Uranium mine logging device and method based on accompanying alpha neutron tube and fast neutron detector

Abstract

The present invention relates to a uranium mine logging device and method based on an accompanying α-neutron tube and a fast neutron detector, belonging to the technical field of neutron uranium mine logging. The device comprises an accompanying α-neutron tube, a fast neutron detector, a data acquisition system and a computer. The accompanying α-neutron tube continuously emits 14MeV fast neutrons into the formation and gives the emission time of each fast neutron; the fast neutron detector detects the prompt fast neutron information generated by the fission reaction of U235 and neutrons in the formation; the data acquisition system obtains the fast neutron signal from the fast neutron detector and transmits it to the computer; the computer controls the accompanying α-neutron tube to continuously generate fast neutrons, obtains the emission time of each fast neutron of the accompanying α-neutron tube, and then obtains the time and energy of the fast neutron through the data acquisition system, and uses the fast time coincidence technology to screen out the total count of fast neutrons in the time window dominated by fission neutrons and above the energy threshold. The device and method provided by the present invention can improve the measurement accuracy of the existing prompt neutron logging instrument.

Description

Technical Field

[0001] The invention belongs to the technical field of neutron uranium mine logging, and in particular relates to a uranium mine logging device and method based on an accompanying alpha neutron tube and a fast neutron detector. Background Art

[0002] At present, uranium mine logging technology is mainly divided into two categories: natural gamma logging and prompt or delayed neutron logging. Natural gamma logging technology determines the uranium content in the formation by measuring the distribution of gamma rays of radium, the decay product of uranium. Due to the possible imbalance of uranium-radium decay, the uranium content obtained by the natural gamma logging method has a large deviation from the true value in the absence of uranium-radium decay imbalance coefficient, so the application occasions are limited. Another type of prompt or delayed neutron logging technology is to emit initial fast neutrons to the formation through a neutron source. The fast neutrons interact with the formation medium and slow down to become epithermal neutrons or thermal neutrons. The thermal neutrons react with the uranium 235 nuclides in the formation to release multiple fast neutrons, which are then slowed down. The uranium content in the formation can be calculated by detecting the relationship between the neutron count rate of epithermal neutrons or thermal neutrons and the time distribution and the uranium content. This technology is a direct quantitative uranium logging technology.

[0003] Therefore, independent research and development of prompt neutron logging technology, key equipment components, and uranium content quantification methods are extremely important for the development of prompt logging instruments with independent intellectual property rights.

[0004] The pulse method uses a pulsed neutron source to emit neutrons to the formation. The pulse width is set to 40μs. The total count rate N(δt) of thermal neutrons in the far-point detector in a window of about 150-2000μs is collected, and the ratio of the count rate of the near-point detector to the far-point detector is R S / L , and the macroscopic capture cross section of thermal neutrons, and finally the uranium content is calculated. In this neutron measurement method, the signal acquisition time width reaches thousands of seconds, and the signal will contain strong background interference, which affects the measurement accuracy of the uranium content. Summary of the invention

[0005] In order to solve the defects of the prior art, the purpose of the present invention is to provide a uranium mine logging device and method based on an alpha neutron tube and a fast neutron detector, which can improve the measurement accuracy of existing prompt neutron logging instruments.

[0006] In order to achieve the above purpose, a technical solution adopted by the present invention is:

[0007] A uranium mine logging device based on an accompanying alpha neutron tube and a fast neutron detector comprises an accompanying alpha neutron tube, a fast neutron detector, a data acquisition system and a computer, wherein:

[0008] The companion α-neutron tube is used to continuously emit 14MeV fast neutrons into the formation and provide the emission time of each fast neutron;

[0009] The fast neutron detector is used to detect multiple prompt fast neutron information generated by the fission reaction of U235 and neutrons in the formation, and obtain the neutron attenuation spectrum, wherein the fast neutron information includes the time and energy of detection;

[0010] The data acquisition system is used to acquire fast neutron signals from the fast neutron detector and transmit them to a computer, and to control the fast neutron detector;

[0011] The computer controls the companion α-neutron tube to continuously generate fast neutrons through a control bus, and obtains the emission time of each fast neutron of the companion α-neutron tube; and obtains the time and energy of the fast neutrons measured by the fast neutron detector through the data acquisition system, and uses the fast time coincidence technology to screen out the total count of fast neutrons within the time window dominated by fission neutrons and above the energy threshold.

[0012] Furthermore, in the uranium mine logging device based on the companion α-neutron tube and the fast neutron detector as described above, the companion α-neutron tube can accurately mark the emission start time of each fast neutron with a time accuracy of nanoseconds, providing accurate time information for fast time coincidence measurement.

[0013] Further, the uranium mine logging device based on the accompanying α neutron tube and the fast neutron detector as described above, the accompanying α neutron tube includes a DT neutron tube and an accompanying α detector connected thereto, which can provide the detection time of the back-facing α particles after the DT reaction; the neutron yield of the accompanying α neutron tube is not less than 5×10 6 ~2×10 7 n / s, meeting the requirement of completing measurement within 10 minutes.

[0014] Furthermore, in the uranium mine logging device based on the accompanying α-neutron tube and the fast neutron detector as described above, the lower limit of the detection time window of the fast neutron detector is 150-250ns, and the upper limit is 2500-4000ns.

[0015] Furthermore, in the uranium mine logging device based on the accompanying α-neutron tube and the fast neutron detector as described above, the lower limit of the neutron energy range detected by the fast neutron detector is not less than 200 keV, which is higher than the energy range of epithermal neutrons and thermal neutrons, thereby achieving the deduction of non-time-related neutrons in the computer screening process and suppressing the environmental background.

[0016] Based on the above device, the present invention provides a method for uranium well logging based on a uranium well logging device accompanied by an alpha neutron tube and a fast neutron detector, comprising the following steps:

[0017] S1. In a standard test well of a uranium mine, within the fast neutron detection time window, a fast neutron detector is used to detect prompt neutrons generated by U235 fission to obtain a neutron decay spectrum, and then the total fast neutron count is obtained by computer screening. Then, the known uranium content value is used to obtain a positive correlation relationship between the total fast neutron count and the uranium content through computer fitting;

[0018] S2. In field drilling, within the fast neutron detection time window, a fast neutron detector is used to detect prompt neutrons generated by U235 fission, and a neutron decay spectrum is obtained, and then the total fast neutron count is obtained by computer screening;

[0019] S3. The theoretical uranium content is calculated based on the positive correlation between the total fast neutron count and the uranium content.

[0020] Further, in the uranium ore logging method based on the accompanying α-neutron tube and the fast neutron detector as described above, step S1 is specifically as follows:

[0021] S101. In the standard test well of uranium mine, 14MeV fast neutrons are emitted into the formation using an accompanying α-neutron tube. The fast neutrons react with U235 directly or after being slowed down by formation elements to produce multiple prompt fast neutrons.

[0022] S102, using fast time coincidence screening technology, screening out the total count of fast neutrons within the time window dominated by fission neutrons and above the energy threshold from the neutron decay spectrum;

[0023] S103. Using the known uranium content value, a computer fitting is performed to obtain a positive correlation relationship between the total fast neutron count and the uranium content.

[0024] Further, in the uranium ore logging method based on the accompanying α-neutron tube and the fast neutron detector as described above, step S2 is specifically as follows:

[0025] In field drilling, an accompanying α-neutron tube is used to emit 14MeV fast neutrons into the formation. The fast neutrons react with U235 directly or after being slowed down by formation elements to produce multiple prompt fast neutrons.

[0026] The fast time coincidence screening technique is used to screen out the total fast neutron counts within the time window dominated by fission neutrons and above the energy threshold from the neutron decay spectrum.

[0027] Further, in the uranium ore logging method based on the accompanying α-neutron tube and fast neutron detector as described above, step S3 is specifically: substituting the total fast neutron count obtained in the field drilling in step S2 into the relationship obtained in step S1 to calculate the theoretical uranium content.

[0028] The uranium mine logging device and method based on the accompanying α-neutron tube and the fast neutron detector of the present invention have the following significant technical effects:

[0029] The invention adopts the fast time coincidence technology of the advanced accompanying alpha neutron tube and the fast neutron detector for prompt fission fast neutron uranium ore logging, which can effectively suppress the environmental background and improve the accuracy of quantitative analysis of uranium content. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a functional block diagram of a uranium mine logging device based on an accompanying α-neutron tube and a fast neutron detector provided in an embodiment of the present invention;

[0031] Figure 2 It is a flow chart of a uranium mine logging method based on an accompanying alpha neutron tube and a fast neutron detector provided in an embodiment of the present invention;

[0032] Figure 3 is to calculate the total neutron count N and uranium content f U Flow chart of the method that complies with the positive correlation equation;

[0033] Figure 4 It is a graph simulating the relationship between the total fast neutron count and the uranium content after the neutron attenuation spectrum is screened by computer in the uranium-containing sandstone formation;

[0034] Figure 5 This is the difference in the neutron measurement time window between the present invention and the prior art. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific embodiments and the accompanying drawings.

[0036] The core concept of the present invention is: when the formation porosity and water mineralization degree are known, the total fast neutron count N and the uranium content f after computer screening within the fast neutron detection time window are U The positive correlation equation can be used to calibrate the correlation coefficient in the standard uranium mine test well. The theoretical uranium content in the formation can be quantitatively analyzed by using the equation in field drilling uranium mine logging.

[0037] Based on the above concept, the present invention provides a uranium mine logging method based on an accompanying α-neutron tube and a fast neutron detector. The method is implemented by a uranium mine logging device based on an accompanying α-neutron tube and a fast neutron detector. Figure 1 As shown, the device is mainly composed of an accompanying α-neutron tube, a fast neutron detector, a control bus, a data acquisition system and a computer, among which:

[0038] The companion α neutron tube is used to continuously emit 14MeV fast neutrons into the formation and can give the emission time of each fast neutron with a time accuracy of nanoseconds, which can provide accurate time information for fast time coincidence measurement. The companion α neutron tube includes the DT neutron tube and the companion α detector docked with it, which can provide the detection time of the back-facing α particles after the DT reaction.

[0039] The fast neutron detector is used to detect multiple prompt fast neutrons produced by the fission reaction of U235 and neutrons in the formation, obtain the neutron decay spectrum, and provide fast neutron information including the time and energy of the fast neutrons detected.

[0040] The data acquisition system is used to acquire neutron signals from the fast neutron detector and transmit them to the computer, and is also used to control the fast neutron detector.

[0041] The computer controls the companion α-neutron tube to continuously generate fast neutrons through the control bus, and obtains the emission time of each fast neutron of the companion α-neutron tube; and obtains the time and energy of the fast neutron measured by the fast neutron detector through the data acquisition system, and uses the fast time coincidence technology to screen out the total count N of fast neutrons within the time window dominated by fission neutrons and above the energy threshold.

[0042] Based on the above device, the present invention provides a uranium mine logging method based on an accompanying α-neutron tube and a fast neutron detector, such as Figure 2 As shown, the method comprises the following steps:

[0043] S1. In the standard test well of uranium mine, within the fast neutron detection time window, the fast neutron detector is used to detect the prompt neutrons produced by U235 fission to obtain the neutron decay spectrum, and then the total fast neutron count N is obtained by computer screening. Then, the total fast neutron count N and the uranium content f are obtained by computer fitting using the known uranium content value. U It conforms to the positive correlation relationship.

[0044] like Figure 3 As shown, the specific steps are:

[0045] S101. In the standard test well of uranium mine, a companion alpha neutron tube is used to emit 14MeV fast neutrons into the formation. The fast neutrons react with U235 directly or after being slowed down by formation elements to produce multiple prompt fast neutrons.

[0046] S102. Using the fast time coincidence technique, the total fast neutron count within the time window dominated by fission neutrons and above the energy threshold is screened out from the neutron decay spectrum.

[0047] S103, using the known uranium content value to obtain the total neutron count N and uranium content f through computer fitting U It conforms to the positive correlation relationship.

[0048] Figure 4 The example shows the simulation of a uranium-bearing sandstone formation when a companion alpha neutron tube is used to launch 4.5×10 6 Under the condition of 14MeV fast neutrons, the neutron decay spectrum is screened by computer, and the total number of fast neutrons N and uranium content f in the time window dominated by fission neutrons and above the energy threshold are compared. U The relationship diagram, Figure 4 The horizontal axis represents the uranium content, and the vertical axis represents the total count of fast neutrons detected. Figure 4 The relationship diagram shown can be used to obtain the total fast neutron count N and uranium content f U The correlation coefficient in the relationship that conforms to positive correlation.

[0049] Figure 5 The figure shows the difference between the method provided by the present invention and the prior art in the neutron measurement time window. The prior art uses a pulsed neutron source to emit neutron pulses to the formation, with a pulse width of about 40μs, a pulse interval time greater than 2000μs, and a detection time window width of about 150-2000μs. The signal will contain strong background interference, affecting the measurement accuracy of uranium content. The present invention uses an accompanying α-neutron tube to continuously emit 14MeV fast neutrons into the formation, and uses a fast neutron detector to detect the neutron decay spectrum. The companion α-neutron tube can accurately mark the emission start time of a single fast neutron, making it easy to screen out the time window dominated by fission neutrons in the time spectrum of the total neutron decay spectrum. The emission start time of the fast neutron is zero; the lower limit of the fast neutron detection time window is 150-250ns, and the upper limit is 2500-4000ns. The detection time window width of the fast neutron detector is less than 1μs, which is much lower than the window width of thousands of μs selected by the existing logging technology. It shortens the detection time window, deducts the non-time-related scattered neutron signals, and is beneficial to reducing the environmental background.

[0050] In addition, the lower limit of the neutron energy range detected by the fast neutron detector is not less than 200 keV, which is higher than the energy range of epithermal neutrons and thermal neutrons. During the computer screening process, a suitable energy threshold can be set between 200-500 keV to deduct non-time-related neutrons, which can effectively suppress the environmental background.

[0051] The neutron yield of the accompanying α-neutron tube is not less than 5×10 6 ~2×10 7 n / s, meeting the requirement of completing measurement within 10 minutes.

[0052] S2. In field drilling, within the fast neutron detection time window, a fast neutron detector is used to detect prompt neutrons produced by U235 fission to obtain a neutron decay spectrum, and the total fast neutron count N is obtained by computer screening.

[0053] The steps are as follows:

[0054] In field drilling, an accompanying α-neutron tube is used to emit 14MeV fast neutrons into the formation. The fast neutrons react with U235 directly or after being slowed down by formation elements to produce multiple prompt fast neutrons.

[0055] The fast time coincidence screening technique is used to screen out the total fast neutron count N within the time window dominated by fission neutrons and above the energy threshold from the neutron decay spectrum.

[0056] S3, according to the total fast neutron count N and uranium content f U It conforms to the positive correlation equation and the theoretical uranium content is calculated.

[0057] Specifically, the total neutron count N obtained in step S2 is substituted into the scaled relational equation in step S1 to calculate the theoretical uranium content f U .

[0058] The present invention provides a uranium mine logging device and method based on an accompanying alpha neutron tube and a fast neutron detector. By adopting the advanced fast time coincidence prompt fission fast neutron uranium mine logging technology of the accompanying alpha neutron tube and the fast neutron detector, the environmental background can be effectively suppressed and the accuracy of quantitative analysis of uranium content can be improved.

[0059] The above embodiments are merely illustrative of the present invention, and the present invention may also be implemented in other specific ways or other specific forms without departing from the gist or essential features of the present invention. Therefore, the described embodiments should be considered illustrative rather than restrictive in any respect. The scope of the present invention should be described by the appended claims, and any changes equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A uranium mine logging device based on an α-neutron tube and a fast neutron detector, characterized in that: The device comprises: a companion alpha neutron tube, a fast neutron detector, a data acquisition system and a computer, wherein: The companion α neutron tube is used to continuously emit 14MeV fast neutrons into the formation and provide the emission time of each fast neutron; the companion α neutron tube includes a DT neutron tube and a companion α detector connected thereto, which can provide the detection time of the back-facing α particles after the DT reaction; the neutron yield of the companion α neutron tube is not less than 5×10 6 ~2×10 7 n / s, meeting the requirement of completing measurement within 10 minutes; The fast neutron detector is used to detect multiple instantaneous fast neutron information generated by the fission reaction of U235 and neutrons in the formation, and obtain the neutron attenuation spectrum. The fast neutron information includes the time and energy of being detected; the lower limit of the detection time window of the fast neutron detector is 150-250ns, and the upper limit is 2500-4000ns; the lower limit of the neutron energy range detected by the fast neutron detector is not less than 200keV, which is higher than the energy range of epithermal neutrons and thermal neutrons, so that non-time-related neutrons can be deducted during computer screening and the environmental background can be suppressed; The data acquisition system is used to acquire fast neutron signals from the fast neutron detector and transmit them to a computer, and to control the fast neutron detector; The computer controls the companion α-neutron tube to continuously generate fast neutrons through a control bus, and obtains the emission time of each fast neutron of the companion α-neutron tube; and obtains the time and energy of the fast neutrons measured by the fast neutron detector through the data acquisition system, and uses the fast time coincidence technology to screen out the total count of fast neutrons within the time window dominated by fission neutrons and above the energy threshold.

2. The uranium mine logging device based on the accompanying α-neutron tube and the fast neutron detector according to claim 1 is characterized in that: The companion α-neutron tube can accurately mark the emission start time of each fast neutron, with a time accuracy of nanoseconds, and provide accurate time information for fast time coincidence measurement.

3. A method for performing uranium well logging using the uranium well logging device based on the accompanying α-neutron tube and the fast neutron detector according to claim 1 or 2, comprising the following steps: S1. In a standard test well of a uranium mine, within the fast neutron detection time window, a fast neutron detector is used to detect prompt neutrons generated by U235 fission to obtain a neutron decay spectrum, and then the total fast neutron count is obtained by computer screening. Then, the known uranium content value is used to obtain a positive correlation relationship between the total fast neutron count and the uranium content through computer fitting; S2. In field drilling, within the fast neutron detection time window, a fast neutron detector is used to detect prompt neutrons generated by U235 fission, and a neutron decay spectrum is obtained, and then the total fast neutron count is obtained by computer screening; S3. The theoretical uranium content is calculated based on the positive correlation between the total fast neutron count and the uranium content.

4. The method for uranium well logging based on the uranium well logging device with α-neutron tube and fast neutron detector according to claim 3 is characterized in that: Step S1 is specifically as follows: S101. In the standard test well of uranium mine, 14MeV fast neutrons are emitted into the formation using an accompanying α-neutron tube. The fast neutrons react with U235 directly or after being slowed down by formation elements to produce multiple prompt fast neutrons. S102, using fast time coincidence screening technology, screening out the total count of fast neutrons within the time window dominated by fission neutrons and above the energy threshold from the neutron decay spectrum; S103. Using the known uranium content value, a computer fitting is performed to obtain a positive correlation relationship between the total fast neutron count and the uranium content.

5. The method for uranium well logging based on the uranium well logging device with α-neutron tube and fast neutron detector according to claim 3, characterized in that: Step S2 is specifically as follows: In field drilling, an accompanying alpha neutron tube is used to emit 14MeV fast neutrons into the formation. The fast neutrons react with U235 directly or after being slowed down by formation elements to produce multiple prompt fast neutrons. The fast time coincidence screening technique is used to screen out the total fast neutron counts within the time window dominated by fission neutrons and above the energy threshold from the neutron decay spectrum.

6. The method for uranium well logging based on the uranium well logging device with α-neutron tube and fast neutron detector according to claim 3, characterized in that: Step S3 specifically includes: substituting the total fast neutron count obtained in the field drilling in step S2 into the relationship obtained in step S1 to calculate the theoretical uranium content.

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