Gaussian Processes for Surrogate Modeling of Discharged Fuel Nuclide Compositions

Several applications such as nuclear forensics, nuclear fuel cycle simulations and sensitivity analysis require methods to quickly compute spent fuel nuclide compositions for various irradiation histories. Traditionally, this has been done by interpolating between one-group cross-sections that have been pre-computed from nuclear reactor simulations for a grid of input parameters, using fits such as Cubic Spline. We propose the use of Gaussian Processes (GP) to create surrogate models, which not only provide nuclide compositions, but also the gradient and estimates of their prediction uncertainty. The former is useful for applications such as forward and inverse optimization problems, the latter for uncertainty quantification applications. For this purpose, we compare GP-based surrogate model performance with Cubic- Spline-based interpolators based on infinite lattice simulations of a CANDU 6 nuclear reactor using the SERPENT 2 code, considering burnup and temperature as input parameters. Additionally, we compare the performance of various grid sampling schemes to quasirandom sampling based on the Sobol sequence. We find that GP-based models perform significantly better in predicting spent fuel compositions than Cubic-Spline-based models, though requiring longer computational runtime. Furthermore, we show that the predicted nuclide uncertainties are reasonably accurate. While in the studied two-dimensional case, grid- and quasirandom sampling provide similar results, quasirandom sampling will be a more effective strategy in higher dimensional cases.Comment: 18 pages, 4 figures, 7 tables. Submitted to Annals of Nuclear Energ

Simulation model to estimate emotions in collaborative networks

This work has been funded in part by the Center of Technology and Systems and the Portuguese FCT-PEST program UID/EEA/00066/2019 (Impactor project), and partly by the GloNet project funded by the European Commission.In recent years, the research on collaborative networks has been pointing to the need to put more emphasis on the social interactions of its participants, along with technical features, as a potential direction to finding solutions to prevent failures and potential conflicts. In this context, a modelling framework called Collaborative EMOtion modelling framework (C-EMO), conceived for appraising the collaborative network emotions that might be present in a collaborative networked environment, is presented, and an implementation approach, based on system dynamics and agentbased simulation modelling techniques, for estimating both the collaborative network emotional state and each member's emotions, is described. The work is divided in two parts: the first considers the design of the models and the second comprises the transformation of these conceptual models into a computer model, providing the proposed simulation model. In order to validate the simulation model, and taking into consideration the novelty of the research area, experiments are undertaken in different scenarios representing several aspects of a collaborative environment and a sensitivity analysis and discussion of the results is performed.publishe

Autonomous dynamic decision making in fuel cycle simulators using a game theoretic approach

A novel methodology for optimizing nuclear fuel cycle transitions that captures interactions between a policy maker and electric utility company is presented. The methodology is demonstrated using a two-person general-sum sequential game with uncertainty that is implemented using a nuclear fuel cycle simulator capable of calculating a material- and technology-constrained material balance, coupled to a multi-objective optimization solver. The solver explicitly treats uncertainties using a stochastic programming approach with chance nodes depicted as a Nature player who moves randomly. The methodology is demonstrated through a Transition Game that features tradeoffs between investments in competing reprocessing and waste disposal technologies, dynamic reactor deployment responses to resolutions in reactor capital cost uncertainty, and the influence of capital subsidies on the future nuclear technology mix. Each player in the game uses a unique set of decision criteria to identify optimal near-term hedging strategies that consider all of Nature’s possible moves as well as the other player’s available decisions. These hedging strategies balance the exchange between the risk of immediate action and delay and maintain flexibility to allow for intelligent recourse decisions once uncertainties are resolved. Results from the Transition Game indicate that early transition to high-temperature gas-cooled reactors is preferred, with the option to abandon the transition following a learning period if capital costs are unfavorable. Under these conditions, transition to used fuel recycling in sodium-cooled fast reactors may be spurred by policy incentives under some certain decision criteria weightings. Otherwise, operating with a baseline set of decision criteria weightings, transition to a closed fuel is never observed when players hedge optimally against Nature’s moves. It is only when players have perfect information regarding Nature’s future moves will transition to a closed fuel be observed.Mechanical Engineerin

Automated Problem-Specific Nuclide-Transition Selection for Reduced Order Modeling

A method for automated library reduction for the nuclide generation code Origen was developed for increased computational efficiency. The requirement for a reduced burnup chain micro-depletion code has been identified in many code frameworks in fuel cycles, neutronics, and nonproliferation where the increased accuracy of a micro-depletion code with hundreds, if not thousands, of nuclides is needed. These large library inventories result in relatively large memory requirements and runtimes that become burdensome within codes that require many depletion zones and/or depletion substeps per time step. However, the tracked nuclides do not equally contribute to the problem, and therefore a subset of the total nuclides can be removed from the system with little loss of accuracy. To do this in a generalized manner the application for the libraries need to be considered. To this end a number of metrics are available to measure library accuracy for a given problem, such as depletion inventory, total activity, gamma dose, decay heat, and individual nuclide inventory. Using these metrics, and their sensitivities to nuclide inventories, it is possible to reduce Origen\u27s full inventory of thousands of nuclides to several hundred nuclides while only affecting the metric of interest by less than 1 pcm (per cent mille or 10^(-5)). The method for this problem specific reduction relies on maintaining the physical meaning of the transition system to the highest degree reasonable. This means maintaining the integrity of the subsystem in relation to its behavior within the full system. Though a number of methods to achieve this have been studied, with varying degrees of success, the most successful method is one that takes a layered approach. This method makes an estimate of the final system through the cutting planes method then makes successive corrections to that estimate in each layer to account for the physical behavior of truncating the transition system that is not present in standard system problems

C-EMO: A Modeling Framework for Collaborative Network Emotions

Recent research in the area of collaborative networks is focusing on the social and organizational complexity of collaboration environments as a way to prevent technological failures and consequently contribute for the collaborative network’s sustainability. One direction is moving towards the need to provide “human-tech” friendly systems with cognitive models of human factors such as stress, emotion, trust, leadership, expertise or decision-making ability. In this context, an emotion-based system is being proposed with this thesis in order to bring another approach to avoid collaboration network’s failures and help in the management of conflicts. This approach, which is expected to improve the performance of existing CNs, adopts some of the models developed in the human psychology, sociology and affective computing areas. The underlying idea is to “borrow” the concept of human-emotion and apply it into the context of CNs, giving the CN players the ability to “feel emotions”. Therefore, this thesis contributes with a modeling framework that conceptualizes the notion of “emotion” in CNs and a methodology approach based on system dynamics and agent-based techniques that estimates the CN player’s “emotional states” giving support to decision-making processes. Aiming at demonstrating the appropriateness of the proposed framework a simulation prototype was implemented and a validation approach was proposed consisting of simulation of scenarios, qualitative assessment and validation by research community peers.Recentemente a área de investigação das redes colaborativas tem vindo a debruçar-se na complexidade social e organizacional em ambientes colaborativos e como pode ser usada para prevenir falhas tecnológicas e consequentemente contribuir para redes colaborativas sustentáveis. Uma das direcções de estudo assenta na necessidade de fornecer sistemas amigáveis “humano-tecnológicos” com modelos cognitivos de factores humanos como o stress, emoção, confiança, liderança ou capacidade de tomada de decisão. É neste contexto que esta tese propõe um sistema baseado em emoções com o objectivo de oferecer outra aproximação para a gestão de conflitos e falhas da rede de colaboração. Esta abordagem, que pressupõe melhorar o desempenho das redes existentes, adopta alguns dos modelos desenvolvidos nas áreas da psicologia humana, sociologia e affective computing. A ideia que está subjacente é a de “pedir emprestado” o conceito de emoção humana e aplicá-lo no contexto das redes colaborativas, dando aos seus intervenientes a capacidade de “sentir emoções”. Assim, esta tese contribui com uma framework de modelação que conceptualiza a noção de “emoção” em redes colaborativas e com uma aproximação de metodologia sustentada em sistemas dinâmicos e baseada em agentes que estimam os “estados emocionais” dos participantes e da própria rede colaborativa. De forma a demonstrar o nível de adequabilidade da framework de modelação proposta, foi implementado um protótipo de simulação e foi proposta uma abordagem de validação consistindo em simulação de cenários, avaliação qualitativa e validação pelos pares da comunidade científica

Assessing vulnerability and modelling assistance: using demographic indicators of vulnerability and agent-based modelling to explore emergency flooding relief response

Flooding is a significant concern for much of the UK and is recognised as a primary threat by most local councils. Those in society most often deemed vulnerable: the elderly, poor or sick, for example, often see their level of vulnerability increase during hazard events. A greater knowledge of the spatial distribution of vulnerability within communities is key to understanding how a population may be impacted by a hazard event. Vulnerability indices are regularly used – in conjunction with needs assessments and on-the-ground research – to target service provision and justify resource allocation. Past work on measuring and mapping vulnerability has been limited by a focus on income-related indicators, a lack of consideration of accessibility, and the reliance on proprietary data. The Open Source Vulnerability Index (OSVI) encompasses an extensive range of vulnerability indicators supported by the wider literature and expert validation and provides data at a sufficiently fine resolution that can identify vulnerable populations. Findings of the OSVI demonstrate the potential cascading impact of a flood hazard as it impacts an already vulnerable population: exacerbating pre-existing vulnerabilities, limiting capabilities and restricting accessibility and access to key services. The OSVI feeds into an agent-based model (ABM) that explores the capacity of the British Red Cross (BRC) to distribute relief during flood emergencies using strategies based upon the OSVI. A participatory modelling approach was utilised whereby the BRC were included in all aspects of the model development. The major contribution of this work is the novel synthesis of demographics analysis, vulnerability mapping and geospatial simulation. The project contributes to the growing understanding of vulnerability and response management within the NGO sector. It is hoped that the index and model produced will allow responder organisations to run simulations of similar emergency events and adjust strategic response plans accordingly

ESARDA 39th Annual Meeting: 2017 Symposium

The 39th ESARDA symposium on Safeguards and Nuclear Non-Proliferation was held in Düsseldorf, Germany from 16-18 May, 2017. The Symposium has been preceded by meetings of the ESARDA Working Groups on 15 May 2017. The event has once again been an opportunity for research organisations, safeguards authorities and nuclear plant operators to exchange information on new aspects of international safeguards and non-proliferation, as well as recent developments in nuclear safeguards and non-proliferation related research activities and their implications for the safeguards community.JRC.G.II.7-Nuclear securit