Neutron fluences were calculated for the first Reactor Vessel Surveillance (RVS) capsules extracted from Koeberg Unit 1 and 2. For the calculation of the Koeberg RVS-capsule dosimetry cross sections a calculational system (called PCDC) was developed on a 32-bit i386/i486 personal computer (PC). This system consists of pre- and post-processors, a 171-group neutron reaction cross section library, a 171-group reactor zone flux spectrum library and an interface with the SAND-II, DOSCROS-84 and IRDF-90 dosimetry libraries. The sensitivity of these cross sections was determined for different reactor model parameters, core conditions and dosimetry libraries. Using the IRDF-90 dosimetry library, a maximum difference of 15% was obtained between the fluences predicted with the non-fissionable dosimeters.