Development and evaluation of an innovative cold spray nozzle for reactor pipe inner wall repair technology

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It still needs several decades until the Fukushima Daiichi nuclear power plant is completely decommissioned. To ensure the safe operation of the power plant during decommissioning, suitable maintenance technology needs to be developed. This research develops the low-pressure cold spray (LPCS) technique for nuclear piping maintenance, which has the advantages of low working temperature, high coating strength, and high flexibility.First, a spiral-shaped LPCS nozzle for coating the pipe's inner wall was designed. The experimental results demonstrated that the spiral nozzle could be used to fabricate the Perfluoroalkoxy Alkane coatings on the pipe's inner wall. This results indicated that the designed LPCS nozzle has the potential of improving the service life of the nuclear pipe. Then, two innovative application was explored: 1) water-leaking pipe repair and 2) underwater coating fabrication. The results demonstrate the feasibility of applying LPCS for on-site pipe repair regarding water leaks and underwater coating. Based on these exciting results, the conventional LPCS nozzle was redesigned to realize the high-deposition efficiency of 304L stainless steel for enhancing the coating strength.