Design aspects of Cupro-Nickel 90:10 to carbon steel weld joints for MSF plants

Desalination Division, BARC is presently installing a 4500m3 per day of Multi Stage Flash (MSF) desalination plant as part of Nuclear Desalination Demonstration Plant (NDDP), Kalpakkam, India. In the mechanical design of the plant, there are a handful number of areas, which are very critical from design as well as fabrication point of view. The weld joint between Tubesheet of Cu:Ni-90:10 and End Cover of Carbon Steel (A516 Gr.70) under severe corrosive environment of sea water is one among them. This joint has been successfully designed after studying the weldability, mechanical, chemical as well as corrosion properties of both the materials and finally arrived at the proper materials for buttering layers on the carbon steel side. The resulting joint was successfully tested with radiographic and ultrasonic tests after putting it through a predefined thermal cycle. The salient features of this experience are described in this paper. (author)