Steam Generator Cleaning Experience at Korean PWRs: 2014 Experience Update

摘要

Since 2007, Korea Hydro & Nuclear Power Co., Ltd. (KHNP) has performed seven (7) steam generator chemical cleaning (SGCC) applications using the EPRI/SGOG process, including both top-of-tubesheet (TTS) and full bundle cleaning applications. The most recent EPRI/SGOG cleanings performed at Hanbit plant were full bundle applications performed with periodic venting (i.e., boiling) at the TTS and at tube support plate (TSP) elevations in order to enhance effectiveness. A primary objective of these recent SGCC applications was to address outer diameter stress corrosion cracking (ODSCC), which has been observed at the TTS and at tube support plate (TSP) elevations in CE-type SGs with Alloy 600 HTMA tubing which are used at several KHNP units. The EPRI/SGOG process has been shown to effectively reduce prevailing rates of ODSCC at the TTS and TSPs at many plants, particularly when applied with venting. This paper provides a summary of recent EPRI/SGOG SG cleaning applications performed by KHNP, including cleaning objectives, cleaning results and lessons learned. The results of eight (8) recent Advanced Scale Conditioning Agent (ASCA) applications performed at several other KHNP units to reduce TSP blockage and to enhance SG thermal efficiency (increase steam pressure) are also discussed briefly.