Abstract
Uncertainty quantification has been extensively applied to nuclear criticality analyses for many years and has recently begun to be applied to depletion calculations. However, regulatory bodies worldwide are trending toward requiring such analyses for reactor fuel cycle calculations, which also requires uncertainty propagation for isotopics and nuclear reaction rates. XSUSA is a proven methodology for cross section uncertainty propagation based on random sampling of the nuclear data according to covariance data in multi-group representation; HELIOS2 is a lattice code widely used for commercial and research reactor fuel cycle calculations. This work describes a technique to automatically propagate the nuclear data uncertainties via the XSUSA approach through fuel lattice calculations in HELIOS2. Application of the XSUSA methodology in HELIOS2 presented some unusual challenges because of the highly-processed multi-group cross section data used in commercial lattice codes. Currently, uncertainties based on the SCALE 6.1 covariance data file are being used, but the implementation can be adapted to other covariance data in multi-group structure. Pin-cell and assembly depletion calculations, based on models described in the UAM-LWR Phase I and II benchmarks, are performed and uncertainties in multiplication factor, reaction rates, isotope concentrations, and delayed-neutron data are calculated. With this extension, it will be possible for HELIOS2 users to propagate nuclear data uncertainties directly from the microscopic cross sections to subsequent core simulations.
Highlights
Uncertainty quantification has been extensively applied to nuclear criticality analyses for many years and has recently begun to be applied to depletion calculations
Regulatory bodies worldwide are trending toward requiring such analyses for reactor fuel cycle calculations, which requires uncertainty propagation for isotopics and nuclear reaction rates
XSUSA is a proven methodology for cross section uncertainty propagation based on random sampling of the nuclear data according to covariance data in multigroup representation; HELIOS2 is a lattice code widely used for commercial and research reactor fuel cycle calculations
Summary
Uncertainty quantification has been extensively applied to nuclear criticality analyses for many years and has recently begun to be applied to depletion calculations. XSUSA [1] is a proven methodology for cross section uncertainty propagation based on random sampling of the nuclear data according to covariance data in multigroup representation; HELIOS2 [2] is a lattice code widely used for commercial and research reactor fuel cycle calculations. The sampling-based uncertainty and sensitivity analysis software XSUSA (“Cross Section Uncertainty and Sensitivity Analysis”) has been developed for evaluating the output uncertainties of neutron transport calculations, stand-alone or in combination with depletion or thermohydraulics, which arise from uncertainties in the underlying nuclear data. To this end, a large number of calculations for the problem under consideration are performed with varied nuclear data. XSUSA is being extended to handle covariance data in other energy group structures, such as the 56group ENDF/B-VII. based covariance data set presently shipping with SCALE 6.2
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