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Aeroball System for In-core Neutron Flux Measurement – AMS

Nuclear power plants (NPPs) monitoring the neutron flux using only ex-core measurement systems and slow measuring or non-calibrated in-core systems will not achieve a detailed mapping of the core. This lack of information about the inner core prevents the operator in running the plant in optimal conditions. This in turn means that a perfect utilization of the power plant performance and an efficient load following is not possible. In the case of unexpected or unforeseen incidents, the operator can not rely on detailed and fast gained real measured data from a calibrated system which allow him to take preventive measures before any safety system may be started.

AREVA NP's Aeroball Measurement System (AMS) is a neutron flux mapping system that allows the plant operator to gain a 3D snapshot of the core in any kind of plant operation mode. It is based on movable vanadium alloy balls (aeroballs). They are pneumatically inserted into a large number of specific core locations for a brief period for activation, removed from the core, and their activation rates are subsequently measured. Thus, the entire flux mapping process can be completed within a very short period of time. This 3D snapshot of the core neutron flux is then transferred to the core calculation computer, such as AREVA NP's ARGOS, in order to calculate the calibration factors for a prompt response from the Cobalt Self-powered Neutron Detectors (Co-SPND). The monitoring system, i.e. AMS, ARGOS and Co-SPND allows continuous monitoring of the core and forms the basis for fast and efficient load following. This is ensured sequentially with high resolution by the AMS, a prompt response by the Co-SPND and additional simulation by ARGOS.

Your benefits

  • Reliable and stable signal acquisition outside the core under “room conditions”
  • All data evolution based on real nuclear measurement
  • Short activation time which allows measurement of 3D power density distribution during transient core conditions
  • Calculation of 3D power density distribution from the AMS activity values with high spatial resolution
  • Already over 530 years of excellent operation experience
  • No nuclear waste and no detector burn-up
  • No moving parts are liable to wear, apart from the balls


The Aeroball Measurement System is installed in pressurized water reactors (PWRs) built by Siemens / KWU. It forms an essential part the EPR reactor in-core instrumentation.

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