Prompt uranium fission neutron logging technique based on epithermal neutron and thermal neutron ratio

A technology of prompt neutron and well logging technology, which is applied in the direction of measuring devices, nuclear radiation exploration, boreholes/well components, etc.

CN103711479AActive Publication Date: 2014-04-09EAST CHINA UNIV OF TECH
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
Publication Date
2014-04-09

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Abstract

The invention discloses a prompt uranium fission neutron logging technique based on the epithermal neutron and thermal neutron ratio. The technique is specifically characterized in that in boreholes, fast neutrons, also called virgin neutrons, are transmitted to formation rock by means of pulsing; the virgin neutrons are successively moderated by in-well medium into epithermal neutrons and thermal neutrons; the thermal neutrons induce 235U fission to radiate prompt uranium fission neutrons, also called secondary neutrons; the secondary neutrons are successively moderated into epithermal neutrons and thermal neutrons, inducing 235U fission again; from any moment t after the virgin neutrons are moderated into the thermal neutrons, the total nE(t) of existing epithermal neutrons in the formation rock is in direct proportion to the total nT(t) of existing thermal neutrons and uranium content qu, namely nE(t)<nT(t) qu. By using a bi-neutron detector and a dual-time detector disposed in the invention to measure time spectra of the epithermal and thermal neutrons and defining an attenuation ratio of the epithermal neutrons to the thermal neutrons as 'E / T', from a moment, when the virgin neutrons are moderated into the thermal neutrons, to any moment, a uranium quantitative real-time algorithm based on saturated seams is constructed.
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Description

technical field

[0001] The invention relates to a pulsed neutron well logging technology for uranium ore exploration drilling, and also a "uranium fission prompt neutron well logging" technology based on the ratio of epithermal neutrons to thermal neutrons. Background technique

[0002] Nuclear logging is nuclear radiation measurement carried out in boreholes. It is a cutting-edge technology that has developed rapidly with the development of contemporary technology and its application in mineral (especially energy mineral) exploration. Nuclear logging is to use the radioactive rays that are naturally produced or artificially induced by formation rocks to study the distribution of rays along the axis of the borehole (well axis), and then determine whether certain nuclides (elements) are contained in the formation rocks, and determine a certain element content. A non-destructive detection method. Compared with nuclear radiation measurements carried out on the ground, many con...

Examples

Embodiment Construction

[0049] The present invention will be described in more detail through the accompanying drawings and specific embodiments below.

[0050] The dual-neutron time spectrometer for uranium fission prompt neutron logging disclosed by the present invention includes a dual-neutron detector, a preamplifier, a shaping and discriminator, a time-spectrum analysis and buffer circuit, a detector high-voltage power supply circuit, a detector Tube low-voltage power supply circuit and other components. Its structure is as image 3 shown.

[0051] (1) Required for making well logging probe 3 He proportional counter tube and double neutron detector.

[0052] When the double neutron detector adopts the upper and lower structure (such as figure 1 shown), two cylindrical 3 He proportional counter tubes make double neutron detectors, and the distance between the detectors should be shortened as far as possible (so that the epithermal neutron attenuation N of the two detectors records E (t ≤20...