The nil-ductility transition temperature (RT/sub NDT/) of a PWR pressure vessel (PV) increases during its lifetime due to neutron-induced radiation damage. If during a pressurized thermal shock (PTS) event the PV is cooled below its RT/sub NDT/ and then repressurized, the vessel may undergo brittle fracture. For several operating reactors it may be necessary to reduce this neutron-induced vessel damage in order to maintain the vessel RT/sub NDT/ below the range of concern. In this study the potential fluence (and hence damage) reduction achievable by selective replacement of peripheral fuel assemblies in which the fuel rods have been replaced by stainless steel rods is considered
