In 2016 Weir Flow France, a subsidiary of global engineering company Weir Group plc, announced that it had secured a multi-million Euro contract to replace pneumatic controls for main steam isolation valves (MSIVs) across 28 reactors belonging to EDF in France. The modifications will be performed at EDF’s 900MW PWRs in France (excluding Bugey and Fessenheim).

The scope of the contract was design, prototyping and testing, supply of 84 new items, on-site installation, supervision and commissioning of the new equipment.

The modification programme is being managed by a Marseille-based subsidiary of EDF, EDF CIPN. It will last seven years and will ensure safety and integrity of flow control equipment throughout the extended operational lifetime of the EDF’s reactors. Weir’s solution incorporates a forged block design for the panels and full integration with MSIVs on site, an approach that offers optimal reliability and equipment lifetime with easy maintenance.

The forged block design, similar to a manifold, allows interconnection of the various channels, simplifying the layout and reduction of fittings and gaskets. These are sources of leakages during the whole life of the equipment including periodic testing and maintenance. The qualification process was completed in 2016.

Weir is working closely with EDF and nuclear partner SPIE Nucléaire. Assembly and testing will be completed in Weir’s St Victoret facility, while project management must be carried out across seven simultaneous sites with an estimated 18,000 person-hours to be delivered by a fully qualified team. The contract follows Weir’s five-year valve maintenance agreement, which was signed in 2012. In future, each MSIV will require periodic maintenance of the valve, the actuator (every 10 years) and the control panel (every 5 years).

Stephane Lamotte, nuclear director Europe, Weir Flow Control France, commented: “We developed an innovative MSIV panel solution in tandem with our partner SPIE to offer a comprehensive end-to-end approach in keeping with EDF’s world-class safety and reliability standards. The project is a significant milestone for our French nuclear business and reflects our capabilities to offer a safe, competitive and comprehensive flow control technology which will significantly upgrade the main steam isolation valve controls across EDF’s French fleet.”

Qualification – project update

The qualification of MSIV control panels consisted of a so-called K3 qualification, according to the nuclear RCC-E standard applicable to material located outside the containment. An accident case – a main steam-line rupture with a steam jet (80 bar, 350°C) in the surroundings of the control panel – was taken into account.

The control panel is an assembly of pneumatic and electrical components including a control cabinet, piping, fittings, on/off valves (ND40) and their actuators, pressure regulators, limit switches, small check-valves and solenoid valves. The equipment size is 2.0×1.5×0.4m and it weighs around 1t. This panel controls opening and closing of MSIV valves installed on the main steam line of French plants with air at 7barg.

Most of the qualification tests were performed at a French test laboratory equipped for mechanical, electrical and environmental tests. They consisted of:

  • Operability tests: operability without seizing; tightness level; opening and closing times; electrical strength.
  • Ageing tests: thermal ageing equivalent to the lifetime of the equipment; mechanical cycles and vibration fatigue tests.
  • Accident tests: seismic tests up to 3g acceleration; steam tests at 100°C and 100% humidity in an environmental test chamber.

The goal was to check that the equipment will withstand the operational and accidental events that could occur within the lifetime of the equipment.

The main tests were witnessed by EDF and are now complete. The project is now in the final qualification documentation phase and qualification should be complete in the next few weeks.

From an engineering standpoint, this project lasted two years from the first thought to the end of qualification tests. It involved engineers and technicians from both engineering and R&D departments. It was a bespoke development and qualification programme, as Weir Flow Control France has delivered before, which ended successfully and demonstrated the company’s know-how in valves and in nuclear areas even outside Weir’s usual activity. 

Photo: Stephane Lamotte, nuclear director Europe, Weir Flow Control France