- 期刊
BWR環境下鋅、鈷離子對304不銹鋼表面氧化膜之影響研究
Effects of Added Zinc and Cobalt on the Oxide Compositions upon Type 304 SS in the Simulated BWR Conditions
摘要
The dissolved oxygen in the reactor water of a boiling water reactor (BWR) operated under normal water chemistry (NWC) condition lies in the range of 200 to 300 ppb in general. Several events of intergranular stress corrosion cracking (IGSCC) on in-reactor components accordingly happened in the past due to this relatively oxidizing environment. However, hydrogen water chemistry (HWC) condition of a BWR could mitigate such failure owing to its relatively reducing environment of the dissolved oxygen decreasing below 10 ppb. There was one main side effect under such HWC operation condition, i.e. shutdown dose rate buildup on the surface of piping out of core due to Co-60 deposit, based on the plant operation experiences. It is known that zinc addition under HWC condition could reduce this shutdown dose rate buildup and recover to the level as that under NWC condition. Thereby, the experimental conditions of test specimen followed the sequence: as received (step1)→NWC (step 2)→HWC (step 3)→HWC/Zn (test 1) or HWC/Co (test 2)→HWC/Zn/Co (test 1) or HWC/Co/Zn (test 2) for the purpose of investigating the mechanism of zinc and cobalt ion competing in penetration into the outer layer of oxide film formed on the surface of Type 304 stainless steel in the simulated BWR conditions. In the paper, SEM was used to observe the morphology and particulate size and EDS was used to analyze the local composition of surface oxide. And, SIMS and ESCA were used for the determination of elemental compositions in the depth profile. We found that the tendency of zinc ion in replace of the metal ions in the spinel oxide formed in the simulated BWR conditions was Fe(superscript 3+), Co(superscript 2+)＞＞Ni(superscript 2+). On the contrary, the tendency of Co(superscript 2+) replacement was Ni(superscript 2+)＞Zn(superscript 2+)＞＞Fe(superscript 2+). And, the capability of Zn(superscript 2+) of reactor water replacing Co(superscript 2+) in the spinel oxide was higher than the reverse. The detailed description and explanation of mechanisms appeared in this text.
並列摘要
The dissolved oxygen in the reactor water of a boiling water reactor (BWR) operated under normal water chemistry (NWC) condition lies in the range of 200 to 300 ppb in general. Several events of intergranular stress corrosion cracking (IGSCC) on in-reactor components accordingly happened in the past due to this relatively oxidizing environment. However, hydrogen water chemistry (HWC) condition of a BWR could mitigate such failure owing to its relatively reducing environment of the dissolved oxygen decreasing below 10 ppb. There was one main side effect under such HWC operation condition, i.e. shutdown dose rate buildup on the surface of piping out of core due to Co-60 deposit, based on the plant operation experiences. It is known that zinc addition under HWC condition could reduce this shutdown dose rate buildup and recover to the level as that under NWC condition. Thereby, the experimental conditions of test specimen followed the sequence: as received (step1)→NWC (step 2)→HWC (step 3)→HWC/Zn (test 1) or HWC/Co (test 2)→HWC/Zn/Co (test 1) or HWC/Co/Zn (test 2) for the purpose of investigating the mechanism of zinc and cobalt ion competing in penetration into the outer layer of oxide film formed on the surface of Type 304 stainless steel in the simulated BWR conditions. In the paper, SEM was used to observe the morphology and particulate size and EDS was used to analyze the local composition of surface oxide. And, SIMS and ESCA were used for the determination of elemental compositions in the depth profile. We found that the tendency of zinc ion in replace of the metal ions in the spinel oxide formed in the simulated BWR conditions was Fe(superscript 3+), Co(superscript 2+)＞＞Ni(superscript 2+). On the contrary, the tendency of Co(superscript 2+) replacement was Ni(superscript 2+)＞Zn(superscript 2+)＞＞Fe(superscript 2+). And, the capability of Zn(superscript 2+) of reactor water replacing Co(superscript 2+) in the spinel oxide was higher than the reverse. The detailed description and explanation of mechanisms appeared in this text.