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Afsse received a solicited request at the end of 2004 in the framework of legionellosis risk prevention, a pulmonary disease spread by bacteria. It was asked to produce an opinion on the levels of intervention and prevention, monitoring and action strategy implemented by EDF, along with an estimation of the exposure of populations around nuclear plants and the assessment of the health and environmental risks associated with water and gas discharges.

Summary of the request:

Solicited request from the DGS, DPPR (Directorate for Risk and Pollution Prevention) and DGSNR (Directorate General for Nuclear Safety and Radioprotection) dated 15 November 2004. After reading and analysing the solicited request and appended documents, the experts organised their work on the basis of three main objectives:

 to determine if the demonstration file of the operator seeking to justify specific Legionella spp intervention limits for the cooling tower of their electricity-generating nuclear plant (TAR CNPE) was admissible. This demonstration was based on the comparison of Legionella spp concentrations in the soil generated by the atmospheric dispersion of emissions from TAR CNPEs and the cooling towers of classified facilities for environmental protection (TAR ICPEs), estimated using modelling tools. EDF reinforced its demonstration with occupational exposure studies;
 to establish if the monitoring procedure of EDF facilities to control Legionella spp levels in the air around its facilities was appropriate;
 to examine the suitability of treatments controlling abundance levels of Legionella spp and the environmental impact of these treatments.
The final objective of this expert assessment was to help the directorates which issued this solicited request to confirm or invalidate the limits currently recommended for TAR CNPEs.

General points & contextual elements:

The fleet of EDF nuclear plants comprises 19 CNPEs, 11 of which are equipped with cooling towers subject to INB regulations. These 11 sites have a total of 32 cooling towers, including 28 TAR CNPEs supplied with river water and subject to DGSNR recommendations on the Legionella risk of TAR INBs.

According to these recommendations, EDF must set up suitable prevention measures to keep the Legionella spp concentration below 5.106 UFC/l in water used in the cooling circuits of all TAR CNPEs except those in Chinon, for which the Legionella spp concentration required is 5.105 UFC/l.

These recommendations also concern how often analyses should take place. Measures for INBs should be carried out: monthly if the Legionella spp concentration is lower than 104 UFC/l; fortnightly if the Legionella spp concentration is between 104 and 105 UFC/l (less than 104 UFC/l for Chinon); weekly if the Legionella spp concentration exceeds 105 UFC/l (104 UFC/l for Chinon).

Legionella levels are monitored through samples from the cold basin, using the standard plate count agar method for Legionella (NF T90-431) as often as recommended by the DGSNR;

Discharges of liquid and gas effluents and samples of the water in this circuit are subject to an authorisation issued at ministerial level, such as the one indicated by decree no. 95-540 of 4 May 1995 on INBs.

Note that the presence and proliferation of Legionella spp in TAR CNPEs belonging to EDF are mainly associated with technological choices:

 to use a cooling system by water dispersion into a flow of air
 to supply the system using surface water
 to pump the water round the circuit several times so as to reduce the volume of sampled water in the river.

The EDF demonstration procedure concerning the currently recommended action limits aims to prove:

 the 5 106 UFC/l limit of Legionella spp as a management limit for its TAR CNPEs, and 5 105 UFC/l of Legionella spp for the TAR CNPEs in Chinon. To achieve this objective, EDF compares Legionella concentrations in the soil generated by the atmospheric dispersion of emissions from TAR CNPEs and TAR ICPEs. These concentrations are estimated using modelling tools.

Although the solicited request does not ask for an examination of occupational exposure or risk, a study called: “Comparison of the seroprevalence of antibodies directed against Legionella pneumophila in workers exposed or not to emissions from nuclear plant cooling towers”, conducted at EDF’s initiative, was examined by the working group experts.





In order to process this solicited request in the framework of the collegial expert assessment, an ad hoc working group called “Legionella – CNPE”, was set up on 4 February 2005, chaired by Mr Bernard Tribollet (CNRS - Université Paris 6). The working group was attached to the Committee of Specialised Experts “Assessment of risks associated with air environments” when it was set up on 10 June 2005.

The various questions identified by the experts were submitted to the whole group and discussed in a plenary session of the working group. This method ensures that all viewpoints are considered and identifies the points requiring more in-depth analysis. Each member was questioned on his or her particular field of expertise and took part in drafting the relevant parts. All internal or external contributions were presented in a plenary session before being validated by members of the working group. At the drafting stage, all experts were asked to read all of the successive versions of the report.

Since the working group has been up and running, experts have carried out a critical study of some thirty confidential documents supplied by EDF from February to June 2005, accounting for more than 1000 pages and heard representatives of the operator on three occasions. The experts appreciated visiting a CNPE site which helped them to interpret data and EDF conclusions more effectively.

Moreover, the experts used recent scientific and technical data on Legionella, regulations in force both in France and countries at a comparable stage of economic development as France and information gathered during hearings of several institutional scientific experts and manufacturers.

Concerning the latter, some operators of similar facilities or suppliers of technologies for large cooling towers were consulted. It must be stressed here that although the manufacturer of EDF TAR ICPE and TAR CNPE mist eliminators was called on several times, he never attended the hearing.

The collegial expert assessment group met during a plenary session 14 times between February 2005 and March 2006 and took part in various telephone conferences. Their work was reported by Bernard Tribollet, chairman of the working group, and by Laurence Mathieu, rapporteur before the Agency’s “air environments” CSE and was debated when it met in October and December 2005.

During 2005, the group of experts worked mainly on the first two (dissemination of Legionella via emissions and appropriateness of monitoring plans set up by EDF).

This work featured in a confidential report which was made available to the experts of the “air environment risks” CSE in December 2005. The CSE adopted this work and produced its opinion in March 2006.

The Agency’s opinion will be published in June 2006, together with the opinion of the “air environment risks” CSE and an overview and conclusion, prepared by the working group.

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