VII. FACTORS AFFECTING FUTURE NUCLEAR AVAILABILITY IN FRANCE

This appendix provides additional insights into the future availability of French nuclear units, complementing the information presented in Section 3.5.3.1. of the report. Over the past decade, the availability of the French nuclear fleet has gradually declined due to various factors. Unfortunately, based on several sources and elements, it is not expected that the availability in the coming years would reach the levels observed a decade ago.

The French nuclear fleet is characterised by a standardised technology, which means that any discovery or issue in one reactor has the potential to affect multiple reactors due to common mode failures or generic issues.

The French nuclear fleet is a key parameter when assessing future adequacy requirements of the European system as it represents more than 60 GW of thermal capacity. The nuclear units were built within a very short time with similar design and elements. One can distinguish 4 types of nuclear units in France:

• 34 (now 32 as Fessenheim was decommissioned) reactors of ‘900 MWe’ units consisting in the oldest reactors;

• 14 reactors of ‘1300 MWe’ units built in the late 70s and 80s;

• 4 reactors of ‘1450 MWe’, also called N4;

The REMIT availability forecasts used as basis in this study for the upcoming three winters are provided

The REMIT forecasts of the nuclear French fleet are the starting point to define the profile of availability used in this study. The REMIT forecasts are then calibrated to the assumed future yearly production levels. This is further detailed in Section 3.5.3.1. of Chapter 3. Figure VI-3 provides a graphical illus- tration of the future nuclear planned availability in France. For the year 2025-26, given that no data was yet available for the last part of the year, the same profile as for 2024-25 was used.

• A reactor being built since 2007 also called the EPR of which the commissioning date is expected in the coming years.

Given that the nuclear fleet was built in a short time, it will undergo life extension works in a similar short time. The very tight plan does not allow to avoid life extension works outside of the winter. In addition, given the large fleet, refuelling and maintenances are occurring whole year long (including in winter).

A large amount of ‘Visites Décennales’ (LTO) are planned in the upcoming years. Any delay in one of those can affect the whole planning. Additional inspections can also be performed in the case of design flaws found in one of the reactors. This is the current situation experienced with the ‘stress corrosion cracking’ issues in the N4 type reactors.

A similar situation to the one currently ongoing was already experienced in winter 2016-17 where a generic issue check led to one third of the nuclear fleet in France to be unavailable during winter [RTE-7]. At the beginning of autumn 2016, the ASN (Nuclear Safety Authority in France) requested the operator to conduct resistance tests on steam generator bottoms manufactured by Japan Casting and Forging Corporation within three months. Throughout the winter, ten 900 MW reactors and two 1450 MW reactors were affected by this procedure, with verifications carried out over several months. In the period leading up to winter, other reactors - in addition to those stopped for inspection - were also shut down for maintenance or incidents, resulting in a situation where more than one-third of the fleet was offline.

Since the winter 2016-17, Elia has always integrated sensitivities on French nuclear availability, and has recommended

Belgian authorities to use a scenario that integrates at least 4 nuclear units as unavailable on top of ‘normal availability’. The French nuclear output is declining since 2016

Since 2016, the annual nuclear generation in France has not exceeded 400 TWh, despite having a stable installed capacity. The French nuclear fleet has been facing an increasing number of events that have impacted its availability, and some of these issues are expected to persist in the coming years. In addition, many other outages were responsible for the decrease in nuclear availability. Figure 3-3 also provides an overview of the nuclear availability during the critical month of January since 2015. The same decrease is observed in winter availability.

Recent stress corrosion cracking findings in several reactors increased the future uncertainty while the maintenance planning was already heavily affected by the COVID-19

The COVID-19 pandemic has heavily affected the maintenance planning as from 2020. The initial planning prior to the pandemic was already very tight with a large amount of planned maintenances due to ‘Visites Décennales’.

The stress corrosion crack findings in October 2021 in several reactors brought the nuclear generation levels in France to unprecedent lows as several reactors had to undergo checks on weldings and repairs. The checks are still ongoing as hundreds of weldings needs to be still checked ([EDF-5], [ASN-1], [LMO-3] and [LEC-1]). It is not excluded that the checks that are going to be performed reveal other issues, such as the larger crack that was detected in the safety injection circuit of reactor number one at the Penly power plant. The reduced availability of the French fleet following those findings will be impacted in the coming years.

The new EPR reactor in Flamanville (1600 MW) commissioning was delayed several times

The present study assumes that the Flamanville new EPR reactor will be commissioned as stated by RTE in their public consultation for the upcoming ‘Bilan Prévisionnel’ [RTE-6]. Hence it is assumed that the reactor would be commissioned as from mid-2024. It is also assumed that the reactor will be closed beginning of 2025 to change the cover of the reactor vessel. It is therefore assumed that it will be fully available as from mid-2025. Any change in those assumptions can further affect the capacity requirements in Belgium.

RTE expects that the nuclear generation uncertainty in France is of around 100 TWh in 2030, which distributed on a yearly basis is corresponding to 11 GW. In its public consultation for the next adequacy study, RTE proposed to use 350 TWh as basis for the nuclear generation of the existing fleet

RTE has recently in its long term ‘Bilan Prévisionnel 2050’ report stated the following in February 2022 [RTE-8]:

The uncertainties regarding the actual production of the nuclear fleet in 2030 amount to around a hundred terawatt-hours per year. This is a significant and increasing uncertainty, related to the current trajectory of nuclear production in France, which exceeds the uncertainties regarding consumption levels or renewable electricity production. (own translation from French)

In RTE’s public consultation for its upcoming adequacy study [RTE-6], it suggests to use 350 TWh as basis for the yearly nuclear generation in France as from 2025. The public consultation document also highlights that two factors could degrade the long-term availability of the nuclear fleet:

• the aging fleet, which could prolong the trend observed in the recent years;

• the uncertainties surrounding the outcome of the fifth tenyear inspection of the 900 MW units starting from 2029, which could result in prolonged unavailability.