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AssigneesL'Etat Francais, Ciments Lafarge S.A.
InventorsRene Alegre, Jacques L. E. Alexandre, Thierry M. M. Barnavon, Jean-Pierre N. Baron, Jacques Cariou, Leon Debray
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Method for analysis of the content of certain elements in a continuous flow of bulk materials by neutron bombardment and measurement of the gamma radiation emitted by such elements, which makes it possible to distinguish between the capture radiation and the activation radiation. The neutron source is a neutron-generating tube which is activated periodically. The signals from a single gamma radiation detector are considered only after neutron emission has ceased, during distinct intervals corresponding to the phenomena of capture and radiation of the activated elements, respectively. The respective signals are treated in two distinct measurement routes, and the measurements are then combined automatically. A third measurements route can be provided for gamma radiation resulting from inelastic collisions. The source and the detector are positioned in a probe lodged in a polyethylene protective tube within the flow of the materials. The installation is used to analyze large flows of minerals without taking samples, in the mining, cement, and aluminum industries.
In a method for analysis by neutron activation to measure the quantity of one or more elements sought in a flow of material in bulk, comprising a step of neutron bombardment in which the flow of material is made to pass close to at least one source of neutrons capable of inducing the emission of gamma rays from said elements, and a step of gamma ray analysis in which specific gamma rays emitted by the elements are detected, measured and sorted according to their energy spectra, to obtain the respective quantities of said elements in the flow of material, the improvement wherein for the neutron source at least one neutron generating tube is provided, in the step of neutron bombardment the neutron generating tube is electrically actuated for intermittent periods to produce pulsed emission of neutrons, and in the step of gamma ray analysis in the time intervals between said pulses the gamma rays from capture and activation by said elements are detected to establish a first spectrum, and in at least one other interval of time gamma rays, from activation only, are detected to establish a second spectrum, the respective values of gamma rays detected in energy ranges corresponding to said first and the second spectra being combined to give an indication of a spectrum containing only gamma rays from capture.
Installation for neutron activation analysis of one or more elements in a flow of material in bulk, comprising a passage for the material, at least one source of neutrons placed close to said passage, and at least one gamma ray detector also placed close to the passage, said passage being in the form of a vertical funnel having a probe containing one neutron generating tube and at least one gamma ray detector positioned in a protective tube inside said funnel, means of measurement for measuring in selective manner the characteristic gamma rays emitted by elements contained in the material, said neutron source being a tube generating neutrons when it is electrically actuated, wherein the installation comprises means connected to the neutron generating tube for controlling cycles of neutron pulses emitted by the generating tube and also said means of measurement, and wherein said means of measurement comprise at least a first channel to measure the gamma rays from activation and capture and a second channel for measuring only the gamma rays from activation, and means of calculation to combine the measures obtained by said first and second channels.
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