Reconstituted Mini Tensile Specimens

In order to evaluate the fracture toughness and Master Curve, the exact values of the tensile and yield strengths determined at the fracture toughness testing temperature are required. The fracture toughness should be measured around the T₀ reference temperature to obtain valid results. Tensile properties — if exists — are generally measured at room temperature, and at the maximum operation temperature of the pressure vessel. If T₀ reference temperature is different from these temperatures a correction formula is used for interpolation or extrapolation. Several times even no reliable tensile results are available, especially in the case of irradiated specimens. Use of irradiated Charpy remnants is a solution to produce tensile bars. A specific method has been developed to produce 12 pieces of flat 2*1 mm cross section tensile specimens made from one half Charpy specimens using stud weld reconstitution. The specimen cutting is made using thin molybdenum wire spark cutting. In order to do so difficulties of handling the small radioactive specimens needed to be solved, special grips were developed for the tensile machine to clamp the miniature tensile specimens. A laser extensometer was used to measure the strain and a video microscope was used to determine the cross section after the fracture without touching the specimen. The paper presents the results obtained on more than 200 irradiated small tensile specimens. These results had been compared to the old surveillance ones.