At Loviisa NPP unit 2, a feedwater pipe rupture occurred on 25 February 1993. The plant is now under control and there were no releases of radioactive material off-site. The rupture occurred during starting up of a feedwater pump. After the pipe rupture, the leakage was rapidly isolated and the operating feedwater pumps stopped. The water levels of the steam generators were controlled by the auxiliary feedwater pumps which started automatically.
The pipe rupture occurred at the turbine hall. A few cubic meters of non-radioactive water flowed on the floor of the turbine hall.
The operators tripped manually the reactor before the initiation of the automatic protection system. Thereafter, the unit was immediately brought to a stable shutdown condition, and preparations to bring the reactor to a cold shut down condition were started by borating the primary circuit.
The cause of the pipe rupture is preliminarily considered to be erosion corrosion. A similar event occurred at Loviisa 1 unit in 1990.
This kind of event is usually classified as level 1 on the International Nuclear Event Scale but because the event was similar to the one in 1990 level 2 would be more appropriate.
Event date: Thu, 25-02-1993