1

INES Levels
INES N/A 
INES 4
INES 0
INES 5
INES 1
INES 6
INES 2
INES 7
INES 3

INES 1: Anomaly

Impact on Defence-in-Depth
  • Overexposure of a member of the public in excess of statutory ­annual limits.
  • Minor problems with safety components with significant defence-in-depth remaining.
  • Low activity lost or stolen radioactive source, device or transport package.
(Arrangements for reporting minor events to the public differ from country to country. Also, it is difficult to ensure precise consistency in rating events between INES Level-1 and Below scale/Level-0)
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INES-event
INES 1

SMALL FIRES CAUSED BY SHORT-CIRCUIT

The short circuit occurred at 14:03 local time at 22 September 1991 in unit no. 6, while start-up tests of the generator were being carried out after annual outage. The short-circuit caused power to be cut off from units 6 and 5, which share a common electrical supply. An auxiliary power supply failed, but power to the safety systems was maintained by an emergency diesel generator. Repair work on the reserve system for electrical supply was started immediately. The event caused actuation of the reactor protection system.

Category: Power Reactor Bulgaria Kozloduy »

INES-event
INES 1

REACTOR START UP WITH DEGRADED REACTOR SHUT DOWN SYSTEMS

During start up tests after refueling the reactor was made critical (zero power) without pressurized scram accus (violation OL&C). The unavailability lasted 3,5 hours and was detected during shift turnover. No initiator and scram challenge occurred. All other safety systems were available. Remaining shut down function during degradation:
- high reactor pressure replace the scram accus (above 30 bars)
- control rod drive system and boron injection system
Basis for rating: Table III.1 of User's Manual
a) Initiator: Rod ejection unlikely (3)

Category: Power Reactor Leibstad Switzerland »

INES-event
INES 1

INOPERABILITY OF HERMETIC COMPARTMENT PRESSURE INDICATORS OF ESFAS

On 4th June 1992 during routine inspection 12 inoperable hermetic compartment pressure indicators of emergency protection system and 2 indicators for emergency command were revealed. This state lasted since 28th May 1992 to 4th June 1992. On 28th May 1992 the refuelling of unit 2 was finished. Since this time the LCO were violated.
This event was justified on level 1 on the basis of p. 4.4b of Users manual (p. III.5.3 of Users Manual from March 92).

Category: Power Reactor Czech Republic Dukovany »

INES-event
INES 1

DEUTERIUM EXCURSION IN MODERATOR COVER GAS

Unit was synchronised at 00-10 hrs on 15.5.92 deuterium (D2) concentration in Mod. cover gas was reported high (8.2%). Repeat sample was analysed & was showing 7.2% thus confirming the earlier observation. Unit was shutdown at 0618 hrs on 15.5.92 as per item 4.2 E of Technical Specification.

Category: Power Reactor India »

INES-event
INES 1

TRITIUM ACTIVITY IN PROCESS WATER RETURN

T.B. Pit tritium activity high. On 28-6-92 at 0100 hrs. T.B. Pit sample started showing activity in the range of 300 pci/cc. MOF also started showing activity in the range of 150 pci/cc to 250 pci/cc.
Justification: The event is rated at level-1 as the resulted in violation of TechSpecs. Care should have been taken when a system, which was not in service, was put in service specially when diluting water was not available.

Category: Power Reactor India »

INES-event
INES 1

CONTAMINATED PARTICLES DISCOVERED ON-SITE

On 10 June 1992 during routine survey a particle with gamma activity 200mR/h was discovered. The particle was found along the route from the Main Entrance towards the Reactor Hall. Seven particles were discovered in all, the last one, with a gamma activity 300 mR/h, was found in the Corridor for Transportation of Fresh Fuel and Equipment of Units 1 and 2. The site of NPP Kozloduy 2 (Units 5 and 6) proved to be uncontaminated. It is supposed that all the particles originated from the Transport Corridor. The investigation continues.

Category: Power Reactor Bulgaria Kozloduy »

INES-event
INES 1

REACTOR SHUTDOWN BY TECHNICAL SPECIFICATIONS APPLICATION (UNUSUAL EVENT)

This event was intitated at 6:10 p.m. on May 9, 1992 when technicians, while performing the functional testing of pressure instruments of reactor recirculation pumps trip for ATWS, put one out of four switch selectors on "testing position" to verify the functional instrumentation operation and due to a mistake in the procedure application and communication deficiency between technicians, the trip logic was completed and a recirculation pump trip occurred. The operators reduced power to about 35% power according to technical specifications and following the abnormal procedures.

Category: Power Reactor Mexico »

INES-event
INES 1

DROPPING OF A SPENT FUEL BUNDLE IN INSPECTION BAY

Unit was operating at 175 MWe and spent fuel discharge was in progress. First pair of spent fuel bundles were received at the Inspection bay in an open tray called the Insert (meant for receiving spent fuel bundles) attached to a Transfer Arm (T/A). The T/A was rotated and aligned to the spent fuel storage bay port in order to discharge the bundles to storage bay. When the T/A Ram was advanced to push the bundles, the front end bundle got stuck at the storage bay port entry and due to the Ram force, the rear end bundle got lifted and toppled out of the insert.

Category: Power Reactor India »

INES-event
INES 1

HEAVY WATER LEAK FROM RUPTURED HOSE

On 24/1/92, Unit was under start up, reactor power was around 2% F.P. and 6 Nos. H.T. circulating pumps were operating. At 0420 hrs. sudden increase in bleed flow indication (from 400 lpm to 1000 lpm) and H.T. storage tank level hunting was observed. Storage tank level was dropping. PHT pressure control signal was 40 ma constant (feed side) and there was no significant hunting in H.T. pressure. Beetles at moderator room floor alarmed. IX room (1188 el. floor) was full of water vapours. Immediately H.T. system cooling was started.

Category: Power Reactor India »

INES-event
INES 1

LOSS OF CLASS III SUPPLY DUE TO FAULT IN CLASS III BUS SUPPLY BREAKER

At 15.30 hrs. of 4.11.91, when unit was under shut down, Class-III bus P supply breaker from Station Auxiliary Transformer tripped on inverse time over current protection. Diesel Generator-1 on Bus-P side started and its breaker closed. But the fault was on Bus side of the supply breaker and hence the DG-1 breaker also tripped on feeding the fault. The breakers connecting bus-P to the other leg, Bus-Q closed. This resulted in tripping of Bus-Q supply breakers also along with the tie breaker.

Category: Power Reactor India »