Nuclear engineering and services

Onet Technologies completes the design and installation of the first "EAS-ND" safety equipment at the Cattenom power plant

The safety of nuclear facilities is a top priority for the nuclear industry. To meet these requirements, Onet Technologies designs innovative solutions, such as the EAS-ND system deployed on 1300 MWe units, including the EDF Cattenom power plant. This major project illustrates the expertise of our teams and our commitment to supporting the nuclear industry with high-level technical solutions. Find out how this system contributes to enhancing the safety of nuclear facilities in the face of the most extreme situations.

What is the EAS-ND system ?

The EAS-ND system (Enclosure Aspersion System - Hard Core) is designed to reinforce the safety of 1300 MWe and N4 nuclear power plants, particularly in the event of a serious accident such as that at Fukushima. It follows on from the EASu system deployed for the 900 MWe range.

This device takes over in the event of EAS/RIS system failure, providing external cooling of the primary circuit, and maintaining pressure and temperature within safe, acceptable limits to prevent damage to the containment (the reactor building). The system thus reduces the risk of early or significant releases into the environment.

The EAS-ND operates with a diversified cold source, provided by EDF's FARN (Force d'Action Rapide du Nucléaire). This source, external to the power plant, can be fresh or salt water, which implies high requirements in terms of corrosion resistance. Via theheat exchanger designed by Onet Technologies, this cold source is used to cool the water taken from the RIS/EAS sumps located at the back of the reactor building, then reinjected into the cooling circuit.

The design, manufacture and installation of EAS-ND exchangers represents a major technical challenge for our teams, both in terms of the complexity of the design and the associated regulatory and logistical constraints.

Background and involvement of Onet Technologies in the deployment of the EAS ND system

Onet Technologies is already in charge of the design and manufacture of EASu exchangers for the 900 MWe unit, a major project launched in 2016 covering the manufacture of a total of 32 units.

For the EAS-ND project, Onet Technologies is broadening its scope to include :

Design and manufacture of 20 exchangers for the 1300 MWe range (P4 and P'4 ranges) and 4 exchangers for the N4 range;
Delivery and on-site installation of 12 exchangers for the P'4 stage (part of a consortium with Onet Technologies, Monteiro and ADF).

The EAS-ND exchanger designed by Onet Technologies: a tailor-made technical challenge marked by high standards

The challenge of the EAS-ND exchangers was met in a tense context, marked by very tight deadlines, at a time when supply chains were still disrupted by the post-Covid crisis and the start of the conflict in Ukraine.

The design, carried out to tight deadlines, incorporated feedback from EASu exchangers as well as EDF's specific requirements for this new project, including a new support configuration based on three partially dismountable legs.

To guarantee corrosion resistance, some of the heat exchangers are made from superduplex stainless steel. This is particularly true of the tube bundle supplied by our subcontractor GNMS/SBER.

This grade of material is not provided for in the RCC-M, the design and manufacturing code used in France's pressurized water reactors. It was therefore necessary to "nuclearize" this grade, i.e. demonstrate its compliance with the very strict requirements of the Nuclear Pressure Equipment (NPE) regulations (see our box below).

Manufacture of the exchangers began in March 2023 by ACM, the boilermaker in charge of production and associated technical documentation.

Installation of the EAS-ND device by Onet Technologies: a second challenge on this EDF project

The challenges didn't end with the design and supply of the exchangers: the on-site installation of the EAS-ND equipment on the P'4 bearing represented another feat to be overcome.

On each P'4 unit, a heat exchanger weighing 12.5 tonnes, 7 metres long and 1.5 metres in diameter had to be transported and installed in particularly cramped premises. The exchanger had to be transported on a cart powered by 4 robots supplied by JNOV-TECH.

The cart is a complex element with several features required for this site: up/down and possible tilting of the exchanger, piloted by a high-performance control system. The interdependent, synchronizable robots are piloted by Onet Technologies personnel, who spent several weeks training in a room simulating the site environment.

The biggest challenge in routing the interchange was to make a 90-degree turn through a veil deconstructed for the occasion, imposing a passage tolerance to the centimetre.

The exchanger supports had to be installed on site six months before delivery.

Installation of the first heat exchanger on the P'4 unit was successfully completed last April at Cattenom 1 during the 2025 unit outage.

Our teams of slingers, foremen and mechanics will shortly be continuing to install the hydraulic circuits, with the help of welders and pipe fitters.

An ongoing collective commitment to the safety of France's nuclear power plants

After Onet Technologies delivered the EAS-ND exchanger for Paluel 1 at the beginning of the year, and then for Cattenom 1 last April, the manufacture of EAS-ND exchangers is continuing for the remaining 18 1300 MWe units, as well as for the 4 N4 units. The performance tests recently carried out with Tibbloc have confirmed the effectiveness of our solution!

This will be followed by further on-site installations on 11 P'4 units, with Onet Technologies, Monteiro and ADF sharing the scope. Our teams will be responsible for the complete installation of the EAS-ND circuit on 3 units.

Thanks to the experience already acquired on 28 EASU exchangers already delivered for 900 MWe reactors, our teams are approaching the preparation phases for circuit installation with confidence.

As part of the VD4 1300 MWe program to extend the operating life of units of this power, Onet Technologies plays a central role in EDF's operations, supplying and installing complete, complex systems.

Thank you to our mobilized teams, and to EDF for its renewed confidence.

Classification of ESPNs in the nuclear sector

In the nuclear sector, pressure equipment is classified according to its role in safety and the stresses to which it is subjected. EAS-ND heat exchangers are classified at level 2, which means they are important to plant safety, even though they are not directly involved in reactor core containment. Their risk category IV is the highest: it implies that this equipment must withstand extreme conditions of pressure, temperature and mechanical stress.

This classification imposes stricter requirements at each stage of the project entrusted to Onet Technologies:

choice of materials,
design,
procurement, manufacturing,
quality control,
documentation, traceability and regulatory inspections.

July 17, 2025
Onet France

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Nuclear engineering and services