Enhancement of random sampling by a combined approach of control variates and Latin hypercube sampling for uncertainty quantification in light water reactor lattice calculations

Fujita, Tatsuya

Journal of Nuclear Science and Technology, 62(5), p.470 - 479, 2025/01

https://doi.org/10.1080/00223131.2024.2448320

This study confirmed the efficiency of a combined approach of the control variates (CV) and the Latin hypercube sampling (LHS), which enhanced the random-sampling-based uncertainty quantification due to cross-section (XS) covariance data, by considering the effect of statistical variation and also performed the sensitivity analyses on the influence due to the selection of alternative parameter to apply CV. The convergence performance for the uncertainty of infinite multiplication factor (k-infinity) during the random sampling was compared between several efficient sampling techniques such as the antithetic sampling (AS), LHS, CV, and the combined approaches of them in the PWR-UO fuel assembly geometry. The k-infinity uncertainty was evaluated by statistically processing several times Serpent2 calculations using perturbed ACE-formatted XS files based on ENDF/B-VIII.0. CV+LHS was more efficient than AS, LHS, and CV+AS. In addition, sensitivity analyses were performed to select alternative parameters used in CV. The 33 mini fuel lattice calculation can improve the efficiency of CV+LHS. The reason was qualitatively considered that this calculation can capture the influence of XS covariance data for Gd isotopes. Consequently, the applicability of CV+LHS for the improvement of convergence performance to evaluate the k-infinity uncertainty during the random sampling was confirmed.

Molecular dynamics analysis of reactor graphite for preparing thermal neutron scattering law

Okita, Shoichiro; Goto, Minoru

Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 10 Pages, 2023/10

Remarks on iron nuclear data for fusion neutron sources

Kwon, Saerom*; Konno, Chikara; Honda, Shogo*; Sato, Satoshi*; Masuda, Kai*

no journal, , 

We examined the accuracy of the iron data in the latest nuclear data libraries (FENDL-3.2b, JENDL-5, ENDF/B-VIII.0 and JEFF-3.3) used in the fusion neutron source design by using QST/TIARA iron experiment with quasi mono-energy neutrons of 40 and 65 MeV and JAEA/FNS iron experiment with DT neutrons. Then we have found the following issues on FENDL-3.2b iron data and specified that the non-elastic, inelastic scattering, (n,2n) reaction and (n,np) reaction data of Fe and inelastic scattering data of Fe caused the issues.1) The calculation results with FENDL-3.2b underestimate the measured neutron fluxes of the continuous energy range (10-60 MeV) by a factor of 0.6 in the TIARA experiment with 65 MeV neutrons. 2) The calculation results with FENDL-3.2b tend to underestimate the measured neutron flux above 10 MeV by a factor of 0.8 at depth of 70 cm and overestimate the measured ones below 10 keV by a factor of 1.3 up to depth of 40 cm in the FNS experiment.