IRRADATION-INDUCED EMBRITTLEMENT OF INCONEL 600 FLUX DETECTORS IN CANDU REACTORS
The early design of flux detectors in use in CANDU? reactors consisted of multiple-paired-coiled detectors sheathed in INCONEL? 600 and wrapped around a Zircaloy carrier rod. The signal from these detectors was carried by INCONEL 600 coaxial cables that were threaded through the carrier-rod and fed back to instru-mentation outside of the reactor core. Failures occurred in early applications that were related to the environment in which the detectors oper-ated (moist or dry air). These failures were mitigated by ensuring that the detectors operated with a He cover gas that acts both to limit corro-sion and as an efficient conductor of heat (gen-erated by nuclear heating). An improved design was introduced consisting of single-individual-replaceable detectors (SIRs) with performance improved by eliminating brazed joints that were susceptible to nitric acid attack. 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 con-cluded that failure occurred because the He cover gas was lost and replaced by air. The ex-amination also showed that those parts of the INCONEL 600 detector wires that had operated at the highest temperature, as evidenced by the degree of localised corrosion, were the most severely embrittled. Parts of the same detector wires that were clearly operating at lower tem-peratures, because they were shiny, remained ductile. Calculations indicate that if the INCONEL 600 material temperature exceeds about 573K (300℃) then it is conceivable that significant swelling and associated embrittle-ment could be expected. This is consistent with the observations indicating that the INCONEL detector wires that had experienced operation at elevated temperatures (>300℃) were embrittled.
M.Griffiths G.A.Bickel S.R.Douglas
Deformation Technology Branch Atomic Energy of Canada Limited Chalk River, Ontario, Canada K0J 1J0
国际会议
18th International Conference on Nuclear Engineering(第18届国际核能工程大会 ICONE 18)
西安
英文
1-6
2010-05-17（万方平台首次上网日期，不代表论文的发表时间）