EDF first-generation design plants have been gradually shut down and are currently being decommissioned (see section 1.4.1.1.6 “Decommissioning of nuclear power plants”).

Generation allocation contracts

In the 1970-80’s, EDF developed industrial cooperation with European operators in the nuclear industry, in the form of generation allocation contracts backed by units of the EDF French nuclear fleet.

In its fleet, EDF has twelve generating units participating in the contracts (up to 1.5GW) with the following European energy companies:

• Fessenheim 1-2: EnBW (17.5%);
• Cattenom 1-2: EnBW (5%);
• Bugey 2-3: Électricité de Laufenbourg⁽¹⁾ (17.5%);
• Tricastin 1 to 4: Electrabel⁽²⁾ (12.5%);
• Chooz B1-B2: Luminus, EDF subsidiary in Belgium (3.3%).

The purpose of these generation allocation contracts is to make available to each partner the proportion of energy generated actually due to him, based on the share of the capacity allocated to him – in return for payment of their share of the construction costs, annual operating costs (including upstream and downstream fuel costs), local taxes and taxes specific to nuclear energy, and the costs relating to decommissioning. In these transactions, the partners have shared with EDF the industrial risks in the development of the fleet and assume the risks linked to performance concerning the current operation of the power plants. On the other hand, they have no operational role.

Furthermore, EDF signed a second type of generation allocation contract relating to a pool of power plants (totalling approximately 2GW) under which EDF makes available to its partners a share of the electricity determined by the level of availability of all or part of a standard fleet, applied to the capacity share reserved to the partners for the units concerned. These contracts mainly concern the following power plants:

• Chooz B1-B2 (N4 initial series unit): Electrabel (21.7%);
• Cattenom 3-4: Électricité de Laufenbourg (7.8%) and the Swiss electricity group CNP (21.8%).

1.4.1.1.2 Operation and technical performance of the nuclear fleet

Nuclear power is a means of generation whose variable cost, mainly fuel-related costs, is low since it represents less than 30% of operating costs⁽³⁾. The main competitive levers of the nuclear fleet in its operating phase are thus the amount of generated energy and the optimisation of fixed operating and maintenance costs. The levers relating to the fuel cycle are further discussed in section 1.4.1.1.4 “The nuclear fuel cycle and related issues”.

Operation methods of the nuclear fleet

Generation cycle and planned outages

To reconcile the challenges linked to the strong variations in seasonal consumption in France, due to its strong temperature sensitivity, the availability of maintenance resources and the efficient use of reactor fuel, EDF has now adopted generation cycles of 12 and 18 months for its fleet. At the end of 2019, this breakdown was as follows:

• 28 units of the 900MW series have an operating cycle of approximately 12 months;
• 6 units of the 900MW series, 20 units of the 1,300MW series and 4 units of the N4 (1,450MW) series have an operating cycle of approximately 18 months.

At the end of these operating cycles, shutdown periods are programmed in order to replace a fraction of the fuel loaded in the core and perform maintenance work.

Two types of planned outages are alternated at the end of each generation cycle:

• an ordinary shutdown for refuelling, for a standard period of approximately 35 days, during which unloading spent fuel and reloading new fuel is the main operation performed; although maintenance or periodic testing is taking place during this type of outage;
• a partial inspection for refuelling and maintenance for which the standard period⁽⁴⁾ lasts approximately 70 days.

Every ten years, the power plant is shut down for a period of 150 days⁽⁵⁾ in average to carry out a ten-year inspection. This length of time varies according to the works and maintenance programme, as well as the series concerned. The programme for a ten-year inspection includes the following:

• unloading of spent fuel and reloading of fresh fuel, as at each outage;
• hydropower test of the primary coolant system, a leak test of the containment, and inspection work of the reactor’s pressure vessel;
• modification work, associated with ten-year safety re-evaluations;
• other specific maintenance operations, in particular renovation or replacement of major components.

At the end of the ten-year inspection, the ASN decides whether to approve the restart of the reactor and then issues technical prescriptions setting the conditions for continuing operation.

Operation of EDF’s nuclear fleet

Nuclear generation resources, owing to their low variable cost are first used for base-load generation, immediately after run-of-river hydropower and other unavoidable renewable energies, as well as the energy purchased under buying obligations from decentralised energy producers. Variations in energy consumption over one year (summer-winter, day-night) and the currently restricted fluidity of wholesale markets due to limited interconnections on the borders lead nuclear energy to be used also for mid-merit generation. High variations in seasonal consumption in France and its major variation during winter months require that planned nuclear fleet outages be concentrated between April and October.

Generation and technical performance

The nuclear fleet produced 379.5TWh in 2019, down 13.7TWh compared to that of 2018.

Nuclear generation expressed in annual energy corresponds to a load factor rate referred to as “Kp” for the French nuclear fleet (defined as the ratio of energy generated to the maximum theoretical energy, or the energy generated if the installed capacity were operated year-round). This rate is obtained by multiplying two coefficients (Kp = Kd × Ku):

• the availability factor (“Kd”) (the available energy⁽⁶⁾ as a percentage of the theoretical maximum energy, or the energy generated if the installed capacity were operated year-round). The Kd depends on outage durations, and is therefore impacted by standard durations and the work programme to be performed;
• a utilisation factor, (“Ku”) (energy generated compared to energy available). The Ku factor reflects environmental, regulatory and social constraints, supply of system services and optimisation implemented by EDF (fuel and modulation).

(1) Axpo Group.
(2) Engie Group.
(3) Operating costs are defined as follows: fuel costs (including downstream expenses in the fuel cycle), operating expenses (purchases and external services, employee expenses)and maintenance costs (expenses and investments). They do not include investments related to construction or decommissioning expenses.
(4) Standard durations represent optimised and realistic reference durations by outage types. They take into account the feedback from past outages. Outage planned durations fluctuate around these standard durations, depending on the work programme to be performed.
(5) Normal period, excluding extreme or exceptional circumstances
(6) Available energy is equal to the maximum theoretical energy less generation losses due to technical reasons inherent to power plants, such as planned outages, unplanned outages due to failure or safety requirements, and performance of regulatory tests.