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http://dx.doi.org/10.20466/KPVP.2019.15.1.071

Evaluation of Fracture Toughness considering Constraint Effect of Reactor Pressure Vessel Nozzle  

Kweon, Hyeong Do (한국수력원자력(주) 중앙연구원)
Lee, Yun Joo (한국전력기술(주) 원자로설계개발단)
Kim, Dong Hak (한국수력원자력(주) 중앙연구원)
Lee, Do Hwan (한국수력원자력(주) 중앙연구원)
Publication Information
Transactions of the Korean Society of Pressure Vessels and Piping / v.15, no.1, 2019 , pp. 71-76 More about this Journal
Abstract
Actual stress distributions in the nozzle of a pressure vessel may not be in plane strain condition, implying that the crack-tip constraint condition may be relaxed in the nozzle. In this paper, a methodology for evaluating the fracture toughness of the ASME Code is presented considering the relaxation of the constraint effect in the nozzle of the reactor pressure vessel. The crack-tip constraint effect is quantified by the T-stress. The equation, which represent the relation between the fracture toughness in the lower constraint condition and the plane strain fracture toughness, is derived using the T-stress. This equation is similar to the method for evaluating the fracture toughness of the Master Curve for low constraint conditions. As a result of evaluating the fracture toughness considering the constraint effect in the reactor inlet, outlet and direct injection nozzles using the proposed equation, it was confirmed that the fracture toughness in the nozzles is higher than the plane strain fracture toughness. Applying the proposed evaluation methodology, it is possible to reflect the relaxation of the constraint effect in the nozzles of the reactor pressure vessel, therefore, the safe operation area on the pressure-temperature limit curve can be prevented from being excessively limited.
Keywords
Constraint Effect; Fracture Toughness; Nozzle; Pressure-Temperature Limits Curve; T-stress;
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