaptation for radioisotope identification in gamma spectroscopy

Training machine learning models for radioisotope identification using gamma spectroscopy remains an elusive challenge for many practical applications, largely stemming from the difficulty of acquiring and labeling large, diverse experimental datasets. Simulations can mitigate this challenge, but the accuracy of models trained on simulated data can deteriorate substantially when deployed to an out-of-distribution operational environment. In this study, we demonstrate that unsupervised domain adaptation (UDA) can improve the ability of a model trained on synthetic data to generalize to a new testing domain, provided unlabeled data from the target domain are available. Conventional supervised techniques are unable to utilize this data because the absence of isotope labels precludes defining a supervised classification loss. Instead, we first pretrain a spectral classifier using labeled synthetic data and subsequently leverage unlabeled target data to align the learned feature representations between the source and target domains. We compare a range of different UDA techniques, finding that minimizing the maximum mean discrepancy (MMD) between source and target feature vectors yields the most consistent improvement to testing scores. For instance, using a custom transformer-based neural network, we achieved a testing accuracy of $0.904 \pm 0.022$ on an experimental LaBr test set after performing unsupervised feature alignment via MMD minimization, compared to $0.754 \pm 0.014$ before alignment. Overall, our results highlight the potential of using UDA to adapt a radioisotope classifier trained on synthetic data for real-world deployment.

Lalor, Peter W.↗
DOE OSTI2021

Assessment of alternative radionuclides for use in a radioisotope thermoelectric generator

238 Pu is the current fuel source for MMRTGs. This is due to favorable properties, such as high decay heat and low gamma emissions. 238 Pu supplies are dwindling rapidly, necessitating the review of potential replacement isotopes for deep space missions. This work considers nine potential replacements, Ac-227, Am-241, Cf-252, Cm-244, Cs-137, Po-210, Sr-90, Th-228, and Th-170. We have assessed performance of alternatives to 238 Pu by modeling the specific decay-heat and gamma spectra of several potential radioisotopes in SCALE-ORIGEN, and comparing these with 238 Pu. An analysis of heat output, heat stability, safety, availability and required mass, baselined against 238 Pu demonstrates that of those radioisotopes studied, 241 Am has properties that make it most conducive for 238 Pu replacement.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Radioisotope production at the Spallation Neutron Source: Design concept of isotope production target

Upon completion of the Second Target Station (STS) Project in the mid 2030s, the Spallation Neutron Source accelerator at Oak Ridge National Laboratory will deliver a 2.7 MW proton beam to the neutron production targets. In the post-STS phase, the accelerator will have a reserve beam power capacity of at least 100 kW beyond what the two neutron production targets will receive, which could potentially be ramped up to 300 kW. In this paper, a design concept for a radioisotope production target that could utilize 250 kW of the reserve beam power capacity is presented. The target consists of thorium discs encapsulated in 316L austenitic steel shells that are cooled by water. The estimated post-irradiation activity of Ac-225 and Ra-225, critical medical radioisotopes used in targeted alpha therapy cancer treatment, is calculated at the end of bombardment after a 14 day long irradiation time. Thermal and structural analyses are performed on the basis of calculated nuclear heating data. The technical feasibility of a high-power target under a 250-kW beam load with an extremely low duty factor of $3.5\cdot 10^{-6}$ is presented from thermal, structural and fatigue lifetime perspectives.

Lee, Yong Joong [ORNL] (ORCID:0000000298381723)↗
DOE OSTI2024

Radioisotope Analysis of Wastewater from Livermore Site Retention Tanks by Gel Laboratory Gross Alpha, Gross Beta and Tritium Sampling Method

Lawrence Livermore National Laboratory discharged approximately 4.4% of the City of Livermore’s total wastewater in 2022 (LLNL’s Annual Site Environmental Report, Chapter 5, 2022). This volume includes wastewater from Sandia National Laboratories (SNL) and some process wastewater from Site 300. Due to the high volume and constituents of the discharge, LLNL works alongside the City of Livermore under permit #1250, requiring wastewater generated to be monitored and sampled in accordance with permit limits. Process wastewater, from buildings with the highest risk to sewer, is collected by wastewater retention tanks throughout the Livermore Site and sampled prior to discharge. Domestic wastewater directly discharges to sanitary sewer. To maintain permit requirements and ensure proper wastewater discharge practices, an internal wastewater audit was conducted during the summer of 2023. Current wastewater practices, regulatory knowledge and risk management across various Livermore Site buildings were evaluated. Workspaces connected to a wastewater retention tank and sanitary sewer drains were major focus areas. Data collected from walk-throughs prompted further evaluation as many practices were reported to be done based on historical usage. A table of concerns was created to showcase reasons for auditing and proceeding action. An analysis of current and historical retention tank usage throughout LLNL Livermore Site buildings with radioisotope results over a 5-year period from 2019 to 2024, was done to assess building trends and any significant changes throughout the 5-year period. Analytes evaluated were Gross Alpha, Gross Beta and Tritium (GABT) of eleven buildings at the Livermore Site, posing the highest risk to sanitary sewer for radioisotopes.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1971

Emitted radiation characteristics of plutonium dioxide radioisotope thermoelectric generators

The nuclear and emitted radiation characteristics of the radioisotope elements and impurities in commercial grade plutonium dioxide are presented in detail. The development of the methods of analysis are presented. Radioisotope thermoelectric generators (RTG) of 1575, 3468 and 5679 thermal watts are characterized with respect to neutron and gamma photon source strength as well as spatial and number flux distribution. The results are presented as a function of detector position and light element contamination concentration for fuel age ranging from 'fresh' to 18 years. The data may be used to obtain results for given O-18 and Pu-236 concentrations. The neutron and gamma photon flux and dose calculations compare favorably with reported experimental values for SNAP-27.

Gingo, P. J.↗
NASA NTRS1973

G-189A analytical simulation of the integrated waste management-water system using radioisotopes for thermal energy

An analytical simulation of the RITE-Integrated Waste Management and Water Recovery System using radioisotopes for thermal energy was prepared for the NASA-Manned Space Flight Center (MSFC). The RITE system is the most advanced concept water-waste management system currently under development and has undergone extended duration testing. It has the capability of disposing of nearly all spacecraft wastes including feces and trash and of recovering water from usual waste water sources: urine, condensate, wash water, etc. All of the process heat normally used in the system is produced from low penalty radioisotope heat sources. The analytical simulation was developed with the G189A computer program. The objective of the simulation was to obtain an analytical simulation which can be used to (1) evaluate the current RITE system steady state and transient performance during normal operating conditions, and also during off normal operating conditions including failure modes; and (2) evaluate the effects of variations in component design parameters and vehicle interface parameters on system performance.

Coggi, J. V.↗
NASA NTRS1991

Radioisotope thermal photovoltaic application of the GaSb solar cell

An examination of a RTVP (radioisotopic thermophotovoltaic) conceptual design has shown a high potential for power densities well above those achievable with radioisotopic thermoelectric generator (RTG) systems. An efficiency of 14.4 percent and system specific power of 9.25 watts/kg were predicted for a system with sixteen GPHS (general purpose heat source) sources operating at 1100 C. The models also showed a 500 watt system power by the strontium-90 isotope at 1200 C at an efficiency of 17.0 percent and a system specific power of 11.8 watts/kg. The key to this level of performance is a high-quality photovoltaic cell with narrow bandgap and a reflective rear contact. Recent work at Boeing on GaSb cells and transparent back GaAs cells indicate that such a cell is well within reach.

Morgan, M. D.↗
NASA NTRS1990

Safety status of space radioisotope and reactor power sources

The current overall safety criterion for both radioisotope and reactor power sources is containment or immobilization in the case of a reentry accident. In addition, reactors are designed to remain subcritical under conditions of land impact or water immersion. A very extensive safety test and analysis program was completed on the radioisotope thermoelectric generators (RTGs) in use on the Galileo spacecraft and planned for use on the Ulysses spacecraft. The results of this work show that the RTGs will pose little or no risk for any credible accident. The SP-100 space nuclear reactor program has begun addressing its safety criteria, and the design is planned to be such as to ensure meeting the various safety criteria. Preliminary mission risk analyses on SP-100 show the expected value population dose from postulated accidents on the reference mission to be very small. It is concluded that the current US nuclear power sources are the safest flown.

Bennett, Gary L.↗
NASA NTRS1992

Cosmogenic radioisotopes on LDEF surfaces

The radioisotope Be-7 was discovered in early 1990 on the front surface, and the front surface only, of the LDEF. A working hypothesis is that the isotope, which is known to be mainly produced in the stratosphere by spallation of nitrogen and oxygen nuclei with cosmic ray protons or secondary neutrons, diffuses upward and is absorbed onto metal surfaces of spacecraft. The upward transport must be rapid, that is, its characteristic time scale is similar to, or shorter than, the 53 day half-life of the isotope. It is probably by analogy with meteoritic metal atmospheric chemistry, that the form of the Be at a few 100 km altitude is as the positive ion Be(+) which is efficiently incorporated into the ionic lattice of oxides, such as Al2O3, Cr2O3, Fe2O3, etc., naturally occurring on surfaces of Al and stainless steel. Other radioisotopes of Be, Cl, and C are also produced in the atmosphere, and a search was begun to discover these. Of interest are Be-10 and C-14 for which the production cross sections are well known. The method of analysis is accelerator mass spectrometry. Samples from LDEF clamp plates are being chemically extracted, purified, and prepared for an accelerator run.

Gregory, J. C.↗