The invention relates to a system for the monitoring and control of the core of a nuclear reactor along which N fission chambers CFi (i=1, 2, . . . , N) are positioned, N being an integer number greater than or equal to 2, in which: computing means (P) are able to compute a statistical estimation of the nth order neutron flux CFi of each fission chamber CFi and a mean value of estimation of the neutron flux that represents the mean neutron flux prevailing in the core of the nuclear reactor, such that = 1 N ⁢ ∑ i = 1 N ⁢ ⁢ CFi ⁢ ⁢ and computing means (M, CMP) are able to compute an ageing indicator (S) for the fission chamber CFi from the statistical estimation value of the neutron flux CFi of the fission chamber CFi.