Our Case Studies Thermal Stresses in the COGD Skirt under Flooded Conditions

Fracture assessments of the gas baffle and circulator outlet gas duct (COGD) for normal operation and overpressure fault loading have recently been carried out as part of the second periodic safety review of two of the client’s nuclear power stations.

These assessments were carried out principally to take account of the latest estimates of the maximum pressure differences across the gas baffle and also to incorporate the latest information on the welding residual stresses. More recently, the work has been extended to consider the fracture assessment at the gas baffle doubler plate and small nozzles in the COGD. A requirement arose as part of the consolidated boiler tube failure safety case to consider the integrity of the gas baffle under a postulated post-trip natural circulation cooling fault.