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At least 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

The quasi-equilibrium framework revisited: analyzing long-term CO 2 enrichment responses in plant–soil models

Abstract. Elevated carbon dioxide ( CO 2 ) can increase plant growth, but themagnitude of this CO 2 fertilization effect is modified by soilnutrient availability. Predicting how nutrient availability affects plantresponses to elevated CO 2 is a key consideration for ecosystemmodels, and many modeling groups have moved to, or are moving towards,incorporating nutrient limitation in their models. The choice of assumptionsto represent nutrient cycling processes has a major impact on modelpredictions, but it can be difficult to attribute outcomes to specificassumptions in complex ecosystem simulation models. Here we revisit thequasi-equilibrium analytical framework introduced by Comins andMcMurtrie (1993) and explore the consequences of specific model assumptionsfor ecosystem net primary productivity (NPP). We review the literature applying this framework to plant–soilmodels and then analyze the effect of several new assumptions on predictedplant responses to elevated CO 2 . Examination of alternativeassumptions for plant nitrogen uptake showed that a linear function of themineral nitrogen pool or a linear function of the mineral nitrogen pool withan additional saturating function of root biomass yield similar CO 2 responses at longer timescales ( >5 years), suggesting that the addedcomplexity may not be needed when these are the timescales of interest. Incontrast, a saturating function of the mineral nitrogen pool with lineardependency on root biomass yields no soil nutrient feedback on thevery-long-term ( >500 years), near-equilibrium timescale, meaning that oneshould expect the model to predict a full CO 2 fertilization effecton production. Secondly, we show that incorporating a priming effect on slowsoil organic matter decomposition attenuates the nutrient feedback effect onproduction, leading to a strong medium-term (5–50 years) CO 2 response. Models incorporating this priming effect should thus predict astrong and persistent CO 2 fertilization effect over time. Thirdly,we demonstrate that using a “potential NPP” approach to represent nutrientlimitation of growth yields a relatively small CO 2 fertilizationeffect across all timescales. Overall, our results highlight thefact that the quasi-equilibriumanalytical framework is effective for evaluating both the consequences andmechanisms through which different model assumptions affect predictions. Tohelp constrain predictions of the future terrestrial carbon sink, werecommend the use of this framework to analyze likely outcomes of new modelassumptions before introducing them to complex model structures.

58 GEOSCIENCES↗
DOE OSTI2025

High-Resolution Model Intercomparison Project phase 2 (HighResMIP2) towards CMIP7

Abstract. Robust projections and predictions of climate variability and change, particularly at regional scales, rely on the driving processes being represented with fidelity in model simulations. Consequently, the role of enhanced horizontal resolution in improved process representation in all components of the climate system continues to be of great interest. Recent simulations suggest the possibility of significant changes in both large-scale aspects of the ocean and atmospheric circulations and in the regional responses to climate change, as well as improvements in representations of small-scale processes and extremes, when resolution is enhanced. The first phase of the High-Resolution Model Intercomparison Project (HighResMIP1) was successful at producing a baseline multi-model assessment of global simulations with model grid spacings of 25–50 km in the atmosphere and 10–25 km in the ocean, a significant increase when compared to models with standard resolutions on the order of 1° that are typically used as part of the Coupled Model Intercomparison Project (CMIP) experiments. In addition to over 250 peer-reviewed manuscripts using the published HighResMIP1 datasets, the results were widely cited in the Intergovernmental Panel on Climate Change report and were the basis of a variety of derived datasets, including tracked cyclones (both tropical and extratropical), river discharge, storm surge, and impact studies. There were also suggestions from the few ocean eddy-rich coupled simulations that aspects of climate variability and change might be significantly influenced by improved process representation in such models. The compromises that HighResMIP1 made should now be revisited, given the recent major advances in modelling and computing resources. Aspects that will be reconsidered include experimental design and simulation length, complexity, and resolution. In addition, larger ensemble sizes and a wider range of future scenarios would enhance the applicability of HighResMIP. Therefore, we propose the High-Resolution Model Intercomparison Project phase 2 (HighResMIP2) to improve and extend the previous work, to address new science questions, and to further advance our understanding of the role of horizontal resolution (and hence process representation) in state-of-the-art climate simulations. With further increases in high-performance computing resources and modelling advances, along with the ability to take full advantage of these computational resources, an enhanced investigation of the drivers and consequences of variability and change in both large- and synoptic-scale weather and climate is now possible. With the arrival of global cloud-resolving models (currently run for relatively short timescales), there is also an opportunity to improve links between such models and more traditional CMIP models, with HighResMIP providing a bridge to link understanding between these domains. HighResMIP also aims to link to other CMIP projects and international efforts such as the World Climate Research Program lighthouse activities and various digital twin initiatives. It also has the potential to be used as training and validation data for the fast-evolving machine learning climate models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6

Projections of future climate change play a fundamental role in improving understanding of the climate system as well as characterizing societal risks and response options. The Scenario Model Intercomparison Project (ScenarioMIP) is the primary activity within Phase 6 of the Coupled Model Intercomparison Project (CMIP6) that will provide multi-model climate projections based on alternative scenarios of future emissions and land use changes produced with integrated assessment models. Here, we describe ScenarioMIP's objectives, experimental design, and its relation to other activities within CMIP6. The ScenarioMIP design is one component of a larger scenario process that aims to facilitate a wide range of integrated studies across the climate science, integrated assessment modeling, and impacts, adaptation, and vulnerability communities, and will form an important part of the evidence base in the forthcoming Intergovernmental Panel on Climate Change (IPCC) assessments. Furthermore, it will provide the basis for investigating a number of targeted science and policy questions that are especially relevant to scenario-based analysis, including the role of specific forcings such as land use and aerosols, the effect of a peak and decline in forcing, the consequences of scenarios that limit warming to below 2°C, the relative contributions to uncertainty from scenarios, climate models, and internal variability, and long-term climate system outcomes beyond the 21st century. In order to serve this wide range of scientific communities and address these questions, a design has been identified consisting of eight alternative 21st century scenarios plus one large initial condition ensemble and a set of long-term extensions, divided into two tiers defined by relative priority. Some of these scenarios will also provide a basis for variants planned to be run in other CMIP6-Endorsed MIPs to investigate questions related to specific forcings. Harmonized, spatially explicit emissions and land use scenarios generated with integrated assessment models will be provided to participating climate modeling groups by late 2016, with the climate model simulations run within the 2017–2018 time frame, and output from the climate model projections made available and analyses performed over the 2018–2020 period.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Chasing the Future: How Will Ocean Change Affect Marine Life?

Understanding the potential consequences of rising ocean carbon levels and related ocean changes for marine life and ecosystems is a high priority for the ocean research community and marine resource management. In the mid-1990s, two geoengineering proposals to mitigate global warming by carbon sequestration in the deep sea led to research measuring the effects of increased deep ocean carbon dioxide levels on marine animals. A few years later, ocean acidification and its effects on marine life became an international research priority. Here we provide an overview of several technical developments by scientists and engineers at the Monterey Bay Aquarium Research Institute (MBARI) that have enabled and enhanced deep-sea exploration and experiments to assess the effects of changing ocean conditions on benthic marine animals. Improvements in remotely operated vehicles (ROVs) have increased the efficiency of dive operations and enabled more complex measurements and experiments at great ocean depths. In situ respirometers and Free Ocean CO 2 Enrichment (FOCE) mesocosms have allowed measurement of physiological and behavioral responses of deep-sea animals to environmental change. A laboratory-based, gas-controlled aquarium system that regulates oxygen and pH in chilled waters was engineered to measure the physiological responses of deep-sea animals and biological communities to expected future environmental conditions. Recently, MBARI engineers and scientists developed an Upwelling Simulator, a lab-based aquarium control system that mimics ocean conditions during coastal upwelling. This system is programmable, allowing independent control of pH, oxygen, and temperature to enable experiments that examine the effects of present-day upwelling conditions, expected future conditions, or other changes in these environmental conditions. In sum, collaboration between the marine operations group, engineers, and scientists at MBARI has advanced methods to explore the ocean and understand the consequences of ocean change for marine organisms and ecosystems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Explainable Machine Learning for Functional Data

Black-box machine learning models are recognized as useful tools for prediction applications, but the algorithmic complexity of some models causes interpretation challenges. Explainability methods have been proposed to provide insight into these models, but there is little research focused on supervised modeling with functional data inputs. We argue that, especially in applications of high consequence, it is important to explicitly model the functional dependence in a black-box analysis to not obscure or misrepresent patterns in explanations. As such, we propose the V ariable importance E xplainable E lastic S hape A nalysis (VEESA) pipeline for training supervised machine learning models with functional inputs. The pipeline is an analysis process that includes the data preprocessing, modeling, and post-hoc explanations. The preprocessing is done using elastic functional principal components analysis, which accounts for vertical and horizontal variability in functional data and, ultimately, allows for explanations in the original data space that identify the important functional variability without bias due to correlated variables. Here, we demonstrate the pipeline on two high-consequence applications: explosives classification for national security and inkjet printer identification in forensic science. The applications exhibit the VEESA pipeline’s ability to provide an understanding of the characteristics of the functional data useful for prediction. Code for implementing the pipeline is available in the veesa R package (and supplemental python code).

Elastic Shape Analysis↗
DOE OSTI2022

Interaction of radio frequency waves with cylindrical density filaments -- scattering and radiation pressure

The propagation of radio-frequency (RF) waves in tokamaks can be affected by filamentary structures, or blobs, that are present in the edge plasma and the scrape-off layer. The difference in the permittivity between the surrounding plasma and interior of a filament leads to reflection, refraction and diffraction of the waves. This, in turn, can affect the power flow into the core of the plasma and reduce the efficiency of heating and/or current generation. The scattering of RF waves, lower hybrid, helicon and ion cyclotron waves, by a single cylindrical filament, embedded in a background plasma, is studied using a full-wave analytical theory developed previously (Ram & Hizanidis, Phys. Plasmas, vol. 23, 2016, 022504). The theory assumes that the plasma in and around a filament is homogeneous and cold. A detailed scattering analysis reveals a variety of common features that exist among the three distinctly different RF waves. These common attributes can be inferred intuitively based on an examination of the cold plasma dispersion relation. The physical intuition is a useful step to understanding experimental observations on scattering, as well as results from simulations that include general forms of edge plasma turbulence. While a filament can affect the propagation of RF waves, the radiation force exerted by the waves can influence the filament. The force on a filament is determined using the Maxwell stress tensor. In 1905, Poynting was the first to evaluate and measure the radiation force on an interface separating two different dielectric media (Poynting, London Edinburgh Dublin Philos. Mag. J. Sci., vol. 9, 1905, pp. 393–406). For ordinary light propagating in vacuum and incident on a glass surface, Poynting noted that the surface is ‘pulled’ towards the vacuum. In a magnetized cold plasma, there are two independent wave modes. Even if only one of these modes is excited by an RF antenna, a filament will couple power to the other mode: a consequence of electromagnetic boundary conditions. This facet of scattering has consequences on the radiation force that go beyond Poynting's seminal contribution. The direction of the force depends on the polarization of the incident wave and on the mode structure of the waves inside and in the vicinity of a filament. It can either pull the filament toward the RF source or push it away. For slow lower hybrid waves, filaments with densities greater than the ambient density are pulled in, while filaments with lower densities are pushed out, thereby enhancing the density in front of the antenna. In the case of fast helicon and ion cyclotron waves, the direction of the force depends on the plasma and wave parameters; in particular, on the ambient density. The radiation force, in all three frequency ranges, is large enough to affect the motion of a filament and could be measured experimentally. This also suggests the possibility of modifying the edge turbulence using RF waves.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Measuring surface albedo for various crops

Surface albedo can affect the energy budget and subsequently cause localized warming or cooling of the climate. When we convert a substantial portion of lands to agriculture, land surface properties are consequently altered, including albedo. Through crop selection and management, one can increase crop albedo to obtain higher levels of localized cooling effects to mitigate global warming. Still, there is little understanding about how distinctive features of a cropping system may be responsible for elevated albedo and consequently for the cooling potential of cultivated lands. To address this pressing issue, we conducted seasonal measurements of surface reflectivity during five growing seasons on annual crops of corn-soybean–winter wheat

albedo↗
DOE OSTI2011

OVERVIEW OF THE COOPERATION BETWEEN THE CHERNOBYL CENTER'S INTERNATIONAL RADIOECOLOGY LABORATORY IN SLAVUTYCH, UKRAINE AND U.S. RESEARCH CENTERS BETWEEN 2000-2010

The International Radioecology Laboratory (IRL) located in Slavutych, Ukraine was created in 1999 under the initiative of the United States Government and the Government of Ukraine in the framework of international cooperation on evaluation and minimization of consequences of the Chernobyl nuclear power plant (ChNPP) accident. Since the time the IRL was founded, it has participated in a large number of projects, including the following: (1) study of radionuclide accumulation, distribution, and migration in components of various ecological systems of the Chernobyl Exclusion Zone (ChEZ); (2) radiation dose assessments; (3) study of the effects of radiation influence on biological systems; (4) expert analysis of isotopic and quantitative composition of radioactive contaminants; (5) development of new methods and technologies intended for radioecological research; (6) evaluation of future developments and pathways for potential remediation of the ChEZ areas; (7) assistance in provision of physical protection systems for ionizing irradiation sources at Ukrainian enterprises; (8) reviews of open Russian language publications on issues associated with consequences of the ChNPP accident, radioactive waste management, radioecological monitoring, and ChNPP decommissioning; (9) conduct of training courses on problems of radioecology, radiation safety, radioecological characterization of test sites and environmental media, and on research methods; (10) conduct of on-site scientific conferences and workshops on the ChEZ and radioecology problems; participation in off-site scientific conferences and meetings; and (11) preparation of scientific and popular science publications, and interactions with mass media representatives. This article provides a brief overview of the major achievements resulting from this cooperation between the IRL and U.S. research centers.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2010

Transportation scenarios for risk analysis.

Transportation risk, like any risk, is defined by the risk triplet: what can happen (the scenario), how likely it is (the probability), and the resulting consequences. This paper evaluates the development of transportation scenarios, the associated probabilities, and the consequences. The most likely radioactive materials transportation scenario is routine, incident-free transportation, which has a probability indistinguishable from unity. Accident scenarios in radioactive materials transportation are of three different types: accidents in which there is no impact on the radioactive cargo, accidents in which some gamma shielding may be lost but there is no release of radioactive material, and accident in which radioactive material may potentially be released. Accident frequencies, obtainable from recorded data validated by the U.S. Department of Transportation, are considered equivalent to accident probabilities in this study. Probabilities of different types of accidents are conditional probabilities, conditional on an accident occurring, and are developed from event trees. Development of all of these probabilities and the associated highway and rail accident event trees are discussed in this paper.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2010

Assessing the near-term risk of climate uncertainty : interdependencies among the U.S. States.

Policy makers will most likely need to make decisions about climate policy before climate scientists have resolved all relevant uncertainties about the impacts of climate change. This study demonstrates a risk-assessment methodology for evaluating uncertain future climatic conditions. We estimate the impacts from responses to climate change on U.S. state- and national-level economic activity from 2010 to 2050. To understand the implications of uncertainty on risk and to provide a near-term rationale for policy interventions to mitigate the course of climate change, we focus on precipitation, one of the most uncertain aspects of future climate change. We use results of the climate-model ensemble from the Intergovernmental Panel on Climate Change's (IPCC) Fourth Assessment Report (AR4) as a proxy for representing climate uncertainty over the next 40 years, map the simulated weather from the climate models hydrologically to the county level to determine the physical consequences on economic activity at the state level, and perform a detailed 70-industry analysis of economic impacts among the interacting lower-48 states. We determine the industry-level contribution to the gross domestic product and employment impacts at the state level, as well as interstate population migration, effects on personal income, and consequences for the U.S. trade balance. We show that the mean or average risk of damage to the U.S. economy from climate change, at the national level, is on the order of $1 trillion over the next 40 years, with losses in employment equivalent to nearly 7 million full-time jobs.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2011

Single Helix to Double Gyroid in Chiral Block Copolymers

An order-order phase transition of chiral block copolymers (BCPs*) from single helix to double gyroid (H* {yields} G) through a nucleation and growth process was demonstrated. The H* and G phases can be obtained by solution casting from fast and slow solvent evaporation, respectively, suggesting that the H* phase is a metastable phase. Consequently, the coexistence of H* and G phases can be found in the solution-cast samples from intermediate solvent evaporation. To truly examine the transition mechanism of the H* {yields} G, electron tomography was carried out to directly visualize the morphological evolution in real space, in particular, the transition zone at interface. Unlike the mechanisms for the transitions of block copolymers (BCPs) by considering the interdomain spacing matching, a significant mismatch in the lattices for the H* {yields} G was found. Consequently, the transition may require an adjustment on the geometric dimensions to justify corresponding lattice mismatch. As a result, the morphological observations from electron tomography offer new insights into BCP phase transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Alternative Approaches to Calculate Benefits of an Energy Imbalance Market With Wind and Solar Energy: Preprint

The anticipated increase in variable generation in the Western Interconnection over the next several years has raised concerns about how to maintain system balance, especially in smaller Balancing Authority Areas (BAAs). Given renewable portfolio standards in the West, it is possible that more than 50 gigawatts of wind capacity will be installed by 2020. Significant quantities of solar generationare likely to be added as well. The consequent increase in variability and uncertainty that must be managed by the conventional generation fleet and responsive loads has resulted in a proposal for an Energy Imbalance Market (EIM). This paper extends prior work to estimate the reserve requirements for regulation, spinning, and non-spinning reserves with and without the EIM. We also discussalternative approaches to allocating reserve requirements and show that some apparently attractive allocation methods have undesired consequences.

17 WIND ENERGY↗
DOE OSTI2012

Predictive Fallout Composition Modeling: Improvements and Applications of the Defense Land Fallout Interpretive Code

This paper outlines several improvements to the Particle Activity Module of the Defense Land Fallout Interpretive Code (DELFIC). The modeling of each phase of the fallout process is discussed within DELFIC to demonstrate the capabilities and limitations with the code for modeling and simulation. Expansion of the DELFIC isotopic library to include actinides and light elements is shown. Several key features of the new library are demonstrated, including compliance with ENDF/B-VII standards, augmentation of hardwired activated soil and actinide decay calculations with exact Bateman calculations, and full physical and chemical fractionation of all material inventories. Improvements to the radionuclide source term are demonstrated, including the ability to specify heterogeneous fission types and the ability to import source terms from irradiation calculations using the Oak Ridge Isotope Generation (ORIGEN) code. Additionally, the dose, kerma, and effective dose conversion factors are revised. Finally, the application of DELFIC for consequence management planning and forensic analysis is presented. For consequence management, DELFIC is shown to provide disaster recovery teams with simulations of real-time events, including the location, composition, time of arrival, activity rates, and dose rates of fallout, accounting for site-specific atmospheric effects. The results from DELFIC are also demonstrated for use by nuclear forensics teams to plan collection routes (including the determination of optimal collection locations), estimate dose rates to collectors, and anticipate the composition of material at collection sites. These capabilities give mission planners the ability to maximize their effectiveness in the field while minimizing risk to their collectors.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

Metrics for Assessment of Smart Grid Data Integrity Attacks

There is an emerging consensus that the nation’s electricity grid is vulnerable to cyber attacks. This vulnerability arises from the increasing reliance on using remote measurements, transmitting them over legacy data networks to system operators who make critical decisions based on available data. Data integrity attacks are a class of cyber attacks that involve a compromise of information that is processed by the grid operator. This information can include meter readings of injected power at remote generators, power flows on transmission lines, and relay states. These data integrity attacks have consequences only when the system operator responds to compromised data by redispatching generation under normal or contingency protocols. These consequences include (a) financial losses from sub-optimal economic dispatch to service loads, (b) robustness/resiliency losses from placing the grid at operating points that are at greater risk from contingencies, and (c) systemic losses resulting from cascading failures induced by poor operational choices. This paper is focused on understanding the connections between grid operational procedures and cyber attacks. We first offer two examples to illustrate how data integrity attacks can cause economic and physical damage by misleading operators into taking inappropriate decisions. We then focus on unobservable data integrity attacks involving power meter data. These are coordinated attacks where the compromised data are consistent with the physics of power flow, and are therefore passed by any bad data detection algorithm. We develop metrics to assess the economic impact of these attacks under re-dispatch decisions using optimal power flow methods. These metrics can be use to prioritize the adoption of appropriate countermeasures including PMU placement, encryption, hardware upgrades, and advance attack detection algorithms.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2012

U.S. Department of Energy Instrumentation and Controls Technology Research for Advanced Small Modular Reactors

Instrumentation, controls, and human-machine interfaces (ICHMI) are essential enabling technologies that strongly influence nuclear power plant performance and operational costs. The U.S. Department of Energy (DOE) has recognized that ICHMI research, development, and demonstration (RD&D) is needed to resolve the technical challenges that may compromise the effective and efficient utilization of modern ICHMI technology and consequently inhibit realization of the benefits offered by expanded utilization of nuclear power. Consequently, key DOE programs have substantial ICHMI RD&D elements to their respective research portfolio. This article describes current ICHMI research to support the development of advanced small modular reactors.

human-machine interface↗
DOE OSTI2013

Additional Studies of the Criticality Safety of Failed Used Nuclear Fuel

Commercial used nuclear fuel (UNF) in the United States is expected to remain in storage for periods potentially greater than 40 years. Extended storage (ES) time and irradiation to high-burnup values (>45 GWd/t) may increase the potential for fuel failure during normal and accident conditions involving storage and transportation. Fuel failure, depending on the severity, could result in changes to the geometric configuration of the fuel, which has safety and regulatory implications. The likelihood and extent of fuel reconfiguration and its impact on the safety of the UNF is not well understood. The objective of this work is to assess and quantify the impact of fuel reconfiguration due to fuel failure on criticality safety of UNF in storage and transportation casks. Criticality analyses are conducted considering representative UNF designs covering a range of enrichments and burnups in multiple cask systems. Prior work developed a set of failed fuel configuration categories and specific configurations were evaluated to understand trends and quantify the consequences of worst-case potential reconfiguration progressions. These results will be summarized here and indicate that the potential impacts on subcriticality can be rather significant for certain configurations (e.g., >20% keff). It can be concluded that the consequences of credible fuel failure configurations from ES or transportation following ES are manageable (e.g., <5% keff). The current work expands on these efforts and examines some modified scenarios and modified approaches to investigate the effectiveness of some techniques for reducing the calculated increase in keff. The areas included here are more realistic modeling of some assembly types and the effect of reconfiguration of some assemblies in the storage and transportation canister.

Marshall, William BJ J↗
DOE OSTI2011

Taking Risk Assessment and Management to the Next Level: Program-Level Risk Analysis to Enable Solid Decision-Making on Priorities and Funding

A multi-level (facility and programmatic) risk assessment was conducted for the facilities in the Nevada National Security Site (NNSS) Readiness in Technical Base and Facilities (RTBF) Program and results were included in a new Risk Management Plan (RMP), which was incorporated into the fiscal year (FY) 2010 Integrated Plans. Risks, risk events, probability, consequence(s), and mitigation strategies were identified and captured, for most scope areas (i.e., risk categories) during the facilitated risk workshops. Risk mitigations (i.e., efforts in addition to existing controls) were identified during the facilitated risk workshops when the risk event was identified. Risk mitigation strategies fell into two broad categories: threats or opportunities. Improvement projects were identified and linked to specific risks they mitigate, making the connection of risk reduction through investments for the annual Site Execution Plan. Due to the amount of that was collected, analysis to be performed, and reports to be generated, a Risk Assessment/ Management Tool (RAMtool) database was developed to analyze the risks in real-time, at multiple levels, which reinforced the site-level risk management process and procedures. The RAMtool database was developed and designed to assist in the capturing and analysis of the key elements of risk: probability, consequence, and impact. The RAMtool calculates the facility-level and programmatic-level risk factors to enable a side-by-side comparison to see where the facility manager and program manager should focus their risk reduction efforts and funding. This enables them to make solid decisions on priorities and funding to maximize the risk reduction. A more active risk management process was developed where risks and opportunities are actively managed, monitored, and controlled by each facility more aggressively and frequently. risk owners have the responsibility and accountability to manage their assigned risk in real-time, using the RAMtool database.

Nelson, J. G.↗
DOE OSTI2014

Risk Estimation Methodology for Launch Accidents.

As compact and light weight power sources with reliable, long lives, Radioisotope Power Systems (RPSs) have made space missions to explore the solar system possible. Due to the hazardous material that can be released during a launch accident, the potential health risk of an accident must be quantified, so that appropriate launch approval decisions can be made. One part of the risk estimation involves modeling the response of the RPS to potential accident environments. Due to the complexity of modeling the full RPS response deterministically on dynamic variables, the evaluation is performed in a stochastic manner with a Monte Carlo simulation. The potential consequences can be determined by modeling the transport of the hazardous material in the environment and in human biological pathways. The consequence analysis results are summed and weighted by appropriate likelihood values to give a collection of probabilistic results for the estimation of the potential health risk. This information is used to guide RPS designs, spacecraft designs, mission architecture, or launch procedures to potentially reduce the risk, as well as to inform decision makers of the potential health risks resulting from the use of RPSs for space missions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗