On April 27, 2010, Electricité de France (EDF), the licensee of Chinon NPP, informed ASN of the accidental exposure on 23 April 2010 of an employee of KELLAL company, an EDF contractor. This worker was exposed during cleaning operations of the fuel pool located in the fuel building of Chinon NPP reactor 4 when he found a high radioactive small metal piece (piece diameter of approx 18 mm).
This building is used for fuel assembly storage where these assemblies are removed from the reactor vessel for, in particular, maintenance operations in the reactor building. Prior to fuel assembly unload, part of the fuel pool is drained and decontaminated. After decontamination, the worker, wearing a leak-tight protection suit, stepped in to control the absence of foreign pieces at the bottom of the pool. During this operation, the worker picked up with his hand a piece generating high levels of radiation. When his operational dosimeter triggered, the worker let the piece at the bottom of the pool and all workers left the workplace.
In France, for workers potentially exposed to ionizing radiation during their work, the annual regulatory dose limits are 20 mSv for whole body and 500 mSv for the body extremities. At EDF request, the French Institute for Radiation Protection and Nuclear Safety (IRSN) and the French Atomic Energy Commission (CEA) made the internal and external dose assessments. The assessments showed that one of the worker’s hands was exposed to a maximum dose of 750 mSv and that the effective dose (whole body) is less than 2 mSv.
ASN carried out an inspection on site on 3 May 2010 to verify the mesures implemented by EDF to secure the workplace, to initiate the worker medical follow-up and to assess the incident root causes. This exposure is due to an inadequate risk analysis and to the lack of procedures to manage the presence of foreign pieces at the bottom of the pool.
EDF and KELLAL proposed to ASN to rate this event at level 2 on INES scale and ASN confirmed this proposal.
Event date: Fri, 23-04-2010