Nanostructural evolution in surveillance test specimens of a commercial nuclear reactor pressure vessel studied by three-dimensional atom probe and positron annihilation

Intergranular Segregation in the Pressure Vessel Steel of a Commercial Nuclear Reactor Studied by Atom Probe Tomography

“…These results are in agreement with the many studies using APT on irradiation-induced CNPs in the matrix of RPV steels reporting that CNPs are enriched with other solute elements, such as Si, Mn, P and Ni. 6,11,2224) (2) In contrast, at the CNPs on dislocation lines in the small angle GB, no enrichment of Si and Ni was evident and only slight enrichment of Mn was observed (Fig. 5(b)).…”

“…1,2,5) We have reported the evolution of these features in surveillance test specimens of commercial reactors, Doel-1 and -2 in Belgium, irradiated up to a neutron dose of ³6 © 10 19 n·cm ¹2 , corresponding to an inservice period of ³30 years in the previous paper. 6) In this paper, we report the GB segregation of impurity/solute atoms in the same specimens. Such observation for dislocations/ GBs are expected to contribute significantly to the understanding of non-hardening embrittlement, which is increasingly important, especially in the case of higher neutron doses for prolonged irradiation periods in aged nuclear reactors.…”

Accelerated Corrosion Tests of Nuclear Reactor Pressure Vessel Materials in NaCl–H₃BO₃ Solutions

“…So, galvanic corrosion characteristic in the examined solutions is similar to corrosion characteristic of non-coupled specimen, in spite of different experimental methods. A reference 7) shows that the contribution of galvanic corrosion is not important, compared with the corrosion of SA533B itself in H 3 BO 3 solution. However, in the mixed solution as shown in this study, galvanic corrosion increased in comparison with that in H 3 BO 3 solution.…”

“…Degradation of the vessel material is checked by inserting surveillance test specimens with the same composition into the vessel. 7) The most important matters are degradation of materials by strong neutron radiation and generation of stress corrosion cracking and if it is found that cladded materials are not destroyed, it is concluded that there is no severe corrosion of the vessel material in a short time.…”

Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (VI) Consistency of the Structural Integrity Evaluation Model for the Weld Joint

“…Nagai and coworkers have pointed out that the mechanism of the irradiation-induced increase in yield strength is quite different between the irradiation at a high dose rate/dose (material testing reactor) and the irradiation at a low dose rate/dose (commercial reactor) with respect to the nanostructural evolution on the nuclear reactor pressure vessel steels. [34][35][36] Using positron annihilation spectroscopy, they investigated the kinetics of irradiation-induced precipitation on reactor pressure vessel (RPV) surveillance specimens of a Calder Hall-type reactor in Japan and on the same RPV material irradiated by the Japan Materials Testing Reactor (JMTR). The investigations revealed that the mechanism resulting from the embrittlement is Cu nanoprecipitation in the RPV steel irradiated in the Calder Hall-type reactor with a low dose rate (4:2 Â 10 8 n/cm 2 s) in the very early stage (2:7 Â 10 17 n/cm 2 ), while matrix defects, such as vacancysolute complexes and dislocation loops, appear in the RPV steel irradiated by the JMTR at a higher dose rate (3:6 Â 10 12 n/cm 2 s).…”