저온 풀림 처리 Alloy 600이 1차수 응력 부식 균열에 가장 예민한 이유

• Published in: 대한금속·재료학회지, 58(12) Vol. 58; no. 12; pp. 815 - 821
• Main Authors: 김성수, Sung Soo Kim, 정종엽, Jung Jong Yeob, 김영석, Young Suk Kim
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 05.12.2020; 대한금속·재료학회
• Subjects: Alloy 600; lattice contraction; mill anneal; neutron diffraction; ordering reaction; PWSCC; 재료공학
• ISSN: 1738-8228; 2288-8241

It has been proposed that a primary water stress corrosion cracking (PWSCC) in pressurized water reactor (PWR) is governed by a lattice contraction due to a short range ordering reaction in Alloy 600. This leads researcher to think that the kinetics of lattice contraction may control a susceptibility of PWSCC in Alloy 600. A lattice variation with ordering treatment at 400 ℃ was systematically investigated using high resolution neutron diffraction(HRPD) in high temperature mill anneal (HTMA), low temperature mill anneal (LTMA), and sensitized (SEN) Alloy 600. The results showed that ordering treatment caused an isotropic lattice contraction due to short range ordering (SRO) reaction. The lattice contractions of (111) plane are saturated to be 0.04% in 4 to 1500 hours at 400 ℃ according to prior treatment condition. The lattice contraction in the magnitude of 0.03% of (111) plane in LTMA Alloy 600 is faster by 8 times and 66 times than that of SEN and HTMA, respectively. This fact may explain why the LTMA is most susceptible to PWSCC through of kinetics of lattice contraction in Alloy 600. Thus, it is possible to conclude that the susceptibility of Alloy 600 to PWSCC is governed by the kinetics of (111) lattice contraction. (Received August 11, 2020; Accepted October 7, 2020)