VI. FRENCH NUCLEAR HISTORICAL AVAILABILITY ANALYSIS

This appendix provides an analysis conducted by Elia on the availability of the French nuclear fleet using historical availability data as published by the French nuclear producer. The analysis reveals a consistent pattern of underestimating the planned unavailability of the French nuclear fleet, resulting in a significant number of units being unavailable during winter seasons. This underestimation ranges from 3 to 17 units (of 900 MW), in addition to what was initially forecasted a few months before the winter season. Figure 3-92 of Chapter 3 gives a visual overview of the impact calculation for each winter.

The nuclear unavailability is clearly underestimated in REMIT

In order to evaluate the accuracy of the forecasted French nuclear availability based on REMIT data, a comparison is made between the availability data from the past 8 years and the actual realised availability as reported by EDF. As illustrated on Figure VI-1, there is a clear, structural under-estimation of the unavailability of the French nuclear fleet in the REMIT data published 1 or 2 years in advance when compared to the actual unavailability.

The figure displays the planned unavailability that was known end of each calendar year as well as the realised planned and forced unavailability of the French nuclear fleet. Each curve (in colour) relates to the predictions made at the end of a specific year in terms of expected planned outages for the upcoming 3 years. The black curve represents the realised planned unavailability across the years. The dotted black curve includes the forced outages (on top of the planned outages already included in the black curve). The difference between the realised planned availability and current forecast (black curve) and the different coloured curves (previous forecasts) is the underestimation of the unavailability.

This analysis confirms that using REMIT availability data without applying a cautious approach is not a reliable method for estimating future French nuclear availabilities. As also indicated in the Chapter 3, the REMIT availability data do not align with forecasted generation by the French producer for future years.

Additionally, this analysis confirms that the availability of nuclear power during winter months in France is progressively decreasing each year. However, the expected REMIT forecasts for upcoming winters still remain at levels observed prior to 2017.

The main difference in forecasted availability is happening during the winter

Figure VI-2 illustrates the evolution of the expected nuclear unavailability during winter based on the forecasted lead time (from 2.5 years before the given winter to right before the winter). The figure clearly demonstrates that the underestimation of the French nuclear fleet’s unavailability extends to the winter period. Furthermore, it is worth noting that the most significant surge in unavailability occurs within the winter season itself. This highlights the challenge of accu- rately predicting and accounting for these sudden jumps in advance to effectively develop additional capacities that can compensate for the reduced availability. This finding reinforces the notion that French nuclear availability poses a short-term risk and strengthens the importance of taking it into account when calculating capacity requirements for Belgium. This is the reason for the integration of this risk under the EU-SAFE scenario of this study.