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이선기(S. K. Lee),이상국(S. G. Lee),박성근(S. K. Park),노영진(Y. J. Rho) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11
The CANDU type reactors require on power refuelling by the two remotely controlled fuelling machines. The refuelling operation is carried out along the coolant direction by the drag force of fuel bundles for most channels. However, for about 30% of channels the coolant flow is not sufficiently high enough to carry fuel bundles to the downstream. Therefore, a device, FARE (Flow Assist Ram Extension) device, is used to create an additional drag force to push the fuel bundles along the coolant flow. The FARE device has been causing the channel flow low phenomena of channels due to more than excessive blockage of coolant flow. The flow rate change for the channels is monitored on line for the coolant flow blockage of the channels. This has initiated the investigation of the FAKE device behavior and the cause and remedy for the problem. The analysis revealed that the channel flow low occurs as the insertion of the FARE device into the active core flow and disappears as the removal of the FARE device from it. In order to eliminate the channel flow low phenomena, flow resistance by the FARE device should be reduced. The analysis has revealed that a too much relaxation of flow resistance would make the FARE device unable to push the fuel bundle string, and a too little relaxation would make the FARE device unable to eliminate the channel flow low phenomena. Suggested design changes include more flow holes in the tube.
원전 안전주입 배관에서의 In-Leakage 에 의한 열성층 현상에 관한 연구
김광추(K. C. Kim),박만흥(M. H. Park),염학기(H. K. Youm),김태룡(T. Y. Kim),이선기(S. K. Lee) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
In case that in-leakage through the valve disk occurs, a numerical study is performed to estimate on<br/> thermal stratification phenomenon in the Safety Injection piping connected with the Reactor Coolant System<br/> piping of Nuclear Power Plant. As the leakage flow rate increases, the temperature difference between top and<br/> bottom of horizontal piping has the inflection point. In the connection point of valve and piping, the<br/> maximum temperature difference between top and bottom was 185K and occurred in the condition of 10<br/> times of standard leakage flow rate. In the connection point of elbow and horizontal piping, the maximum<br/> temperature difference was 145K and occurred in the condition of 15 times of standard leakage flow rate. In<br/> the vertical piping of Safety Injection piping, the near of connection point between elbow and vertical piping<br/> showed the outstanding thermal stratification phenomenon in comparison with another region because of<br/> turbulent penetration from Reactor Coolant System piping. In order to prevent damage of piping due to the<br/> thermal stratification when in-leakage through the valve disk occurs, the connection points between valve and<br/> piping, and the connection points between elbow and piping need to be inspected continually.
김광추(K. C. Kim),박만흥(M. H. Park),염학기(H. K. Youm),김태룡(T. Y. Kim),이선기(S. K. Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Numerical study is carried out for thermal stratification on residual heat removal piping connected with<br/> RCS piping of NPP. The turbulent penetration length reaches to 1^st isolation valve. Thermal stratification<br/> mainly occurs in the horizontal piping connected with elbow. The maximum temperature difference occurs in<br/> the location where horizontal piping starts passing elbow. The temperature difference between upper and<br/> lower of horizontal piping changes with valve leak, curve radius of elbow, pipe thick and connection of hotleg<br/> injection line. Thermal stratification effect in the backward of 1^st valve is small when piping thick is not<br/> considered and when valve is isolated, but is large when piping thick is considered or when valve leaks.
노영진(Y. J. Roh),이선기(S. K. Lee),박준현(J. H. Park),이상국(S. G. Lee) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.11
Active mechanical equipment such as pumps and valves used in nuclear plant systems should be qualified for operation and integrity in accordance to the requirements of ASME QME-1 or KEPIC MF. However qualification test for active mechanical equipment is being conducted in abroad because there are no large capacity test facilities for functional qualification of valve under high temperature-high pressure within the country. The purpose of this study is to introduce qualification methods and procedures for valves used in nuclear plant systems by functional qualification test facilities under high temperatures and pressure in accordance to the Code of ASME QME-1.
밸브누설이 존재하는 안전주입계통배관에서의 열성층 유동해석
박만흥(M.H.Park),김광추(K.K.Kim),김태룡(T.Y.Kim),이선기(S.K Lee),김경훈(K.Y. Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
A numerical analysis has been performed to estimate the effect of thermal stratification in the safety<br/> injection system piping lines. This phenomenon of thermal stratification is usually observed in the piping<br/> lines of the safety injection system that is connected high pressure and high temperature system as well<br/> as this system is isolated by isolation valve normally.<br/> This piping lines may be identified as the source of fatigue in the piping system due to the thermal<br/> stress loading which are associated with plant operating modes. The turbulent penetration length,<br/> generally, reaches to 1^st isolation valve in safety injection system piping from reactor coolant system at<br/> normal power operation when a high temperature coolant does not leak out through 1^st isolation valve. At<br/> that time, therefore, the thermal stratification does not appear in the piping between RCS piping and 1^st<br/> isolation valve of safety injection system piping.<br/> When a high temperature coolant leak out through the 1^st isolation valve by any damage of isolation<br/> valve, however, the thermal stratification can occur in the safety injection system piping. At that top and<br/> bottom leakage, the maximum temperature difference of fluid between top and bottom in the piping is,<br/> respectively, estimated about 20 and 27℃. But the thermal load and potential for branch pipes is<br/> considered insignificant, since the maximum temperature difference is less than 27.8℃(maximum<br/> potential temperature difference). Therefore, it is considered that this will be ignored the effect of thermal<br/> stratification in safety injection system piping with valve leakage.