INES-event
INES 1

FEEDWATER TUBE RUPTURE DUE TO EROSION CORROSION

One pipe of the feedwater system of Loviisa 1 broke. The ruptured tube was situated in the turbine hall of the unit. Water and steam flew into the turbine hall. The operation of the Unit was stopped by a manual reactor scram immediately after trip of all feedwater pumps. Both auxiliary feedwater pumps started as planned and the transient in the steam generator level was small. The leak was isolated in about twenty minutes. The local damages to nearby cables and smaller pipelines were significant but no important functions were lost besides the main feedwater system. The leaked water and steam did not include radioactive nuclides. The incident did not endanger the radiation safety at the plant or the environment, and no persons were injured. Investigations have indicated that the wall thickness of the ruptured pipe has been decreased due to erosion corrosion. Also in other four feedwater pipelines at the unit no. 1 as well as in four corresponding lines at the unit no. 2, the erosion corrosion had caused some decrease in the wall thickness.
BASIS FOR RATING: Initiator: loss of feed water flow (expected).
Safety function availability: full. Real.
This justifies level 0 or 1. The event revealed some deficiencies in thesurveillance program, thus 1 (preliminary) is selected instead of 0.
DIFFICULTIES IN RATING:

Location: LOVIISA-1
Event date: Mon, 28-05-1990
Nuclear event report
Legenda & explanation