The IAEA CRP on HTGR uncertainties: Sensitivity study of PHISICS/RELAP5-3D MHTGR-350 core calculations using various SCALE/NEWT cross-section sets for Ex. II-1a

Rouxelin, Pascal; Strydom, Gerhard; Alfonsi, Andrea; Ivanov, Kostadin

doi:10.1016/j.nucengdes.2017.12.008

Cited by 6 publications

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“…where Z 1 is the posterior covariance matrix of estimated parameters and it is shown in (8), and after applying Woodbury matrix identity, it is reformed as ( 9):…”

Section: U-235mentioning

confidence: 99%

“…In order to systematically and thoroughly investigate the uncertainties propagation in pebble-bed HTGR, an IAEA Coordinated Research Plan (CRP) [2,3] has been initiated after the start of OECD/NEA UAM-LWR [4]. Recent advances regarding uncertainty propagation analysis in pebble-bed HTGR mainly concern the nuclear cross section uncertainties propagation in reactor neutronic calculations [5][6][7][8][9]. As pebble-bed HTGR allows fuels recirculation during fuel cycles and adopts higher fuel enrichment (8.5 wt.%), fuels usually could achieve larger burnup values, and then fission product yields could be nonnegligible uncertainty sources in reactor burnup and decay heat calculations.…”

Section: Introductionmentioning

confidence: 99%

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Lognormal-Based Sampling for Fission Product Yields Uncertainty Propagation in Pebble-Bed HTGR

Wang

Cui

Guo

et al. 2020

Science and Technology of Nuclear Installations

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Uncertainty analyses of fission product yields are indispensable in evaluating reactor burnup and decay heat calculation credibility. Compared with neutron cross section, there are fewer uncertainty analyses conducted and it has been a controversial topic by lack of properly estimated covariance matrix as well as adequate sampling method. Specifically, the conventional normal-based sampling method in sampling large uncertainty independent fission yields could inevitably generate nonphysical negative samples. Cutting off these samples would introduce bias into uncertainty results. Here, we evaluate thermal neutron-induced U-235 independent fission yields covariance matrix by the Bayesian updating method, and then we use lognormal-based sampling method to overcome the negative fission yields samples issue. Fission yields uncertainty contribution to effective multiplication factor and several fission products’ atomic densities at equilibrium core of pebble-bed HTGR are quantified and investigated. The results show that the lognormal-based sampling method could prevent generating negative yields samples and maintain the skewness of fission yields distribution. Compared with the zero cut-off normal-based sampling method, the lognormal-based sampling method evaluates the uncertainty of effective multiplication factor and atomic densities are larger. This implies that zero cut-off effect in the normal-based sampling method would underestimate the fission yields uncertainty contribution. Therefore, adopting the lognormal-based sampling method is crucial for providing reliable uncertainty analysis results in fission product yields uncertainty analysis.

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“…where Z 1 is the posterior covariance matrix of estimated parameters and it is shown in (8), and after applying Woodbury matrix identity, it is reformed as ( 9):…”

Section: U-235mentioning

confidence: 99%