Papers by Keyword: Flow Accelerated Corrosion

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Authors: Kyung Ha Ryu, Na Young Lee, Il Soon Hwang
Abstract: Flow Accelerated Corrosion (FAC) has become a hot issue because of aging of passive components. Ultrasonic Technique (UT) has been adopted to inspect the secondary piping. UT, however, covers only narrow region, which results in numerous detecting points and thus takes time. In this paper, we suggested a Wide Range Monitoring (WiRM) concept with Equipotent Switching Direct Current Potential Drop (S-DCPD) method to monitor the thickness of piping. Since the DCPD method covers area, not a point, it needs less monitoring points. We use the SDCPD method to screen the candidate area to monitor. Based on the monitoring results, we can determine the inspection area. To improve the applicability to the piping system, we suggested the Equipotent concept, which eliminates the leakage current. Finite element analysis results and developed resistance model are presented for the simple analysis to describe the wall thinning by DCPD signals. And also validation test results are presented, from which we can identify the consistency of the model and the experiment.
Authors: Sung Ho Lee, Han Sub Chung, Tae Ryong Kim, Su Cheol Jeon
Authors: Na Young Lee, Chi Bum Bahn, Sang Geun Lee, Ji Hyun Kim, Il Soon Hwang, Joon Hyun Lee, Jung Taek Kim, Vincent Luk
Authors: Ki Woung Sung, Hyun Il Seo, Uh Chul Kim, Wan Young Maeng
Abstract: In the nuclear power plants (NPPs), wall thinning of the piping materials is generally caused by a flow-accelerated corrosion (FAC) and leads to a rupture with no warning unless it is detected and repaired in a timely manner. To reduce the FAC, it is better to use low-alloy steels, such as 1Cr-½Mo and 2¼Cr-1Mo, having higher FAC-resistance than carbon steel. Meanwhile, in the secondary water chemistry at the NPPs in Korea, hydrazine concentration is maintained within the range of 100~150 ppb. For applying these low-alloys to a piping material, we investigated the influence of hydrazine concentration on their FAC. An experiment was carried out at pH25°C of 9 controlled with ammonia in a deoxygenated aqueous solution containing 0~250 ppb-hydrazine by using a FAC test loop at 250°C for 300 hours. Experimental weight loss showed a hydrazine concentration dependency of the FAC in this concentration range, giving minimum at 150 ppb.
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