1. Need for nuclear instrumentation

1.1 Functional use of excore instrumentation

The EPR reactor's excore nuclear instrumentation consists of ionization chambers and proportional counters used for core protection, monitoring and regulation of core reactivity.

Core reactivity is a quantity representing the rate of increase of the neutron population. The neutron population resulting from a chain reaction increases exponentially with reactivity. It is therefore essential to control the rate of increase.

To determine this rate of increase, it is necessary to be able to detect neutrons in order to obtain an image of their population at each instant. This is achieved using excore detectors, which are used from the moment the first fuel assembly is loaded into the vessel in the...