Influence of Feed Water Distribution Pipe Replacement on the Water Chemistry in the Steam Generators at Loviisa NPP

Abstract

Imatran Voima Oy , (IVO) operates two Russian designed nuclear power plants of type VVER440/2 13. Unit 1 has been operating since 1977 and unit 2 since 198 1. First damage of feed water distribution (FWD) pipes was observed in 1989. In closer examinations FWD-pipe T-connection and distribution nozzles suffered from severe erosion corrosion damage. Similar damages have been found also in other VVER-440 type NPPs. In 1994 the first FWD-pipe was replaced by a new design mounted over the tube bundle instead of the old FWD-pipe, which was located inside the tube bundle. The purpose of this paper is to describe the new FWD-pipe and discuss its effects on the steam generator chemistry.