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RISS 인기검색어
- 검색키워드
- 저자 : 최선영(Sun Yeong Choi) (검색결과 5 건)
- 무료
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최선영(Sun Yeong choi),최영환(Young Hwan Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
The purpose of this paper is to analyze piping failure trend of safety pipings in domestic nuclear power plants. First. database for the piping failure was constructed with 105 data fields. The database includes plant population data. event data. and service history data. 7 kinds of piping failures in domestic NPPs were investigated. Among the 7 cases. detailed root causes were investigated for 3 cases. The first one is pipe wall thinning in main feedwater pipings of Westinghouse 3 loop type plants. The root cause of the wall thinning was flow accelerated corrosion near welding area. The next one is leak event in chemical and volume control system(CVCS) due to vibration. Some cracks occurred in socket welding area. The events showed that the integrity of socket weld is very vulnerable to vibration. The last one is also a leak event in primary sampling line in Korean standard reactor due to thermal fatigue. Although the structural integrity was not maintained by the events. there was no effect on nuclear safety ill the above 3 piping failure eases.
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원자력발전소 주제어실 다중 경보 패턴에 의한경보/비정상 대응 체계 개발
최선영 ( Sun Yeong Choi ),정원대 ( Wong Dea Jung ) 한국안전학회(구 한국산업안전학회) 2014 한국안전학회지 Vol.29 No.3
The number of abnormal operation procedures (AOPs) for mitigating a plant abnormal status amounts to about one hundreds for the most of 1000MWe optimized power plant (OPR1000) and it is expected that the number of AOPs would be increased to cope with an abnormal status occurred newly. However, it is not well organized for operators to select a proper AOP from alarms occurred in main control room (MCR) during a plant abnormal status. It may be a burden to operators since the selection of AOP to respond an abnormal status is authorized by operators. When multiple alarms occur in MCR, it would take more time to respond them than a single alarm. To reduce the efforts, various MCR operation support systems have been developed. The purpose of this study was to develop a multi-alarm pattern card to select an appropriate AOP effectively when multiple alarms occurs in a single upper layout (UL)of MCR. It can be applied for an operation support tool as well as an education tool.
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최영환(Young Hwan Choi),최선영(Sun Yeong Choi),허남수(Nam Su Huh) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Recently, the integrity of socket weld is regarded as a safety concern in nuclear power plants because lots of failures and leaks have been widely reported in the socket weld. The purposes of this paper are to perform piping failure analysis on the socket weld in domestic nuclear piping including the estimation of the piping failure frequency and the evaluation of the socket weld integrity. The ASME Code Sec. Ⅲ requires 1/16inch gap between piping and fitting in the socket weld and weld leg of 1.09*t where t is the pipe thickness. The effects of the requirements in the ASME Code Sec. Ⅲ on the socket weld integrity were evaluated using 3 dimensional finite element method(FEM). The results are as follows; (1) The socket weld is susceptible to the vibration if the vibration levels exceed the requirement in the ASME Code OM. (2) The effect of the pressure or temperature transient loads on socket weld in CVCS and PSS is not significant because of the very low frequency of the transient during the plant lifetime operation. (3) 'No gap' is very risky to the socket weld integrity for the specific systems having the vibration condition to exceed the requirement in the ASME Code OM and/or the transient loading condition from p=0 and T=25℃ to P=15.51㎫ and T=288℃. To such systems, RT to examine the gap during construction stage is strongly recommended. (4) The reduction of weld leg 0.75*t from 1.09*t with 'no gap' can affect on the socket weld integrity by a factor of 1.5.
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최영환(Young Hwan Choi),최선영(Sun Yeong Choi),김홍기(Hong Key Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The reliability of nuclear piping can be assured by performing the intended function under operating conditions and by maintaining the integrity during the design life time. The reliability of nuclear piping should be controlled through the all stages of design, construction, and operation. During the design stage, mechanical integrity, material selection, water chemistry design, and operation condition should be comprehensively considered. The nuclear piping should be constructed, manufactured, installed, and inspected according to the codes, standards, and regulations. The piping failure and aging during operation should be managed by using the in-service inspection, leakage detection, and aging management. In this study, the characteristics of nuclear piping and welding were reviewed and the piping failure cases and related databases were investigated. We proposed guidelines and methods for the piping design, piping management, piping aging management, and the measurement of material properties in order to enhance the reliability of nuclear piping.
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