원전 2차계통의 수화학 변화가 배관감육에 미치는 영향 분석

윤훈 ( Hun Yun ),황경모 ( Kyeong Mo Hwang ),문승재 ( Seung Jae Moon ) 한국부식방식학회(구 한국부식학회) 2015 Corrosion Science and Technology Vol.14 No.6

Pipe wall-thinning by flow-accelerated corrosion (FAC) is a significant and costly damage of secondary system piping in nuclear power plants (NPPs). All NPPs have their management programs to ensure pipe integrity from wall-thinning. This study analyzed the pipe wall-thinning caused by changing the amine, which is used for adjusting the water chemistry in the secondary system of NPPs. The pH change was analyzed according to the addition of amine. Then, the wear rate calculated in two different amines was compared at the steam cycle in NPPs. As a result, increasing the pH at operating temperature (Hot pH) can reduce the rate of FAC damage significantly. Wall-thinning is affected by amine characteristics depending on temperature and quality of water.

원전 배관의 두께 측정 데이터에 대한 신뢰도 분석 방법 및 적용

윤훈 ( Hun Yun ),황경모 ( Kyeong Mo Hwang ),이효승 ( Hyo Seoung Lee ),문승재 ( Seung Jae Moon ) 한국부식방식학회(구 한국부식학회) 2015 Corrosion Science and Technology Vol.14 No.1

Pipe wall-thinning by flow-accelerated corrosion and various types of erosion is significant damage in secondary system piping of nuclear power plants(NPPs). All NPPs in Korea have management programs to ensure pipe integrity from degradation mechanisms. Ultrasonic test(UT) is widely used for pipe wall thickness measurement. Numerous UT measurements have been performed during scheduled outages. Wall-thinning rates are determined conservatively according to several evaluation methods developed by Electric Power Research Institute(EPRI). The issue of reliability caused by measurement error should be considered in the process of evaluation. The reliability analysis method was developed for single and multiple measurement data in the previous researches. This paper describes the application results of reliability analysis method to real measurement data during scheduled outage and proved its benefits.

원전 2차계통의 출력증강 운전에 따른 배관감육 영향 분석

윤훈 ( Hun Yun ),황경모 ( Kyeong Mo Hwang ),이효승 ( Hyo Seoung Lee ),문승재 ( Seung-jae Moon ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.3

Piping and equipment are degraded by flow-accelerated corrosion (FAC) in nuclear power plants. FAC causes numerous problems and nuclear utilities maintain programs to control FAC. The key parameters influencing FAC are hydrodynamic conditions, water chemistry, and effect of materials. Recently, a nuclear utility has planned slight power uprates in Korea. Operating conditions need to be changed in the secondary system according to power uprates. This study analyzed the effect of wall-thinning caused by power uprates. The change of operation data in the secondary cycle is reviewed, and wall-thinning rates are analyzed in the main lines. As a result, two phase (mixture of water and steam) lines have a greater impact than a water line under power uprate conditions. Also, the quality of steam is the most important factor for FAC in two phase lines.

원전 배관의 반복 측정 데이터에 대한 신뢰도 분석 방법

윤훈 ( Hun Yun ),황경모 ( Kyeong Mo Hwang ) 한국부식방식학회(구 한국부식학회) 2013 Corrosion Science and Technology Vol.12 No.3

Safety is a major concern in Nuclear Power Plants (NPPs). Piping systems in NPPs are very complex and composed of many components such as tees, elbows, expanders and straight pipes. The high pressure and high temperature water flows inside piping components. As high speed water flows inside piping, the pipe wall thinning occurs in various reasons such as FAC (Flow Accelerated Corrosion), LDIE (Liquid Droplet Impingement Erosion) and Flashing. To inspect the wall thinning phenomenon and protect the piping from damages, piping components are checked by UT measurement in every overhaul. During every overhaul, approximately 200~300 components (40,000~60,000 UT data) are examined in NPPs. There are some methods from EPRI for evaluating wear rate of components. However, only few studies have been conducted to find out the raw data reliability for the wear rate evaluation. Securing the reliable raw data is the key factor for a reasonable evaluation. This paper suggests the reliability analysis method for the repeatedly measured data for wear rate evaluation.

예측모델 및 실험을 통한 액적충돌침식 손상 평가

윤훈(Hun Yun),황경모(Kyeong Mo Hwang) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.10

유동가속부식(FAC)은 가장 잘 알려진 탄소강 배관 손상 메커니즘으로 현재 국내 전 원전에서는 유동가속부식으로 인한 감육현상을 관리할 수 있는 체계적인 방안이 수립되어 있다. 그러나, 발전소 배관은 다양한 침식손상 메커니즘에 의해 여전히 손상을 받고 있다. 대표적인 침식 메커니즘은 캐비테이션, 액적충돌침식(LDIE), 플래싱, 고체입자침식(SPE)이다. 본 논문에서 기술하는 액적충돌침식 은 손상 예측이 어렵고, 관리를 위한 체계적인 방안도 수립되어 있지 않다. 본 논문에서는 실제 발전소 현장에서 발생한 사례를 바탕으로 기존에 개발된 예측 모델과 실험을 통해 얻어진 상관식을 비교하여 액적충돌침식으로 인한 손상을 평가할 수 있는 방법을 제시하였다. Flow-accelerated corrosion (FAC) is a well-known phenomenon that may occur in piping and components. Most nuclear power plants have carbon-steel-pipe wall-thinning management programs in place to control FAC. However, various other erosion mechanisms may also occur in carbon-steel piping. The most common forms of erosion encountered (cavitation, flashing, Liquid Droplet Impingement Erosion (LDIE), and Solid Particle Erosion (SPE)), have caused wall thinning, leaks, and ruptures, and have resulted in unplanned shutdowns in utilities. In particular, the damage caused by LDIE is difficult to predict, and there has been no effort to protect piping from erosive damage. This paper presents an evaluation method for LDIE. It also includes the calculation results from prediction models, a review of the experimental results, and a comparison between the UT data in the damaged components and the results of the calculations and experiments.

배관감육 평가를 위한 UT 측정 신뢰도 분석

윤훈 ( Hun Yun ),황경모 ( Kyeong Mo Hwang ) 한국부식방식학회(구 한국부식학회) 2012 Corrosion Science and Technology Vol.11 No.4

UT (Ultrasonic Test), one of the non-destructive tests, is the most common thickness measurement method for evaluating the wear rate in NPPs (Nuclear Power Plants). UT is used widely because it is easy and safe for use. However some amount of error inevitably occurs in attempting to measure the thickness. The error, that could make the thickness data thicker or thinner, may affect estimation of wear rate in pipes. NPPs are composed of a lot of pipes and components. Some of them are tested to check the current status during RFO (Re-Fueling Outage). Reliability analysis of UT is essential for evaluating pipe wear rate and establishing the long-term management plan in NPPs. This paper reviewed the cause of error occurrence and presented the UT data reliability analysis method. Also, this paper shows the application result of reliability analysis to the UT data acquired in NPPs.

예측모델 및 실험을 통한 액적충돌침식 손상 평가에 대한 연구

윤훈(Hun Yun),황경모(Kyeong Mo Hwang) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4

유동가속부식(FAC)은 가장 잘 알려진 탄소강 배관 손상 메커니즘으로 현재 국내 전 원전에서는 유동가속부식으로 인한 감육현상을 관리할 수 있는 체계적인 방안이 수립되어 있다. 그러나, 발전소 배관은 다양한 침식손상 메커니즘에 의해 여전히 손상을 받고 있다. 대표적인 침식 메커니즘은 캐비테이션, 액적충돌침식(LDIE), 플래싱, 고체입자침식(SPE)이다. 본 논문에서 기술하는 액적충돌침식은 손상 예측이 어렵고, 관리를 위한 체계적인 방안도 수립되어 있지 않다. 본 논문에서는 실제 발전소 현장에서 발생한 사례를 바탕으로 기존에 개발된 예측 모델과 실험을 통해 얻어진 상관식을 비교하여 액적충돌침식으로 인한 손상을 평가할 수 있는 방법을 제시하였다. FAC is a well-known phenomenon that may occur in piping and components. Most nuclear power plants have carbon steel pipe wall thinning management programs in place to control flow-accelerated corrosion (FAC). However, various erosion mechanisms may also occur in carbon steel piping. The most common forms of erosion encountered, cavitation, flashing, LDIE(Liquid Droplet Impingement Erosion), and SPE(Solid Particle Erosion), have caused wall thinning, leaks, and ruptures and results in unplanned shutdowns in utilities. Especially LDIE is difficult to predict damage and there has not been an effort to protect piping from erosive damage. This paper presents the evaluation method for the LDIE. This paper also includes the calculation result using prediction models, the review of the experiment result, and the comparison between the UT data in the damaged component and the results of calculation and experiment.

〈기술논문〉 원전 탄소강 배관의 국부감육 현상과 난류 속도성분의 상관관계 확인

윤훈(Hun Yun),황경모(Kyeong Mo Hwang),진태은(Tae Eun Jin),김경훈(Kyung Hoon Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

A study to identify the relation between turbulence coefficient and local wall thinning inside carbon steel piping was performed. Experiments and numerical analyses for the several types of downscaled piping components took place and the results were compared with each other. Based on the results indicating that flow behaviors inside piping components can be sufficiently simulated by numerical analysis, numerical analysis for the models magnified to the actual size of plants was carried out. To identifythe relation between turbulence coefficients and local wear rate, numerical analysis was performed for 17 components of 9 types included in feedwater system. Turbulence coefficients resulting from numerical analysis were compared with local wear rates based on the measured data. From the comparison of the results, the vertical flow velocity component (Vr) flowing again to the wall after having separated due to geometrical configurations or colliding with wall directly at an angle of some degrees was analogous to the configuration of local wall thinning. From the least squares fitting result, it was derived that the average relationship between the Vr and local wear rate is in proportion to 0.55 time of the Vr adding 0.1 with the standard deviation of 0.65.

원전 2차측 배관 감육여부 판별을 위한 Total Point Method 전산 알고리즘 개발

오영진,윤훈,문승재,한경희,박병욱,Oh, Young Jin,Yun, Hun,Moon, Seung Jae,Han, Kyunghee,Park, Byeong Uk 한국압력기기공학회 2015 한국압력기기공학회 논문집 Vol.11 No.2

Pipe wall-thinning by flow-accelerated corrosion (FAC) and various types of erosion is a significant and costly damage phenomenon in secondary piping systems of nuclear power plants (NPPs). Most NPPs have management programs to ensure pipe integrity due to wall-thinning that includes periodic measurements for pipe wall thicknesses using ultrasonic tests (UTs). Nevertheless, thinning evaluations are not easy because the amount of thickness reduction being measured is often quite small compared to the accuracy of the inspection technique. U.S. Electric Power Research Institute (EPRI) had proposed Total Point Method (TPM) as a thinning occurrence evaluation method, which is a very useful method for detecting locally thinned pipes or fittings. However, evaluation engineers have to discern manually the measurement data because there are no numerical algorithm for TPM. In this study, numerical algorithms were developed based on non-parametric and parametric statistical method.

시계열 이미지 분석을 위한 딥러닝 기반의 시간축 이미지 분석 제안

박재한(Jae Han Park),윤훈(Hun Yun),임재성(Jae Seong Im),신수용(Soo Young Shin) 한국통신학회 2023 한국통신학회 학술대회논문집 Vol.2023 No.6