Uncertainties for Swiss LWR spent nuclear fuels due to nuclear data

Abstract

Abstract. This paper presents a study of the impact of the nuclear data (cross sections, neutron emission and spectra) on different quantities for spent nuclear fuels (SNF) from Swiss power plants: activities, decay heat, neutron and gamma sources and isotopic vectors. Realistic irradiation histories are considered using validated core follow-up models based on CASMO and SIMULATE. Two Pressurized and one Boiling Water Reactors (PWR and BWR) are considered over a large number of operated cycles. All the assemblies at the end of the cycles are studied, being reloaded or finally discharged, allowing spanning over a large range of exposure (from 4 to 60 MWd/kgU for ≃9200 assembly-cycles). Both UO 2 and MOX fuels were used during the reactor cycles, with enrichments from 1.9 to 4.7% for the UO 2 and 2.2 to 5.8% Pu for the MOX. The SNF characteristics presented in this paper are calculated with the SNF code. The calculated uncertainties, based on the ENDF/B-VII.1 library are obtained using a simple Monte Carlo sampling method. It is demonstrated that the impact of nuclear data is relatively important (e.g. up to 17% for the decay heat), showing the necessity to consider them for safety analysis of the SNF handling and disposal.

Sensitivity Analysis of PWR Spent Fuel Due to Modelling Parameter Uncertainties Using Surrogate Models

“…In another work considering cross sections and fission yields [5], the maximum burnup uncertainty is about 2.4% at 15 GWd/tU, maximum decay heat uncertainty is 7% at 2 -4 years of cooling, maximum uncertainty in activity is ~6% at 50 -100 years of cooling, maximum uncertainty in neutron source is 18% at 1,000 -5,000 years of cooling, and maximum uncertainty in gamma source is ~9% at 2 -4 years of cooling.…”

“…Until now, most of the works carried out have been based on the propagation of nuclear data uncertainties on uncertainty in SNF characteristics [4][5]. Little attention has been paid to uncertainties in SNF due to uncertainties in modelling parameters [6][7] and this will be the focus of this study as it relates to pressurized water reactor (PWR) spent nuclear fuel (SNF) source terms.…”

Analysis for the ARIANE BM1 and BM3 samples: nuclide inventory and decay heat

“…For the present analysis, the irradiation history for this assembly is not extracted from the ARIANE report, but directly from the PSI database called CMSYS. Such database is normally used for core licensing calculations for the Swiss regulator, and contains all detailed information regarding reactor cycle operations and conditions, necessary for CASMO5 and SIMULATE simulations; interested readers can find more information in references [10][11][12][13][14][15][16][17]. Generally, the PSI database contains a more detailed irradiation history compared to the ARIANE report, with variations of boron concentrations and temperatures at every irradiation step.…”

Impact of H in H2O thermal scattering data on depletion calculation: k∞, nuclide inventory and decay heat

“…The justification for the observed variations is still not clear, and additional calculations would be necessary. It nevertheless shows that the decay heat is not sensibly affected by the thermal scattering data, given that the impact of other nuclear data are not less than 1% for cooling time longer than 1 year and burnup higher than 50 MWd/kgU [33,34].…”