Comparison of the calculation accuracy of the neutronic characteristics of a heavy liquid metal cooled fast reactor model using various evaluated neutron data libraries

The paper analyses the neutron data and covariance matrixes, which are crucial for the computational prediction of neutronic characteristics of fast neutron reactors with uranium-plutonium fuel and currently available in the state-of-the-art versions of evaluated nuclear data libraries: ENDF/B-VIII, JENDL-5, TENDL 2021, JEFF 4T1. The newly obtained covariance data are compared to the data that was presented in the Russian evaluated nuclear data library BROND 3.1. A simplified model of a fast neutron reactor with mixed dense nitride uranium-plutonium fuel and heavy liquid metal coolant was used to calculate the spread in neutronic performance values and their uncertainties due to neutron data using different evaluated nuclear data libraries for the following characteristics: effective multiplication factor, effective delayed neutron fraction, Doppler reactivity coefficient, breeding ratio and gain, reactivity margin for fuel burnup and other fuel burnup characteristics. It has been observed that, on the whole, the uncertainties of the reactor functionals have decreased when estimated using state-of-the-art versions of evaluated neutron data libraries, compared to previous releases of those libraries. The paper also examines changes in target accuracies for predicting the main neutronic characteristics of fast neutron reactors over the past decades, as well as evaluates the requirements for neutron data uncertainties to achieve the recently declared target accuracies. The main findings of this study are presented in two aspects: first, in terms of the effects evaluated neutron data from different libraries have on the accuracy of calculations for the key neutronic characteristics of fast reactors; and second, in terms of the potential for improving the accuracy of predicted neutronic characteristics of fast reactors by considering the results of reactor physics measurements.