This study of EBR-II operating behavior, which began with a reexamination of the thermal analysis of fuel pins under varying rates of coolant flow, incorporates the recent interpretations of the bowing behavior of the subassemblies. The nonlinear bowing effects are combined with the linear expansion effects in equations that express the power-reactivity decrement as a function of both power and flow. Comparison with experiments indicates agreement to within a few inhours. Differentiation of the equations leads to expressions for power and flow coefficients of reactivity. The reduced flow data are used to determine an effective average thermal expansion coefficient for the fuel.