If a nuclear power plant shuts down automatically, how do you find the cause? A nuclear power plant is extremely complicated and there are hundreds of sensors and control points. Determining the sequence of events that led to the shutdown is an important diagnostic. How is this done?

The reactor in a nuclear power plant resides in a massive structure called a containment building. In the event of a breach in the pressure boundary of the reactor vessel, the containment building is designed to keep radioactive materials from the environment. Many of the important sensors and valves are located within the containment building. A signal conditioning system collects the sensor inputs to a central location and converts the low level sensor outputs to a standard +/-10 Vdc output.

The conditioned sensor signals are sent to an A/D converter that creates a digital value for each reading. There are often several hundred readings and these are organized into a serial data stream sent at very high speed so that fast-moving events can be recorded. The readings are in serial format so that they can be transmitted over a fiber optic cable to achieve the greatest possible data transmission rates. Another reason for data to be transmitted over single fiber optic cable is that this limits the number of penetrations, or holes) in the containment building.

The serial data is received at an external computer, and stored continuously so that a shutdown event can be investigated immediately.