Annealing Requirements for Flow-Formed Containment Vessels for Type B Radioactive Materials

Flow forming, an advanced version of metal spinning, is becoming a popular technique for the fabrication of containers for the storage and transportation of radioactive materials. A previous article by the authors^[1] gave a cursory review of the operation, benefits, and possible problems associated with this method. The same article also addressed the ASME Boiler & Pressure Vessel Code (ASME BPVC) requirements^[2] of the method, and recommended desirable quality control measures. One of the recommendations was that the product be annealed after flow forming, even though the authors were not yet convinced that ASME BPVC always requires it. The current article reports new findings from a comprehensive review of material specifications, which ASME BPVC chose to adopt, or to ignore, for pressure application. The new findings suggest that ASME BPVC actually prefers annealing, so that the cold work has an insignificant effect on the product’s properties. Each ASME BPVC specification describes key property requirements and heat treatments to help meet the requirements.