Leak before break assessment for class 1 piping in sodium-cooled fast reactors

Yada, Hiroki ; Takaya, Shigeru  ; Wakai, Takashi ; Machida, Hideo*

In the in-service inspection of sodium cooled fast reactors, an examination by continuous leak monitoring is considered for components constituting a sodium boundary. The continuous leak monitoring examinations are premises in a LBB (leak before break) being established. In previous LBB evaluation, the axial crack of the elbow flank has been evaluated, because in the piping system of the fast reactor with high thermal expansion, high stress is generated in the elbows flank. However, the LBB evaluations for circumferential cracks are important in the point of continuous leak monitoring in the in-service inspection. In this study, the load conditions in the LBB assessments for circumferential cracks were examined and LBB characteristics of 1 class 1 pipes of the prototype fast breeder reactor "Monju" were evaluated as an example.