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Yanggu, South Korea

Kim J.H.,Korea University | Kim Y.J.,Korea University | Lee S.H.,KHNP Co. | Bae H.Y.,Korea University | And 7 more authors.
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2011

In pressurized water reactors (PWRs), the reactor pressure vessel (RPV) upper head contains numerous control re drive mechanism (CRDM) nozzles. In the last 10 years, the incidences of cracking in alloy 600 CRDM nozzles and the associated welds has increased significantly. Several axial and circumferential cracks have been found in CRDM nozzles European PWRs and U.S. nuclear power plants. These cracks are caused by primary water stress corrosion crackir (PWSCC) and have been shown to be driven by welding residual stresses and operational stresses in the weld regio Therefore, detailed finite-element (FE) simulations for the Korea Nuclear Reactor Pressure Vessel have been conducted order to predict the magnitudes of the weld residual stresses in the tube materials. In particular, die weld residual stress resul are compared in terms for nozzle location, geometry factor r0/t, geometry of fillet, and adjacent nozzle. © 2011 The Korean Society of Mechanical Engineers. Source

Kang H.T.,KHNP Co. | Sung C.H.,KHNP Co. | Lee J.K.,KHNP Co.
Nuclear Engineering and Design | Year: 2011

This paper presents a standpoint of signal interface for a phased upgrade of instrumentation and control (I&C) systems in a pressurized water reactor (PWR) type nuclear power plant (NPP) in Korea. YongGwang nuclear (YGN) power plant units 3 and 4, which was constructed as a basis model for an optimized power reactor 1000 (OPR1000), is selected as a demonstration model for the presentation. A methodology for building interface requirements is suggested for a phased I&C systems upgrade, maintaining the same functions as those of existing systems, improving functions without violating the compliance requirements, and establishing a safe and economical upgrade schedule. For this, signal interfaces, from the standpoint of safety systems, between I&C cabinets in auxiliary electrical equipment rooms (EER) A and B and the main control room (MCR), the signal interface between the cabinet and the main control board (MCB), and the signal interface between the cabinet and the remote shutdown panel (RSP) are described. This paper focuses on the description of the following interface requirements, reflecting the phased upgrade strategies: system configuration, signal interface, and cabinet configuration. The suggested phased upgrade strategies include the following: non-safety I&C systems should be upgraded in phase 1, safety I&C systems should be upgraded in phase 2, and the MCR should be upgraded in phase 3. The findings presented in the paper can be reliably used to understand upgrade of I&C systems and to implement I&C systems for phased upgrades based on digital technologies. © 2011 Elsevier B.V. All rights reserved. Source

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