Obsolescence and CFSI: Why Legacy Systems Need Extra Vigilance

Obsolescence is an unavoidable consideration when maintaining equipment throughout the operational life of a nuclear facility. Technology evolves, manufacturers discontinue product lines and replacement components become increasingly difficult to source. However, the equipment relying on those components may still be required to operate safely and reliably for many years.

When a component is readily available from its original manufacturer or an approved distributor, there is generally an established route for confirming its origin, specification and conformity. Once that component becomes obsolete, this route may no longer be available.

Organisations may need to explore alternative sources, including independent brokers, surplus stock, refurbished equipment or reclaimed components. While these options can sometimes provide a viable solution, they can introduce additional uncertainty around the component’s history, condition and authenticity.

For example, a replacement component may carry the correct manufacturer’s markings but have an unclear supply history. Alternatively, a refurbished item may appear suitable for its intended application, but lack the documentation needed to establish what work has been completed or whether its performance has been adequately verified.

These uncertainties do not automatically mean an item is counterfeit or fraudulent. They do, however, increase the importance of inspection, verification and traceability.

The challenge becomes particularly significant when an obsolete component is essential to maintaining an operational system. Delivery pressures and limited availability can make an alternative source appear attractive, but accepting a replacement without sufficient assurance may introduce greater risks further down the line.

Availability alone does not establish suitability. The replacement must also meet the relevant technical, quality and safety requirements.

Effective obsolescence management requires more than identifying a component that appears to perform the same function.

At AMS Nuclear, our approach focuses on understanding the original equipment, its operating requirements and the wider system in which it is installed. This allows us to assess suitable replacement options while maintaining the engineering assurance expected within the nuclear industry.

Where original components are no longer available, there are several potential approaches depending on the application, condition of the existing equipment and relevant safety requirements.

Before developing a replacement solution, it is important to establish exactly what the original component was designed to do.

This may involve reviewing existing drawings, technical specifications, operating documentation and system interfaces to understand how the component interacts with the wider equipment.

Where documentation is incomplete or the original design is no longer fully supported, reverse engineering may be required to establish the necessary design characteristics.

Reverse engineering is not simply about reproducing the physical appearance of a component. It involves understanding the technical requirements that allow it to perform its intended function, including electrical characteristics, mechanical interfaces, environmental conditions and operational behaviour.

By establishing these requirements, engineers can make informed decisions about the suitability of potential replacements rather than relying on assumptions.

In some cases, the most appropriate solution may be to develop a replacement that maintains the original component’s fit, form and function.

This means considering three important requirements:

• Fit: The replacement must be compatible with the existing installation, including its physical dimensions, connections and interfaces.
• Form: The replacement must have the necessary physical and design characteristics for its intended application.
• Function: The replacement must deliver the required operational performance and behaviour within the wider system.

However, demonstrating fit, form and function is only part of the process.

For nuclear applications, replacement components must also be assessed against the applicable safety classification, technical specifications, environmental requirements and quality assurance arrangements.

Depending on the application, this may involve design reviews, calculations, inspection, testing and formal verification activities.

The objective is to demonstrate that the replacement is suitable for its intended purpose, rather than assuming that a component described as equivalent will necessarily provide the same level of performance.

Whether a replacement is sourced, refurbished or newly engineered, maintaining appropriate documentation is essential.

Traceability provides the evidence needed to establish a component’s origin, manufacturing history, specification and conformity with the relevant requirements.

For newly developed replacements, this may include design documentation, material records, inspection results, test reports and verification evidence.

For refurbished or reclaimed components, additional consideration may be required to establish their previous service conditions, refurbishment history and current condition.

Where supporting information is missing or inconsistent, those gaps need to be understood and addressed through appropriate engineering assessment and verification.

At AMS Nuclear, maintaining clear technical documentation and applying appropriate quality controls are integral to our approach to engineering delivery.

By considering traceability from the outset, rather than treating it as a final administrative activity, organisations can strengthen confidence in both the replacement component and the decisions supporting its use.

When working with a supplier to address obsolescence, the ability to source or manufacture a replacement is only one part of the assessment.

Operators and Tier 1 contractors should also understand how the supplier establishes technical suitability, verifies conformity and manages uncertainty.

Several questions can help establish whether the appropriate controls are in place.

How is the original component’s specification established?

A supplier should be able to explain how it identifies the relevant technical requirements, particularly where original manufacturer information is limited or unavailable.

How are replacement components verified?

Where a component has been reverse engineered, refurbished or developed as an alternative, there should be a defined approach to inspection, testing and verification appropriate to its intended application.

What happens when documentation is incomplete?

Missing information should not automatically be treated as acceptable. Suppliers should have arrangements for identifying gaps, assessing their significance and determining what additional evidence is required.

How is equivalence demonstrated?

A replacement described as equivalent should be supported by technical evidence demonstrating that it meets the necessary requirements. Similar appearance or functionality alone may not provide sufficient assurance.

How is traceability maintained?

Suppliers should be able to demonstrate how component provenance, material records, manufacturing information and verification documentation are controlled throughout the process.

These questions help distinguish between simply obtaining a replacement part and delivering an engineered solution supported by appropriate quality assurance.

Obsolescence and CFSI are closely connected. As original components become harder to obtain, the potential for uncertain provenance, incomplete documentation and unverified alternatives increases.

Managing these risks effectively requires a coordinated approach involving engineering, procurement, quality assurance and supplier oversight.

Rather than treating obsolescence as an isolated sourcing challenge, organisations should consider it as part of their wider asset management and supply-chain assurance arrangements. Identifying ageing components early, understanding replacement requirements and establishing suitable engineering solutions can reduce the pressure to accept alternatives without adequate verification.

For AMS Nuclear, this reflects our wider approach to designing, building and supporting safety-critical electrical, control and instrumentation (EC&I) systems. By combining technical expertise with robust engineering and quality processes, we help clients address obsolescence challenges while maintaining confidence in the systems they depend on.

The aim is not simply to replace what is no longer available. It is to ensure that what comes next is properly engineered, verified and supported for continued operation.