On November 22, 1995 Ignalina 2 was under normal operation at the thermal power of 3750 MW. Electrical power of turbogenerators TG 3/4 was 500 MW/700 MW respectively. At 15:11 pm the fastacting valves between a group of the ECCS pressurized tanks and the reactor spuriously opened. The operator took notice of the opening and shut the valves off. The other two ECCS trains stayed in waiting mode. The opening caused the release of 12 tons of the water from the ECCS pressurized tanks. Reactor power was decreased by 450 MW to investigate the cause of the opening. At 17:11 pm the affected ECCS train was brought back into the waiting mode and reactor power started building up. Justification of rating: Table II A-2 of INES users manual.