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B(C6F5)3‐catalyzed tandem double hydrofunctionalization reactions initiated by intramolecular hydroamination of unactivated alkynes are described herein. In the hydroamination/hydroallylation reaction, in situ preparation of anhydrous B(C6F5)3 from B(C6F5)3 ⋅ nH2O and the use of 2,6‐di‐tert‐butylphenol as a proton source were effective. In the hydroamination/hydrocyanation reaction, a combination of B(C6F5)3 ⋅ nH2O and H2O as the proton source provided good results., ファイル公開：2020/07/01

The radiation induced segregation (RIS) at grain boundary (GB) in neutron irradiated type 316 stainless steel (SS) under boiling water reactor (BWR) condition was simulated by using the Fe-Cr-Ni-Si-Mo system model in which vacancy and interstitial mechanisms were considered for solute migration. The material constants used in the model were fixed to fit the experimental results on RIS at GB. The calculated depth and width of concentration profiles near GB in type 316 SS were comparable to the reported experimental results. The degrees of GB segregation were enhanced at lower neutron flux, and the tendency of flux dependence was similar to experimental results. The theoretical model is applicable to predict the RIS at GB to type 316 SS irradiated in BWR.

Degradation of weldability caused by helium, which is generated by nuclear transmutation in neutron irradiated material, is an important issue to be addressed in planning of proactive maintenance of light water reactor core internal components. In this work, the weldability of neutron-irradiated stainless steel and nickel-base alloy, which are major constituting materials for components, was practically evaluated. The weldability was first examined by TIG welding in relation to the weld heat input and helium content using various specimens (made of SUS304 and SUS316L) sampled from reactor internal components. The specimens were neutron irradiated in a boiling water reactor to fluences from 4 × 1024 to 1.4 × 1026 n/m2 (E>1 MeV), and resulting helium generation ranged from 0.1 to 103 appm. The weld defects were characterized by dye penetrant test and cross-sectional metallography. The weldability of neutron-irradiated stainless steel was shown to be better at lower weld heat input and lower helium content. To evaluate mechanical properties of welded joints, thick plates (20 mm) specimens of SUS304 and Alloy 600 were prepared and irradiated in Japan Material Test Reactor (JMTR). The helium content of the specimens was controlled to range from 0.11 to 1.34 appm selected to determine threshold helium content to weld successfully. The welded joints had multiple passes by TIG welding process at 10 and 20 kJ/cm heat input. The welded joints of thick plate were characterized by dye penetrant test, cross-sectional metallography, tensile test, side bend test and root bend test. It was shown that irradiated stainless steel containing below 0.14 appm of helium could be welded with conventional TIG welding process (heat input below 20 kJ/cm). Nickel-base alloy, which contained as much helium as stainless steel could be welded successfully, could also be welded with conventional TIG welding process. These results served as basis to evaluate the applicability of repair welding to actual reactor components.