Maintaining Reliable Generator Cooling Through Precision Chemical Control

Heysham 2 is an Advanced Gas-cooled Reactor (AGR) station forming part of the UK’s nuclear generation fleet. As with all large turbine generators, the stator windings are cooled by a dedicated water system designed to remove heat and maintain stable electrical performance.

Within this system, maintaining precise water chemistry is essential. Correct pH control protects copper conductors and other system components, ensuring the cooling circuit continues to operate efficiently throughout the life of the plant.

Station engineers had identified that variations in conductivity and dissolved oxygen could lead to copper oxide deposition within the stator cooling circuit. Under certain conditions, these deposits can dissolve and redeposit elsewhere in the system, increasing the risk of fouling or localised corrosion.

To address this, EDF Energy issued a technical specification for a new caustic dosing system capable of maintaining the stator water within the recommended pH range, ensuring stable chemistry and continued protection of generator components.

AMS Nuclear was tasked with designing and supplying a dosing system that could reliably introduce caustic solution into the stator cooling circuit while integrating seamlessly with the station’s existing monitoring and control infrastructure.

Rather than simply providing equipment, the AMS Nuclear engineering team approached the project as a system integration challenge – ensuring dosing accuracy, operational safety and compatibility with the existing stator water conditioning plant.

The resulting design centred around a digital dosing pump capable of injecting caustic solution into the stator pressurised water circuit, ensuring reliable delivery into the system.

To maintain safe and stable operation, the system incorporated a range of monitoring and protection features, including:

• Conductivity-based interlocks to prevent dosing outside safe operating conditions
• Caustic storage tank with low-level monitoring to prevent dry operation
• Flowmeter with low-water-flow sensing to confirm suitable system conditions before dosing
• Configurable start-up and shutdown logic to prevent overdosing
• Local monitoring and control capability for operator visibility and adjustment

These features ensure the dosing system responds automatically to plant conditions while maintaining full operational transparency for station staff.

AMS Nuclear followed a structured delivery process aligned with EDF Energy’s engineering and quality assurance requirements.

Detailed System Design

The project began with a technical review of EDF’s proposed configuration and the existing stator water conditioning plant. This ensured the new dosing system would integrate correctly with established injection points and monitoring equipment.

Manufacture and Equipment Supply

AMS Nuclear coordinated the manufacture and assembly of the dosing system components, ensuring all equipment met the technical specification and was suitable for operation within a nuclear generation environment.

Quality Assurance and Compliance

The project was delivered under a Quality Assurance Grade 3 classification, with inspection and verification processes aligned with EDF’s quality requirements and recognised nuclear industry standards.

Strict supply chain controls were also applied to prevent counterfeit or suspect items entering the system.

Documentation and Lifecycle Support

To support installation, commissioning, and ongoing maintenance, AMS Nuclear provided a full documentation package including:

• Technical design documentation
• System wiring diagrams and schematics
• Instrument calibration certificates
• Operation and maintenance manuals
• Verification and conformity documentation

This documentation ensures the equipment can be maintained effectively throughout its operational lifecycle.

Projects such as this demonstrate how targeted engineering solutions can support the continued operation of nuclear generating assets.

The Heysham 2 dosing system highlights several important principles:

• Precise chemistry control is critical to protecting generator cooling circuits.
• Integrated monitoring and interlocks are essential to ensure chemical dosing systems operate safely.
• Robust documentation and quality processes enable maintainability throughout the plant lifecycle.
• Carefully engineered upgrades can enhance system performance without major infrastructure changes.

These insights are transferable across similar stator water systems throughout the wider nuclear generation fleet.