Specimen reconstitution is a technique which allows limited amounts of material to be used effectively for mechanical testing. In this respect the technique can partly act as an alternative for specimen miniaturization. As welding is the commonly used fusion method there is an inherent risk of annealing of irradiated material, which could lead to non-conservative test results in irradiation embrittlement studies. The objective of this study was to characterize in detail temperature transients in welding and the load carrying capacity of the weld seams. The technique was also verified with Charpy-V and fracture toughness tests using irradiated material.