SPECTRON, a neutron noise measurement system in frequency domain

Abstract : This paper is dedicated to the presentation and the validation of SPECTRON, a new neutron noise measurement system developed at the CEA centre of Cadarache. The apparatus is designed for the measurement of the $\beta_{eff}$ parameter (mean fraction of delayed neutrons) from cores of experimental nuclear reactors with the help of Cohn-$\alpha$ method. An integrated electronic system is used to record the current from fission chambers. Data spectra computed from measurement data processed by dedicated software in order to estimate the reactor transfer function and then the mean fraction of delayed neutron as well as prompt neutron generation time. After a review of the pile noise measurement method, the Spectron architecture is presented; Then, the validation procedure is described and experimental results are given to prove the proper operation of our new measurement system. It is shown that every technical requirement needed for proper measurement of neutron noise is fulfilled. Measurements in real condition performed on the experimental CEA's nuclear reactor MINERVE allows validating the good operation of Spectron.