Uncertainty analysis of unprotected transient overpower of small natural circulation lead-bismuth cooled fast reactor

Abstract

BackgroundTypical transient accidents pose a great challenge to the safe operation of lead-bismuth fast reactors.PurposeThis study aims to apply uncertainty analysis methods to transient calculations to reduce the "uncertainty band" of transient parameters and obtain more accurately assess reactor safety characteristics.MethodBased on the self-developed fast reactor analysis CFD/PFS code, non-parametric statistical methods was employed to carry out the uncertainty analysis of the unprotected overpower accident (UTOP) of small natural circulation lead-bismuth cooled fast reactor. Three types of uncertain input parameters, i.e., thermal-hydraulic model parameters, neutron physical model parameters, and fuel manufacturing tolerances, were considered according to the literature and engineering experience. Based on the uncertainty analysis procedure SIMLAB, the Latin hypercube sampling (LHS) was carried out for the input parameters, and the uncertainty of the transient safety parameters was quantitatively analyzed. Finally, the sensitivity of the input parameters to the transient safety parameters was evaluated by the correlation coefficient analysis method.Results & ConclusionComputational results show that uncertainty bands of target parameters, such as peak cladding temperature and peak fuel temperature, can all envelop the nominal value. The maximum tolerance of peak fuel temperature is 2 757.25 K, and the maximum tolerance of peak cladding temperature is 1 208.66 K. The analysis results indicate that the fuel average temperature and the reactivity feedback coefficient are the main sources of uncertainty.

Keywords

• lead-bismuth cooled fast reactor
• cfd/pfs
• utop
• uncertainty analysis
• sensitivity analysis