| Summary: | 碩士 === 國立清華大學 === 工程與系統科學系 === 90 === Incidents of intergranular stress corrosion cracking (IGSCC) and irradiation-assisted stress corrosion cracking (IASCC) of stainless steel components in the primary coolant circuits of boiling water reactors (BWRs) are occurring with increasing frequency as the power reactors age. In the past decade, the HWC technique has been widely adopted as a measure for mitigating IGSCC and IASCC in BWR vessel internal components. However, this technique is not without problems. Along with the application of HWC is a shortcoming of exerting a high man-REM cost on the operator due to elevated radiation fields. Furthermore, it is not at all clear that HWC is effective in protecting some components against IGSCC, particularly for protecting in-vessel components that are exposed to high gamma and neutron fields. Therefore, new technologies, such as inhibitive coatings, were brought into consideration to enhance the effectiveness of HWC . In this study, an experiment will be conducted to investigate the effects of inhibitive coating with TiO2, ZrO2, and ZrO(NO3)2 by chemical immersion at 150℃on Type 304 SS. Measurements of electrochemical corrosion potential (ECP) and slow strain rate tensile (SSRT) tests in simulated BWR circulation loop to investigate the effects of inhibitive coating with zirconium oxide and with a compound containing zirconium oxide on Type 304 . Test results showed that the treated SS specimens exhibited lower ECP than the pre-oxidized specimen, and the specimens exhibited lower ECP in higher than in lower hydrogen consumption. Increasing hydrogen concentration and treating IPC both can reduce ECP. In the SSRT test results, all tested specimens showed less IGSCC in higher hydrogen concentration, and had the longer elongation and fracture time. In the same water chemistry environments, pre-oxidized one had less IGSCC, the lowest elongation and the shortest fracture time. The results indicated that IPC did prolong the crack initial times to get longer fracture times, larger maximum fracture stress, and less second cracks. That can provide protection against IGSCC.
|
|---|
