Is neutron radiation exposure always detrimental to metals (steels)?
It is well established that irradiated metals and alloys exhibit increased mechanical strength accompanied by reduced ductility, commonly referred to as irradiation strengthening and embrittlement. We talk about radiation damage and environmental degradation of metals following radiation exposure. Indeed, there have been numerous conferences and symposia held and planned on this subject, which include research work and discussions with the central theme being the damage created in materials by neutron radiation exposure. Radiation embrittlement in metals is believed to be due mainly to (1) changes in flow properties because of the interaction of dislocations with irradiation-produced defects1, and (2) precipitation of transmutation-produced gases and irradiation-induced segregation at grain boundaries which are potential fracture sites2. Contrary to the previously observed radiation embrittlement in metals, I report here that neutron irradiation of mild steel improved both the mechanical strength and ductility at 373 K even at relatively high (∼1018 neutrons cm−2), fast (>1 MeV) neutron doses. To my knowledge, such improvement has never been observed before.
Chapter 8–Review and Analysis of Reactor Vessel Surveillance Programs
The problem of neutron radiation embrittlement of reactor pressure vessel steels has been addressed in earlier chapters by direct review of specific vessel surveillance programs. To end this study, (all available surveillance results are summarized and analyzed within the context of current codes, rules, and standards. The results provide bases for certain modifications of future surveillance programs, surveillance analysis procedures and, possibly, for guiding criteria for developing Federal regulations and voluntary consensus standards and codes.) In compiling this volume the views of all the major U.S. vendors of lightwater reactor (LWR) nuclear steam supply systems have been provided. Further, at least by inference, the radiation embrittlement status of all of the older U.S. reactors generally can be determined. The elements critical to evaluating a reactor's status as to radiation embrittlement-for example, the neutron exposure, the comparative properties of component steels, and the influence of fabrication (welding)-have been reviewed in the perspective of several different authors. This final chapter seeks to unify recommendations where possible and, more importantly, to provide a summary of the most important data now available from all U.S. operating reactors.
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.