This standard provides guidance for performing and validating the sequence of steady-state calculations leading to prediction@ in all types of commercial nuclear reactors@ of (1) reaction-rate spatial distributions; (2) reactivity; (3) change of isotopic compositions with time. The standard provides (1) guidance for the selection of computational methods; (2) criteria for verification and validation of calculational methods used by reactor core analysts; (3) criteria for evaluation of accuracy and range of applicability of data and methods; (4) requirements for documentation of the preceding.