Irradiation of a worker during an intervention on a defective gamma ray projector: ASN rates the incident level 2 on the INES scale
On 16th July 2014, the Director of the regional agency of the Welding Institute of Latresne (Gironde département) informed ASN of the accidental exposure of a worker to ionising radiation on 11th June 2014.
During a weld inspection operation carried out by two employees of the Welding Institute on a worksite in Pau (Pyrénées Atlantiques department) using gamma radiography equipment1, the radioactive source of the gamma ray projector jammed inside its guide tube.
Using a metal rod found on site, one of the operators managed to free the jammed source and return it to the safe position in the body of the device. During this operation, the operator was directly exposed to the radiation emitted by the radioactive source.
Development of the operator's dosimeter revealed that he had received a dose of 22.94 millisieverts in June, essentially during that one operation of 11th June.
For workers likely to be exposed to ionising radiation in the course of their professional activity, the annual regulatory dose limits for twelve consecutive months are 20 millisieverts for the whole body and 500 millisieverts for a skin surface area of 1 cm2.
The regional department of the Welding Institute was informed of this event on 8th July. It notified ASN of the event on 16th July. The Bordeaux regional division of ASN conducted a reactive inspection at the head office of the Welding Institute in Latresne (Gironde department) to clarify the circumstances of the incident. The follow-up letter to this inspection is posted on the ASN website (link).
ASN notes that the initiative taken by the operators to manipulate the device in order to unblock the radioactive source is not in conformity with the license issued to the Welding Institute authorising the use of gamma ray projectors, and underlines the abnormally long time taken to notify ASN of the incident.
Insofar as this single incident resulted in a worker being exposed to a radiation dose exceeding the regulatory annual limit, ASN has provisionally rated the event level 2 on the INES scale, which counts 8 levels, from 0 to 7.
ASN press contact: Emmanuel Bouchot - 01 46 16 41 44 – firstname.lastname@example.org
Consult the follow-up letter (07/28/2014 - in french)
1. Gamma radiography, or industrial radiography, is an imaging technique used for the non-destructive inspection of metallic parts. The part to inspect is placed between a powerful radioactive source (usually cobalt-60 or iridium 192) and a photographic plate. The gamma ray projector is the device used to manoeuvre the radioactive source safely.