On the morning of 14 February 2014, a radiography company was performing non-destructive testing by industrial radiography with a 1,22 GBq Ir-192 source to several pipe joints in a chemical plant. The operations were performed by three operators (A, B and C) in a platform at nearly 12 meters height over the floor. In order to reduce the level of radiation in the area a tungsten collimator was fixed at the tip of guide tube.
For all the operations the gamma projector was lifted with a rope up to platform and the operator A climbed by a ladder taking the guide tube with the collimator fixed putting it inside the left pocket of his work vest. At the platform the operator A connected the guide tube then fixed the films to the joints and then coming down and operator B made the exposure. Operator C marked the films for being fixed in the tests.
The operators wore personnel alarm detectors, OSL dosimeters and also one portable radiation monitor.
In one of these operations the radioactive source became detached and did not return to its safe position. The operators were not aware of this situation because the high noise from engines and machines in the work zone did not allow hearing their personnel alarm detectors but also because the portable radiation monitor was not used for monitoring the operations. According the reenactment of accident the unaware exposure happened in the last three joint tests.
After the test of last three joints they became hearing the alarm detector while walking away from the noise environment. At the discovery of situation they performed a monitoring to the gamma projector and guide tube discovering that the source was not inside the projector but in the tip of guide tube.
The operators left the gamma projector and guide tube on the floor and then proceeding to recover the Ir-192 source which was safely placed inside the gamma projector in some 5 minutes using tongs and portable shielding. The operators notified the event to company manager which took them to a clinic for medical assessment.
The operator was in contact with the radioactive source around 30 minutes, having proved that the left hip was the most exposed area.
The operator did not show any early symptoms at whole level although after 12 hours began to be noticed redness in the left hip. Currently the redness is disappearing.
The doses received by the operator A were estimated less than 0,5 Gy to whole-body and the localized dose to its left hip was appraised in 16 Gy as average. Doses to operators B and C were 15,85 mSv and 17 mSv.
Preliminary investigations indicate that the main cause was the non-compliance of protection procedures, for instance, the regular monitoring was not performed. Currently the investigations are under way to determine other contributors to the event. The regulatory body issued an order to the radiography company for stopping operations until causes are well.
