INES-event
INES 0

RELEASE OF IODINE 131 FROM THE TURBINE SYSTEM AT RINGHALS 1

The turbine systems at Ringhals unit 1 were opened three days after the turbine was shut down for refurbishment. When the systems were exposed to air, iodine was released from the surfaces of the primary (steam) system. The release of iodine was expected, but the release rate was higher than expected. The iodine was released to the air in the turbine hall where approximately 70 persons were working without respiratory protective devices (face masks). Face masks were not issued as the continuous air monitor had not reached the alarm level 1 DAC (Derived Air Concentration). The incident was discovered when persons were stopped in the exit monitors due to elevated, but still low levels of contamination. The personnel will use face masks a few days to avoid unnecessary problems with alarms at exit monitors. All persons involved with work on the turbine systems will be measured in a whole body counter within one week.
All persons who were exposed to elevated but still low levels of iodine in the air were whole body monitored directly after the incident. Only three persons were above the Swedish formal report level 0.5% of the Annual limit of Intake (ALI). The highest intake was 0.59% of ALI which is equivalent to 0.09 mSv effective dose equivalent.

Location: RINGHALS-1
Event date: Sat, 09-07-1994
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