Embrittlement of the Loviisa reactor pressure vessel monitored. Loviisan reaktoripaineastian haurastuminen hallittavissa

Embrittlement of the pressure vessel at the Loviisa nuclear power plant was already discovered during the first years of the plant operation. An embrittled pressure vessel does not pose any problems during normal operation. Embrittled steel in a pressure vessel may, however, involve a safety risk during exceptional situations, especially if the structure has cracks. The pressure vessel of Loviisa unit 1 will probably be heat-treated during the annual maintenance scheduled for 1996. When steel is heated at a temperature that is 200 degrees higher than the operating temperature, the material recovers completely. Embrittlement of the pressure vessel has been monitored by means of test rods in the reactor. The test rods are made of the same material as the pressure vessel. The pressure vessel at both units have also undergone several inspections, by means of ultrasound, eddy current and TV-cameras. On the basis of these inspections, it is certain that critical areas not contain any cracks. (orig.).