Abstract: Methods, systems and computer program products for selecting input data, including operational parameters for a nuclear system using a reduced order model of a complex computational model are provided. The complex computational model includes a set of equations that describe the nuclear system. An adjoint model associated with the complex model can be obtained, and output data from the adjoint model can be calculated using a plurality of r random sets of input data to the adjoint model. A degree of correlation of the calculated adjoint output data can be determined. A plurality of k reduced correlation subsets of the plurality of r adjoint output data sets can be downselected based on the degree of correlation, such that k<r. The plurality of k reduced correlation subsets of the adjoint output data can be input as a plurality of input data sets to the complex computational model to provide a plurality of k output data sets.