In 2020, installed nuclear generation capacity declined for the first time since 2009, dropping from 63.1 GW to 61.4 GW. This followed the permanent closure of the last two 900 MW reactors at the Fessenheim power plant, which was disconnected from the grid on 29 June. Commissioned in 1977, it was the oldest nuclear power plant in France. The closure reduced the share of nuclear power in the French mix to 45.1 %.
Nuclear generation contracted by 11.6 % year-on-year, to 44 TWh, the lowest level on record since 1993. This represented 67.1 % of total electricity generated in France for the year. The decrease in generation was attributable to the closure of Fessenheim and, more importantly, to a lesser availability of nuclear power plants and to the health crisis. The year-on-year decline in nuclear generation directly linked to the Covid crisis is estimated at 34 TWh (see section on nuclear power plant unavailability below).
Nuclear power plant unavailability up sharply
Data from the European Network of Transmission System Operators for Electricity, which has 34 member countries and 41 transmission system operator (TSO) members. Its purpose is to promote important aspects of electricity policy such as security, renewable energy development and the power market. ENTSO-E works closely with the European Commission and is the backbone of the European electricity market Transparency Platform
Most of the plant unavailability times were reported as scheduled outages. Unavailability was naturally higher during the warmer months of the year, this to guarantee greater availability in winter, when demand rises.
Longer maintenance periods
Average nuclear power plant unavailability rose sharply in 2020, to 22.3 GW from 17.8 GW in 2019, contributing to a steep drop in nuclear generation.
Unavailability reached its highest point for the year on 7 July 2020, with an average of 37.9 GW unavailable that day, or more than 60 % of installed capacity. This was the result of maintenance cycles overlapping at numerous French nuclear power plants. Indeed, maintenance work was extended on much of the French nuclear fleet in 2020 as a direct consequence of the health crisis, which slowed maintenance efforts. Some reactors were also stopped in the second and third quarters of 2020 to save fuel and thus guarantee maximum availability in winter, when demand can surge
The impact of the crisis was significant
EDF’s January 2020 forecast for unavailability across its entire nuclear fleet over the year was 11 GW lower than the actual figure. Its forecast did not take into account unscheduled unavailability, variations in Real power actually available, which can be different from a plant’s theoretical power. For nuclear power plants, maximum available power is sensitive to external factors, such as: the temperature of the cooling source (river or sea water), reactors operating at the end of their fuel cycle (with less efficient fuel that needs to be replaced), or other technical or external constraints, extended shutdowns or other planned stoppages not foreseen in January 2020. One year prior, in January 2019, EDF’s full-year unavailability forecast was 7.2 GW below the actual figure.
Comparing 2020 to 2019, when plant operating conditions were closer to normal, the difference represents an average of 3.9 GW (11 – 7.2 = 3.9 GW).
It is possible to deduce that operation in degraded mode, under the constraints created by the health crisis in 2020, increased average unavailability by 3.9 GW relative to 2019, equivalent to about 34 TWh.