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

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 »

INES-event
INES 1

FUEL BUNDLE DAMAGE DURING TRANSFER TO SPENT FUEL BAY

During a fuel transfer operation using fuelling grapples, an irradiated fuel bundle was damaged at the outlet of the discharge port and a broken fuel element fell on the floor of the spent fuel bay room. The emergency sprinklers were activated in the room and a sectorial alert was initiated in the reactor building and the fuel bay areas. The broken element was recovered within hours and was deposited in the bay. The ambient irradation levels fell to normal after decontamination of the room. No fuel escaped from the element and atomspheric contamination remained below detection levels.

Category: Power Reactor Canada »

INES-event
INES 1

INCREASE ACTIVITY OF WASTE WATER FROM THE A-1 AND V-1 NPPS

The continuous measurement of a waste water activity monitored activity increase. The evaluated check sample contained activity of 1400 Bq/l. The next evaluation of the same check sample contained 210 Bq/l. Both these values exceeded the limited value (37 Bq/l). The activity increase was probably caused by a released contaminated soil into the waste water channel. Total amount of released activity was 4.62 x 10E7 Bq. This released activity value represents about 0.2% of the annual limited value.

Category: Power Reactor Bohunice Slovakia »

INES-event
INES 1

SMALL STEAM LEAK FROM THE MAIN FALNGE OF THE PRIMARY COOLANT PUMP NO. 6

Unit 4 was operated at full power on 7 September 1991. A small steam leak from the main flange of the primary coolant pump no. 6 was discovered.
On 12 September the leak increased. The Beta-gas specific activity measured in the pump room was 0.7 x 10E-9 CI/L. The gamma dose rate was 7.5 mkr/s at contact.

Category: Power Reactor Bulgaria Kozloduy »

INES-event
INES 1

INADVERTENT STEAM RELEASE INTO THE REACTOR HALL DUE TO STOP OF PUMP IN RESIDUAL HEAT REMOVAL SYSTEM

During shutdown both residual heat removal pumps stopped inadvertently. The reactor was shut down for the yearly outage and the pump stop was not discovered until four hours later when the pressure vessel lid was dismantled. During the pump stop the water temperature increased to 98 degrees C.
BASIS FOR RATING: Level 1, Table 1 A-1R, chapter 4.5
DIFFICULTIES IN RATING:

Category: Power Reactor Barsebäck Sweden »

INES-event
INES 1

DEVIATION FROM OPERATING INSTRUCTIONS

During outage a search light fell into the main recirculation loop. To be able to examine the bottom of the RPV three control rod guide tubes had to be removed from the reactor core. An exemption from the regulatory body, SKI, for doing this was necessary as the rods belonged to three different scram groups. This was granted on the condition that an extra independent verification was made by use of a TV camera. This extra control though included in the operation instruciton was not executed.
BASIS FOR RATING: Level 1. Table 1 A - 1R, Chapter 4.5
DIFFICULTIES IN RATING:

Category: Power Reactor Oskarshamn Sweden »

INES-event
INES 1

NEW RADIOACTIVE "HOT SPOTS" DISCOVERED AT KOZLODUY NPP

On 6th August 1991, two new contaminated spots on Kozloduy NPP where discovered. The location of the spots is south-west of the administrative building, inside the NPP fence. The surface of each spot is about 100 cm2. Samples of soil are taken for investigation. The gamma activity of the samples is 0.5 to 1.5 (mR/h) at contact. After the samples were removed the gamma-activity of the spots decreasaed to the level of the natural background activity.

Category: Power Reactor Bulgaria Kozloduy »

INES-event
INES 1

CONTAMINATION OF SOIL ON SITE

During the period from July 22 to August 6, 1991, several hot spots have been discovered at Kozloduy NPP. One being a leak of radioactive water (from the tunnel linking the reactor building Unit 1 and the auxiliary building) which has contaminated one square meter of the ground on site. This leak is probably due to a crack in the concrete through which the recent rains transported active particles. The activity of the soil was 2.5m rem/hour at contact. Investigation of the causes and implementation of corrective actions are in progress.

Category: Power Reactor Bulgaria Kozloduy »

INES-event
INES 1

REACTOR SCRAM AND COOLDOWN BECAUSE OF LEAKAGE IN A PRIMARY CIRCUIT MEASURING SYSTEM

The event took place during the start up of the unit after refuelling. Due to a leak in the reactor pressure measuring system steam blew out in a room where transmitters of measuring systems were installed. Some transmitters failed, among others those measuring water level in the steam generators no. 1, 2 and 3 for protective purposes. The reactor protection shut down the reactor. The unit was cooled down to investigate the cause of the failure and to begin the repair work. During cooldown the leak was located and climated by closing out the affected section.

Category: Power Reactor Hungary Paks »

INES-event
INES 1

FIRE IN LOW LEVEL RADIOACTIVE WASTE STORAGE


The storage is situated east of the on-site station switchgear, far away from the reactor buildings. The fire was extinguished by plant fire protection forces before it caused significant damage. The causes of the fire are being investigated. No on-site or off-site releases.

Category: Power Reactor Bulgaria Kozloduy »