Dose in excess of regulatory limits to a worker operating in a bunker where a cobalt source was used, in Toulouse
On Wednesday 12th March 2008, a worker of the HIREX Engineering company working for the ONERA company was incidentally exposed during several minutes to a cobalt-60 source of high activity (18,5 TBq thus of category 1) (cf. ASN Notice of 18th March 2008 on www.asn.fr).
This worker operated in a bunker used for the irradiation of electronic components while the source was not in its safe position. This abnormal position of the source is due to a wrong operation of this source carried out a little before. In this case, the interlocks should have prevented the access to the bunker. These anomalies were not immediately identified by the operators.
When this incident was discovered, the source was returned to its safe position. ASN who was informed of the incident on 13th March 2008, immediately prohibited the use of the installation by ONERA.
ASN accompanied by the labour inspectorate and IRSN experts carried out an inspection at the site of the event on 7th March 2008. The inspections findings confirm that the incident results from technical and organisational malfunctions as well as regulatory violations. In particular, the evidence of failures of safety provisions aimed at impeaching the access to the bunker was provided as well as gaps in the training and the supervision of operators which did not allow to immediately notice the loss of control of the radioactive source.
Care was taken, by his attending physician, of the worker with the assistance of IRSN physicians who are specialised in this type of event. The dose reconstruction and the results of the biological examination performed by IRSN led to evaluate the dose to this worker at 120 mSv.
Based of the dosimetric consequences ASN provisionally rates this incident at INES level 3.
Together with its technical support organisation IRSN, ASN pursues investigations to determine the precise circumstances of this incident. ASN has undertaken dedicated preventive actions towards other industrial facilities using similar materials.