Uncertainty quantification and source identification of critical safety parameters in CiADS via sensitivity analysis

The safe disposal of nuclear waste is a major problem for sustainable development of fission nuclear energy. Accelerator driven subcritical systems (ADS) have excessive high-energy spallation neutrons, and are the preferred technological approach for transmutation of nuclear waste. ADS has the characteristics of wide neutron energy distribution range and complex nuclear fuel composition, which creates significant uncertainty in safety analysis and affects the reliability of safety parameter calculation results. An uncertainty quantification methodology for safety parameter is proposed based on the adjoint weighted perturbation theory, and an uncertainty analysis program MCSU is developed. Using a comprehensive nuclear data covariance library that is established in this paper, the uncertainties of important safety parameters of China Initiative Accelerator Driven System (CiADS) are quantified. Furthermore, an energy-dependent uncertainty contribution factor method is employed to identify isotopes, cross-sections, and energy ranges contributing most significantly to the overall uncertainty. The results demonstrated that uncertainties caused by nuclear data far exceed the accuracy limit requirements of advanced nuclear systems, the accuracy of nuclear data needs to be improved, especially in the high-energy region, the research results provide guidance for improving the reliability of safety parameters.