Uncertainty in the Burnup Reactivity Swing of Liquid-Metal Fast Reactors

The uncertainty in the burnup reactivity swing δk_b attributable to nuclear data uncertainties is analyzed using depletion-dependent sensitivity coefficients for single- and multicycle equilibrium depletion. Four systems are analyzed with design features that encompass many of the design options considered for current U.S. advanced liquid-metal reactor cores. These systems, while characterized by very different δk_b values in the range from —0.22 to 3.87% Δk, exhibit much smaller differences in their δk_b uncertainties, which range from 0.18 to 0.33% Δk. The δk_b uncertainties depend primarily on the design choices of core size and fissile fuel type, as well as whether the analysis represents multicycle effects. For all reactors analyzed, the burnup swing uncertainty is dominated by the ²³⁸U capture reaction. The potential for reducing uncertainties by a factor of 3 by use of available integral experiment results is also demonstrated.