Ignalina

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INES-event
INES 1

OVEREXPOSURE OF OPERATOR DURING CALIBRATION OF IN-CORE SENSORS

On November 30, 1995 in in-core sensors where calibrated during operation of Unit 2 reactor at the thermal power of 3750 MW. While lowering a sensor, one of the involved operators entered the reactor hall and was inside for 1.5-2 minutes. The operator was exposed to 5 ber. Since the beginning of this year his accumulated dose has amounted to 5.3 ber that is above the specified annual man-rem dose limit.
INES rating level 1 under defence in depth
Justification: Section I.I.2 and III.5 of INES User's Manual

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 1

AUTOMATIC REACTOR UNLOADING DUE TO SPURIOUS OPENINGS OF VALVES BETWEEN A GROUP OF ECCS PRESSURIZED TANKS AND REACTOR

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.

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 0

AUTOMATIC REACTOR UNLOADING DUE TO TURBOGENERATOR TRIP BY OPERATOR

On November 12, 1995 Ignalina NPP-1 was under normal operation at thermal power of 3100 MW. Electrical power of turbogenerators TG-1/2 was 650 MW/300 MW respectively. At 3:59 am the operator tripped TG-2. The automatic reactor protection system decreased the reactor power to 2400 MW.

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 0

INFRINGEMENT OF THE REACTOR PRIMARY CIRCUIT INTEGRITY

On November 3, 1994 at 0:30 am unit 1 was shut down due to a leak in the primary circuit. With reference to the standard monitoring system the leak rate is about 10 litres/hour. The leak is located in unattended reactor building compartment 409/2 with the suction and pressure headers and large diameter primary circuit piping situated therein. The allowable leak rate for this compartment is 120 litres/hour. The exact location of the leak will be determined after reactor cooldown.
Provisional INES rating is level 0 (Table II 1-1 INES User's Manual)

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 0

AUTOMATIC REACTOR SHUTDOWN CAUSED BY GENERATOR TRIP

On August 9, 1994 unit 1 was under normal operation codntions at a thermal power of 2100 MW with turbogenerator no. 2 at an electrical power of 750 MW. At 3:17 am an exciter failure caused a generator trip and subsequent turbine trip followed by the reactor shutdown. The generator trip was caused by wrong switching of the exciter current circuits. The safety systems functioned in full.
INES level 0 (Table II - A1 user's manual)

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 0

REACTOR SHUTDOWN CAUSED BY LEAKAGE THROUGH A JOINT WELD IN THE ECCS PIPEWORK

On August 21, 1994 Unit 1 was under normal operation conditions at a thermal power of 2340 MW with turbogenerator no. 2 at an electrical power of 750 MW. At 20:00 am routine surveillance detected the increased leakage in reactor building room 208/l where the ECCS pipe headers were located. The radiation monitoring system confirmed the presence of water leakage in the reinforced leaktight compartments encasing the left loop of the coolant recirculation circuit. At 21:32 the reactor was shut down in order to locate and eliminate the leak.

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 1

MALFUNCTION IN THE SYSTEM OF NEUTRON CONTROL OF REACTOR POWER FOLLOWING THE REPLACEMENT OF A CONTROL ROD SWITCH

On July 11, 1994, Unit 2 was under normal operation at a thermal power of 2100 MW, when one of the two control rod switches was replaced in order to correct a small malfunction. After the replacement the switch was tested. In the neutral position the local automatic control rod selected for test performance failed to function (it was lifted upwards by 0.5m). The switch was replacedby a new one and tested again. This time the test was successful. It later emerged that interconnection in the first switch was not made to design.

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 0

AUTOMATIC REACTOR SHUTDOWN CAUSED BY SPURIOUS CLOSING OF THE GATE VALVE AT THE PIPELINE FEEDING THE MAIN CONDENSATE HEATER WITH HEATING STEAM

On July 8, 1994 unit 2 was under normal operation conditions at a thermal power of 2180 MW. The reactor was operated in a single turbogenerator mode. Turbogenerator no. 4 was at an electrical power of 690 MW. At 2:07 am the gate valve at the pipeline feeding the main condensate heater (Low Pressure Heater no. 4) with heating steam closed spuriously because of a failure of the control circuit. The increased water level in LPH no. 4 caused TG no. to trip. The reactor was shut down by the reactor protection system

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 1

DETERIORATION OF THE PRIMARY CIRCUIT INTEGRITY

In the afternoon of Feb. 25, 1994 unit no. 2 of Ignalina NPP was shut down to locate the leakage in the primary circuit unservicable compartment enclosing the multipurpose valves and reactor channel flowmeters and eliminate its causes. On February 28 the primary circuit underwent pressure and visual tests. The leaks were detected in the detachable joints of multipurpose valve 38-42 and ball-type flowmeter 13-18. The leaks were caused by the damage of the sealing gaskets. The event was provisionally rated as INES level 0, as per table II (A-1).

Category: Power Reactor Ignalina Lithuania »

INES-event
INES 1

FAILURE OF THE FOAM FIRE-EXTINGUISHING SPRINKLER SYSTEM TO OPERATE FOR 16 HOURS DUE TO FROZEN PIPES

The event occurred while unit 1 was in normal operation. The foam fire-extinghushing sprinkler system is meant for fighting a fire in the oil systems of the turbine building and main circulation pumps. In the morning of 7 February unit 1 pumps were put oput of operation for maintenance. The said fire extinguishing system was integrated with the similar system in unit 2. The latter with pumps ready to bstarted automatically. In the afternoon the regular

Category: Power Reactor Ignalina Lithuania »