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원전감육배관 UT 두께측정 결과의 신뢰도 평가를 위한 다자비교시험
이승준(Seung-Joon Lee),이원근(Won-Geun Yi),이준현(Joon-Hyun Lee),이성호(Sung-Ho Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
The reduction of pipe-thickness induced by flow accelerated corrosion (FAC) is one of the most serious problems on the maintenance of piping system in nuclear power plants (NNP). If the thickness of a pipe component is reduced below the critical level, it cannot sustain pressure and consequently results in leakage or rupture. For this reason, wall thinning by FAC has been inspected in secondary side piping systems in NPPs. In this research Round Robin Test (RRT) was conducted to verify confidence of wall thinning measurement system in NPP. 12 inspectors from 3 companies participated and 23 specimens were used according to standard practice in RRT. The gage R&R analysis was introduced in regard to repeatability and reproducibility that are affected to measurement system errors. Confidence intervals of thickness measurement system were obtained.
원전 CEDM 노즐의 밀봉보수용접시 발생하는 잔류응력에 대한 해석적 연구
강종호(Jong-Ho Kang),정윤교(Yoon Gyo Jung),장윤찬(Yun-Chan Jang),이재봉(Ja-Bong Lee),이원근(Won-Geun Yi),조영태(Young Tae Cho) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.2
The reactor vessel closure head has many CEDM nozzles through which the control element drive mechanisms pass. The CEDM nozzle weld region of the reactor vessel closure head is composed of Alloy 600 material. It has been found that cracks occur due to the high stress generated during normal operation of the nuclear power plant and the contact environment with the primary cooling water. Seal Weld Repair blocks the environmental factor that may causes primary water stress corrosion cracking(PWSCC) by covering Alloy 600 weld region which is susceptible to PWSCC with Alloy 690 resistant to the stress corrosion cracking. In this study, a finite element analysis was performed to evaluate the effect of residual stress formation by seal weld repair in the nuclear power plant CEDM nozzle. The thickness of the welded structure and the number of welded layers were considered as variables. As a result, we showed that seal weld repair for J-groove weldment of CEDM nozzle can release the tensile residual stress so that the possibility of occurrence of PWSCC can be reduced. Also, it has shown that a multi-layer is more effective and thicker weld bead is more secured for reducing residual stresses in J-groove weld.