Preliminary oil risk estimates showed that oil transportations pose a significant core damage risk for Loviisa PWR located at the southern coast of Finland. Oil transportation has increased in the Gulf of Finland during the last few years and will further increase in the coming years enhancing the importance of this risk. Therefore, a more detailed assessment of oil spill impact frequencies has been performed for Loviisa nuclear power plant (NPP) taking into account hydrometeorological conditions, oil properties and leakage sizes as well as recent oil spill statistics. During cold shutdown states the loss of service water due to excessive sea vegetation or other clogging material in the sea is an essential risk contributor because the normal residual heat removal system and the emergency cooling systems are cooled by the same service water system. Oil of tankers and cargo-carrying ships as well as other potentially fouling cargo may clog the sea water cooling systems. Nevertheless, the crude oil transportations in the Gulf of Finland pose maybe the biggest threat. In the preliminary oil risk estimate for Loviisa NPP critical amount of oil was estimated to hit the plant with a frequency of 8·10~(-3)/year. This estimate was based on the frequency in the Gulf of Finland for oil spills of tens of thousands of tons and larger, which were assumed to hit the plant with certainty. The preliminary core damage frequency due to an oil spill was 5.4·10~(-8)/year during power and 8.6·10~(-6) at annual refueling outage.
展开▼
