Simplified Method for Damage Inference Based on Out-Reactor Test Results

Damage inference based on out-reactor test results is important for reactor component remaining life assessment and maintenance planning. Regarding material plastic deformation and creep with changing material property data with temperatures, the damage inference calculation could be complicated and computationally intensive. In the paper, to present a simplified method for damage inference, a thermal cycling testing sample designed by Idaho National Laboratory was utilized in a finite element model. The material property data applied in the model were from ASME BPVC Section II part D and related code cases, the creep damage in the sample was introduced through a temperature transient with the highest temperature of 650 °C for 10,000 hours. MPC Omega approach described in API579 part 10, Larson-Miller equation based time fraction and Kocks-Merking model were applied to calculate material creep strain and damage. With the total strain results from the SS316 driving column in the finite element model, the creep damage of the SS316 sample was estimated through an MS EXCEL spreadsheet. The simplified method for creep damage inference gives the conservative result, i.e., around 15% higher than that from finite element calculations. The methodology presented in the paper shows a quick and reliable approach for damage inference from out-reactor test results.