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All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the Orbiter Experiment (OEX) subsystem

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Orbiter Experiments (OEX) hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the NASA FMEA/CIL baseline with proposed Post 51-L updates included. A resolution of each discrepancy from the comparison is provided through additional analysis as required. The results of that comparison for the Orbiter OEX hardware are documented. The IOA product for the OEX analysis consisted of 82 failure mode worksheets that resulted in two potential critical items being identified.

Compton, J. M.↗
NASA NTRS1991

Improved silicon nitride for advanced heat engines

The results of a four year program to improve the strength and reliability of injection-molded silicon nitride are summarized. Statistically designed processing experiments were performed to identify and optimize critical processing parameters and compositions. Process improvements were monitored by strength testing at room and elevated temperatures, and microstructural characterization by optical, scanning electron microscopes, and scanning transmission electron microscope. Processing modifications resulted in a 20 percent strength and 72 percent Weibull slope improvement of the baseline material. Additional sintering aids screening and optimization experiments succeeded in developing a new composition (GN-10) capable of 581.2 MPa at 1399 C. A SiC whisker toughened composite using this material as a matrix achieved a room temperature toughness of 6.9 MPa m(exp .5) by the Chevron notched bar technique. Exploratory experiments were conducted on injection molding of turbocharger rotors.

Yeh, Harry C.↗
DOE OSTI2024

Taylor-Couette Flow Modeling (Rev.1)

The Taylor-Couette Flow is a form of viscous flow in which fluid flows between two cylindrical walls with a prescribed rotation. A diagram is shown on the right (Figure 1) where Ω is the rotational velocity, H is the distance between the two cylinders, R is the radius the outer cylinder, r is the radius of the inner cylinder and L is the length of the cylinders. When the rotating inner cylinder reaches a critical velocity, the flow of the liquid becomes unstable and creates vortices in between the layers. In this experiment, the Taylor-Couette cylinders were modeled so that the vortices would be created after reaching a critical velocity. After the initial experiment, the velocity of the inner cylinder was decreased and increased to look at how the results changed.

42 ENGINEERING↗
DOE OSTI2016

Finalizing the {sup 63}Cu and {sup 65}Cu Resonance Evaluations for the ENDF/B-VIII Release

The resolved resonance region evaluation for the only two natural isotopes of copper ({sup 63}Cu and {sup 65}Cu) was carried out at the Oak Ridge National Laboratory (ORNL) in support of the US Department of Energy (DOE) Nuclear Criticality Safety Program (NCSP). The particular interest in the isotope of copper arose because it was linked with poor performance of the Zeus series of integral benchmarks from the International Criticality Safety Benchmark Evaluation Project (ICSBEP). Good agreement between the calculated and experimentally measured values for the ICSBEP benchmarks is essential to the NCSP because the ICSBEP benchmarks are used for validation purposes of criticality safety calculations. The particular set of four Zeus experiments had a highly-enriched uranium core with a thick copper-reflector resulting in a large sensitivity of the criticality of these systems to the cross section of copper in the intermediate energy range. Sobes et al. presented the effect of the newly resolved resonance region evaluations for the two isotopes of copper on the Zeus integral benchmarks, as well as 23 other benchmarks from the ICSBEP during the 2016 ANS Annual Meeting. The results presented in Ref. were calculated with the ENDF/B-VII.1 cross section libraries used for all other materials. However, it is suggested that the resolved resonance region evaluations for the isotopes of copper should not be judged only on their performance in the integral benchmark calculations especially when the ENDF/B-VII.1 cross sections are used for all of the other isotopes. Three reasons are provided for this. First and foremost, a new evaluation is an assessment of the physics of the nucleus of the particular isotope, and the goal of an application agnostic nuclear data evaluation is to improve evaluation by fitting state-of-the art R-Matrix formalism to highly precise experimental cross section measurements. The improved performance in the integral benchmarks should only come as a consequence of the improvement in the physics of the evaluation. Secondly, there is some uncertainty in the nuclear data evaluation of the cross section of all isotopes, so there could be some error in evaluating another isotope used in calculating the integral benchmark experiment. Such an error may have been having a compensating effect, in combination with the previous evaluations for the isotopes of copper. Thirdly, with the two isotopes of copper proposed for inclusion in the upcoming release of the ENDF/B-VIII library, performance of the new resonance evaluation for copper should be evaluated based on the calculation of the integral benchmarks with all of the evaluations proposed for inclusion in the ENDF/B-VIII release. These benchmarking results using the ENDF/B-VIII evaluations as they converge closer to their final form will be presented at the conference. This summary stresses the importance of the physics of the evaluation and reviews some of the steps taken in finalizing a resolved resonance region evaluation. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

Nucleon Axial Radius and Muonic Hydrogen — A New Analysis and Review

Weak capture in muonic hydrogen (μH) as a probe of the chiral properties and nucleon structure predictions of quantum chromodynamics (QCD) is reviewed. A recent determination of the axial-vector charge radius squared, , from a model independent z expansion analysis of neutrino-nucleon scattering data is employed in conjunction with the MuCap measurement of the singlet muonic hydrogen capture rate, , to update the induced pseudoscalar nucleon coupling derived from experiment, and predicted by chiral perturbation theory. Accounting for correlated errors this implies , confirming theory at the 8% level. If instead, the predicted expression for is employed as input, then the capture rate alone determines , or together with the independent z expansion neutrino scattering result, a weighted average . Sources of theoretical uncertainty are critically examined and potential experimental improvements are described that can reduce the capture rate error by about a factor of 3. Muonic hydrogen can thus provide a precise and independent value which may be compared with other determinations, such as ongoing lattice gauge theory calculations. The importance of an improved determination for phenomenology is illustrated by considering the impact on critical neutrino-nucleus cross sections at neutrino oscillation experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

An overview of the 2014 revision of ANSI/ANS-ANS-8.1-2014, 'Nuclear criticality safety in operations with Fissionable Materials Outside Reactors' - 14577

A revision to the American National Standards Institute (ANSI)/American Nuclear Society (ANS) standard, 'Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors' [ANSI/ANS-8.1 (ANS-8.1)], was completed and published in 2014. The approved scope for the 2014 revision included two major efforts: (1) an editorial revision to clarify the meaning of the process analysis requirement (PA) and the double contingency principle recommendation (DCP) and (2) the generation of new subcritical limits for uranium and uranium compounds for enrichments less than 10 wt % {sup 235}U. After a clarification request was submitted regarding the PA and DCP in 2009, the scope of the revision became focused almost entirely on the editorial revision. With approval from the ANS-8 subcommittee chairman, the computational effort was postponed until the editorial revision could be completed. The 2014 revision of ANS-8.1 involved nuclear criticality safety experts from 14 different sites, each with many years of experience, either maintaining the standard as a working group member or as a criticality safety practitioner. Many of the represented sites had implemented the PA with the language of the DCP to ensure that process operations with fissionable materials would be subcritical. However, the early working group deliberations made it clear that the general industry focus was on the DCP rather than the PA, which requires that 'all normal and credible abnormal conditions remain subcritical'. Over the course of the revision, two new definitions and a new appendix (Appendix B) were developed to enhance understanding of the PA and DCP. The emphasis of Appendix B is on the requirement for subcriticality (PA) rather than the DCP. The phrase 'credible abnormal conditions' in the PA is broader in meaning than 'changes in process conditions,' as recommended by the DCP. This is because a single credible abnormal condition can potentially affect multiple independent process conditions, and consequently, multiple process parameters, simultaneously. The DCP is a technical practice meant to support the PA and cannot be applied to all situations. However, when it can be properly applied, the DCP technical practice, in most cases, ensures compliance with the PA because two unlikely, independent, and concurrent changes in process conditions are generally judged not to be a credible abnormal condition, as specified in the PA. This paper elaborates on the intense working group discussions over the course of the ANSI/ANS-8.1 standard revision and summarizes the modifications made to the revised standard. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Status and plans of the NA61/SHINE physics program

One of the NA61/SHINE experiment's goals is to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. This is to be achieved by performing a two-dimensional phase diagram (T- Micro-Sign {sub B}) scan-measuring hadron production in collisions of various beam particles and targets at various beam energies. NA61/SHINE also collects data for the T2K experiment, which are just about to be published.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1991

Shape selection criterion for cellular array during constrained growth of binary alloys - Need for low gravity experiment

Development of steady-state periodic cellular array is one of the critical problems in the study of nonlinear pattern formation during directional solidification of binary alloys. The criterion which establishes the values of cell tip radius and spacing under given growth condition is not known. Theoretical models, such as marginal stability and microscopic solvability, have been developed for purely diffusive regime. However, the experimental conditions where cellular structures are stable are precisely the ones where the convection effects are predominant. Thus, the critical data for meaningful evaluation of cellular array growth models can only be obtained by partial directional solidification and quenching experiments carried out in the low gravity environment of space.

Tewari, Surendra N.↗
DOE OSTI2023

Predicting fatal heat and humidity using the heat index model

A unique wet-bulb temperature of 35°C is often used as the threshold for human survivability, but recent experiments have shown that a person’s core temperature starts to rise at a wide range of critical wet-bulb temperatures. Here, it is shown that the model underlying the heat index correctly predicts those critical wet-bulb temperatures, explaining 95% of the variance in the values observed in laboratory heat-stress experiments. This is the first time the heat-index model has been validated against physiological data from laboratory experiments. For light and moderate exertion in an indoor setting, the heat index model predicts that the critical wet-bulb temperature ranges from 20 to 32°C, depending on the relative humidity, consistent with experimental results. Furthermore, for the same setting and exertion, the heat index model predicts fatal wet-bulb temperatures ranging from 24 to 37°C. Recent experiments have identified the critical combinations of heat and humidity, in an indoor setting, above which an individual is unable to maintain a standard core temperature, indicating severe heat stress. It is shown here why this state of severe heat stress cannot be predicted using the wet-bulb temperature. Instead, it is shown that the recently extended heat index model can explain nearly all of the variance in the observed critical combinations of temperature and humidity, and can be used to calculate fatal combinations.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1983

A versatile ground data display system for Spacelab experiments

A microprocessor-based data capture and display system suited to the needs of many Spacelab experimenters is described. Although developed specifically for the needs of the FAUST UV astronomy telescope, several features of the system may make it attractive to other groups who need to interact with their Spacelab data in real or near-real time. The display system captures data from the serial data stream originating in the Spacelab experiment computer input/output (ECIO) data channel, and can reformat and display several hundred variables per second in real time. The system offers a combination of CRT display and analog paper strip-chart output. A facility is also provided for simultaneously creating floppy-disk records of short segments of data according to prearranged criteria, to allow detailed examination of critical events in the operation of the experiment. The simplicity, economy, reliability, and flexibility of the display system suggest its use for monitoring a variety of low- and medium-data-rate Spacelab experiments.

Werthimer, D.↗
DOE OSTI2013

Radon induced surface contaminations in low background experiments

In neutrinoless double-beta decay and dark matter searches, one of the main issues is to increase the experimental sensitivity through careful material selection and production, minimizing the background contributions. In order to achieve the required, extremely low, counting rates, very stringent requirements must be fulfilled in terms of bulk material radiopurity. As the experimental sensitivity increases, the bulk impurities in the detector components decrease, and surface contaminations start to play an increasingly significant role In fully active detectors, like cryogenic particle detectors, surface contaminations are a critical issue (as shown by the CUORICINO experiment). {sup 222}Rn is by far the most intense source of airborne radioactivity, and if a radio-pure material is exposed to environment where the Radon concentration is not minimized, {sup 210}Pb and {sup 210}Po contaminations can occur. The mechanisms and the dynamics of Radon-induced surface contaminations are reviewed, and specific solutions to prevent and to reject the induced background are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

Optimal experimental design using eigenvalue-based criteria with Pyomo.DoE

New developments in automated optimal experimental design within the PSE+ software ecosystem. Advancements in user experience (to reduce the time taken to perform optimal experiment design) and computational capabilities (allowing more diverse experimental design) are shown with an example relevant to critical minerals and materials. Also, a small tutorial on science-based optimal experimental design and novel contributions therein are presented.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1981

The STD/MHD codes - Comparison of analyses with experiments at AEDC/HPDE, Reynolds Metal Co., and Hercules, Inc

Data from sufficiently well-instrumented, short-duration experiments at AEDC/HPDE, Reynolds Metal Co., and Hercules, Inc., are compared to analyses with multidimensional and time-dependent simulations with the STD/MHD computer codes. These analyses reveal detailed features of major transient events, severe loss mechanisms, and anomalous MHD behavior. In particular, these analyses predicted higher-than-design voltage drops, Hall voltage overshoots, and asymmetric voltage drops before the experimental data were available. The predictions obtained with these analyses are in excellent agreement with the experimental data and the failure predictions are consistent with the experiments. The design of large, high-interaction or advanced MHD experiments will require application of sophisticated, detailed and comprehensive computational procedures in order to account for the critical mechanisms which led to the observed behavior in these experiments.

Vetter, A. A.↗
DOE OSTI2022

Steady-State Irradiation of Characterized Instruments for Nuclear Thermal Rockets Using In-Pile Experiment Apparatus

The development of nuclear rocket technology is critical for further exploration of extra-terrestrial bodies. Nuclear rockets can provide various advantages over current chemical rockets. However, the harsh environment provides several challenges regarding instrument performance. Temperature extremes, radiation (reactor and space), and the inability to conduct traditional maintenance activities can lead to severe degradation in instrument performance. To better understand the effects of radiation on instrumentation, an irradiation campaign has been designed to test a set of instruments provided by a collaborator in the aerospace industry. Details concerning instrument performance before and after irradiation are provided to allow for an analysis of the tested instruments. Additionally, the design of the irradiation test is described in detail.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Saturn Radiation Dose Environment Characterization

To understand the environment where a time-resolved hard x-ray spectrometer (AXIOM) might be fielded, experiments and simulations were performed to analyze the radiation dose environment underneath the Saturn vacuum dome. Knowledge of this environment is critical to the design and placement of the spectrometer. Experiments demonstrated that the machine performance, at least in terms of on-axis dose, has not significantly changed over the decades. Simulations of the off-axis dose were performed to identify possible spectrometer locations of interest. The effects from the source and dome hardware as well as source distributions and angles of incidence on the radiation environment were also investigated. Finally, a unified radiation transport model was developed for two widely used radiation transport codes to investigate the off-axis dose profiles and the time-dependent x-ray energy spectrum. The demonstrated equivalence of the unified radiation transport model between the radiation transport codes allows the team to tie future time-dependent x-ray environment calculations to previous integral simulations for the Saturn facility.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Planned Steady State Irradiation of Characterized Instruments for Nuclear Thermal Rockets Using In-Pile Experiment Apparatus

The development of nuclear rocket technology is critical for the further exploration of extraterrestrial bodies. Nuclear rockets are capable of providing various advantages over current chemical rockets. However, the harsh environment provides a number of challenges regarding instrument performance. Temperature extremes, radiation (reactor and space), and the inability to conduct traditional maintenance activities can lead to a severe degradation in instrument performance. To better understand the effects of radiation on instrumentation, an irradiation campaign has been designed to test a set of instruments provided by a collaborator in the aerospace industry. Details concerning pre-irradiation performance are provided for a future comparison to the irradiated performance. Additionally, the design of the irradiation test is described in detail.

Floyd, Dan↗
DOE OSTI2020

Effect of Nuclear Data Covariances on Integral Experiment Design with Sensitivity and Uncertainty Analysis

Washington River Protection Solutions (WRPS) uses MCNP6.2 and the Whisper code for criticality safety analyses of the Hanford Tank Farm. Together the codes derive baseline upper subcritical limits (USLs) for the waste models using experimental benchmarks. Whisper returns higher USLs, i.e. , has less of a conservative penalty, when the neutronic similarity of the experimental benchmarks to the application is high. Unfortunately, few critical benchmarks have high similarity to the Hanford tanks. The waste in the tanks is highly dilute in plutonium and contains large masses of weakly neutron-absorbing elements like iron and manganese. Experimental benchmarks typically have low sensitivity to these absorbers because they are present as structural materials. Lacking similar benchmarks, new Thermal Epithermal eXperiment (TEX) configurations with high Pu content and interstitial iron absorbers have been designed for the criticality safety validation. The features of the design have been iterated upon to maximize the similarity between the experiment and different Hanford waste models. The similarity is quantified with sensitivity analysis and uncertainty quantification using the representativity coefficient, or c k . The representativity calculation requires nuclear data covariances, which may differ between nuclear data libraries and between library versions. Because of these variations, the optimal design may depend on the nuclear data covariances library. A scenario can be envisioned where an experiment is designed, and c k is maximized, with one set of covariance data. However, when the covariance data is changed, say from ENDF/B-VII.1 to ENDF/B-VIII.0, and the benchmark is used in a criticality safety evaluation, the experiment becomes suboptimal with respect to c k . In this paper, we present how the optimal design of the new TEX experiments varied depending on the nuclear data covariances used to calculate c k . We compare ENDF/B-VII.1 and ENDF/B-VIII.0, as if the library had been updated since the design of the experiment. Additionally, we use JEFF3.3 to simulate if the covariance data of a different library had been used. The results show that the covariances do have an important effect on the designs, less so for thermal systems (where the data are more consistent between evaluations) and more so for epithermal systems where more differences exist.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1997

X-Ray Transmission Microscope Development

We have succeeded in meeting the goals set out in the proposal. A cadre of detector technologies is available to suit the requirements of the experiment. Resolutions of both real-time and absolute limits to resolution exceed the initial aspirations. Obtaining sufficient contrast is still a significant limitation but can be overcome by Judicious selection of the specimen composition. This can only take time and trial and error for a successful result. The 4th generation furnace provides the capability of real-time in-situ observations of composite alloy development. A low detection sensitivity however, has still made it difficult to observe dendritic growth, although it has been 'seen' in raw video; it was not a recordable signal. We have examined flight ampoules with XTM to observe particle and thermocouple placement, crucible flaws and cracks in collaboration with the Particle Pushing and Engulfment flight experiment (Dr. Stefanescu, UA, P.I.). The value of an in flight XTM to guard against experiment failure and safety assurance is obvious. Although not attributable to equipment limitations, a quest to observe particle pushing was not successful. We tried at length to prepare specimens that would demonstrate particle pushing. Instead, we were successful in imaging the interface deformation due to the thermal field distortion of a ceramic particle or void and to compare to calculated shapes. In theory, we should have been able to make major inroads to this field if the particles could be pushed and the velocities adjusted to make critical measurements. On the other hand, critical issues of sample preparation for the PEP flight experiment were established, particularly the clustering of particles and trapped voids. In this regard, the XTM did prove very useful so that flight specimens would work as expected and to perform post flight analysis. Although not a clear result, particle pushing of precipitates was observed in an Al-Si-Mn alloy. It may be that to be pushed, the particles need to be small and have clean surfaces like one might obtain from in-situ precipitation. The ability to image features in real time skill enable more fundamental and detailed understanding of solidification dynamics in microgravity than had previously been possible, thus, allowing the full benefits of microgravity experiments be applied towards rigorous testing of critical solidification models. The XTM is also a valuable tool for post solidification metallography. The 3-dimensional distribution of solute and solidification features within the specimen volume can be viewed without sectioning or other treatment when the solute has sufficiently higher atomic mass than the solvent. Thus the XTM could provide the first practical method for on orbit microstructural (metallographic) analysis by the astronauts or by telescience.

Kaukler, William F.↗

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