diagnostics related to the identified weak points and their recurrence needs to be improved. The ASN reviews of the event reports received in 2021 revealed no particular weakness regarding the competence of the teams in charge of the in-depth analysis of significant events. The quality and availability of the human resources assigned to the analyses are satisfactory on all the sites, whether in terms of numbers or of competence. The involvement of OHF skills in the analysis phase is satisfactory on the majority of the sites. 2.7 Personnel radiation protection 2.7.1 Exposure of personnel to ionising radiation Exposure to ionising radiation in a nuclear power reactor comes primarily from the activation of corrosion products in the primary system and fission products in the fuel. All types of radiation are present (neutrons, α, β and γ), with a risk of internal and external exposure. In practice, more than 90% of the doses received come from external exposure to β and γ radiation. Exposure is primarily linked to maintenance operations during reactor outages. The average collective dosimetry on all the reactors (Graph 5), and the average dose received by the workers for one hour of work in a controlled area (Graph 6) rose in 2021 by comparison with 2020, which had been marked by several reactor outage postponements. These values reach a level comparable to that of 2019, before the Covid-19 pandemic. The doses received by the workers are broken down as illustrated above in Graphs 7 and 8. Graph 8 shows the breakdown of the workers according to whole body external dosimetry. As in 2020, the dosimetry for 75% of the exposed workers was less than 1 mSv (millisievert) in 2021, which corresponds to the annual regulation limit for the public. The annual regulation limit for whole body external dosimetry (20 mSv) was exceeded on no occasion in 2021. Graph 8 shows the trend in whole body average individual dosimetry according to the categories of disciplines of the workers in the NPPs. As in previous years, the most exposed worker categories are personnel in charge of heat insulation, welding, monitoring, mechanical work and ancillary systems. The doses recorded by the most exposed workers are up by comparison with 2020. Significant contamination events The number of significant contamination events concerning workers in the NPPs fell in 2021: four events were reported in 2021, as against eight in 2020 and seven in 2019. Of these events, three led to exposure greater than one quarter the annual EXTERNAL CONTAMINATION OF A WORKER IN THE CRUAS-MEYSSE NPP On 24 August 2021, during the check conducted at the exit from the controlled area in Cruas-Meysse NPP reactor 2, contamination was detected on a worker. The medical service immediately took charge of the employee and located the radioactive particle causing the contamination at the nape of the neck. The particle was removed. Despite the investigations carried out along the route followed by the worker, the areas or points of contamination that could have caused this contamination could not be determined. Consequently, EDF conducted an evaluation of the received dose considering that the particle was present from the moment the worker entered the reactor building until the particle was removed. This evaluation gives a dose at the nape of the worker’s neck exceeding the regulation limit set for the equivalent dose to the skin (500 mSv for a skin surface area of 1 cm²). ASN carried out an inspection on the site on 31 August 2021. The inspectors checked that EDF had taken all necessary steps for adequate management of the event and analysis of its causes. Owing to the regulatory occupational exposure limit being exceeded, this event was rated 2 on the INES scale (ratings from 0 to 7 in ascending order of severity). The previous Significant Radiation protection Event (ESR) of level 2 reported by an EDF NPP dates back to 2015. GRAPH Trend in mean individual dosimetry according to the categories of trades of the workers in the NPPs 8 0 0.5 1.0 1.5 2.0 2.5 3.0 Risk prevention Welding Auxiliaries Mechanical Expert appraisal Tests Electricity Checksinspections Thermal insulation Administrative 2018 2019 2020 2021 Mean dose (mSv) Source : EDF. This Graph includes data from the Fessenheim NPP until 2020. ASN Report on the state of nuclear safety and radiation protection in France in 2021 301 10 – THE EDF NUCLEAR POWER PLANTS 08 07 13 04 10 06 12 14 03 09 05 11 02 AP 01
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