Continuous neutron flux measurement process and a device for performing the same

1,021,434. Reactors. GROUPEMENT ATOMIQUE ALSACIENNE ATLANTIQUE. Feb. 26, 1964 [Feb. 26, 1963], No. 8030/64. Heading G6C. The neutron flux in a nuclear reactor is continuously measured by passing one or more series of equal volumes of a neutron-activatable fluid through the reactor, in each series one volume passing freely through the reactor and the other volume or volumes being slowed down for a definite period of time at the point or points of measurement, measuring the activities of the volumes at the outlet of the reactor and, from the differences in activity between the volume which passed directly through the reactor and the other volume or volumes, determining the neutron flux at the point or points of measurement. Argon is suitable as the neutronactivatable fluid, A-40 giving by a n-γ reaction A-41 which decays to K-41 with the emission of #- and #-radiations. Preferably the #-radiation is measured. In one arrangement, a number of measuring channels are distributed throughout a reactor core, each channel consisting of a compensating duct and a measuring duct. The latter includes an activation chamber which comprises a cylinder having a conical entry and exit at the ends and fitted internally with either a number of symmetrically disposed baffles or a helical guiding ramp.