Uncertainty Quantification and Predictive Computational Science


Book Description

This textbook teaches the essential background and skills for understanding and quantifying uncertainties in a computational simulation, and for predicting the behavior of a system under those uncertainties. It addresses a critical knowledge gap in the widespread adoption of simulation in high-consequence decision-making throughout the engineering and physical sciences. Constructing sophisticated techniques for prediction from basic building blocks, the book first reviews the fundamentals that underpin later topics of the book including probability, sampling, and Bayesian statistics. Part II focuses on applying Local Sensitivity Analysis to apportion uncertainty in the model outputs to sources of uncertainty in its inputs. Part III demonstrates techniques for quantifying the impact of parametric uncertainties on a problem, specifically how input uncertainties affect outputs. The final section covers techniques for applying uncertainty quantification to make predictions under uncertainty, including treatment of epistemic uncertainties. It presents the theory and practice of predicting the behavior of a system based on the aggregation of data from simulation, theory, and experiment. The text focuses on simulations based on the solution of systems of partial differential equations and includes in-depth coverage of Monte Carlo methods, basic design of computer experiments, as well as regularized statistical techniques. Code references, in python, appear throughout the text and online as executable code, enabling readers to perform the analysis under discussion. Worked examples from realistic, model problems help readers understand the mechanics of applying the methods. Each chapter ends with several assignable problems. Uncertainty Quantification and Predictive Computational Science fills the growing need for a classroom text for senior undergraduate and early-career graduate students in the engineering and physical sciences and supports independent study by researchers and professionals who must include uncertainty quantification and predictive science in the simulations they develop and/or perform.







Verification, Validation and Uncertainty Quantification of Multi-Physics Modeling of Nuclear Reactors


Book Description

Verification, Validation and Uncertainty Quantification in Multi-Physics Modeling of Nuclear Reactors is a key reference for those tasked with ensuring the credibility and reliability of engineering models and simulations for the nuclear industry and nuclear energy research. Sections discuss simulation challenges and revise key definitions, concepts and terminology. Chapters cover solution verification, the frontier discipline of multi-physics coupling verification, model validation and its applications to single and multi-scale models, and uncertainty quantification. This essential guide will greatly assist engineers, scientists, regulators and students in applying rigorous verification, validation and uncertainty quantification methodologies to the M&S tools used in the industry. The book contains a strong focus on the verification and validation procedures required for the emerging multi-physics M&S tools that have great potential for use in the licensing of new reactors, as well as for power uprating and life extensions of operating reactors. Uniquely--and crucially for nuclear engineers--demonstrates the application of verification, validation and uncertainty methodologies to the modeling and simulation (M&S) of nuclear reactors Equips the reader to develop a rigorously defensible validation process irrespective of the particular M&S tool used Brings the audience up-to-speed on validation methods for traditional M&S tools Extends the discussion to the emerging area of validation of multi-physics and multi-scale nuclear reactor simulations




Quantifying Uncertainty in Nuclear Analytical Measurements


Book Description

Dedicated specifically to nuclear analytical techniques, this publication is intended to assist scientists using alpha, beta and gamma spectrometries, neutron activation and XRF analyses, and other nuclear analytical methods, in assessing and quantifying the sources of uncertainty in their daily measurements.




Evaluation of Quantification of Margins and Uncertainties Methodology for Assessing and Certifying the Reliability of the Nuclear Stockpile


Book Description

Maintaining the capabilities of the nuclear weapons stockpile and performing the annual assessment for the stockpile's certification involves a wide range of processes, technologies, and expertise. An important and valuable framework helping to link those components is the quantification of margins and uncertainties (QMU) methodology. In this book, the National Research Council evaluates: how the national security labs were using QMU, including any significant differences among the three labs its use in the annual assessment whether the applications of QMU to assess the proposed reliable replacement warhead (RRW) could reduce the likelihood of resuming underground nuclear testing This book presents an assessment of each of these issues and includes findings and recommendations to help guide laboratory and NNSA implementation and development of the QMU framework. It also serves as a guide for congressional oversight of those activities.







Uncertainty Quantification for Nuclear Density Functional Theory and Information Content of New Measurements


Book Description

Statistical tools of uncertainty quantification can be used to assess the information content of measured observables with respect to present-day theoretical models, to estimate model errors and thereby improve predictive capability, to extrapolate beyond the regions reached by experiment, and to provide meaningful input to applications and planned measurements. To showcase new opportunities offered by such tools, we make a rigorous analysis of theoretical statistical uncertainties in nuclear density functional theory using Bayesian inference methods. By considering the recent mass measurements from the Canadian Penning Trap at Argonne National Laboratory, we demonstrate how the Bayesian analysis and a direct least-squares optimization, combined with high-performance computing, can be used to assess the information content of the new data with respect to a model based on the Skyrme energy density functional approach. Employing the posterior probability distribution computed with a Gaussian process emulator, we apply the Bayesian framework to propagate theoretical statistical uncertainties in predictions of nuclear masses, two-neutron dripline, and fission barriers. Overall, we find that the new mass measurements do not impose a constraint that is strong enough to lead to significant changes in the model parameters. As a result, the example discussed in this study sets the stage for quantifying and maximizing the impact of new measurements with respect to current modeling and guiding future experimental efforts, thus enhancing the experiment-theory cycle in the scientific method.







Multiscale and Multiphysics Modeling of Nuclear Facilities with Coupled Codes and its Uncertainty Quantification and Sensitivity Analysis


Book Description

In this book, the author provides a deep study into multiscale and multiphysics modeling of nuclear facilities, underscoring the critical role of uncertainty quantification and sensitivity analysis to ensure the confidence in the numerical results and to identify the system characteristics. Through an in-depth study of the liquid metal cooling system from the TALL-3D loop to the SMDFR core, the research highlights the natural circulation instability, strong coupling effects, perturbation tolerance, and system stability. The culmination of the research is the formulation of an optimized uncertainty-based control scheme, demonstrating its versatility beyond the nuclear domain to other energy sectors. This groundbreaking work not only advances the comprehension and utilization of coupling schemes and uncertainty methodologies in nuclear system modeling but also adeptly bridges the theoretical constructs with tangible application, positioning itself as an indispensable resource for design, safety analysis, and advanced numerical modeling in the broader energy sector.