Smart Sensors

Sensors for nuclear applications have historically been relatively simple analogue devices. However, the sensor industry is increasingly using microprocessor-based "smart sensors". They have potential benefits such as greater accuracy and better noise filtering, and in many cases their analogue counterparts are no longer manufactured. However, smart sensors (as it is the case for most COTS) are sold as black boxes despite the fact that their safety justification might require knowledge of their internal structure and development process.

The justification of sensors presents two challenges: they are software based and the software constitutes a valuable intellectual investment by manufacturers, which they wish to protect.

In this series of projects funded by the UK nuclear industry we have:

• Established a close relationship with smart sensor manufacturers, who provide us with software and supporting information for our research.



• Developed a safety justification approach for smart sensors that consists of:



• feasibility of qualification - assessment of how the culture and co-operation might affect the project risk
• qualification: establishing excellence of production argument and deployment of challenge, confidence building activities


• Analysed assembler and C smart sensor software



• Code structure analysis - concurrent program threads and absence of deadlocks.
• Code criticality analysis.
• Code integrity assessment.
• Redundant code analysis.
• Failure integrity analysis.
• Predictable execution assessment - predictable ordering of software functions, input-output conversion accuracy and timing analysis