Varfolomeyev, I.I.VarfolomeyevHolzer, W.W.HolzerBeukelmann, D.D.BeukelmannMayinger, W.W.Mayinger2022-03-102022-03-102005https://publica.fraunhofer.de/handle/publica/347923Finite element analyses have been performed to investigate behaviour of postulated cracks in the longitudinal weld of a 90° pipe elbow in the reactor coolant line of a German PWR. At the extrados a pipe whip restraint is welded on the outer surface of the elbow in order to prevent pipe whip for the postulated double-ended rupture. However, this arrangement significantly increases the effort for non-destructive testing (NDT) during in-service inspections. Moreover, weld sections of about 80 mm to 160 mm length cannot be accessed by NDT from outside. According to the German RSK (Reactor Safety Commission) Guideline, cracks postulated in areas of restricted access for NDT or in non-examinable zones should not cause a catastrophic failure of the reactor coolant line. To assure the safety of the pipe elbow against crack initiation and unstable propagation, numerical stress and crack driving force calculations are carried out taking into account the real geometry of the pipe whip restraint. Both Service Level A Loadings and Service Level D Loadings (e.g. earth quake, plane crash) are investigated. For comparison purposes the same elbow geometry without restraint is analysed. The material Ji value and the slope dJ/da of the measured JR-curve are employed as criteria for crack initiation and instability. The result suggest the critical length of a through crack (2c) at initiation to be of some 800 mm which is considerably larger than the length of the non-examinable zone. Furthermore, by comparing the s lope of the Jappl(2c) curve with the material resistance curve, a conclusion can be drawn that no crack instability may occur for any crack size below the length of the pipe whip restraint. The restraint arrangement considerably increases t he carrying capacity and residual strength of the elbow.enpipe whip restraintelbowcritical crack sizePWR531620conference paper