2

INES Levels
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INES 2: Incident

Impact on People and Environment:
  • Exposure of a member of the public in excess of 10 mSv.
  • Exposure of a worker in excess of the statutory annual limits.
Impact on Radiological Barriers and Control:
  • Radiation levels in an operating area of more than 50 mSv/h.
  • Significant contamination within the facility into an area not expected by design.
Impact on Defence-in-Depth:
  • Significant failures in safety ­provisions but with no actual ­consequences.
  • Found highly radioactive sealed orphan source, device or transport package with safety provisions intact.
  • Inadequate packaging of a highly radioactive sealed source.
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INES-event
INES 2

INOPERABILITY OF NEUTRON FLUX MEASUREMENT DURING COLD SHUTDOWN

After the monthly control of the nuclear monitoring system on July 25 it was not noticed by the personnel, that the ionization chambers of the low and middle range of the monitoring system after controlling were driven out of their working range and not driven back.

This faulty position was observed 24 hours later after controlling by a shift-physicist.

During this period of 24 hrs the nuclear monitoring system for the cold shutdown stage of the reactor was not available. The shutdown concentration of boric acid in the primary circuit during this time was cB=17.1 g/l.

Category: Power Reactor Germany Greifswald »

INES-event
INES 2

EXCESSIVE DEPRESSURIZATION OF THE PRIMARY CIRCUIT DUE TO A PRESSURIZER SAFETY VALVE THAT FAILED TO CLOSE

On August 20, 1974 at 11.20 a.m. a trip on turbine TG-1 occurred resulting in high bearing and casing vibrations (bearing 6:60). At trip time, generator 2 was delivering about 140 MVar. Resulting from a failure of the steam dump system to operate, with the consequence that the relief valve did not open. That resulted in a rapid rise of coolant temperture, steam pressure and pressurizer level and pressure. At 160 bar of pressure in the primary, the pressurizer pressure relief valves opened, lowering rapidly the pressure in the primary.

Category: Power Reactor Beznau Switzerland »

INES-event
INES 2

REACTOR COOLANT LEAK ON THE WATER CLEANING SYSTEM WHILE CONNECTED TO THE PRIMARY CIRCUIT

During normal power operation after checking the resin content of the K-filter and connection of the water cleaning system with the primary circuit, a leakage of the seal of the fill-in nozzle at the filter occurred. The nozzle is situated in the reactor hall out of the pressure room system. The personnel violated several operating instructions but the reactor was not shut down as prescribed in such situations.

Category: Power Reactor Germany Greifswald »

INES-event
INES 2

REACTOR COOLANT LEAK DURING ON POWER REFUELLING DUE TO FUELLLING MACHINE DROP

During routine refuelling at full power, a reactor coolant leak of 1.4 Mg/hr developed in the fuelling vault. Operators determined that the east fuelling bridge had dropped 40 cm. The reactor was shutdown and cooled. Coolant pressure was maintained by transfer from other units and recovery from sump. Total leakage was 22 Mg ( approx. 10% of inventory). No safety system operation was required with the exception of containment box-up on high activity after one hour. There was no abnormal release of radioactivity to the environment.

Category: Power Reactor Canada »