Instrumentation of chemical and radiochemical monitoring in nuclear power plants

In France, most electricity (around 80%) is generated by PWR (Pressurized Water Reactor) nuclear power plants, with 58 units spread across nineteen CNPE (Centre Nucléaire de Production d'Électricité) nuclear power plants.

The operation of a nuclear power plant must meet a number of requirements:

• safety first and foremost, for obvious reasons;

• availability, so that this energy remains available when it is needed, and to reduce its cost;

• the longevity and long-term performance of components, for economic and availability reasons;

• reliability and low operating costs in line with the above objectives;

• the lowest possible environmental impact (chemical, radiochemical and thermal emissions) and dosimetry.

The longevity of equipment through the control of chemical conditioning, circuit pollution and corrosion of materials was explained in the file. "Water chemistry and corrosion in PWRs", while water resource management was covered in the dossier. "Industrial water management for nuclear power generation".

The purpose of this dossier is to detail the chemical and radiochemical monitoring instrumentation needed to meet the various objectives set out above.

This section describes the most fundamental chemical and radiochemical controls used in plant operation. In most cases, these continuous controls are the basis for decisions to adjust the chemical conditioning of the circuit in question, to identify any drift, anomaly or pollution in a circuit, and to decide whether or not to continue operating the unit, and under what conditions.

For each continuous control, the reader can learn about the purpose of the control on the circuit concerned, the expected values and limits of parameters in normal operation, the principle of retransmission of values and certain alarms to the control room to ensure the necessary responsiveness in the event of an anomaly.

The operating principles of the various types of chemical automaton are also explained.

Lastly, the main manual checks on samples taken by hand are listed, as are the reasons for using this type of measurement rather than an on-line robot.