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DOE OSTI2013

Benefits of creating a cross-country data framework for energy efficiency

As manufacturers now sell a similar range of consumer electronics and home appliances to major markets around the world, the task of identifying a product’s energy efficiency rating has usually been the responsibility of each country and its respective government agency. This has led to a multitude of energy efficiency testing procedures, ratings, and certifications, resulting in disparate data being captured on identical products. Furthermore, lack of consistent product identification criteria means product energy performance is not easily connected to relevant information about the product such as market availability, price or real world energy consumption. This paper presents a new data standard for reporting energy performance and related product information that can be adopted internationally. To inform the development of this standard, we explore the existing energy efficiency market data for the two example products of TVs and Room Air Conditioners. This paper discusses current/future use cases of appliance level energy efficiency data across all stakeholders, including consumers, retailers/manufacturers, global standards organizations, third party service providers, and regulatory agencies. It also explains the key benefits of moving to a common international data framework for energy efficiency, such as: 1) a centralized product information repository for comparing energy use, ratings/certifications, and pricing data 2) improved access to relevant consumer electronics and appliance data to facilitate new policy development and harmonization across markets 3) enablement of retailers and other third parties to embed actionable energy efficiency information as part of the consumer experience.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2024

Annual Performance Testing of Tracer Gas Detectors for use in Radionuclide NESHAP Compliance Testing

Los Alamos National Laboratory’s (LANL’s) compliance with Radionuclide NESHAP0F 1 regulations is managed by the Radioactive Air Emissions Management (RAEM) team, part of LANL’s Compliance Programs group (EPC-CP). One area of the Radionuclide NESHAP addresses requirements for siting a stack sample system. Prior to commissioning a new stack sampling system, the ANSI Standard for stack sampling requires that the stack sample location must meet several criteria, including uniform mixing of tracer gas (sulfur hexafluoride, SF 6 ) and tracer aerosol (liquid oil droplets) in the air stream. This memorandum will specifically focus on the tracer gas portion of the ANSI Standard. For these mix tests, tracer gas is injected into the stack air stream and the resulting air concentrations are measured across the plane of the stack at the proposed sampling location. The coefficient of variation of the media concentration must be under 20% when evaluated over the central 2/3 area of the stack or duct.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Assessment of Demographic, Genetic, and Imaging Variables Associated With Brain Resilience and Cognitive Resilience to Pathological Tau in Patients With Alzheimer Disease

Importance: Better understanding is needed of the degree to which individuals tolerate Alzheimer disease (AD)-like pathological tau with respect to brain structure (brain resilience) and cognition (cognitive resilience). Objective: To examine the demographic (age, sex, and educational level), genetic (APOE-ε4 status), and neuroimaging (white matter hyperintensities and cortical thickness) factors associated with interindividual differences in brain and cognitive resilience to tau positron emission tomography (PET) load and to changes in global cognition over time. Design, setting, an participants: In this cross-sectional, longitudinal study, tau PET was performed from June 1, 2014, to November 30, 2017, and global cognition monitored for a mean [SD] interval of 2.0 [1.8] years at 3 dementia centers in South Korea, Sweden, and the United States. The study included amyloid-β-positive participants with mild cognitive impairment or AD dementia. Data analysis was performed from October 26, 2018, to December 11, 2019. Exposures: Standard dementia screening, cognitive testing, brain magnetic resonance imaging, amyloid-β PET and cerebrospinal fluid analysis, and flortaucipir (tau) labeled with fluor-18 (18F) PET. Main outcomes and measures: Separate linear regression models were performed between whole cortex [18F]flortaucipir uptake and cortical thickness, and standardized residuals were used to obtain a measure of brain resilience. The same procedure was performed for whole cortex [18F]flortaucipir uptake vs Mini-Mental State Examination (MMSE) as a measure of cognitive resilience. Bivariate and multivariable linear regression models were conducted with age, sex, educational level, APOE-ε4 status, white matter hyperintensity volumes, and cortical thickness as independent variables and brain and cognitive resilience measures as dependent variables. Linear mixed models were performed to examine whether changes in MMSE scores over time differed as a function of a combined brain and cognitive resilience variable. Results: A total of 260 participants (145 [55.8%] female; mean [SD] age, 69.2 [9.5] years; mean [SD] MMSE score, 21.9 [5.5]) were included in the study. In multivariable models, women (standardized β = -0.15, P = .02) and young patients (standardized β = -0.20, P = .006) had greater brain resilience to pathological tau. Higher educational level (standardized β = 0.23, P < .001) and global cortical thickness (standardized β = 0.23, P < .001) were associated with greater cognitive resilience to pathological tau. Linear mixed models indicated a significant interaction of brain resilience × cognitive resilience × time on MMSE (β [SE] = -0.235 [0.111], P = .03), with steepest slopes for individuals with both low brain and cognitive resilience. Conclusions and relevance: Results of this study suggest that women and young patients with AD have relative preservation of brain structure when exposed to neocortical pathological tau. Interindividual differences in resilience to pathological tau may be important to disease progression because participants with both low brain and cognitive resilience had the most rapid cognitive decline over time.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2018

Estimation of Cadmium uptake by tobacco plants from laboratory leaching tests

The objective of the present study was to determine the impact of cadmium (Cd) concentration in the soil on its uptake by tobacco plants, and to compare the ability of diverse extraction procedures for determining Cd bioavailability and predicting soil-to-plant transfer and Cd plant concentrations. The pseudo-total digestion procedure, modified Tessier sequential extraction and six standard single-extraction tests for estimation of metal mobility and bioavailability were used for the leaching of Cd from a native soil, as well as samples artificially contaminated over a wide range of Cd concentrations. The results of various leaching tests were compared between each other, as well as with the amounts of Cd taken up by tobacco plants in pot experiments. In the native soil sample, most of the Cd was found in fractions not readily available under natural conditions, but with increasing pollution level, Cd amounts in readily available forms increased. With increasing concentrations of Cd in the soil, the quantity of pollutant taken up in tobacco also increased, while the transfer factor (TF) decreased. Linear and non-linear empirical models were developed for predicting the uptake of Cd by tobacco plants based on the results of selected leaching tests. The non-linear equations for ISO 14870 (diethylenetriaminepentaacetic acid extraction - DTPA), ISO/TS 21268-2 (CaCl2 leaching procedure), US EPA 1311 (toxicity characteristic leaching procedure - TCLP) single step extractions, and the sum of the first two fractions of the sequential extraction, exhibited the best correlation with the experimentally determined concentrations of Cd in plants over the entire range of pollutant concentrations. This approach can improve and facilitate the assessment of human exposure to Cd by tobacco smoking, but may also have wider applicability in predicting soil-to-plant transfer.

02 PETROLEUM↗

DOE OSTI2019

The Precision of Product Consistency Tests with Reference Glasses ARM-1 and SRM 623

An interlaboratory study (ILS) was conducted in 2014 to measure the precision with which the ASTM-International product consistency test method A (PCT-A) can be performed using properly prepared samples of reference glass ARM-1 or SRM 623 and test parameter values near the centers of ranges specified in procedure ASTM C1285. The ILS did not evaluate the full range of test parameter values allowed in the PCT-A method and the results do not represent the precision that should be expected if extreme values of the ranges are used. However, the precision measured in the ILS quantified the precision of tests conducted with mean parameters that were used to estimate the effects of individual parameters. Follow-on tests were conducted to assess the effects of several individual test parameter values on the test response and uncertainties in the derived glass dissolution rates. The effects of particle size distributions in glass samples prepared by wet- and dry-sieving methods, methods to remove fines, and the limiting parameter values for the water-to-glass (w/g) mass ratio and test duration allowed in PCT-A were measured. Test responses for all variations except test duration exceeded the precision measured in the ILS for conducting triplicate PCT-A tests within a single laboratory. The accuracy of glass dissolution rates derived from PCT results benefits from using a tighter control of these test variables than required in ASTM C1285. Comparison with previous analyses of the method shows how use of the relative standard deviation to represent the test precision can be misleading, and that the mean response and standard deviation should both be considered.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Study on the recycling of waste PVC compounds from electrical wires

The good mechanical, thermal and electrical properties of poly (vinyl chloride) (PVC) make it a polymer used in many applications, among which is the coating of wires and cables. The processing of PVC for this application is made using the extrusion process. The PVC waste resulting from extrusion can be recycled or placed on landfills. The objective of this work is to develop recycling methods to decrease the amount of PVC stored in landfills. This work evaluated the influence of successive processing of PVC on the final properties of the obtained compound, which will be used in the process of coating wire and cable by extrusion. The mechanical properties of the electrical wires were assessed according to the Brazilian Association of Technical Standards (ABNT NBR 6251). Tests of tensile strength, elongation at break, before and after thermal aging in an oven with air circulation for a period of 168 hours at 100 °C were performed. The degradation of the PVC compound was carried out through Fourier transform infrared spectroscopy (FTIR) and mechanical properties evaluation. The results showed that the compound can be reprocessed five times keeping the minimum requirements of the ABNT NBR 6251 Standard. Reprocessing was stopped upon color changing (yellowing) of the compound. Yellowing is a characteristic degradation behavior by dehydrochlorination of PVC. FTIR analysis showed changes at 1600 cm{sup −1}, 1430 cm{sup −1}, 685 cm{sup −1} and 614 cm{sup −1} bands. The performance of the PVC compound for coating electrical wire and cable was fair, meeting the requirements of the ABNT NBR 6251 Standard even after five reprocessing cycles.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Common Information Model for Electromagnetic Transients (CIM for EMT): CRADA 533 [Abstract only}

The control and protection functions of inverter-based resources (IBR) have raised concerns with bulk system reliability. Most of the current interest lies with solar photovoltaic generation but increasing amounts of storage would pose the same risks. Newer North American Electric Reliability Corporation (NERC) guidelines call for electromagnetic transient (EMT) studies of IBR and recommend that transmission operators collect distributed energy resource (DER) data to support such modeling. IEEE Standard P2800.1 is defining tests for model parameterization, so good model data should become available from inverter vendors. (EMT studies also apply to large power transformer reliability, and transformer vendors can provide EMT models.) Utilities don’t currently have the rest of the bulk system represented for EMT studies at large scale. An International Electrotechnical Commission (IEC) standard Common Information Model (CIM) provides a way of supporting these detailed models from physical asset data, e.g., conductors, towers, transformer data sheets, control block diagrams, while avoiding software vendor lock-in. CIM-for-EMT, with proposed schema extensions and open-source converters, provides a way to exchange EMT data between organizations and tools. This project leverages Office of Electricity (OE) funding of CIM-for-EMT code base through the GridAPPS-DTM project, and of GridPACKTM (parallelized transmission solver), for interoperability testing in CIM-for-EMT. The project also leverages partner PGSTech investments in EMTP® interoperability with CIM.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2018

Tribological Behavior of a Cr{sub 2}O{sub 3} Ceramic Coating/Steel Couple Under Dry Sliding and Heavy Loading Conditions

This work evaluates the effects of heavy loadings on a Cr{sub 2}O{sub 3} ceramic coating/steel couple under dry sliding and in conditions similar to those occurring in heavy-duty diesel engines. Two types of wear tests were performed by a standard pin-on-disc tribometer under high constant and variable loads. Before wear tests, microstructure and mechanical properties of coating and steel were determined by optical emission spectrometry, optical microscopy, roughness, microhardness and x-ray diffractometry (XRD). The friction coefficient was directly calculated by the tribometer. The wear rate of Cr{sub 2}O{sub 3} ceramic coating was evaluated by the wear volume and that of pins by weighing them before and after tests. The wear tracks on pins and coating surfaces were analyzed by XRD and by scanning electron microscopy with energy-dispersive spectroscopy. For all loads except the lowest constant one, the results indicated high friction and wear involving material removal from the coating surface, through a severe-oxidational wear associated with extensive cracking of the surface of the coating, softening of the carburizing steel and removal of the carburized layer of pins. The wear mechanism was mild-oxidational under the lowest constant load, which was therefore suggested as the limit for acceptable performance of the sliding couple under study.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Use of Mini-CT Specimens for Fracture Toughness Characterization of Irradiated Highly Embrittled Weld

In the 1990’s, the Heavy Section Steel Irradiation Program at the ORNL performed investigation of the shape of the fracture toughness master curve for reactor pressure vessel steel highly embrittled because of irradiation exposure. A radiation-sensitive reactor pressure vessel (RPV) weld with intentionally enhanced copper content, designated KS-01, has been characterized in terms of static initiation (KJc) and Charpy impact toughness in the unirradiated and irradiated conditions. The objective of this original project was to investigate the ability of highly embrittled material to maintain the shape of the unirradiated transition fracture toughness curve, as well as to examine the ability of the Charpy 41-J shift to predict the fracture toughness shift at such high level of embrittlement. Irradiation of this weld was performed at the University of Michigan Ford Reactor in the new HSSI irradiation-anneal-reirradiation (IAR) facility. Broken specimens from that project have been saved in ORNL storage. To verify applicability of Mini-CT specimens for fracture toughness characterization of RPV materials as part of the DOE Light Water Reactor Sustainability Program, Mini-CT specimens were machined from broken Charpy specimens and tested according to ASTM E1921 standard. As result of this study, the fracture toughness of this weld derived by testing Mini-CT specimens in the unirradiated and irradiated conditions is compared to previously reported fracture toughness derived by large number of conventional specimens.

Sokolov, Mikhail A.↗

DOE OSTI2024

Radiometric Testing of Germicidal UV Products, Round 2: Upper-Room Luminaires (CALiPER Report)

This report analyzes the independently tested performance of eight germicidal ultraviolet (GUV) upper-room luminaires marketed for use in occupied spaces and purchased between March and June 2023. Three of the luminaires used UV-emitting LEDs, and the remaining five luminaires used low-pressure mercury (LPM) lamps. Product testing covered radiometric and electrical performance for each luminaire. Initial performance was measured for all eight products, and four were additionally measured after 100 h and 500 h of operation. Measured performance was compared against manufacturer or vendor claims. Specifiers and buyers of GUV products need accurate performance claims and data to deploy GUV technology safely and effectively. As with the CALiPER GUV Round 1 report, this CALiPER GUV Round 2 report demonstrates that manufacturers and vendors need significant education and training to accurately test and report the performance of their GUV products. Further development of industry consensus standards and guidelines may address testing limitations and improve test methods, product performance, and the accuracy of performance claims.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2013

NREL Controllable Grid Interface for Testing MW-Scale Wind Turbine Generators (Poster)

In order to understand the behavior of wind turbines experiencing grid disturbances, it is necessary to perform a series of tests and accurate transient simulation studies. The latest edition of the IEC 61400-21 standard describes methods for such tests that include low voltage ride-through (LVRT), active power set-point control, ramp rate limitations, and reactive power capability tests. The IEC methods are being widely adopted on both national and international levels by wind turbine manufacturers, certification authorities, and utilities. On-site testing of wind turbines might be expensive and time consuming since it requires both test equipment transportation and personnel presence in sometimes remote locations for significant periods of time because such tests need to be conducted at certain wind speed and grid conditions. Changes in turbine control software or design modifications may require redoing of all tests. Significant cost and test-time reduction can be achieved if these tests are conducted in controlled laboratory environments that replicate grid disturbances and simulation of wind turbine interactions with power systems. Such testing capability does not exist in the United States today. An initiative by NREL to design and construct a 7-MVA grid simulator to operate with the existing 2.5 MW and new upcoming 5-MW dynamometer facilities will fulfill this role and bring many potential benefits to the U.S. wind industry with the ultimate goal of reducing wind energy integration costs.

17 WIND ENERGY↗

DOE OSTI2019

Hydrodynamic and Structural Response Modeling of a Prototype Floating Membrane Reservoir System for Pumped Storage Hydropower

Hydrodynamic, computational fluid dynamics, and finite-element modeling were performed for a novel floating membrane reservoir system design for closed-loop pumped storage hydropower application. The conceptual design, which is now protected under an invention disclosure with a patent pending, offers a potential low-cost, low-impact solution to address the high costs, long investment return periods, and environmental disruptions encountered with traditional pumped storage development while offering modularity to enable replication at many locations. Prior to physical tests on a prototype, this paper documents the response analysis and modeling completed to simulate hydraulic and structural performance under different reservoir deployment and alignment arrangements, evaluate system stability, and refine the conceptual design. The results indicate that the excitation frequency from vortex shedding is at least an order of magnitude lower than the water sloshing frequencies in the reservoir, the structural natural frequency of the entire reservoir, and the vibrational frequencies of the side membranes, although excitation frequencies from other sources could cause mechanical resonance under certain conditions. To control destabilizing effects and prevent rocking motion and vibration, the authors conclude that the design could be improved by including a support structure around the floating reservoir, which could also provide floating-membrane containment, improve safety, and facilitate vertical reservoir movement. These conclusions, based on hydrodynamic and structural response modeling, help define specifications for upcoming full-scale prototype construction, deployment, and testing. This study demonstrates standard modeling technique application to an innovative design for which similar applications have not been previously evaluated. As a result, the refined design is capable of improving the scalability and feasibility of pumped storage hydropower in the United States and will be considered for commercialization following prototype testing.

13 HYDRO ENERGY↗

DOE OSTI2014

SU-E-I-41: Non-Cartesian MR Image Reconstruction with Integrated Gradient Non-Linearity Correction

Purpose: Nonlinearities in the spatial encoding gradients of MRI systems cause geometric distortion in images. Typically, this is retrospectively corrected via image-domain interpolation (a.k.a., “gradwarp”) albeit with a loss of spatial resolution. For non-Cartesian MRI, the latter problem is exaggerated by noise and undersampling artifact. In this study, we describe a novel correction strategy that accounts for gradient nonlinearities during — rather than after — non-Cartesian MRI reconstruction, and demonstrate that this approach mitigates the resolution loss that can occur with standard methods. Methods: To test the proposed method, the American College of Radiology (ACR) quality control phantom was scanned on at 1.5 T (General Electric, v16.0, “zoom” gradient) using a 1.6x undersampled 3D non- Cartesian Shells trajectory (GRE, FOV=24 cm3, 120 shells, 16552 shots, 512 readout, matrix=2403). Image reconstruction was first performed via standard k-space density-compensated gridding and retrospectively corrected via cubic spline interpolation. Image reconstruction was then separately performed using a k-space and image-domain densitycompensated type-3 non-uniform fast Fourier transform (NUFFT), which provides a direct mapping between non-Cartesian k-space samples and warped image space voxel locations. Thus, no separate distortion correction procedure is needed for the proposed approach. The gradient distortion field was determined using vendor provided calibration data. Results: Phantom scan results show that both processing approaches successfully correct geometric distortion. However, visual inspection of the ACR phantom spatial resolution inserts shows that the proposed strategy preserves the resolution of the nominal (uncorrected) reconstruction while “gradwarp” imparts marked spatial blurring (especially for the 1.0 and 1.1 mm inserts) and thus resolution loss. Conclusion: We've presented a novel reconstruction strategy for non-Cartesian MRI that corrects for gradient nonlinearities during — rather than after — reconstruction, and thus better preserves image resolution than traditional interpolation-based methods. This approach is expected to be especially advantageous when imaging with non-standard magnet geometries. NIH RR018898; NIH EB10065.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2016

Invited Article: miniTimeCube

We present the development of the miniTimeCube (mTC), a novel compact neutrino detector. The mTC is a multipurpose detector, aiming to detect not only neutrinos but also fast/thermal neutrons. Potential applications include the counterproliferation of nuclear materials and the investigation of antineutrino short-baseline effects. The mTC is a plastic 0.2% 10 B - doped scintillator (13 cm) 3 cube surrounded by 24 Micro-Channel Plate (MCP) photon detectors, each with an 8×8 anode totaling 1536 individual channels/pixels viewing the scintillator. It uses custom-made electronics modules which mount on top of the MCPs, making our detector compact and able to both distinguish different types of events and reject noise in real time. The detector is currently deployed and being tested at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) nuclear reactor (20 MW th ) in Gaithersburg, MD. A shield for further tests is being constructed, and calibration and upgrades are ongoing. The mTC's improved spatiotemporal resolution will allow for determination of incident particle directions beyond previous capabilities.

47 OTHER INSTRUMENTATION↗

DOE OSTI2026

Adapter Signaling Evaluations on EVs [Slides]

In case J3400 and J3400/1 define a basic analog signaling approach for DC charging adapters to communicate over-temperature events to both the EV and EVSE. They also require the EV to implement mitigation and corrective actions in cases where the EVSE does not respond to adapter thermal signals. In this study, multiple production vehicles were evaluated for responsiveness to assess field readiness and ensure consistent performance in accordance with the SAE J1772, J3400 and J3400/1 standards. A series of test cases were developed and executed across different vehicles, using an adapter thermal breakout fixture designed by NLR for evaluations. The results revealed notable variations in behavior: some vehicles expected to comply with J1772 were found to be non-responsive under certain conditions. Additionally, while some EV OEMs appear to align with the J3400 standard, discrepancies exist due to its evolving nature, resulting in inconsistent implementation of the latest requirements. These findings highlight the need for alignment within standards organizations to ensure consistent interpretation, encourage compliance, and reduce potential confusion across implementations.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2016

Linear multispecies gyrokinetic flux tube benchmarks in shaped tokamak plasmas

Verification is the fundamental step that any turbulence simulation code has to be submitted in order to assess the proper implementation of the underlying equations. We have carried out a cross comparison of three flux tube gyrokinetic codes, GENE [F. Jenko et al., Phys. Plasmas 7, 1904 (2000)], GKW [A. G. Peeters et al., Comput. Phys. Commun. 180, 2650 (2009)], and GS2 [W. Dorland et al., Phys. Rev. Lett. 85, 5579 (2000)], focusing our attention on the effect of realistic geometries described by a series of MHD equilibria with increasing shaping complexity. To simplify the effort, the benchmark has been limited to the electrostatic collisionless linear behaviour of the system. A fully gyrokinetic model has been used to describe the dynamics of both ions and electrons. Several tests have been carried out looking at linear stability at ion and electron scales, where for the assumed profiles Ion Temperature Gradient (ITG)/Trapped Electron Modes and Electron Temperature Gradient modes are unstable. The capability of the codes to handle a non-zero ballooning angle has been successfully benchmarked in the ITG regime. Finally, the standard Rosenbluth-Hinton test has been successfully carried out looking at the effect of shaping on Zonal Flows (ZFs) and Geodesic Acoustic Modes (GAMs). Inter-code comparison as well as validation of simulation results against analytical estimates has been accomplished. All the performed tests confirm that plasma elongation strongly stabilizes plasma instabilities as well as leads to a strong increase in ZF residual and GAM damping.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Economy and Emissions Impacts from Solazyme Fuel in UPS Delivery Vehicles

To improve understanding of the potential fuel economy and emissions impacts from switching a fleet of vehicles from conventional petroleum diesel to synthetic renewable diesel, the National Renewable Energy Laboratory (NREL) conducted fuel economy and emissions analyses at NREL's Renewable Fuels and Lubricants (ReFUEL) Laboratory. Representative test cycles were developed based on real-world data from six package delivery vehicles and six class 8 day-cab tractors operated by UPS in the Dallas, Texas, area. A three-week in-field data collection period yielded 170 days of real-world vehicle operations data that NREL used to select representative standard drive cycles for testing. Fuel economy and emissions tests at the ReFUEL Laboratory showed that, in general, when switching from conventional diesel to renewable diesel observed changes in tailpipe carbon dioxide (CO2), fuel consumption, and fuel economy are primarily driven by changes in fuel properties such as the hydrogen-to-carbon ratio, density, and lower heating value (LHV). The vehicles tested with the renewable diesel showed a consistent 4.2% reduction in tailpipe CO2 emissions, but a 3.5%-4.8% reduction in fuel economy compared with local pump diesel. This is consistent with the 4.2% lower volumetric LHV of the sourced renewable diesel compared to the pump diesel. The UPS package car tested on renewable diesel also demonstrated a 4.1% oxides of nitrogen (NOx) reduction. NOx emissions from the UPS selective-catalyst-reduction-equipped tractor were an order of magnitude lower than the package car but showed relatively higher variability in results from cycle to cycle.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2020

Predicting Biological Cleanliness: An Empirical Bayes Approach for Spacecraft Bioburden Accounting

To comply with the international planetary protection policy set forth by the Committee on Space Research and NASA Agency level requirements, spacecraft destined to biologically sensitive planetary bodies have to minimize terrestrial biological contamination. Analysis, testing and inspection are the standard forward verification activities that are used to demonstrate compliance with the biological contamination requirements. For testing of spacecraft surface areas, a swab or wipe sample is collected from surfaces prior to last access and subsequently processed in the lab using NASA Approved Planetary Protection Methods for Culture Based Assays. Raw data resulting from this assay is then statistically treated employing a mathematical paradigm stemming from the 1970’s Viking Lander Project to generate the bioburden density and total microbial bioburden present. This standard approach arbitrarily accounts for error and provides an upper conservative bound as it reports the maximum number of spores estimated to be present on flight hardware surfaces. A bioburden density estimate factors in the following variables: the observed bioburden count, representative volume processed, sampling efficiencies. Notably, to account for error in the approach, a 0 observed count is arbitrarily changed to a count of 1 for each hardware grouping. The data generated by spacecraft bioburden verification campaigns in the past have resulted in <80% of wipes and <90% of swabs containing a bioburden count of 0. As such, having a robust and well documented statistical approach for dealing with the probability of low incident rates is necessary to be able to estimate spacecraft bioburden. Being able to statistically describe the bioburden distribution and associated confidence level is a gamechanger for the development of bioburden allocations during mission design and will allow for tighter management of risk throughout spacecraft build. Thus, Empirical Bayes statistical approach was evaluated to estimate the microbial bioburden on spacecraft to mitigate the aforementioned mathematical concerns and provide a probabilistic bioburden distribution of the flight hardware surface. For application of this approach to performing bioburden calculations, a range of non-informative prior assumptions on hardware surfaces are explored for Bayesian analyses while informative priors using posterior distributions from prior assays are utilized for Empirical Bayes analyses. Several non-informative priors are currently under investigation to assess fitness including use of these priors to serve as a foundation to build off of NASA specification values or a basis of risk to account for unknowns during the integration and testing process. Informative priors under consideration are generated using sampled bioburden values from hardware originating within like processing environments (e.g. vendor cleaning process or similar assembly process), temporal spacecraft status events as a prediction for hardware cleanliness of future samples, and heritage system bioburden actuals to predict allocation for subsequent missions. Informative priors and probabilistic bioburden distributions are then validated using data sets from the Mars Exploration Rover, Mars Science Laboratory, and InSight missions. Using Empirical Bayes approach to generate a probabilistic bioburden distribution as demonstrated through mission use cases provides a valid approach for use in the end-to-end requirements verification process.

97 MATHEMATICS AND COMPUTING↗