BOILING WATER REACTOR CORE SHROUD REPAIR

摘要

Cracking in the circumferential welds of boiling water reactor (BWR) core shrouds has been observed in a number of plants worldwide. The loss of a circumferential weld in the core shroud could affect the ability of the plant to safely shutdown following a seismic event or an accident such as a main steam or recirculation line break. This paper presents a simple, reliable and readily installed core shroud repair which addresses this problem. The repair has been approved by the NRC and installed in two operating BWRs. It consists of several preloaded tie-rods with integral radial supports located around the outside of the core shroud. This paper addresses key design features of the repair, including those which minimize the potential for loss of preload and future cracking of the shroud, even during plant transients which inject relatively cold water into the reactor vessel. The innovative non-linear seismic restraint system design is also addressed along with the seismic analysis approach and typical results.