한국부식방식학회

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초고온가스로용 Alloy 617의 불순물 함유 헬륨/공기 중에서 고온부식 특성
A very high-temperature gas reactor (VHTR) is one of the next generation nuclear reactors owing to its
safety, high energy efficiency, and proliferation-resistance. Heat is transferred from the primary helium loop
to the secondary helium loop through an intermediate heat exchanger (IHX). Under VHTR environment
Alloy 617 is being considered a candidate Ni-based superalloy for the IHX of a VHTR, owing to its good
creep resistance, phase stability and corrosion resistance at high temperature. In this study, high-temperature
corrosion tests were carried out at 850 - 950oC in air and impure helium environments. Alloy 617 specimens
showed a parabolic oxidation behavior for all temperatures and environments. The activation energy for
oxidation was 154 kJ/mol in helium environment, and 261 kJ/mol in an air environment. The scanning
electron microscope (SEM) and energy-dispersive x-ray spectroscopy (EDS) results revealed that there were
a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbide after corrosion
test. The thickness and depths of degraded layers also showed a parabolic relationship with the time. A
corrosion rate of 950oC in impure helium was higher than that in an air environment, caused by difference
in the outer oxide morphology.
KEYWORDs : VHTR, Alloy 617, helium, high-temperature corrosion, oxidation
AUTHORs : 정 수 진†·이 경 근·김 동 진·김 대 종

Page : 93 - 101 DOWNLOAD
EN-DCPD 방법을 이용한 Alloy 600 재료의 국부부식균열 연구
The object of this work is to establish an electrochemical noise(EN) measurement technique combined with a direct current potential drop(DCPD) method for monitoring of localized corrosion cracking of nickel-based alloy, and to analyze its mechanism. The electrochemical current and potential noises were measured under various conditions of applied stress to a compact tension specimen in a simulated primary water chemistry of a pressurized water reactor. The amplitude and frequency of the EN signals were evaluated in both time and frequency domains based on a shot noise theory, and then quantitatively analyzed using statistical Weibull distribution function. From the spectral analysis, the effect of the current application in DCPD
was found to be effectively excluded from the EN signals generated from the localized corrosion cracking. With the aid of a microstructural analysis, the relationship between EN signals and the localized corrosion cracking mechanism was investigated by comparing the shape parameter of Weibull distribution of a mean
time-to-failure.
KEYWORDs : corrosion fatigue, direct current potential drop method, electrochemical noise measurement,Nickel-base alloy, primary water stress corrosion cracking, Weibull distribution function
AUTHORs : 이 연 주·김 성 우·김 홍 표†·황 성 식

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가압형 경수로 압력용기 재료인 저합금강의 동적 붕산 부식 실증 연구
This work is concerned with an evaluation of dynamic boric acid corrosion (BAC) of low alloy steel for
reactor pressure vessel of a pressurized water reactor (PWR). Mockup test method was newly established
to investigate dynamic BAC of the low alloy steel under various conditions simulating a primary water
leakage incident. The average corrosion rate was measured from the weight loss of the low alloy steel
specimen, and the maximum corrosion rate was obtained by the surface profilometry after the mockup
test. The corrosion rates increased with the rise of the leakage rate of the primary water containing boric
acid, and the presence of oxygen dissolved in the primary water also accelerated the corrosion. From the
specimen surface analysis, it was found that typical flow-accelerated corrosion and jet-impingement occurred
under two-phase fluid of water droplet and steam environment. The maximum corrosion rate was determined
as 5.97 mm/year at the leakage rate of 20 cc/min of the primary water with a saturated content of oxygen
within the range of experimental condition of this work.
KEYWORDs : boric acid corrosion, flow-accelerated corrosion, low alloy steel, mockup test, reactor pressure vessel, primary water leakage
AUTHORs : 김 성 우†·김 홍 표·황 성 식

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배관감육관리에 활용되는 CHECWORKS 프로그램의 열수력해석 방법론 검증에 관한 연구
In general, pipelines at nuclear power plants are affected by various types of degradation mechanisms and may be ruptured after gradually thinning. FAC (Flow-Accelerated Corrosion) is typical aging mechanism affecting the secondary side piping system. In Korea nuclear power plants, CHECWORKS program have
been used for management of wall thinning damages. However, sometimes, CHECWORKS program shows wrong results at the stage of NFA (Network Flow Analysis) in case of complex pipelines. This paper describes the calculation results of pressure drop in a complex pipeline and single line by using the CHECWORKS
program and the analysis results are compared with those of engineering calculation results including errors between them.
KEYWORDs : Flow-Accelerated Corrosion(FAC), CHECWORKS, Network Flow Analysis(NFA), Wear Rate Analysis(WRA), Wall Thinning
AUTHORs : 서 혁 기†· 황 경 모

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Evaluation of the inhibitive characteristics of 1,4-dihydropyridine derivatives for the corrosion of mild steel in 1M H2SO4
The present investigation deals with the corrosion inhibition of mild steel in 1M H2SO4 with 1, 4-dihydro pyridine and its derivatives prepared using microwave activation method. The synthesis of inhibitor was confirmed by IR spectra. The effect of 1, 4-dihydropyridine derivatives on the corrosion inhibition of mild steel in 1M H2SO4 was studied using weight loss and electrochemical polarization techniques. Influence of temperature (303-333K) and synergistic effect of halide ions (I–, Br– and Cl–) on the inhibition behaviour was also studied. Corrosion products on the metal surface were analyzed by scanning electron microscopy (SEM) and a possible mechanism of inhibition by the compounds is suggested. Thermodynamic parameters
were calculated using weight loss data in order to elaborate the mechanism of corrosion inhibition. Polarization measurements revealed that the studied compounds acted as mixed type inhibitor but slightly anodic in nature. Electrochemical impedance measurements revealed that the compounds were adsorbed onto the carbon steel surface and the adsorption obeyed the Langmuir adsorption isotherm. The synergistic effect of halide ions on the IE increases with increase in concentration. The IE obtained from atomic absorption spectrophotometric studies was found to be in good agreement with that obtained from the conventional weight loss method. SEM revealed the information of a smooth, dense protective layer in presence of the inhibitors.
KEYWORDs : dihydro pyridine, IE, impedance, polarization, SEM
AUTHORs : P. Sounthari, A. Kiruthika, J. Sai santhoshi, S. Chitra†, K. Parameswari, and A. Selvaraj

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