Uncertainty analysis of the control rod drop based on the adaptive collocation stochastic perturbation method

•A deterministic simplified model of the control rod drop and fluid flow is established.•A fifth-order adaptive collocation stochastic perturbation (ACSP) method is established to approximate the random responses.•The uncertainty analysis of the CR drop based on the ACSP method is carried out in both large and small reactor.•The research results can provide guidance for the analysis and design optimization of the control rod scram process.