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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

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 »

INES-event
INES 1

ONE FUEL ASSEMBLY TILTED DURING REFUELLING

Because of an interlock on the refuelling machine was released during refuelling the gripper of the manipulator hit the top of one control rod. A fuel assembly was raised again. No damages were caused to the assembly neither to its neighbouring assemblies. The control rod was replaced.
BASIS FOR RATING:
DIFFICULTIES IN RATING:

Category: Power Reactor Ringhals Sweden »

INES-event
INES 1

DEVIATION FROM THE NORMAL ON-LOAD REFUELING REGIME DUE TO FUEL ASSEMBLY SEPARATION FROM THE CONNECTING BAR

The unit was operating at nominal power. While performing scheduled refueling (replacement) of a spent fuel assembly (FA) in the 41-40 fuel channel FA separation from the connecting bar occurred, which is a deviation from the normal refueling process. In accordance with the technical specification the unit was scrammed by emergency protection system button. The 41-40 returned to its usual location. Radiation situation in the central hall, sanitary-protective zone and in the supervision area remained unchanged. Breach of unit limiting conditions for operation was not observed.

Category: Power Reactor Russian Federation Smolensk »

INES-event
INES 1

REVEAL OF INADVERTENTLY CLOSED MANUAL SERVICE VALVES AT VERIFICATION TESTS OF THE SCRAM SYSTEM BEFORE PREPARATIONS TO RESTART

During test of the hydraulic scram system with cold water after service of an electrical rod drive it was revealed that a group of rods did not respond to demand. The reason was that a manual service valve was closed. All the other corresponding valves were also closed. Normally these valves are closed when the reactor vessel head is put on or off. These procedures are governed by specific instructions. Due to misconception the operating personnel supposed that the valves were already open.
Basis for the rating: Chapter 4.4b, deviation from written instruction.

Category: Power Reactor Forsmark Sweden »

INES-event
INES 1

HIGH ACTIVITY IN TB PIT

From 0930 hrs of 09/07/91 onwards Turbine building pit samples of Unit-2 started showing tritium activity. Presence of Argon 41 & Xe was also reported.
On July 13, 1991 samples from main outfall (discharge point to lake) indicated tritium activity above 3 pci/ml which is a non-conformance with TechSpecs. This situation continued up to July 15, 1991. Based on review of Station Technical specification, the limit for tritium discharge into lake has since been revised to 15 pci/ml with effect from July 18, 1991.

Category: Power Reactor India »

INES-event
INES 1

LEAKAGE IN THE GASEOUS WASTE PROCESSING SYSTEM (GWPS)

During normal operation pressure decreases were observed in two (2) gas decay tanks of GWPS. The release time was approximately 4 hours and the estimated total radiation dose to the whole body of a critical individual was 10-4 mrem. The affected tanks were promptly isolated.
BASIS FOR RATING: As per INES Users' Manual page 10, "Failure of the barriers themselvesleading to radiological consequences will generally result inclassification by criteria 1 and 2 of the scale". As estimated dose waswell below the accepted limits the event was rated as level 1.
DIFFICULTIES IN RATING:

Category: Power Reactor Brazil »