Some BNIs (in particular the nuclear power plants operated by EDF and the EURODIF facility) discharge cooling water effluent, known as "thermal discharges" into watercourses or into the sea, either directly for those plants operating in "open" circuit, or after cooling in cooling towers, venting some of the heat into the atmosphere.

Thermal discharges from power plants into watercourses leads to a temperature rise, between upstream and downstream of the discharge, of between a few tenths of a degree and several degrees. They are therefore regulated in the nuclear power plant discharge licence orders.

A committee for monitoring exceptional thermal discharges from electricity generating plants was set up to monitor the impact of these discharges on the watercourses.

From the environmental standpoint, the regulatory limits aim to prevent a modification of the receiving environment, in particular fish life, and to ensure acceptable health conditions if water is taken for human consumption downstream.

These limits can thus differ according to the environment and the technical characteristics of each plant.

The organisational, administrative and technical steps taken following the 2003 heat wave and drought mean that the drought encountered in 2005 was dealt with in good conditions, in particular ensuring full compliance with the discharge licences applicable.

For several years, particular attention has been paid to the chronic or accidental effects on the environment of both conventional and nuclear industries. With respect to the nuclear industry, the interministerial order of 31 December 1999 sets the general requirements to be met by BNIs concerning environmental protection. It supplements the texts specific to each plant on this subject, i.e. the discharge licences or the operating licences for installations classified on environmental protection grounds located on plant. More particularly, and in addition to the onsite emergency rules (staff training, safety instructions, maintenance of installations, etc.), the order specifies objectives for protection against fire, lightning, noise, or the risks of accidental pollution of the environment (water and atmosphere).

Most of the requirements were applicable on 15 February 2002, two years after the date of publication in the Official Gazette. However, if the operators can prove that they are experiencing difficulties, article 48 of the order of 31 December 1999 provides for extra time allowances, without however exceeding 15 February 2006.

Considerable work has been done by the operators to check the installation conformity with the requirements of the order, to identify deviations, evaluate and implement the conformity work required or propose preventive measures such as to achieve a level equivalent to that of those requirements that cannot be met. For its part, the ASN analysed these requests before ruling on the operators' proposals. The ASN also conducted spot-checks during the site inspections on the completeness and accuracy of the information provided in the dossiers. As and when necessary, dates for installation conformity work were set by the Director General for Nuclear Safety and Radiation Protection.