Siemens announced on 10 March that it had achieved the first successful commercial installation and continuing safe operation of a 3D-printed part in a nuclear power plant. The replacement part, a metallic 108mm-diameter impeller for a fire protection pump that is in constant operation, has been installed at the Krško NPP in Slovenia in January. The original impeller had been in operation since the plant was commissioned in 1981 and the manufacturer is no longer in business.
Siemens’ team of experts in Slovenia reverse-engineered and created a “digital twin” of the part. The company’s additive manufacturing (AM) facility in Finspång, Sweden, housed at the Siemens Industrial Turbomachinery business, then applied its advanced AM process using a 3D printer to produce the part.
3D printing is a way of manufacturing metal or plastic parts directly from design data, using lasers to fuse together high-performance materials layer by layer. The technique enables components, including one-off specialist items, to be made relatively quickly from 3D design data, which can even be obtained by scanning an existing item. Metal parts can be printed in a wide range of materials including titanium, stainless steel and brass, to a high resolution.
Meeting the Krško NPP’s stringent quality and safety assurance requirements required extensive testing that was performed jointly with plant operator Nuklearna Elektrarna Krško (NEK) over several months. Further material testing at an independent institute as well as a CT scan showed that the material properties of the 3D-printed part were superior to those of the original.
The Krško plant provides more than one-quarter of Slovenia’s and 15% of Croatia’s electricity. Siemens has been performing modifications and providing service on the plant’s non-nuclear side, including turbine, generator and auxiliary equipment, for more than 10 years.
Siemens operates a state-of-the-art AM production facility in Finspång where is has been advancing this technology since 2009. Siemens extensively uses AM for rapid prototyping and has introduced serial production solutions for rapid manufacturing of small fuel mixers and for rapid repair of burner tips for mid-size gas turbines. The first 3D-printed burner component for a Siemens heavy-duty gas turbine has been in successful commercial operation in a power plant in Brno, Czech Republic, since June 2016.
"Obsolete, non-OEM parts are particularly well-suited for this new technology as they and their designs are virtually impossible to obtain," Siemens said. "This technology thus allows mature operating plants to continue operating and achieving or, as in the Krško case, even extending, their full life expectancy."
Siemens said it plans to continue its research and development with Krško into the use of 3D-printed parts. It said they are "looking at advancing the design of parts that are most difficult to produce using classical manufacturing techniques, such as lightweight structure with improved cooling pattern", Siemens said.
3D printing technology has already found applications within other parts of the nuclear industry. The UK's Sellafield Ltd announced in May 2014 it was working with 3D specialist companies 3T RPD and Central Scanning to create metal and plastic components, parts and one-offs to help meet the challenges of decommissioning. The company used 3D blue-LED scanning technology to design a replacement lid for a 40t solid waste transfer container.
Photo: This photo shows the original, obsolete water impeller, Siemens' 3D printed prototype and the resulting 3D-printed replacement installed and operating in Krško NPP in Slovenia (Credit: Siemens)