The fl ash evaporator modules are the core installations of any MSF Desalination plant. These are normally rectangular modules consisting of brine fl ash chambers and vapour condensers generally mounted at high elevations based on NPSH considerations of brine re-circulation pumps. BARC has recently constructed a 4500 m3/day MSF Desalination plant coupled to 235 MWe nuclear reactor at Kalpakkam in the southern region of India. The plant consists of 39 nos of fl ash evaporation stages distributed among 10 nos of large fl ash evaporator modules of different sizes, arranged in a longitudinal layout (long tube design). The smallest of these modules has internal dimensions 2.20 m width, 2.95 m height and 11.30 m length and the largest module is 3.10 m wide, 3.50 m high and 16.30 m long. Major materials of construction include carbon steel, stainless steel, cupro-nickel and inconel. The rectangular geometry, massive size, number of internal compartments, built in condenser, the corrosive seawater environment, et...