Summary
Residual stress and strain measurements were performed on a mock-up consisting of a 160 mm thick low-alloy ferritic steel plate of type SA-508 Class 3 with a single layer weld deposited strip cladding of austenitic stainless steel E308L. The cladding was manufactured with submerged arc strip welding adapted to a procedure used for reactor pressure vessels in the 1970s. Comprehensive measurements of the thermal response during welding was recorded to provide information e.g. for validation of numerical modelling. Detailed through thickness measurements of residual stresses were performed using the methods deep hole drilling and incremental centre-hole drilling, at two different locations in the as-welded state and at three different locations after post weld heat treatment.
Residual stress and strain measurements were performed on a mock-up consisting of a 160 mm thick low-alloy ferritic steel plate of type SA-508 Class 3 with a single layer weld deposited strip cladding of austenitic stainless steel E308L. The cladding was manufactured with submerged arc strip welding adapted to a procedure used for reactor pressure vessels in the 1970s. Comprehensive measurements of the thermal response during welding was recorded to provide information e.g. for validation of numerical modelling. Detailed through thickness measurements of residual stresses were performed using the methods deep hole drilling and incremental centre-hole drilling, at two different locations in the as-welded state and at three different locations after post weld heat treatment.
Neutron embrittlement of the reactor pressure vessel generally limits the possible long-term operation of a nuclear power plant to e.g. 60 or 80 years. Sufficient remaining safety margins with respect to fracture has to be verified by structural integrity analyses that consider the plant surveillance tests results, defects in and near the cladding, the dimensioning load cases, and also residual stresses in the reactor pressure vessel. For these reasons good understanding and well documented estimates of the residual stresses in the cladding are very valuable.
The residual stresses measured in the mock-up deviates from the residual stresses in a cladded reactor pressure vessel, since the mock-up was not subjected to pressure test. However, the detailed results presented in this report are very valuable for validation of numerical modelling, which can be used to predict the residual stress state including effects of pressure tests and operational loads, for cylindrical geometries, and for cladding processes other than submerged arc strip welding.