LAUSR

Abstract There is an inevitable uncertainty in the coupled neutronic/thermal–hydraulic calculations, which are used for simulating the performance of nuclear reactors, due to the influence of design parameters and initial conditions. The application of uncertainty analysis methods in such calculations can reduce the “uncertainty zone” of calculation results as well as the unnecessary safety margin of the reactor. In this study, based on the combination of user-defined function (UDF) of FLUENT, a computational fluid dynamics (CFD) code, with the neutron dynamics model, fuel pin heat transfer model, and SIMLAB software, an uncertainty analysis platform called CFD/PFS is developed. The CFD/PFS platform is used to simulate the unprotected transient overpower (UTOP) accident in the small modular natural circulation lead–bismuth alloy cooled fast reactor-10MWth (SNCLFR-10) reactor, which is followed by uncertainty quantification. The results of uncertainty and sensitivity analysis justify the good reliability and accuracy of coupled neutronic/thermal–hydraulic calculations. The titular values of transient parameters, such as peak reactivity and peak fuel temperature, are within the bilateral tolerance limits, and the relative deviation between these values and the limit values is less than 3.95%. As far as UTOP accident, Doppler coefficient is found to be the main source of uncertainty, which has the most significant effect on reactor safety.