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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Preparing for safe and compliant open air demolition at Hanford's plutonium finishing plant - 15100

The Plutonium Finishing Plant (PFP), located in the 200 West Area of the U.S. Department of Energy (DOE) Hanford Site, began operations in 1949 and produced plutonium metal during the Cold War. Production was stopped in 1989, the facility was formally shut-down in 1996, and material stabilization completed in 2004. DOE contractor CH2M HILL Plateau Remediation Company (CH2M HILL) is tasked with the plant's deactivation, decommissioning, decontamination and demolition, to be completed by September 30, 2016. The project team, partnering with DOE-Richland Operations Office (DOE-RL), is exploring, evaluating and implementing efficiencies to safely and compliantly prepare the facility for demolition. Since 2008, employees have prepared approximately 75 percent of the complex for demolition. More than 90 percent of the 232 glove boxes have been removed from ventilation and more than 80 percent of pencil tank units have been dispositioned. As decontamination, deactivation and removal nears completion on the remaining glove boxes, pencil tanks and other radiological and chemical processing infrastructure, CH2M HILL and DOE-RL are making preparations to demolish PFP itself, a Hazardous Category II nuclear facility (HazCat II). Conventional techniques used to demolish buildings heavily contaminated with radiological hazards typically involve extensive hands-on work to remove Material at Risk (MAR) and decontaminate the building to low levels before conventional demolition techniques can be used to remove the building. A safe and more cost effective approach is packaging MAR located in hard to access areas of the plant and removing it during demolition. That process, combined with affixing remaining contamination to walls, floors and equipment, performing detailed air dispersion modeling before demolition and air monitoring and dust suppression during demolition, will reduce employee risk and is more efficient in demolishing a HazCat II facility. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Safe and Secure Management of Disused Radioactive Sealed Sources in Egypt - 19063

Radioactive sources offer many benefits in medicine, industry and education but the lack of appropriate long-term management when they eventually become disused has led to accidents, in some cases with serious consequences, and increased their vulnerability for use in a malicious act. This lack is evident in the absence of clearly defined policy and strategy, responsibilities and resources to meet those responsibilities for safe, secure and sustainable management of disused sources. The strengthening of national legislative and regulatory infrastructures globally has led to major improvements in the protection and control of radioactive sources. Nevertheless, in many countries, radioactive sources were in use before such infrastructures had been developed or adequately strengthened and were therefore not under regulatory control. The paper presents some aspects from Egyptian experience related to safe and secure measures for management of Cs-137, Ra-226 and Co-60 sealed sources. Data relating to the disused radioactive sealed sources, DSRS inventory as well as the arrangements made in order to prepare for conditioning of sources is presented. The efforts made by technical staff and radiation protection team for all arrangements and details such as conditioning set-up, working area, leakage test, certified stainless capsules, radiation protection measures and sources characterization in addition to all security measures for stored DSRS are also presented. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Applying Technology and Experience to Ensure Safe In Situ Decommissioning - 19587

Permanent entombment of a radioactively contaminated facility as a decommissioning option (In Situ Decommissioning, ISD) has been completed for DOE facilities at the Savannah River Site (P and Reactors, HWCTR reactor), Hanford (U Canyon) and Idaho (CP-601/604),and is currently being considered for implementation at a limited number of selected DOE facilities as well as for the NPD and WR-1 reactors in Canada and various facilities in the United Kingdom. A general description of an ISD project encompasses an entombed facility which in some cases is limited to just the below-grade portion of a facility with the above-ground portion being decommissioned, packaged and disposed in a conventional manner. The entombed portions of the facility are of robust construction, generally of reinforced concrete exterior, that provides a migration barrier between internal contamination and the environment with significant internal void spaces backfilled or grouted. The scope of entombment may include ancillary equipment and structures and may contain radioactive and hazardous materials and contamination within the facility and waste imported from outside the facility. ISD is most often a permanent decommissioning end-state although in some instances (e.g. the U.K.) there may be a need to revisit the ISD facility after 300 years to effect traditional decommissioning. The defined completion (the end-state) of the decommissioned facility is therefore project-specific and in conformance with environmental approval processes and planned future activities. In all cases however, the final condition is passive, meaning that there are no requirements for ongoing operational systems or equipment within the decommissioned facility. ISD projects in the USA are presumed to be under indefinite institutional control of the U.S. Government. The regulatory framework in the U.S. is currently in place to provide assurance that the risk posed by an ISD facility is within regulatory acceptance criteria. (The framework in the U.K. and Canada is evolving towards that in the USA). Special emphasis is placed on the fact that an entombed facility is not considered a waste disposal facility; rather it is a decommissioning end-state option. ISD does not eliminate the need for effective and careful management of contaminated materials and structures, nor does it serve to abandon contaminated buildings in place. Further, ISD is safe and cost-effective for a relatively small number of facilities across the DOE Complex. This paper explores the current programmatic considerations and technical aspects of the ISD process and discuss the measures taken to ensure that an 'entombed' facility is safe for both site workers and the general population. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

TRISO Fuel for High-Temperature Passively-Safe Nuclear Reactors

The poster entitled "TRISO Fuel for High-Temperature Passively-Safe Nuclear Reactors" presents reasons why TRISO fuel is a safe nuclear fuel. The poster contains four blocks: Multiple barriers to fission product release, Thermal stability, Chemical compatibility and Safety and Performance. Each block present information on the TRISO fuel in terms of the mechanical, chemical and thermal properties. In summary the safety and performance of the TRISO fuel based on the experimental results is shown.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Safe passage of American Eels through a novel hydropower turbine

Abstract Objective Study the effects of downstream passage through a novel turbine designed for fish safety, the Restoration Hydro Turbine (RHT), on American Eels Anguilla rostrata in a recirculating turbine test facility. Methods A 55‐cm‐diameter RHT was operated under 10 m of hydraulic head and 667 revolutions/min. In total, 131 eels were passed through the turbine and 43 eels were used as experimental controls (length = 33.9–65.5 cm). High‐speed video of passage through the runner region was captured for 89% of turbine‐passed eels, and injury and behavioral effects were recorded immediately before and after passage, as well as after a 48‐h holding period. A subset of 37 eels was additionally examined with X‐ray imaging for internal injuries. Result The 48‐h survival rate for both treatment and control groups was 100%, with no major internal or external injuries present after the holding period. Conclusion This is a substantial improvement over eel survival rates through conventional Kaplan and Francis turbines, which may range from 40% to 95%, and suggests that hydropower turbines designed for safe downstream fish passage could be implemented without major impacts to eels.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

A Data-Driven Framework for Power System Event Type Identification via Safe Semi-Supervised Techniques

Herein this paper investigates the use of phasor measurement unit (PMU) data with deep learning techniques to construct real-time event identification models for transmission networks. Increasing penetration of distributed energy resources represents a great opportunity to achieve decarbonization, as well as challenges in systematic situational awareness. When high-resolution PMU data and sufficient manually recorded event labels are available, the power event identification problem is defined as a statistical classification problem that can be solved by numerous cutting-edge classifiers. However, in real grids, collecting tremendous high-quality event labels is quite expensive. Utilities frequently have a large number of event records without in-depth details (i.e., unlabeled events). To bridge this gap, we propose a novel semi-supervised learning-based method to improve the performance of event classifiers trained with a limited number of labeled events by exploiting the information from massive unlabeled events. In other words, compared to existing data-driven methods, our method requires only a small portion of labeled data to achieve a similar level of accuracy. Meanwhile, this work discusses and addresses the performance degradation caused by class distribution mismatch between the training set and the real applications. Based on the proposed safe learning mechanism, our model does not directly use all unlabeled events during model training, but selectively uses them through a comprehensive evaluation procedure. Numerical studies on a sizable PMU dataset have been used to validate the performance of the proposed method.

42 ENGINEERING↗
DOE OSTI2025

Safe Reinforcement Learning-Based Transient Stability Control for Islanded Microgrids With Topology Reconfiguration

This paper proposes a safe reinforcement learning (RL)-based transient stability emergency control (TSEC) method for islanded microgrids. RL requires extensive interaction with the environment to learn control strategies, hence, a data-driven approach is used as a substitute for time-consuming time-domain simulation calculations. Deep sigma point processes (DSPP), which is a Gaussian process model, is utilized to predict the normal distribution of transient stability of microgrids and to construct a transient stability chance constraint. Reward-constrained policy optimization (RCPO) can simultaneously achieve objective prediction, policy learning, and constraint cost coefficient update across multiple timescales. RCPO interacts with the DSPP-based microgrid environment through a multi-process parallel manner, greatly increasing the training speed. Case studies on a real islanded microgrid demonstrate that the proposed method can efficiently and quickly obtain the optimal emergency control strategy while adhering to all hard constraints.

14 SOLAR ENERGY↗
NASA NTRS2001

Passive imaging based hazard avoidance for spacecraft safe landing

In this paper, a new and fast passive sensing based hazard avoidance approach for spacecraft safe landing is suggested. This approach contains two important algorithms: a texture based landing site selection algorithm and a landing site slope estimation algorithm.

spacecraft safe landing passive imaging homography↗
NASA NTRS1995

(abstract) The Design of a Benign Fail-safe Mechanism Using a Low-melting-point Metal Alloy Coupler

Because the alpha proton X ray spectrometer (APXS) sensor head on the Mars Pathfinder rover, Sojourner, is placed on Martian soil by the deployment mechanism (ADM), the rover would be crippled if the actuator fails when the mechanism is in its deployed position, as rover ground clearance is then reduced to zero. This paper describes the unique fail-safe mounted on the ADM, especially the use of a low-temperature-melting alloy as a coupler device. The final form of the design is a low-melting-point metal pellet coupler, made from Cerrobend, in parallel with a Negator spring pack. In its solid state, the metal rigidly connects the driver (the actuator) and the driven part (the mechanism). When commanded, a strip heater wrapped around the coupler melts the metal pellet (at 60(deg)C), allowing the driven part to turn independent of the driver. The Negator spring retracts the mechanism to its fully stowed position. This concept meets all the design criteria, and provides an added benefit. When the metal hardens the coupler once again rigidly connects the actuator and the mechanism. The concept presented here can easily be applied to other applications. Anywhere release devices are needed, low-melting-point couplers can be considered. The issues to be concerned with are thermal isolation, proper setting of the parts before actuation, and possible outgassing concerns. However, when these issues are overcome, the resulting release mechanism can promise to be the most light, simple, power conserving alternative available.

low-melting-point alloys couplers Negator springs ↗
NASA NTRS2005

A novel tiered sensor fusion approach for terrain characterization and safe landing assessment

This paper presents a novel tiered sensor fusion methodology for real-time terrain safety assessment. A combination of active and passive sensors, specifically, radar, lidar, and camera, operate in three tiers according to their inherent ranges of operation. Low-level terrain features (e.g. slope, roughness) and high-level terrain features (e.g. hills, craters) are integrated using principles of reasoning under uncertainty. Three methodologies are used to infer landing safety: Fuzzy Reasoning, Probabilistic Reasoning, and Evidential Reasoning. The safe landing predictions from the three fusion engines are consolidated in a subsequent decision fusion stage aimed at combining the strengths of each fusion methodology. Results from simulated spacecraft descents are presented and discussed.

fuzzy reasoning↗
NASA NTRS2006

Passive imaging based multi-cue hazard detection spacecraft safe landing

Accurate assessment of potentially damaging ground hazards during the spacecraft EDL (Entry, Descent and Landing) phase is crucial to insure a high probability of safe landing. A lander that encounters a large rock, falls off a cliff, or tips over on a steep slope can sustain mission ending damage. Guided entry is expected to shrink landing ellipses from 100-300 km to -10 km radius for the second generation landers as early as 2009. Regardless of size and location, however, landing ellipses will almost always contain hazards such as craters, discontinuities, steep slopes, and large rocks. It is estimated that an MSL (Mars Science Laboratory)-sized lander should detect and avoid 16- 150m diameter craters, vertical drops similar to the edges of 16m or 3.75m diameter crater, for high and low altitude HAD (Hazard Detection and Avoidance) respectively. It should also be able to detect slopes 20' or steeper, and rocks 0.75m or taller. In this paper we will present a passive imaging based, multi-cue hazard detection and avoidance (HDA) system suitable for Martian and other lander missions. This is the first passively imaged HDA system that seamlessly integrates multiple algorithm-crater detection, slope estimation, rock detection and texture analysis, and multicues- crater morphology, rock distribution, to detect these hazards in real time.

hazard detection↗
NASA NTRS2005

Safe Agents in Space: Preventing and Responding to Anomalies in the Autonomous Sciencecraft Experiment

This paper describes the design of the Autonomous Sciencecraft Experiment, a software agent that has been running on-board the EO-I spacecraft since 2003. The agent recognizes science events, retargets the spacecraft to respond to the science events, and reduces data downlink to only the highest value science data. The autonomous science agent was designed using a layered architectural approach with specific redundant safeguards to reduce the risk of an agent malfUnction to the EO-I spacecraft. The agent was designed to be "safe" by first preventing anomalies, then by automatically detecting and responding to them when possible. This paper describes elements of the design that increase the safety of the agent, the anomalies that occurred during the experiment, and how the agent responded to these anomalies.

autonomous science agent↗
DOE OSTI2016

A Stabilized, Intrinsically Safe, 10% Efficient, Solar-Driven Water-Splitting Cell Incorporating Earth-Abundant Electrocatalysts with Steady-State pH Gradients and Product Separation Enabled by a Bipolar Membrane

An efficient, stable, and intrinsically safe solar water-splitting device is illustrated using a III–V tandem junction photoanode, an acid-stable, earth-abundant hydrogen evolution catalyst, and a bipolar membrane. The integrated photoelectrochemical cell operates under a steady-state pH gradient and achieves ≈10% solar-to-hydrogen conversion efficiency, >100 h of stability in a large (>1 cm2) photoactive area in relation to most previous researches.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Machine‐learning‐based construction of barrier functions and models for safe model predictive control

Abstract In this paper, we propose a control Lyapunov‐barrier function‐based model predictive control method utilizing a feed‐forward neural network specified control barrier function (CBF) and a recurrent neural network (RNN) predictive model to stabilize nonlinear processes with input constraints, and to guarantee that safety requirements are met for all times. The nonlinear system is first modeled using RNN techniques, and a CBF is characterized by constructing a feed‐forward neural network (FNN) model with unique structures and properties. The FNN model for the CBF is trained based on data samples collected from safe and unsafe operating regions, and the resulting FNN model is verified to demonstrate that the safety properties of the CBF are satisfied. Given sufficiently small bounded modeling errors for both the FNN and the RNN models, the proposed control system is able to guarantee closed‐loop stability while preventing the closed‐loop states from entering unsafe regions in state‐space under sample‐and‐hold control action implementation. We provide the theoretical analysis for bounded unsafe sets in state‐space, and demonstrate the effectiveness of the proposed control strategy using a nonlinear chemical process example with a bounded unsafe region.

Chen, Scarlett↗
DOE OSTI2022

Domain-Specific Type-Safe APIs for Hierarchical Scientific Data with Modern C++

General-purpose library application programming interfaces (APIs) for self-describing hierarchical scientific data storage, such as the HDF5 and NetCDF libraries, are traditionally of runtime nature. Runtime errors for entry existence and data types are typically caught later in the development process of higher-level application-specific APIs. In this paper, we propose exploiting modern C++ metaprogramming features to add compile-time type-safety to improve the interaction with a well-defined metadata-rich scientific schema in domain-specific hierarchical datasets. We tackle two aspects of common use: (i) direct data access, (ii) flexible “in-memory” index models for efficient search and data processing. The proposed APIs use C++17’s template type auto deduction features, C++11’s enum class for type-safety and C-style preprocessor macros for generative templated code. We showcase the pros and cons of our initial work on the standard NeXus schema used for annotating and storing experimental neutron scattering data at several facilities around the world on top of HDF5. Extendable compile-time type-safe APIs are a desirable feature that could be indexed by any modern integrated development environment (IDE). Hence, such APIs can help ease the learning curve for domain scientists using a less error-prone software interaction to enhance the findability of their data without resorting to a domain-specific language (DSL).

Godoy, William↗
DOE OSTI2024

Equivariant, safe and sensitive — graph networks for new physics

This study introduces a novel Graph Neural Network (GNN) architecture that leverages infrared and collinear (IRC) safety and equivariance to enhance the analysis of collider data for Beyond the Standard Model (BSM) discoveries. By integrating equivariance in the rapidity-azimuth plane with IRC-safe principles, our model significantly reduces computational overhead while ensuring theoretical consistency in identifying BSM scenarios amidst Quantum Chromodynamics backgrounds. The proposed GNN architecture demonstrates superior performance in tagging semi-visible jets, highlighting its potential as a robust tool for advancing BSM search strategies at high-energy colliders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Uterine Artery Embolization for Retained Products of Conception with Marked Vascularity: A Safe and Efficient First-Line Treatment

ObjectiveTo report our clinical practice regarding a case series of retained products of conception (RPOC) with marked vascularity (MV) managed with selective uterine artery embolization (UAE) as first-line treatment.MethodsThis was a monocentric, retrospective study of 31 consecutive cases of RPOC with MV diagnosed by Doppler ultrasound in the context of postpartum/postabortal bleeding. The primary outcome was the absence of rebleeding following embolization.ResultsRPOC with MV occurred after abortion in 27 out of 31 patients (87%). The time elapsed between delivery/abortion and UAE ranged from 1 to 210 days (mean 55.7 ± 45 days). Primary clinical success was achieved in 23 women (74.2%) following a single embolization. In total, 27 out of 31 women (87%) had been exclusively managed by UAE with conservative success. Although procedural success was achieved in this number, six women had a further procedure to evacuate RPOC despite procedural success. Large uterine arteriovenous (AV) shunts associated with RPOC were observed in five cases (16.1%), among which two were successfully treated after a single UAE and one after two UAEs, while hysterectomy was performed in the last two cases despite two and three UAE procedures respectively. RPOC was histologically proven in ten cases (32.2%) including four out of five cases of uterine AV shunt.ConclusionRPOC with MV can present with large uterine AV shunt, particularly in case of late management. Uterine artery embolization is an effective and safe first-line treatment, and should be evaluated for this indication in larger prospective trials.

62 RADIOLOGY AND NUCLEAR MEDICINE↗