Status of the pulse tube of the service water storage tank for the secondary circuit at the Dukovany-1 reactor unit

The inner diameter reduction, chemical composition and origin of deposits, and corrosion damage of the internal pipe surface were determined on a specimen taken from the secondary circuit piping. Made of ferritic steel, the pipe had been exposed to service water for 12 years. The pipe had been affected by pitting corrosion, the pits being as large as 2 mm and as deep as 0.3 mm, with the ferritic matrix exposed. The corrosion loss was estimated to be 0.6 mm. The deposit layers contained oxides of Fe, Ca, C, Si, S, Cr, P, Cu, Mn, Mg, Na, and traces of Ni, K, Al and filled the inner cross section of the pipe to 57-92%. (M.D.)