Nuclear data uncertainty influence on the breeding ratio in sodium-cooled fast reactor systems

Nuclear data are a main uncertainty source in neutron transport simulations making their consideration in reactor safety necessary. This arises anew with the state-of-the-art reactors known as Generation IV. Some of the reactors suggests providing the reactivity margin below the effective delayed neutron fraction excluding prompt criticality accidents, and the breeding ratio is the key factor in this. Consequently, assessing a degree of the breeding ratio accuracy is of interest. Therefore, in this work, the breeding ratio uncertainties are analyzed by performing a sensitivity and uncertainty analysis of the MET1000 and MOX3600 models with respect to nuclear data using SCALE. As a result, the breeding ratio uncertainties are obtained approximately equal to 2% as the main contributors are 239Pu(n, gamma), 238U(n, gamma), and 238U(n, n'). The uncertainty sources between the models are compared, and 16O preponderantly increases the total uncertainty not directly by its uncertainty but by its impact on the spectrum.

Automated summary

Nuclear data are a significant uncertainty source in neutron transport simulations for reactor safety. Generation IV reactors propose providing reactivity margin below the effective delayed neutron fraction, making the breeding ratio a key factor. Therefore, assessing the accuracy of the breeding ratio is important. This study analyzes the breeding ratio uncertainties by conducting a sensitivity and uncertainty analysis of the MET1000 and MOX3600 models using SCALE. The main contributors to the breeding ratio uncertainties are 239Pu(n, gamma), 238U(n, gamma), and 238U(n, n'). The comparison of uncertainty sources between the models reveals that 16O predominantly increases the total uncertainty through its impact on the spectrum.