Universal Registration Document 2022

As announced in  January  2022, inspections of the Taishan  1 reactor’s fuel assemblies following the technical issue encountered during its second operating cycle showed mechanical wear on certain assembly components. This kind of wear has already been observed in several reactors of the French nuclear fleet. For the future commissioning of Flamanville 3, a solution has been examined with the ASN.

EDF’s proposed strategy for the Flamanville EPR (supply of around sixty reinforced fuel assemblies) was presented to the High Committee for Transparency and Information on Nuclear Safety (Haut Comité pour la transparence et l’information sur la sécurité nucléaire, HCTISN) on 7 June 2022.

In January 2023, the IRSN issued a favourable opinion of EDF’s proposed strategy, and the ASN will finalise its examination by the end of the first quarter of 2023.

Repair work to the main secondary circuit welds continued during the first half of the year. 122 welds are concerned (36 penetration welds and 86 non-penetration welds).

At 31 December 2022, 56% had been repaired, 65% had been approved for stress-relieving heat treatment, and 32% were completed and valid after stress-relieving heat treatment. Work is totally finished on the welds on the reactor containment building, which were the most complex cases, and they have been declared valid.

Concerning the SIS (Safety injection system)/CHR (Containment heat removal) filtration sumps, EDF proposed a new filtration system which has been trialled and produced results considered satisfactory by the IRSN. Following these trials, in September 2022 EDF replaced the existing filters with finer filters. EDF also decided to reduce the quantities of potential debris that is known to clog up filters. The work to reduce potential debris is practically complete, and should be finished by the end of the first quarter of 2023.

After corrosion was observed on pressuriser valves at the Olkiluoto EPR (Finland), EDF and Framatome carried out equipment checks and also detected traces of corrosion on the Flamanville EPR’s valves. EDF and Framatome decided to respond to this finding by changing the material used for certain components of the pilot control valves. Several corrosion stress tests were conducted to select the best material. The components have been made and will be installed in the reactor building in early 2023. The ASN is continuing its examination of the operation and reliability of the pressuriser valves.

On 16 December 2022, EDF adjusted the schedule for the Flamanville 3 project: the nuclear fuel loading is now scheduled for the 1st quarter of 2024 ⁽¹⁾. The estimated cost to completion has been raised from €12.7 billion to €13.2 billion ⁽²⁾.

This schedule update is mainly due to supplementary studies that were needed to establish a new process for the stress-relieving heat treatment ⁽³⁾ (SHRT) of some welds that have been upgraded in the last two years, which are located close to sensitive equipment for the nuclear plant’s operation.

After the nuclear fuel loading, the start-up operations will continue, notably including inspections of all the reactor safety systems, equipment testing and qualification all the way through the temperature and pressure increases of the nuclear steam supply system, and then during the reactor ramping up. At 25% of nominal power, the reactor will be connected to the national electricity grid.

The last few months have seen further achievements in the pre-operation phase of the Flamanville EPR:

• the complex work of upgrading the main secondary circuit penetration welds is complete, and all the welds have been deemed compliant with the break preclusion concept. These first of their kind operations were achieved using remotely operated equipment and required more than twelve months of analyses and qualification prior to implementation at Flamanville;
• system performance testing of electrical equipment and fuel loading operations has been completed and they have been declared compliant with requirements.

2.1.2 Grand Carénage programme

Since 2014 EDF has been implementing its Grand Carénage industrial refurbishment programme for the French nuclear fleet, designed to enhance reactor safety and extend their operating lifetimes significantly beyond 40 years. The most recent estimate of the programme’s cost for the period 2014-2025, established in late 2021, is €50.2 billion in current euros. This cost factors in the third 10-year inspections for the Group’s 1300MW reactors, a significant portion of the safety improvements undertaken following lessons learned from the Fukushima incident, including construction and operation of 56 emergency diesel generators, creation of auxiliary feedwater pumps at each nuclear plant in operation, and performance of the fourth 10-year inspections of the Group’s 900MW reactors.

To continue the investments necessary to operate the Group’s nuclear fleet in complete safety significantly beyond 40 years, on 31 March 2022 EDF’s Board of Directors validated a new roadmap for the Grand Carénage programme running from 2022 to 2028. The cost estimate for this new period is €33 billion in current euros, or an annual expenditure of €4.7 billion. The extended programme will enable the Group to conduct studies and the fourth 10-year inspections of the 1300MW series, conduct preliminary studies for operation of the 900MW reactors beyond 50 years, in accordance with the multi-year energy programme adopted by France in April 2020, and complete the still substantial maintenance and renovation work on major components, so that power plants can remain in operation for more than 50 years. The broader scope of the programme also covers new safety requirements resulting from the generic opinion of France’s Nuclear Safety Authority (ASN) on the fourth 10-year inspections of the 900MW reactors, building on experience from the review with the ASN of the fourth 10-year inspections for 900MW and 1300MW reactors.

The third 10-year inspections of 1300MW reactors are entering their final phase (the last 5 are scheduled for 2023 and 2024). In the 900MW series, ten fourth 10-year inspections have been successfully completed and one is in progress (at Blayais 1). For the 1450MW series, the final second 10-year inspection has been launched at Civaux 2.

Examination with the ASN of the generic phase of the fourth 10-year inspections of the 1300MW series began in 2021 and is continuing. Examination with the ASN of procedures for the 30-year milestone of the 1450MW series, and inspection of the first reactor is expected for 2029.

Additionally, major investments have been made following the lessons of Fukushima: 56 emergency diesel generators have been constructed and put into operation, and every power plant has a permanent or provisional auxiliary feedwater system. Major components (including steam generators and main unit transformers) have also been replaced at many production units.

2.1.3 Stress corrosion

In late 2021, during preventive maintenance checks on reactor 1 at the Civaux nuclear power plant, scheduled as part of its ten-year inspection, defects were detected close to welds on the pipes of the safety injection system (SIS) circuit. Preventive checks were then carried out on the Civaux 2, Chooz 1 and Chooz 2 reactors, which also belong to the N4 series, and similar defects were identified. Preventive maintenance checks conducted during the ten-year inspection of reactor 1 at the Penly nuclear power plant also found similar defects on the SIS circuit.

Through expert assessments and analyses conducted during 2022, EDF identified the reactors where the SIS circuit pipes are the most susceptible to stress corrosion. They are the 16 most recent reactors: the four N4 reactors, and twelve P’4 1300MW reactors.