A Two-Step Approach to Uncertainty Quantification of Core Simulators

Yankov, A.; Collins, Benjamin; Klein, M.; Jessee, Matthew Anderson; Zwermann, W.; Velkov, K.; Pautz, Andreas; Downar, Thomas J.

doi:10.1155/2012/767096

Cited by 21 publications

(6 citation statements)

References 6 publications

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“…e one-step approach relies on the stochastic sampling method on both lattice and core levels and is named as such because it involves a one-to-one connection between lattice calculations to generate the few-group cross section library and the core calculation that read this library as input [13]. e two-step approach combines the stochastic sampling and deterministic methods.…”

Section: Core Physicsmentioning

confidence: 99%

Best-Estimate Plus Uncertainty Framework for Multiscale, Multiphysics Light Water Reactor Core Analysis

Hou

Avramova

Ivanov

2020

Science and Technology of Nuclear Installations

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Tremendous work has been done in the Light Water Reactor (LWR) Modelling and Simulation (M&S) uncertainty quantification (UQ) within the framework of the Organization for Economic Cooperation and Development (OECD)/Nuclear Energy Agency (NEA) LWR Uncertainty Analysis in Modelling (UAM) benchmark, which aims to investigate the uncertainty propagation in all M&S stages of the LWRs and to guide uncertainty and sensitivity analysis methodology development. The Best-Estimate Plus Uncertainty (BEPU) methodologies have been developed and implemented within the framework of the LWR UAM benchmark to provide a realistic predictive simulation capability without compromising the safety margins. This paper describes the current status of the methodological development, assessment, and integration of the BEPU methodology to facilitate the multiscale, multiphysics LWR core analysis. The comparative analysis of the results in the stand-alone multiscale neutronics phase (Phase I) is first reported for understanding the general trend of the uncertainty of core parameters due to the nuclear data uncertainty. It was found that the predicted uncertainty of the system eigenvalue is highly dependent on the choice of the covariance libraries used in the UQ process and is less sensitive to the solution method, nuclear data library, and UQ method. High-to-Low (Hi2Lo) model information approaches for multiscale M&S are introduced for the core single physics phase (Phase II). In this phase, the other physics (fuel and moderator), providing feedback to neutronics M&S in a LWR core, and time-dependent phenomena are considered. Phase II is focused on uncertainty propagation in single physics models which are components of the LWR core coupled multiphysics calculations. The paper discusses the link and interactions between Phase II to the multiphysics core and system phase (Phase III), that is, the link between uncertainty propagation in single physics on local scale and multiphysics uncertainty propagation on the core scale. Particularly, the consistency in uncertainty assessment between higher-fidelity models implemented in fuel performance codes and the rather simplified models implemented in thermal-hydraulics codes, to be used for coupling with neutronics in Phase III is presented. Similarly, the uncertainty quantification on thermal-hydraulic models is established on a relatively small scale, while these results will be used in Phase III at the core scale, sometimes with different codes or models. Lastly, the up-to-date UQ method for the coupled multiphysics core calculation in Phase III is presented, focusing on the core equilibrium cycle depletion calculation with associated uncertainties.

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Section: Core Physicsmentioning

confidence: 99%

Best-Estimate Plus Uncertainty Framework for Multiscale, Multiphysics Light Water Reactor Core Analysis

Hou

Avramova

Ivanov

2020

Science and Technology of Nuclear Installations

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“…Recent works show that 1000 calculations are enough to permit optimal convergence of the statistical moments of significance for any given response function [6][7][8].…”

Section: Cross Section Covariance Librarymentioning

confidence: 99%

Uncertainty Propagation for LWR Burnup Benchmark Using Sampling Based Code Scale/Sampler

Campolina

Frýbort

2018

APP

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Abstract.Sampling based method is adopted in many fields of engineering and it is currently used to propagate uncertainties from physical parameters and from nuclear data, to integral indicators of nuclear systems. The total uncertainty associated with a model simulation is of major importance for safety analysis and to guide vendors about acceptable tolerance limits for nuclear installations parts. This work presents some calculations to propagate uncertainties for a nuclear reactor fuel element modeled in SCALE/TRITON, using the sampling tool SCALE/SAMPLER. Results showed that the influence of input uncertainties on k inf is more pronounced in the fresh core other than the depleted core and the contribution from studied manufacturing uncertainties is smaller than the contribution of nuclear data uncertainties.

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“…This is partly possible due to the UAM-OECD benchmark for U&S analysis in LWR. Yankov et al 2012 performs a UQ comparing TSUNAMI and SAMPLER for the TMI model in the OECD/NEA benchmark framework. SCALE6.2.1 version and its module SAMPLER with TRITON/NEWT 2D lattice code are used in this thesis for nuclear data uncertainty propagation purposes.…”

Section: Scale621/samplermentioning

confidence: 99%

“…All uncertainty methods have two limitations, (i) the needed resources may be prohibitive, and (ii) the results may change a lot among uncertainty methods. See Yankov et al 2012, where two different UQ methods are used in a Pressurized Water Reactor (PWR) with some discrepancies in the relative power distribution.…”

Section: Introduction What Is This and What Do We Want?mentioning

confidence: 99%

Uncertainty Quantification and Sensitivity Analysis for Cross Sections and Thermohydraulic Parameters in Lattice and Core Physics Codes. Methodology for Cross Section Library Generation and Application to PWR and BWR.

Melia¹

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"There are three certainties in life: death, taxes and bugs in computer codes." Modified quote of Benjamin Franklin"Hi ha tres certeses en la vida: la mort, impostos i errades en programes informàtics."Modificació de la cita de Benjamin Franklin "Hay tres certezas en la vida: la muerte, impuestos y fallos en programas informáticos." Modificación de la cita de Benjamin Franklin AbstractThis PhD study, developed at Universitat Politècnica de València (UPV), aims to cover the first phase of the benchmark released by the expert group on Uncertainty Analysis in Modeling (UAM-LWR). The main contribution to the benchmark, made by the thesis' author, is the development of a Matlab program requested by the benchmark organizers. This is used to generate neutronic libraries to distribute among the benchmark participants. The UAM benchmark pretends to determine the uncertainty introduced by coupled multi-physics and multi-scale LWR analysis codes. The benchmark is subdivided into three phases:1. Neutronic phase: obtain collapsed and homogenized problem-dependent cross sections and criticality analyses.2. Core phase: standalone thermohydraulic and neutronic codes.3. System phase: coupled thermohydraulic and neutronic code.In this thesis the objectives of the first phase are covered. Specifically, a methodology is developed to propagate the uncertainty of cross sections and other neutronic parameters through a lattice physics code and core simulator. An Uncertainty and Sensitivity (U&S) analysis is performed over the cross sections contained in the ENDF/B-VII nuclear library. Their uncertainty is propagated through the lattice physics code SCALE6.2.1, including the collapse and homogenization phase, up to the generation of problem-dependent neutronic libraries. Afterward, the uncertainty contained in these libraries can be further propagated through a core simulator, in this study PARCSv3.2. The module SAMPLER -available in the latest release of SCALEand DAKOTA 6.3 statistical tool are used for the U&S analysis. As a part of this process, a methodology to obtain neutronic libraries in NEMTAB format -to be used in a core simulator-is also developed. A code-to-code comparison with CASMO-4 is used as a verification. The whole methodology is tested using a Boiling Water Reactor (BWR) reactor type. Nevertheless, there is not any concern or limitation regarding its use in any other type of nuclear reactor.The Gesellschaft für Anlagen und Reaktorsicherheit (GRS) stochastic methodology for uncertainty quantification is used. This methodology makes use of the high-fidelity model and nonparametric sampling to propagate the uncertainty. As a result, the number of samples (determined using the revised Wilk's formula) does not depend on the number of input parameters but only on the desired confidence and uncertainty of output parameters. Moreover, the output Probability Distribution Functions (PDFs) are not subject to normality. The main disadvantage is that each input parameter must have a pre-defined PDF. If possible, input PDFs are de...

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A Two-Step Approach to Uncertainty Quantification of Core Simulators

Cited by 21 publications

References 6 publications

Best-Estimate Plus Uncertainty Framework for Multiscale, Multiphysics Light Water Reactor Core Analysis

Best-Estimate Plus Uncertainty Framework for Multiscale, Multiphysics Light Water Reactor Core Analysis

Uncertainty Propagation for LWR Burnup Benchmark Using Sampling Based Code Scale/Sampler

Uncertainty Quantification and Sensitivity Analysis for Cross Sections and Thermohydraulic Parameters in Lattice and Core Physics Codes. Methodology for Cross Section Library Generation and Application to PWR and BWR.

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