• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.191-198
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• 2008

Flow accelerated corrosion (FAC) phenomenon of low alloy carbon steels in nuclear power plant has been known as one of major degradation mechanisms. It has a potential to cause nuclear pipe rupture accident which may directly impact on the plant reliability and safety. Recently, the equipotential switching direct current potential drop (ES-DCPD) method has been developed, by the present authors, as a method to monitor wall loss in a piping. This method can rapidly monitor the thinning of piping, utilizing either the wide range monitoring (WiRM) or the narrow range monitoring (NaRM) technique. WiRM is a method to monitor wide range of straight piping, whereas NaRM focuses significantly on a narrow range such as an elbow. WiRM and NaRM can improve the reliability of the current FAC screening method that is based on computer modeling on fluid flow conditions. In this paper, the measurements by ES-DCPD are performed with signal sensitivity analyses in the laboratory environment for extended period and showed the viability of ES-DCPD for real plant applications.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.401-406
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• 1997

발전소 기동 및 저출력 운전시 원자력발전소(PWR) 터빈운전원(T/O)들은 증기발생기 수위제어를 위해 배전반(MCR)에 증기발생기 수위제어 관련 경험이 있는 운전원 3명 이상이 좁은 보드앞에서 각자 S/G A, B, C의 주요 파라미터들을 감시하며 수동운전하게 된다. 이렇게 운전원들이 많은 위험부담을 안고 수동운전하는 이유는 증기발생기 수위제어는 증기발생기 내부의 광역수위 측정범위가 약 14.2(m)이고, 주요 제어변수를 측정하는 협역수위는 약 3.2(m)로 매우 적어서 물의 Swell, Shrink 현상과 급수온도의 영향으로 제어하기 매우 어렵기 때문이다. 그러나 DCS(Distributed Control System)내의 한 부분인 공정감시제어를 위한 MMI(Man Machine Interface) Software를 사용하면 한사람이 증기발생기 수위제어 전 계통의 감시 및 제어가 가능하게 된다. 또한 과거나 현재의 변화 추이 및 문제점 분석은 물론, 계통의 결함 발생시 경보가 발생하여 경보발생 화면을 선택할 경우 어느 부분에서 결함이 발생했는지를 보여준다. 만약 이 화면을 운전원이 아닌 현장 Engineer가 보았을 경우는 결함부분의 확인 및 결함카드 보수가 가능하여 운전원들의 작업부담 감소와 이로 인한 다른 계통 점검 시간을 충분히 확보할 수 있다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.7
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• pp.550-557
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• 2017

Ionospheric delay, which affect the accuracy of GNSS positioning, is generated by electrons in Ionosphere. Solar activity level, region and time could make change of this delay level. Dual frequency receiver could effectively eliminate the delay using difference of refractive index between L1 to L2 frequency. But, Single frequency receiver have to use limited correction such as ionospheric model in standalone GNSS or PRC(pseudorange correction) in Differential GNSS. Generally, these corrections is effective in normal condition. but, they might be useless, when TEC(total electron content) extremely increase in local area. In this paper, monitoring algorithm is proposed for local ionospheric anomaly using multiple reference stations. For verification, the algorithm was performed with specific measurement data in Ionospheric storm day (20. Nov. 2003). this algorithm would detect local ionospheric anomaly and improve reliability of ionospheric corrections for standalone receiver.