氧化鋯被覆與不同304不?袗?氧化膜對於溶氫與溶氧在模擬沸水式反應器環境中的電化學特性影響研究

Electrochemical Characteristics of Oxygen and Hydrogen on ZrO2 Treated Type 304 Stainless Steels with Different Surface Oxide Structures in Simulated Boiling Water Reactor Environments

簡源進(Yuan-Chin Chien)

指導教授 ： 蔡春鴻 ； 葉宗洸

國立清華大學/原子科學院/工程與系統科學系/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00377

摘要

無資料

關鍵字

沸水式反應器 ； 沿晶應力腐蝕龜裂 ； 氧化鋯 ； 抑制性被覆 ； 極化掃瞄

並列摘要

Incidents of intergranular stress corrosion cracking (IGSCC) have been readily observed in boiling water reactors (BWRs) for many years. The electrochemical corrosion potential (ECP) is a major indicator for IGSCC susceptibility of stainless steel components in 288 °C pure water. In the early 1980s, the technology of hydrogen water chemistry (HWC) was developed to mitigate the IGSCC problems in BWRs. However, HWC has side effects of exposing operators to elevated level of radiation and high hydrogen cost. To reduce these side effects, a novel technique of zirconium oxide (ZrO2) coating that eventually requires no hydrogen addition has been proposed.
In this study, electrochemical polarization analyses and ECP response monitoring were conducted to investigate the impact on ZrO2 treated specimens in simulated BWR environments. Prior to the electrochemical tests all specimens were thermally sensitized and pre-oxidized in high temperature water containing either 300 ppb O2 or 50 ppb H2. Afterwards, the specimens were treated with 100 nm ZrO2 by hydrothermal deposition at 90 °C and 150 °C for one week. The morphologies of the specimens were examined by scanning electron microscopy and energy dispersive X-ray spectroscopy. The hematite (α-Fe2O3) and magnetite (Fe3O4) structures of oxides were identified by Raman spectrum.
The objective of this study was to evaluate the effectiveness of ZrO2 treatment on specimens with different oxide structures. Differences between the sizes and the packing densities of the oxide particles produced from different water chemistry condition could be clearly observed on the SEM images. Based on observation, the coating density of ZrO2 on the oxides with a hematite structure was greater than on those with a magnetite structure. From the electrochemical potentiodynamic polarization results, we observed lower electrochemical corrosion potentials, corrosion current densities, and exchange current densities on the treated specimens than on the untreated ones in high temperature water with either dissolved oxygen or dissolved hydrogen only. Furthermore, the ECPs and surface morphologies of the ZrO2 treated specimens showed almost no changes after ten days of immersion in 288 °C water. The overall results indicated that the ZrO2 treatment could effectively reduce the corrosion rate of Type 304 stainless steel in simulated BWR environments.