Nuclear data uncertainty and sensitivity analysis of the VHTRC benchmark using SCALE. (December 2017)

• Record Type: Journal Article
• Authors: Bostelmann, Friederike; Strydom, Gerhard
• Is Part Of: Annals of nuclear energy. Volume 110(2017:Dec.)
• Page Start: 317
• Page End: 329
• Publication Date: 2017-12
• Subjects: HTGR -- VHTRC -- SCALE -- Uncertainty analysis -- Sensitivity analysis; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2017.06.052
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: Nuclear data uncertainty analyses of the VHTRC experiment are performed. The random sampling approach is compared to perturbation theory. keff uncertainties of 0.58% and 0.66% are obtained with ENDF/B-7.0 and 7.1, resp. Top contributor to the keff uncertainties is the neutron multiplicity of U-235. Moderator-to-fuel ratio has important impact on nominal and uncertainty results. Abstract: The Very High Temperature Critical Assembly (VHTRC) experiment represents one of the few data sets available for the validation of HTGR lattice physics. Within the framework of the IAEA Coordinated Research Project on HTGR Uncertainty Analysis in Modeling, uncertainty and sensitivity analyses of this graphite-moderated facility are performed as the validation reference to the prismatic MHTGR-350 fuel block calculations. Nominal multi-group and continuous-energy criticality calculations with the KENO-VI Monte Carlo code of the SCALE code package are compared with the continuous-energy Monte Carlo Code Serpent. Good agreement with a maximum difference of 250 pcm is obtained. The experimental data set, however, differs by several hundred pcm with the results of both codes when using the ENDF-VII.0 library. When using ENDF/B-VII.1 data, this difference is reduced to a few hundred pcm and the calculations lie within the experimental error bars. Uncertainties of the VHTRC multiplication factors due to uncertainties in nuclear data are determined with SAMPLER/KENO-VI of SCALE 6.2 and with continuous-energy TSUNAMI of SCALE 6.2. For all experimental configurations, the obtained uncertainty is found to be 0.58% when using ENDF/B-VII.0 data. The top contributor to this uncertainty is the average number of neutrons per fission event of U-235. With ENDF/B-VII.1 data, uncertainties of about 0.66% are obtained in particular due to an increased uncertainty of U-235 nu-bar in the latest ENDF release. When considering these nuclear data uncertainties, the obtained 1σ uncertainty intervals are overlapping with the experimental error bars.