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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Radiation sensitivity of silicon imaging sensors on missions to the outer planets.

Review of the results of an investigation of the magnitude of the degradation effects of radiation on the operating characteristics of camera tubes using silicon diode arrays in the space environment, and discussion of the radiation damage mechanisms concerned. The effects produced by bombardment of bare-silicon-diode arrays or vidicon tubes with 85-kV X rays, Cobalt 60 gamma rays, 1 MeV and 11 MeV electrons, 3 MeV and 142 MeV protons, and reactor neutrons are presented. Interference effects produced by radiation bombardment during operation of television tubes are investigated, and limiting fluxes of electrons and protons are given.

Brucker, G. J.↗
DOE OSTI2025

A review of radiation-induced damage to quantum dots

Quantum dots (QDs) are versatile nano structures that have applications in many fields of research and production, including biosensor technology, computing, photovoltaics, and optoelectronics. QDs have gained interest in the field of radiation detection because of their relative ease of production, tunable photoluminescence, and sensitivity to ionizing radiation. The photoluminescent properties of QDs diminish proportionally to prolonged ionizing radiation interactions, leading many groups to seek out these materials as potential candidates for the next generation of inexpensive, easily manufactured dosimetry and sensors. To use QDs in these applications, the mechanisms of radiation damage to the nanomaterial must be clearly understood and characterized. Herein, we review the study of ionizing radiation damage to QDs. First, the synthesis and properties of QDs are briefly discussed. Next, the radiation damage to QDs due to heavy charged particles, fast electrons, high energy photons, and neutrons are detailed. After this, experimental methods and modelling of QDs in radiation environments are examined. Lastly, future research directions are provided. The goal of this review is to aid in understanding the ionizing radiation effects on QD-based devices.

Snow, Jesse [University of Utah, Salt Lake City, U↗
DOE OSTI2025

Non-destructive structural characterization of graphite components using mechanical resonance and deep learning

As compared to conventional nuclear reactors, microreactors have the potential to significantly reduce construction timelines and capital costs, decreasing the barriers for advanced nuclear reactor technologies. However, the lower power output of these microreactors (typically < 20 MWe) creates challenging economics if operation and maintenance costs cannot be sufficiently reduced. The compact size of these designs presents an opportunity for comprehensive in-situ structural health monitoring to provide real-time feedback in order to reduce operational costs associated with maintenance and downtime. Many microreactor concepts use graphite for both in-core neutron moderation and as a structural material, which has typically required some form of periodic and laborious inspection. This report provides a description and assessment of recent work with graphite to couple acoustic-based experimental measurements and characterization with machine learning models to mature structural health monitoring capabilities and generate benefits for the nuclear microreactor industry. With resilient embedded sensors in development in other programs funded by the US Department of Energy’s Office of Nuclear Energy and elsewhere, the work described herein builds upon previously funded efforts to mature non-destructive testing technology that relates measured vibrational signatures to structural changes, using a combination of new experimental measurements and machine learning processing. Building on past successful demonstrations of predictive workflows to identify structural changes in a hexagonal stainless steel test article with excellent acoustic propagation, we first performed baseline characterization on graphite samples with canonical geometries to ensure compatibility and confidence in the applied techniques for a material with distinctly different mechanical properties. In contrast to efforts in previous years, we worked exclusively with unidirectional vibration data that is more comparable to those expected from the existing embedded sensor technologies which are suitable for deployment in a reactor setting. Established acoustic and modern machine-learning-based characterization approaches were applied to the resulting datasets from these simple geometries. Both approaches were found to be highly capable of detecting even small geometric irregularities amongst nominally identical samples. As such, we then moved to testing these approaches for detection of artificial local stress perturbations introduced into a more complex geometry: a hexagonal block with drilled holes. A main outcome of this work is that a generalizable ML workflow can be used to detect and predict the characteristics of small artificial anomalies in a graphite component with a relevant geometry. While this work was performed using surficial vibration data, we expect the approach to be flexible and viable for other monitoring scenarios, such as those with different arrangements or types of sensor arrays. As compared to previously funded efforts, an existing ML workflow based on neural networks was enhanced through the addition of recently developed Fourier neural operators. As applied to previously collected and new vibration datasets, prediction accuracies of anomaly characterizations were greatly improved with minimal added computational cost. As trained on small durations of vibration data (tens of seconds) collected over a realistic number of locations, the model was able to reliably determine the presence of a subtle stress anomaly and begin to provide location estimates. Such an approach is likely to be viable for more relevant reactor damage scenarios for graphite components, such as progressive crack growth or creep.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Retractable Sensor for Reactor Experiments

This presentation is to orient a mechanical or nuclear engineering senior design team so that they can help solve an instrumentation problem found in high power test reactors. Test reactors such as the Advanced Test Reactor (ATR) at the Idaho National Laboratory are used to irradiate nuclear fuels and materials to evaluate performance after high levels of exposure to a reactor in-pile environment. The purpose of the experiments is to determine property changes as the materials or fuels are bombarded with fast neutrons (and thermal (slow) neutrons as well). Typically, the irradiation must take place at a very specific temperature. Sometimes other parameters are monitored as well as properties such as creep, or gas composition, etc. However, the fast neutrons cause changes in not only the materials, but also in the transducers that are placed in the neutron flux, e.g., thermocouples or optical fibers. This task will be limited to considering temperature measurements. Thermocouples experience decalibration from not only the neutron flux, but also from the very high temperatures that are sometimes measured. Optical fibers darken in a neutron or gamma flux. However, it takes quite a few hours, or days for these changes to manifest. High power test reactors typically run at a constant power and so the temperature in an experiment is fairly stable over time. Because the changes are typically very slow, even a single temperature measurement per day, would provide 95% of a perfect data set. The basic concept of this effort is to push a very small diameter thermocouple or optical fiber into the location to be measured, leave it for 30 seconds or so for it to come to equilibrium, and transmit the signal, and then pull it up and away from the high neutron flux and high temperature region. The distance the thermocouple or fiber would need to move is on the order of 50 – 100 cm. By doing this, the thermocouple junction or optical fiber would spend only a few hours in the high flux/high temperature environment over the life of the irradiation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Concepts for Autonomous Operation of Microreactors

Microreactor concepts have seen increasing interest in recent years given their potential use for meeting energy needs in remote and grid-isolated communities. Given the small power outputs of microreactors and the potential for remote siting, there is a need to reduce operational staffing levels to improve their economic viability. A key enabling technology for this purpose is autonomous control that enables autonomous operation of microreactors. While several options for autonomous control exist, the level of human operator involvement in operational decision making needs to be defined as part of the system design process. Once this separation of function is achieved, several options exist for autonomous control ranging from simple automation of some procedures to fully autonomous operational mode decision making and execution.A critical aspect of autonomous decision making is the ability to have as complete an awareness of the system state as possible. In addition to data on temperature, pressure, flow, and neutron flux, measurements of the condition of important components will be necessary. This type of information will allow the autonomous control system to adapt its decision making to any changing conditions within the reactor, thereby not compromising safety while continuing to operate for as long as possible. Several technical advances are needed before widespread use of autonomous control in microreactors. These include sensor and instrumentation technologies that are capable of long term, unattended operation in harsh environments, technologies for inferring the state of the microreactor system or subsystems in an automated fashion, algorithms for predictive decision making that account for the assessed condition of the microreactor subsystems as well as the potential impact on those components of any operational decision, and actuators and control system hardware that are also long-lived in a harsh environment. In addition, given the need to remotely monitor the operations, cybersecurity requirements will likely need to be imposed to ensure secure operations.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
NASA NTRS2011

Carbon Nanotube Based Nanotechnology for NASA Mission Needs and Societal Applications

Carbon nanotubes (CNT) exhibit extraordinary mechanical properties and unique electronic properties and therefore, have received much attention for more than a decade now for a variety of applications ranging from nanoelectronics, composites to meeting needs in energy, environmental and other sectors. In this talk, we focus on some near term potential of CNT applications for both NASA and other Agency/societal needs. The most promising and successful application to date is a nano chem sensor at TRL 6 that uses a 16-256 sensor array in the construction of an electronic nose. Pristine, doped, functionalized and metal-loaded SWCNTs are used as conducting materials to provide chemical variation across the individual elements of the sensor array. This miniaturized sensor has been incorporated in an iPhone for homeland security applications. Gases and vapors relevant to leak detection in crew vehicles, biomedical, mining, chemical threats, industrial spills and others have been demonstrated. SWCNTs also respond to radiation exposure via a change in conductivity and therefore, a similar strategy is being pursued to construct a radiation nose to identify radiation sources (gamma, protons, neutrons, X-ray, etc.) with their energy levels. Carbon nanofibers (CNFs) grown using plasma enhanced CVD typically are vertical, individual, freestanding structures and therefore, are ideal for construction of nanoelectrodes. A nanoelectrode array (NEA) can be the basis for an affinity-based biosensor to meet the needs in applications such as lab-on-a-chip, environmental monitoring, cancer diagnostics, biothreat monitoring, water and food safety and others. A couple of demonstrations including detection of e-coli and ricin will be discussed. The NEA is also useful for implantation in the brain for deep brain stimulation and neuroengineering applications. Miniaturization of payload such as science instrumentation and power sources is critical to reduce launch costs. High current density (greater than 100 mA/per square centimeters) field emission capabilities of CNTs can be exploited for construction of electron gun for electron microscopy and X-ray tubes for spectrometers and baggage screening. A CNT pillar array configuration has been demonstrated, not only meeting the high current density needs but more importantly providing long term emitter stability. Finally, supercapacitors hold the promise to combine the high energy density of a battery with the high power density of capacitors. Traditional graphite electrodes have not delivered this promise yet. A novel design and processing approach using MWCNTs has shown a record 550 F/g capacitance along with significant device endurance. This supercapacitor is suitable for railgun launch application for NASA, powering rovers and robots, consumer electronics and future hybrid vehicles.

Li, Jing↗
DOE OSTI2024

Bubble Mass Transport Measurement in the Large-Scale Test Loops at Oak Ridge National Laboratory

Molten salts are complex fluids that incorporate multi-phase behavior depending on the chemistry and the physical properties of the entrained components. These components include the carrier salt, the actinide fuel, and fission, activation, and corrosion products, the concentrations of which depends on the burnup history of the salt. Radionuclide transport from the salt into the cover gas / off-gas system depends on volatility as predicted by thermochemistry, but data from the Molten Salt Reactor Experiment (MSRE) conducted in the late 1960s suggest that bubble formation and transport are also important. Anomalously high fractions of noble metals were found in the off-gas system and were attributed to transportation with parent salt aerosols and their association with rising noble gas bubbles. The prediction of such phenomena requires coupled neutronic, thermal hydraulic, and chemical equilibrium calculations, the framework of which is being developed within the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program supported by the US Department of Energy (DOE) Office of Nuclear Energy (NE). However, separate effects tests and models of experiments using tools such as SAM and Thermochimica can guide model developers through important processes. Conversely, model development guides the choice of experiments and systems to provide data that are relevant for validation. This report describes several experiments that tracked gas transport in molten salts, ranging from small-scale systems to large-scale loops. Gas transportation in a molten salt, LiCl-KCl, has been studied using the shadowgraph technique. Sensors such as residual gas analysis, Raman spectroscopy, and laser-induced breakdown spectroscopy have been tested for off-gas measurements. These data were used to interpret how the gases move through the upstream salt / cover gas and the interface between them. Differential pressure measurements were able to detect individual gas bubbles as they popped at the liquid–gas interface. Salt aerosols were collected on a cascade impactor. Their formation was also observed directly via the shadowgraph method, and most of these aerosols were launched ballistically into the cover gas. Fine mists could also be observed. Convection currents through the salt were visualized and can be used to calculate the thermophysical properties of the salt itself. The apparatuses described in this report and in a previous work (McFarlane et al. 2023) have been commissioned and are available for use in making further measurements of salt/surrogate fission product behavior. Novel approaches using neutron imaging are planned for the study of fluoride salts, which cannot be contained in quartz, so shadowgraph visualization is not available. Bubble transport in convective flow and in a slow-moving salt column are planned. The mobile laser-induced breakdown spectroscopy (LIBS) system is available for several applications, including iodine capture in a molten hydroxide scrubber, H2 transport though molten salts to complement Raman analysis, and online tracking of salt aerosol generation, transport, and deposition. This report summarizes the findings from FY24 and the plans for FY25. The work completes milestone M2AT-24OR0702013 of the DOE-NE Advanced Reactor Technology, Molten Salt Reactor Campaign, DOE-NE-5.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Magnetoelectric effect arising from a field-induced pseudo Jahn-Teller distortion in a rare-earth magnet

Magnetoelectric materials are attractive for several applications, including actuators, switches, and magnetic field sensors. Typical mechanisms for achieving a strong magnetoelectric coupling are rooted in transition metal magnetism. In sharp contrast, here we identify CsEr(MoO 4 ) 2 as a magnetoelectric material without magnetic transition metal ions, thus ensuring that the Er ions play a key role in achieving this interesting property. Our detailed study includes measurements of the structural, magnetic, and magnetoelectric properties of this material. Bulk characterization and neutron powder diffraction show no evidence for structural phase transitions down to 0.3 K and therefore CsEr(MoO 4 ) 2 maintains the room temperature P2/c space group over a wide temperature range without external magnetic field. These same measurements also identify collinear antiferromagnetic ordering of the Er 3+ moments below T N =0.87K. Complementary dielectric constant and pyroelectric current measurements reveal that a ferroelectric phase with a maximum polarization P~0.6 nC/cm 2 emerges when applying a modest external magnetic field, which indicates that this material has a strong magnetoelectric coupling. Finally, we argue that the magnetoelectric coupling in this system arises from a pseudo Jahn-Teller distortion induced by the magnetic field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1975

A balloon-borne Ge/Li/ spectrometer for gamma-ray astronomy

On June 10, 1974, a new high-resolution gamma ray spectrometer operating in the energy range of 0.05 to 10 MeV was successfully balloon-flight tested. This system uses four 40 cu cm Ge(Li) crystals in a single cryostat as prime sensors. A 6.35 cm thick CsI (Na) shield provides background rejection and collimation, defining a solid angle of 0.095 sr. Cooling is provided by a liquid-nitrogen dewar. The system was highly stable with spectral resolution of better than 2.5 keV at 1 MeV for the flight duration. The background total count rate was about 20 counts/sec. Numerous lines were observed, most of which originated from secondary neutron interactions in the spectrometer. The sensitivity of the system to line emissions originating in cosmic point sources is 0.0001 to 0.001 photons per sq cm s over the energy range.

Jacobson, A. S.↗
DOE OSTI2025

Fiber-optic bolometers with high-temperature tolerance and reduced time constants for fusion plasma diagnostics

Fiber-optic bolometers (FOBs) designed for plasma radiation measurement in magnetically confined fusion environments have been previously developed and tested at the DIII-D tokamak. These FOBs utilize a silicon Fabry–Perot interferometer at the fiber tip for temperature measurement and a gold disk as a radiation absorber. This paper presents recent advancements in the development of FOBs with reduced cooling time constants and enhanced temperature tolerance. We also demonstrate high-temperature operation and report findings from irradiation tests. By incorporating a copper sensor holder as a thermal sink and integrating two closely packed sensor heads into a compact design, the cooling time constants were reduced to ∼100 ms in vacuum, while minimizing uncertainties caused by temperature gradients. The FOBs were subjected to heating at 400 °C for five hours, with no observed degradation in noise performance post-heating. High-temperature operation tests were conducted at ∼220 °C using a 404 nm square-wave modulated laser to simulate the plasma radiation. In addition, four FOBs constructed from copper-coated pure-silica fibers were fabricated and underwent irradiation testing, enduring a total γ-radiation dose of 15.2 MGy and a neutron fluence of 1.6 × 10 18 n/cm 2 . As a result, the FOBs maintained their physical integrity and the optical signal shows high visibility throughout the test.

42 ENGINEERING↗
DOE OSTI2019

Properties of HPK UFSD after neutron irradiation up to 6e15 n/cm 2

In this article we report results from a neutron irradiation campaign of Ultra-Fast Silicon Detectors (UFSD) with fluences of 1e14, 3e14, 6e14, 1e15, 3e15 and 6e15 neq/cm 2 . The UFSD used in this study are circular 50 μm thick Low-Gain Avalanche Detectors (LGAD), with a 1.0 mm diameter active area. Hamamatsu Photonics (HPK), Japan, produced the UFSD with pre-irradiation internal gain in the range 5–70 depending on the bias voltage. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90 Sr β-source. The leakage current, internal gain and the timing resolution were measured as a function of bias voltage at -20 °C and -30 °C. The timing resolution of each device under test was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction discriminator (CFD) method for both. The dependence of the gain upon the irradiation fluence is consistent with the acceptor removal mechanism; at -20 °C the highest gain decreases from 70 before radiation to 2 after a fluence of 6e15 n/cm 2 . Consequently, the timing resolution was found to deteriorate from 20 ps to 50 ps. The results indicate that the most accurate time resolution is obtained varying with fluence the CFD value used to determine the time of arrival, from 0.1 for pre-irradiated sensors to 0.6 at the highest fluence. Key changes to the pulse shape induced by irradiation, i.e. (i) the contribution of charge multiplication not limited to the gain layer zone, (ii) the shortening of the rise time and (iii) the reduced pulse height, were compared with the WF2 simulation program and were found to be in agreement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

ASCENT: a balloon-borne hard x-ray imaging spectroscopy telescope using transition edge sensor microcalorimeter detectors

Core collapse supernovae are thought to be one of the main sources in the galaxy of elements heavier than iron. Understanding the origin of the elements is thus tightly linked to our understanding of the explosion mechanism of supernovae and supernova nucleosynthesis. X-ray and gamma-ray observations of young supernova remnants, combined with improved theoretical modeling, have resulted in enormous improvements in our knowledge of these events. Here, the isotope Ti44 is one of the most sensitive probes of the innermost regions of the core collapse engine, and its spatial and velocity distribution are key observables. Hard x-ray imaging spectroscopy with the Nuclear Spectroscopic Telescope Array (NuSTAR) has provided new insights into the structure of the supernova remnant Cassiopeia A (Cas A), establishing the convective nature of the supernova engine. However, many questions about the details of this engine remain. We present here the concept for a balloon-borne follow-up mission called A SuperConducting ENergetic x-ray Telescope (ASCENT). ASCENT uses transition edge sensor gamma-ray microcalorimeter detectors with a demonstrated 55-eV full-width half maximum energy resolution at 97 keV. This 8- to 16-fold improvement in energy resolution over NuSTAR will allow for high-resolution imaging and spectroscopy of the Ti44 emission. This will allow for a detailed reconstruction of gamma-ray line redshifts, widths, and shapes, allowing us to address questions such as, What is the source of the neutron star kicks? What is the dominant production pathway for Ti44? Is the engine of Cas A unique?

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Active Compensation of Radiation Effects on Optical Fibers for Sensing Applications

Neutron and gamma irradiation is known to compact silica, resulting in macroscopic changes in refractive index (RI) and geometric structure. The change in RI and linear compaction in a radiation environment is caused by three well-known mechanisms: (i) radiation-induced attenuation (RIA), (ii) radiation-induced compaction (RIC), and (iii) radiation-induced emission (RIE). These macroscopic changes induce errors in monitoring physical parameters such as temperature, pressure, and strain in optical fiber-based sensors, which limit their application in radiation environments. We present a cascaded Fabry–Perot interferometer (FPI) technique to measure macroscopic properties, such as radiation-induced change in RI and length compaction in real time to actively account for sensor drift. The proposed cascaded FPI consists of two cavities: the first cavity is an air cavity, and the second is a silica cavity. The length compaction from the air cavity is used to deduce the RI change within the silica cavity. We utilize fast Fourier transform (FFT) algorithm and two bandpass filters for the signal extraction of each cavity. Inclusion of such a simple cascaded FPI structure will enable accurate determination of physical parameters under the test.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Dopant, coating, and grating effects in silica optical fibers under extreme neutron irradiation

Radiation effects on fiber Bragg gratings (FBGs) have been studied but data gaps related to the effects of displacement damage resulting from high fast neutron fluence remain. In this work, Type-I and Type-II FBGs inscribed in optical fibers with various core dopants (Ge and F) and fiber coatings (acrylate, polyimide) were monitored in situ during 75 days of neutron irradiation to a peak fast (>0.1 MeV) neutron fluence of 3 X 10 21 n fast /cm 2 . Further, the reflected intensity of the Type-I FBGs inscribed in a Ge-doped core fiber decreased by > 30 dB within 7 h of irradiation (10 19 n fast /cm 2 ), whereas Type-II FBGs inscribed in a pure silica core fiber eventually approached >40 dB attenuation after accumulating a fast neutron fluence on the order of 10 20 n fast /cm 2 . Type-II FBGs inscribed in F-doped core fiber improved stability: the attenuation approached an equilibrium value in the range of 10 to 20 dB.

47 OTHER INSTRUMENTATION↗
DOE OSTI1994

Nuclear Safety [Vol. 35, No. 2, July-December 1994]

Nuclear Safety is a journal that covers significant issues in the field of nuclear safety. Its primary scope is safety in the design, construction, operation, and decommissioning of nuclear power reactors worldwide and the research and analysis activities that promote this goal, but it also encompasses the safety aspects of the entire nuclear fuel cycle, including fuel fabrication, spent-fuel processing and handling, and nuclear waste disposal, the handling of fissionable materials and radioisotopes, and the environmental effects of all these activities. Table of Contents for this issue follows. GENERAL SAFETY CONSIDERATIONS: 179 Consideration of Postaccident Consequences in the Determination of Safety Objectives for Future Nuclear Power Plants in France, D. Queniart, A. Sugier, and J. Lochard; ACCIDENT ANALYSIS: 187 Nuclear Safety Research: The Phebus FP Severe Accident Experimental Program, P. von der Hardt, A. V. Jones, C. Lecomte, and A. Tattegrain; 205 Containment Performance Analysis of the Advanced Neutron Source Reactor at the Oak Ridge National Laboratory, S. H. Kim, R. P. Taleyarkhan, and V. Georgevich; 213 Assessment of Fission Product Deposits in the Reactor Coolant System: The DEVAP Program, G. Le Marois and M. Megnin; 222 Erratum to “A Review of the Available Information on the Triggering Stage of a Steam Explosion," Vol. 35, No. 1, CONTROL AND INSTRUMENTATION: 223 Effects of Normal Aging on Calibration and Response Time of Nuclear Plant Resistance Temperature Detectors and Pressure Sensors, H. M. Hashemian; DESIGN FEATURES: 235 Defense in Depth Against the Hydrogen Risk—A European Research Program, F. Fineschi; ENVIRONMENTAL EFFECTS: 246 Technical Note: A Preliminary Analysis of the Risks to Hong Kong Resulting from Potential Accidents of Daya Bay Nuclear Power Plant, Z. Shi and X. Wei; OPERATING EXPERIENCES: 253 Reactor Shutdown Experience, Compiled by J. W. Cletcher; SPECIAL SECTION ON TMI-2 VESSEL INVESTIGATION PROJECT: 256 Three Mile Island—New Findings 15 Years After the Accident A. M. Rubin and E. Beckjord; 269 Relocation of Molten Material to the TMI-2 Lower Head, J. R. Wolf, D. W. Akers, and L. A. Neimark; 280 Insight Into the TMI-2 Core Material Relocation Through Examination of Instrument Tube Nozzles, L. A. Neimark; 288 Physical and Radiochemical Examinations of Debris from the TMI-2 Lower Head, D. W. Akers and B. K. Schuetz; 301 Results of Metallographic Examinations and Mechanical Tests of Pressure Vessel Samples from the TMI-2 Lower Head, D. R. Diercks and G. E. Korth; 313 Margin-to-Failure Calculations for the TMI-2 Vessel, J. Rempe, L. Stickler, S. Chavez, G. Thinnes, R. Witt, and M. Corradini; U.S. NUCLEAR REGULATORY COMMISSION INFORMATION AND ANALYSES: 328 1993 Accident Sequence Precursor (ASP) Program Results, L. N. Vanden Heuvel, J. W. Cletcher, D. A. Copinger, J. W. Minarick, B. W. Dolan, and P. D. O’Reilley; RECENT DEVELOPMENTS: 339 Reports, Standards, and Safety Guides, D. S. Queener; 345 Proposed Rule Changes as of June 30, 1994; ANNOUNCEMENTS: 234 Thirty-First Annual Meeting of the National Council on Radiation Protection and Measurements; 356 1995 International Incineration Conference; 358 Fifth International Controls and Instrumentation Conference; 359 ANS International Topical Meeting on Safety of Operating Reactors; 359 Fifth International Conference on Nuclear Criticality Safety; 360 International Conference on Probabilistic Safety Assessment Methodology and Applications; 351 The Authors; 357 Reviewers of Nuclear Safety, Vol. 35.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

A Data-driven approach to Core Power distribution reconstruction in a Nuclear Reactor

This report presents the initial development of a data-driven approach for reconstructing the core power distribution in a nuclear reactor (power shape synthesis) using ex-core sensors. Traditional techniques rely on deploying a large number of detectors throughout the reactor core. However, this approach is not feasible for innovative reactor concepts like Advanced Reactors and Microreactors. First, the tight lattice pitch, designed to maximize power density, limits the space available for sensors. Secondly, the harsh operating conditions are not compatible with commercially available detectors. The method proposed in this work integrates high-fidelity modeling with data-driven techniques to accurately reconstruct power distribution across various reactor types, thereby reducing the reliance on in-core sensors. Purdue University Reactor One (PUR-1) was selected as the test case. The CAD model representing the latest configuration of the PUR-1 core was imported into the OpenMC simulation framework, and the model was built. Additionally, the previously developed MCNP6 model was updated. The two models were assessed against the data collected during an experimental campaign conducted in July 2024. Thirty gold foils were placed in three Irradiation Assemblies in PUR-1 core. Using the measured activity of the irradiated foils, the neutron flux at different core locations was estimated.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

Assessment of Readout Techniques for Passive Monitors

This fiscal year (FY) 2023 report on passive temperature sensors covers two main objectives: to demonstrate that the optical dilatometer can successfully process disc shaped silicon carbide (SiC) temperature monitors (TMs), and to demonstrate proof of concept for using the capacitance readout method to read printed melt wires. The SiC objective was successfully met by annealing and analyzing, via optical dilatometry, all eight 3-mm SiC discs provided by the Nuclear Science User Facilities (NSUF) Idaho State University (ISU) Nanostructured Steels for Enhanced Radiation Tolerance (N SERT) experiment, which was irradiated at Idaho National Laboratory (INL)’s Advanced Test Reactor (ATR). Per the ISU N SERT experiment, capsule 1 (KGT 3828 1 and KGT 3828-2) had a design temperature of 300°C +/- 50°C and an exposure of 2 dpa +/- 10%; capsule 2 (KGT 4600 and KGT 4609) had a design temperature of 300°C +/- 50°C and an exposure of 6 dpa +/- 10%; capsule 3 (KGT 4639 C and KGT 4639-D) had a design temperature of 500°C +/- 50°C and an exposure of 6 dpa +/- 10%; and capsule 4 (KGT 3841 3 and KGT 3841 4) had a design temperature of 500°C +/- 50°C and an exposure of 2 dpa +/- 10%. The target exposure rates, in dpa, are the neutron damage for various types of nanostructured steels. All but three SiC TMs (KGT 4600, KGT 4639 D, and KGT 3841 4) revealed averaged peak irradiation temperatures that fell within the design temperature ranges. The three SiC TMs that did not fall within the design temperatures ranges were at least 100°C below that target temperature. Furthermore, SiC TM KGT 3841 C revealed two irradiation regimes: one closer to the 300°C design temperature, and the other closer to the 500°C design temperature. Also, all the SiC TMs’ averaged peak irradiation temperatures came in anywhere between 20°C and 240°C below the irradiation temperatures predicted by the thermal models. This showed the optical dilatometry method to be a reliable and less time intensive process for determining averaged peak irradiation temperatures from passive SiC TMs such as rods and discs. Under the Advanced Sensors and Instrumentation (ASI) program in FY-23, Boise State University (BSU) proposed to demonstrate proof of concept for using a capacitance readout technique applicable to printed melt wires; however, they were stymied by the complexity of the capacitance readout method. In support of the BSU work, INL developed an additively manufactured (AM) ceramic package for encapsulating the new melt wires. Inks were synthesized at BSU that used new protocols rather than following previously established protocols implemented at INL, and testing of various temperatures was conducted at BSU to evaluate the melting behaviors of the printed melt wires. The result was that the capacitance readout technique showed promise but also created more challenges than originally anticipated. For example, the tin ink synthesized at BSU showed unusual melting behaviors that did nothing to enhance the performance of the final printed melt wire prototype in terms of the capacitance readout method. To make the proof of concept work when applied to the printed melt wires, the ASI program would need to invest further resources and time. Consequently, the program is not planning to continue this proof of concept work in FY-24, based on the progress and findings achieved in FY-23.

36 MATERIALS SCIENCE↗
NASA NTRS1984

3 keV to 2 MeV observations of four gamma-ray bursts

Simultaneous X and gamma ray spectra were obtained for four gamma ray burst events using satellite instrumentation. The P78-1 satellite proportional counters recorded X-ray data in the 3-10 keV range, while Pioneer Venus Orbiter and ISEE 3 sensors had a 3 keV lower limit for events. The positively correlated data covered the events GB 790307, 790325, 790504, and 790731. The time histories of the X and gamma ray energies did not correlate well. The post-gamma ray phase of GB 790307 displayed features of simple cooling, and in conjunction with soft X-ray data suggested an origin in an optically thin fireball. However, the data were equally well-fitted by a model of an emitting hot spot on a neutron star. The data negated any concept that gamma ray bursts evolve similarly to classical X-ray bursts.

Laros, J. G.↗