PULSED NEUTRON METHOD FOR URANIUM WELL LOGGING

The physical principles of a new method for uranium detection based on use of a pulsed source of neutrons are presented. The method employs measurement of the neutron time distributions in rock media following a burst of fast neutrons. A time‐ and energy‐dependent (but space‐independent) theory is developed for the four principal time distributions that follow production of fission neutrons by each of the two possible reactions: 1. Prompt thermal fission of [Formula: see text]: a. Epithermal neutron time distribution, b. Thermal neutron time distribution. 2. Delayed fission of uranium: a. Neutron time distribution due to delayed fission in [Formula: see text], b. Neutron time distribution due to delayed fast fission in [Formula: see text]. Theoretical analysis of these phenomena leads to the conclusion that the detection of uranium in rocks is possible using either the epithermal neutron time distribution from the prompt fission of [Formula: see text] by thermal neutrons or the delayed neutron distribution from fast neutron fission of [Formula: see text] or thermal neutron fission of [Formula: see text]. Experiments performed on laboratory models of uranium ore show the feasibility of detecting fission neutrons and the validity of the theory presented in the paper. For normal borehole‐logging measurements, a pulsed neutron source with an average output of about [Formula: see text] n/sec is needed.