Radiation overexposure of personnel while performing refuellig activities

A team of plant Centralized Maintenance Service was performing refuelling activities at the unit, which was in planned outage. Personal dosimeter readings after these activities showed that three team members were exposed to doses exceeding those specified in the work order for performing activities in the controlled area (value of 0.4 rem): one worker was exposed to a dose of 9 rem (90 mSv) exceeding the annual maximum permissible value, second worker - of 1,7 rem (17 mSv) and the third worker received a dose of 1 rem (10 mSv). Cause of radiation overexposure of three people was violation by the personnel of refuelling operating procedure as well as of the radiation safety regulations while handling the nuclear spent fuel, namely, while entering the Spent Fuel Storage Tank (SFST-3) for transferring casings with spent fuel assemblies to the SFST storage section while some other casings with spent fuel assemblies were in the "upper" position in the SFST-3.
Exposure of the public, contamination of NPP equipment, rooms and site as well as of the off-site territory did not occur.
Justification of rating: Personnel exposure above the annual maximum permissible value (5.0 rem) occurred. The event is rated under the "On-site impact" criterion: level 2 was chosen according to Section II-.2.2 of the User's Manual.

Location: 
BILIBINO UNIT D
Event date: 
Sat, 1998-03-14
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