NEUTRON DOSIMETRY FOR ADVANCED PRESSURIZED-WATER REACTORS

A review is presented of recent developments in the field of neutron d osimetry, and includes codes and calculational procedures, activation dosimetry together with retrospective dosimetry techniques, and the us e of sapphire as a direct damage monitor. Improvements in the applicat ion of the Monte Carlo method through acceleration techniques and incr eased computing power have made it feasible to model neutron transport in PWRs with greater precision. The advent and perfection of new dete ctor materials has resulted in the development of activation dosimeter packs which can characterize the energy ranges of those neutrons that create the majority of displaced atoms in reactor steels. The importa nce of thermal neutrons in contributing to displacement damage is disc ussed. These data together are used to support and adjust theoretical dosimetry techniques to produce good estimates of the damage dose in t erms of displacements per atom (dpa). The dpa unit is found to provide a good damage correlation parameter for mechanical property changes i n reactor materials irradiated in different neutron spectra. A direct damage monitor based on sapphire has been developed which can measure directly the displacement dose in irradiated steels. Input of these ne w and improved dosimetry techniques to advanced PWR systems is highlig hted.