Post-irradiation examination of encapsulated INCONEL 600 coiled flux detectors that had failed after several years of service in a CANDU reactor showed that many of the detector wires inside the carrier rod were broke...Post-irradiation examination of encapsulated INCONEL 600 coiled flux detectors that had failed after several years of service in a CANDU reactor showed that many of the detector wires inside the carrier rod were broken. It was concluded that failure occurred because the He cover gas was lost and replaced by air. Because He is a better thermal conductor than air, and because nuclear heating is significant, the temperature of the assembly increased. The examination showed that those parts of the INCONEL 600 detector wires that had operated at the highest temperature were the most severely embrittled. Parts of the same detector wires that were operating at lower temperatures remained ductile. The temperature dependence for the embrittlement of INCONEL 600 material can be explained in terms of the transition from recombination-dominated to sink-dominated reaction-rate kinetics for point defect accumulation at sinks. Cavity formation and accumulation at grain boundaries could weaken the material and result in the observed brittle intergranular failure.展开更多
文摘Post-irradiation examination of encapsulated INCONEL 600 coiled flux detectors that had failed after several years of service in a CANDU reactor showed that many of the detector wires inside the carrier rod were broken. It was concluded that failure occurred because the He cover gas was lost and replaced by air. Because He is a better thermal conductor than air, and because nuclear heating is significant, the temperature of the assembly increased. The examination showed that those parts of the INCONEL 600 detector wires that had operated at the highest temperature were the most severely embrittled. Parts of the same detector wires that were operating at lower temperatures remained ductile. The temperature dependence for the embrittlement of INCONEL 600 material can be explained in terms of the transition from recombination-dominated to sink-dominated reaction-rate kinetics for point defect accumulation at sinks. Cavity formation and accumulation at grain boundaries could weaken the material and result in the observed brittle intergranular failure.
