Future-Proofing Effluent Monitoring at Torness

Effluent management systems are fundamental to the safe and compliant operation of nuclear power stations. At Torness Power Station, accurate monitoring of sludge and supernatant levels within Active Effluent Treatment Plant (AETP) tanks is essential to maintaining process control and meeting environmental obligations.

As part of ongoing lifecycle management, EDF identified the need to modernise its level measurement capability. The existing system, while historically effective, had reached a stage where long-term supportability and maintainability were becoming increasingly constrained.

This created an opportunity to not only replace legacy instrumentation, but to improve measurement performance and establish a consistent approach that could be deployed across multiple sites.

The challenge extended beyond simple instrumentation replacement. The AETP tanks contain a complex mixture of media, including water, ion exchange resins, graded sands, anthracite and sludge. Each layer presents different physical properties, making reliable interface detection technically demanding.

EDF required a solution that could:

• Accurately detect multiple material interfaces within a single tank
• Perform consistently in harsh and variable process conditions
• Avoid signal interference between adjacent instruments
• Be validated against representative operating conditions before deployment

In addition, all work needed to align with nuclear quality assurance requirements and be supported by robust evidence to satisfy regulatory scrutiny.

AMS Nuclear approached the challenge as an engineering problem to be solved, not simply a product to be selected.

We began with a structured optioneering exercise, reviewing available COTS technologies and assessing their suitability for multi-phase level measurement. Rather than relying on a single sensing method, we developed a hybrid approach – combining complementary technologies within a single probe assembly to improve reliability and measurement confidence.

To validate the concept, AMS Nuclear designed and manufactured a dedicated test facility, including:

• Five clear acrylic test tanks to allow visual verification of behaviour
• Representative media layers replicating actual plant conditions
• Custom mounting systems to trial multiple instruments in close proximity

This enabled controlled testing of instrument performance under realistic scenarios, including filling, draining and disturbance of media layers.

All work was delivered in line with nuclear industry expectations, including:

• QA Grade 3 classification
• ISO 9001-aligned quality management processes
• Formal test plan development and EDF approval prior to trials
• Full traceability and controls to mitigate counterfeit or suspect items

This ensured that the solution was not only technically effective, but fully compliant and auditable.

The testing phase was designed to build confidence through evidence.

AMS Nuclear conducted a comprehensive series of trials, including:

• Functional response testing across varying media compositions
• Assessment of sensor performance during insertion and removal
• Simulation of tank filling and draining conditions
• Verification of signal integrity when instruments operated in close proximity
• Extended soak testing to evaluate long-term behaviour in sludge environments

EDF personnel were involved throughout, witnessing key stages of testing and contributing to the evaluation process. This collaborative approach ensured alignment and transparency at every stage.

The outcome was a clear, evidence-based recommendation of the most suitable instrumentation configuration, supported by a detailed test report and defined pathway to deployment.

The success of the Torness trials established more than a single-site solution.

The validated design demonstrated that:

• Reliable measurement of complex, multi-phase media is achievable using integrated COTS technologies
• Instrumentation performance can be confidently predicted through representative testing
• A single engineered solution can be adapted for deployment across multiple stations

With further programmes already identified for other EDF sites, including Heysham 2, the project provides a foundation for a consistent, fleet-wide approach to sludge level monitoring.

This project highlights the value of combining practical engineering experience with structured validation.

Key takeaways include:

• Integration over selection: The most effective solutions often come from combining technologies, not choosing between them
• Testing reduces risk: Replicating plant conditions in a controlled environment enables confident decision-making
• Design with deployment in mind: Developing the prototype as a potential permanent installation accelerated the path to implementation
• Think beyond the site: Early consideration of fleet-wide applicability maximises long-term value

As AMS Nuclear continues to support the UK nuclear industry, this approach ensures that solutions are not only compliant and reliable but designed to deliver lasting impact.