High Temperature Leak Before Break Assessments

摘要

The use of Leak Before Break (LbB) arguments is well established in the nuclear industry. A 'detectable leakage'rnLbB procedure, similar to that of NUREG 1061, is commonly used. Such a procedure is included in the UK R6 defectrnassessment procedures and involves achieving an adequate margin between the evaluated critical crack length and therndetectable leakage crack length. However, experience in applying LbB methods with the effects of creep included in thernanalysis is still limited. This paper contains results of calculations aimed at assessing how these influences impact upon thernsafety margins achieved in a low temperature application.rnIt has been demonstrated that the limiting crack length reduces with creep time. This has a detrimental effect whenrnproducing a high temperature LbB case. It has also been shown that the length of crack required for a detectable leakagernreduces with creep time, the effect being most noticeable for long creep times. This has a beneficial effect when producing arnhigh temperature LbB case.