The Reactor Pressure Vessel Level (RPVL) measurement system provides information on the coolant inventory to enable counter measures to be taken if necessary e.g. primary pressure relief, start and stop injection of coolant.
The basic principle used by the RPVL measurement system is the change in heat transfer between water in a liquid and gaseous phase. For this reason a sensor comprises a heated and an unheated thermocouple.
The level monitoring is based on the difference in temperature between the two thermocouples, which is higher when water is in a gaseous rather than liquid state.
