Sfen’s Response to the Public Consultation on the 1300 MWe PSR: Preventing the Risk of Over-Complicating the Operating Limits and Conditions (OLC)
As the French Nuclear Safety and Radiation Protection Authority (ASNR) is conducting a public consultation on the continued operation of 20 EDF 1300 MWe reactors beyond their fourth Periodic Safety Review (PSR), the Sfen warns of the increasing complexity of the Operating Limits and Conditions (OLC). Based on feedback from the 900 MWe fleet and from Flamanville 3, it calls for a strong commitment to simplicity and operability from the outset, in order to preserve the performance of the facilities and their teams.
Pierre-Marie Abadie, President of the ASNR, noted during his May 22 hearing before the Senate that the OLCs of nuclear power plants are becoming increasingly complex and rigid. He stated that “there is a collective willingness [with EDF] to move towards greater simplification,” both for the existing fleet and for the future EPR2 reactors.
The ASNR opened a public consultation on its website from May 16 to June 15 regarding the conditions for the continued operation of EDF’s 20 1300 MWe reactors beyond their fourth PSR. As with the PSR of the 900 MWe reactors, ambitious safety targets have been set for the 1300 MWe units — namely, to bring their safety level closer to that of more recent third-generation reactors. Sfen stresses the importance of addressing the complexity of OLCs for the 1300 MWe reactors now, rather than simplifying them later.
Reminder: What are Operating Limits and Conditions?
The Operating Limits and Conditions (OLC) of a nuclear reactor define the authorized operating parameters of the reactor and the procedures to be followed by the operating personnel. They are prepared by the nuclear plant operator and approved by the safety authority. The OLCs specify rules for normal operation (start-up and shutdown procedures), the operating limits of the reactor (pressure, temperature, power), the equipment required under specific operating modes, monitoring and inspection procedures, and operating instructions in the event of incidents or accidents.
An Ambitious Upgrade Program for the 1300 MWe Series
The modernization project for the 20 1300 MWe reactors is a continuation of the work successfully carried out on the 32 900 MWe reactors. This approach applies both to equipment (around 200 modifications are planned for the 1300 MWe fleet) and to reference documentation, ultimately affecting nuclear operations. EDF is the only operator taking on this dual challenge. A key issue in the development of future OLCs will be to improve the operability of the reactors in anticipation of their extended lifetime.
Recent Warnings about the Complexity of OLCs
Sfen had already documented, at its 2024 Fall Convention, the complexity of the OLCs for Flamanville 3. Part of this complexity stems from a larger number of components involved in the EPR design, but also from increasingly detailed and restrictive operational documentation. This trend appears more pronounced in France than in other countries operating similar technologies (PWR, EPR). For example, the OLCs of the Olkiluoto 3 EPR in Finland comprise 900 pages, whereas those of Flamanville 3 exceed 4,000 pages. Beyond the page count, the number of constraints (e.g., prohibited equipment configurations in many reactor states, required reactor fallback within extremely short deadlines) can undermine the implementation of maintenance programs.
Complexity and Efficiency
A few examples: some maintenance operations are spread out over time due to the constraints imposed by the Operating Technical Specifications (OTS); fallback actions required within one hour cause power transients that could have been avoided with more time to assess the most appropriate measures for the situation. At the Sfen Convention, the Flamanville 3 teams testified about the significant time needed, during tests or in the event of an anomaly, to determine whether an intervention is allowed and to understand the applicable procedures. They reported that this complexity increases the burden on teams. Since any deviation from the OLCs is subject to regulatory oversight, this complexity has led the operator to request exemptions — granted by the ASNR — raising questions about the appropriateness of some rules relative to the actual safety concerns.
Shared Warning Signals
Aware of the situation, the ASNR noted in its 2024 Nuclear Safety Report that the complexity of the OLCs “can lead to a loss of meaning in the operators’ work and have an impact on risk control.” In 2024, the ASNR also brought together the industry and stakeholders through the COFSOH (Steering Committee on Social, Organisational and Human Factors) to reflect on the growing complexity of nuclear plant operation. A summary of these discussions is expected in 2025.
In its 2024 report, the General Inspectorate for Nuclear Safety and Radiation Protection (IGSNR) also confirmed that “France has moved away from international practices regarding OLCs.” It added: “our approach, of dizzying sophistication, has reached the end of a system.” Field operators echoed this: “We have to choose between the letter and the spirit […] Knowledge of the rules has taken precedence over knowledge of the machine.”
The ASNR states that “EDF has initiated short- and medium-term simplification efforts, as well as a long-term project to completely redesign its OLCs.” The goal of this simplification is to enhance the usability and clarity of the reference framework for operators, leading to better operational safety. EDF’s “OLCs of the Future” project has been launched to develop proposals that will lead to an ASNR position by 2027, enabling the future EPR2 to benefit from these improvements from the outset.
Opportunities to Prevent Over-Complexification
The key issue in evolving the OLCs is to adopt a balanced approach to safety requirements. One first opportunity identified by Sfen concerns the number of safety-classified components. A recent EDF report submitted to a standing group of ASN shows that, for the 900 MWe units, the number of safety-classified components, which remained relatively stable between PSR 3 (7,500) and PSR 4 (8,000), doubled in PSR 4 to 17,000, with a corresponding increase in operational constraints: +25% in periodic tests between PSR3-900 and final PSR4-900 status, +75% in OTS events over the same period.
In its 2024 report, the IGSNR warned — in its chapter on internal flooding risks — that classifying a large number of additional valves as safety-related would further increase complexity. It advised “tempering the classification mechanism” because “if everything is classified, classification loses all meaning,” which in turn increases the burden of emergency procedures and OLCs. “In the event of flooding, teams are expected to consult study notes with potentially countless combinations. When the time comes, rather than looking up a study to close a valve, knowing the layout and systems seems safer.”
A second opportunity concerns operating procedures for incident or accident conditions, which tend to include more and more predefined scenarios regardless of their actual likelihood. This risks making the procedures overly complex and less effective in more likely situations. As illustrated by the Three Mile Island accident, what actually happens may not be what was anticipated — and teams must be able to adapt to the real situation. They will do so more effectively if their working environment hasn’t been made unnecessarily complicated.
The Human Factor at the Core of Nuclear Safety
Particular attention should be paid to the Nuclear Rapid Response Force (FARN), which must not be overly burdened with tasks stemming from predefined scenarios in safety studies, in order to maintain “its capacity to handle the unexpected.” On this point, the IGSNR warns against the belief “that a system of rules, procedures and controls can substitute for professionalism, competence, and sound judgment.” In fact, a decomplexification approach seeks to ease overly strict control mechanisms. This means restoring trust and operational leeway to field teams.
In return, field teams must strengthen their capacity for action: “decomplexifying means fighting the illusion of control. We must push responsibility down and expect the field to train more, practice more, apply judgment, make and own decisions,” the IGSNR stresses.
Thus, the competence and training of the personnel on nuclear sites — combined with the operability of fixed or mobile equipment — lie at the heart of safety. Operators must be able to deliver on this with the right balance between rules and responsible management by those working in the facilities. ■