Influence of the Edge Effect in Pipeline–Nozzle Welds During “Leak Before Break” Validation

An appraisal was made of the influence of the edge effect, which is induced when branch-pipes are welded to the nozzles of a multiple forced circulation loop of power units with RBMK-1000, on the stress-strain state of the welds between the branch-pipes and the pipelines attached to them during the process of validating the concept “leak before break” (LBB). On the basis of finite-element modeling and an analytical solution of a problem of theoretical elasticity – the pinching of the edge of a cylindrical shell, it is shown that the edge generates local stresses, whose distribution is skew-symmetric with respect to the equidistant surface of the nozzle. These stresses do not contribute to the ductile failure of structural elements. In addition, on account of the rapid damping the response from the effect does not affect the stressed state of the welds between branch-pipes and pipelines. It is shown based on the findings that the approaches to the computational validation of the LBB concept for such welds are identical to those applied to the welds on straight sections of pipelines and do not need additional correction.