Radioactive gauge, lost and found

On October 12th 2012 during the removal of a detector from an industrial densitometer, technicians of a greek aluminium company in Voiotia realized that the lock mechanism of a Cs-137 source (5 mCi - 1993), as well as the source itself were missing. Two engineers, trained in radiation protection, blocked the area on a 10 m radius and started the search using a portable detector. The source was found near an open surface drainage stream covered in a sediment crust at a distance of a few meters from the housing. Using a shovel and a lead container they collected the source and transported it to the source storage facility within the company premises. The lock mechanism has not been found. The maximum dose rate indication on the portable detector was 320 μSv/h, while the cumulative dose was no more than 15 μSv, which is in accordance to the calculations performed by GAEC.
After the source recovery, GAEC was notified about the incident. Soil samples collected from the place where the source was located and the wipe test performed on the source showed that there was no radioactive leak to the environment. The undergoing investigation in the industry indicates that the last time the source was known to be within the shielding was on June 26th 2012. On that day due to pipe maintenance operations, the source housing was removed for a short time from its proper position. The loss of the source was not noted earlier due to the fact that the densitometer was out of use. Assuming that the source has remained at the position it was found for the whole period it was missing, given the fact that it was in a very low occupation area, and according to the information provided by the industry, workers performing occasionally operations in proximity to the area have spent there no more than a total time of two hours.
GAEC has verified the dose measurements and calculations performed by the company technicians.
The case is not closed yet since additional information from the company regarding the investigation of the causes of the incident, and the future actions to be taken, is expected.

Taking into consideration
• the source category (5)
• the fact that the source positioning was not verified for a period of about four months
• there was no exposure of any members of the public or workers
the provisional INES rating is “1”.

Location: Aluminium SA
Event date: Fri, 12-10-2012
Nuclear event report
Legenda & explanation