[en] The purpose of this work was to validate the MOCUP program for burn-up analysis. Two well-documented benchmarking problems were used to validate MOCUP itself and the application way. One benchmark consists of three PWR pin-cell burn-up cases. The other benchmark is a fast reactor (burner) burn-up problem. From the comparisons of our MOCUP results by using appropriate program parameters with those obtained from measurement and/or other computer codes, it has been concluded that: (a) with few exceptions, the MOCUP results of isotopic compositions fall within the range of those calculated by different codes; (b) MOCUP results for the actinide concentration are in agreement with the measurement values to within 11% (for most of the actinides, the deviations are less than 5%) and for all fission products studied, the deviations are less than 10%, except for ¹⁴⁹Sm; and (c) the MOCUP predictions of reactivity change with burn-up are in good agreement with the reported values