Measurement technologies that enable sensing of plant conditions - both important process variables and component conditions – are vital to the safe and cost-effective operation and maintenance of nuclear power plants. Key process parameters that must be sensed to operate an advanced reactor include neutron flux, temperature, pressure, flow, and level. For active components such as control rod drives and valves, position is an important measurement, while the assessing the integrity of passive structural components is an important element of maintaining safety. In all cases, in-situ continuous monitoring of these conditions is expected to provide information that enables timely decision making. However, the adverse conditions in and around nuclear power reactors challenges the ability for long-term in-situ continuous monitoring. Further, past experience with some reactor concepts has indicated potential limitations in measurement technology, such as an absence of a sensing technology for some process variables, unsatisfactory measurement reliability for some technologies, or the need for an overly large safety margin to account for measurement uncertainty.

Several advances in recent years have attempted to address these challenges, and include new sensor designs and material choices that improve sensor survivability and algorithms that enable timely detection of sensor and component degradation. An example is the use of new piezoelectric materials for designing ultrasonic sensors. These sensors may be applied for the nondestructive evaluation (NDE) of structural components which is one of the pillars on which the nuclear industry’s defense in depth policy has been based. Ultrasonic sensors are also useful for monitoring process variables such as flow and temperature. In-situ monitoring using these, and other, sensors requires the ability to ensure that the sensors are functional and reliable. Generally, the reliability of sensors is assured through periodic calibration. Online monitoring of sensor calibration provides an economic alternative, by detecting sensors that are drifting out of calibration and enabling in-situ recalibration. In this presentation, we discuss these and other advances that is aimed at enhancing the economic viability of future nuclear power systems while maintaining adequate safety margins.