An algorithm for reducing the relative standard deviation of neutron multiplicity measurements

Abstract

The application discloses a kind of algorithm for reducing the relative standard deviation of neutron multiplicity measurement, it is related to nuclear material measurement technical field, the method includes the following steps: S1, when neutron pulse reaches detection system, neutron pulse is pre-delayed;S2, after pre-delaying, neutron pulse enters true coincidence pulse window, the pulse number in window is recorded, and true multiple coincidence neutron pulse count R+A that is superimposed with accidental multiple coincidence pulse is obtained;S3, neutron pulse passes through long delay queue, enters accidental coincidence pulse window, and the pulse number in window is recorded, and accidental multiple coincidence neutron pulse count A is obtained;S4, to neutron pulse, the R+A and A value corresponding to each pulse are carried out multiplicity statistics in steps S1-S3, and the multichannel statistics diagram of R+A and A is obtained;S5, R+A and A are subtracted after being counted, and true multiple coincidence neutron pulse count R distribution is obtained.The method provided by the application can effectively reduce the volatility of neutron multiplicity measurement result, improve the measurement accuracy of equipment.

Description

Technical Field

[0001] This invention belongs to the field of nuclear materials measurement technology, specifically relating to an algorithm for reducing the relative standard deviation of neutron multiplicity measurements. Background Technology

[0002] Neutron multiplex measurement is an important method for measuring nuclear materials, primarily used in nuclear material accounting. Its function is to measure the mass and oxide content properties of plutonium. Plutonium can emit two or more neutrons simultaneously during spontaneous fission, and these neutrons are temporally correlated. Using a neutron multiplex measurement signal processing device, it is possible to analyze whether the neutrons emitted by the radioactive material being measured are induced fission neutrons or spontaneous fission neutrons, thereby eliminating interference from induced fission neutrons and accurately measuring the mass of plutonium. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an algorithm to reduce the relative standard deviation of neutron multiplicity measurement. Using this method, the fluctuation of measurement results can be effectively reduced, that is, the relative standard deviation of measurement results can be reduced, and the measurement accuracy of measurement equipment can be improved.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] An algorithm for reducing the relative standard deviation of neutron multiplicity measurements includes the following steps:

[0006] S1. After the neutron pulse arrives at the detection system, the neutron pulse signal is pre-delayed;

[0007] S2. After the pre-delay, the neutron pulse enters the true coincidence pulse window. The number of pulses in the true coincidence pulse window is recorded to obtain the true multiple coincidence neutron pulse count R+A, which is superimposed with the accidental multiple coincidence neutron pulse.

[0008] S3. The neutron pulse passes through a long delay queue and then enters the accidental coincidence pulse window. The number of pulses in the accidental coincidence pulse window is recorded to obtain the accidental multiple coincidence neutron pulse count A.

[0009] S4. When each neutron pulse arrives, execute steps S1-S3 to perform multivariability statistical analysis on the R+A and A values ​​corresponding to each pulse, and obtain multichannel statistical graphs of R+A and A.

[0010] S5. After the predetermined time is reached, the pulse count R+A in the true coincidence pulse window and the pulse count A in the random coincidence pulse window are subtracted to obtain the distribution of the true multiple coincidence neutron pulse count R.

[0011] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurement as described above, step S1 uses a delay queue to pre-delay the neutron pulse signal, and the pre-delay time is adjustable in the range of 0-7.5 microseconds.

[0012] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurement as described above, step S2 uses a pulse counter to count pulses within the delay queue time window by recording the number of pulses entering and leaving the true coincidence pulse window. The gate width time of the true coincidence pulse window is adjustable in the range of 10-256 microseconds.

[0013] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurements as described above, step S3 specifically includes:

[0014] S31. After the neutron pulse passes through the first long delay queue, it enters the first accidental coincidence pulse window. The number of pulses C1 in the first accidental coincidence pulse window is recorded.

[0015] S32. After the neutron pulse passes through the second long delay queue, it enters the second accidental coincidence pulse window. The number of pulses C2 in the second accidental coincidence pulse window is recorded.

[0016] S33. After the neutron pulse passes through the third long delay queue, it enters the third accidental coincidence pulse window. The number of pulses C3 in the third accidental coincidence pulse window is recorded.

[0017] S34. Take the middle value of the counts of C1, C2, and C3, which is the accidental multiple coincidence neutron pulse count A.

[0018] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurements as described above, the gate width time of the first long delay queue in step S3 is adjustable in the range of 3072-4096 microseconds.

[0019] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurements as described above, the gate width time of the second long delay queue and the third long delay queue in step S3 is adjustable in the range of 10-512 microseconds.

[0020] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurement as described above, the gate width time of the first accidental coincidence pulse window, the second accidental coincidence pulse window, and the third accidental coincidence pulse window in step S3 is adjustable in the range of 10-256 microseconds, and is the same as the gate width time of the true coincidence pulse window.

[0021] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurement as described above, step S3 uses a pulse counter to count the pulses within the delay queue time window by recording the number of pulses entering and exiting the three accidental coincidence pulse windows.

[0022] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurement as described above, the multiplicity statistical analysis in step S4 is specifically as follows: using the values ​​of R+A and A as addresses, R+A and A each have N channels, defined as channels 0 to N-1. If the number of recorded pulses is between 1 and (N-2), then it is recorded in the corresponding channel; if the number of recorded pulses is greater than or equal to N-1, then all are recorded in channel N-1, thereby obtaining the multichannel statistical graphs of R+A and A.

[0023] Furthermore, in the algorithm for reducing the relative standard deviation of neutron multiplicity measurement as described above, R+A and A each have 256 channels. If the number of recorded pulses is between 1 and 254, it is recorded in the corresponding channel; if the number of recorded pulses is greater than or equal to 255, they are all recorded in channel 255.

[0024] Compared with existing technologies, the algorithm for reducing the relative standard deviation of neutron multiplicity measurements provided by this invention has the following beneficial effects:

[0025] This invention rapidly analyzes and processes neutron pulse signals to statistically determine their distribution over time, providing the distribution results of the total neutron count, coincidence count, and multiplicity per unit time. Compared to other technical solutions, the invention's innovation lies in its method of opening three windows for detecting accidental coincidence neutron pulses and taking the median value of these three values. This effectively reduces the probability of a true coincidence pulse falling within an accidental coincidence neutron pulse window, thereby reducing the fluctuation of the measurement results, decreasing the relative standard deviation of the measurement results, and improving the measurement accuracy of the measuring equipment. Attached Figure Description

[0026] Figure 1 This is a flowchart of an algorithm for reducing the relative standard deviation of neutron multiplicity measurements provided in an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the principle of multiple coincidence counting for neutron signals.

[0028] Figure 3 Timing diagram of neutron signal multiplicity analysis algorithm;

[0029] Figure 4 This is a flowchart of the neutron signal multiplicity analysis algorithm. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] To reduce the relative standard deviation of neutron multiplicity measurements, this invention provides an algorithm for reducing the relative standard deviation of neutron multiplicity measurements. Figure 2The diagram illustrates the principle of neutron multiple coincidence counting used in this algorithm. Since multiple coincidence neutron pulses follow a Rossi-alpha distribution, this invention obtains the true multiple coincidence neutron pulse count (i.e., R+A) and the random multiple coincidence neutron pulse count (i.e., A) by collecting the number of pulses within two time windows R+A and A that are relatively far apart. Subtracting the two yields the true multiple coincidence neutron pulse count (i.e., R).

[0032] Specific implementation method: A delay queue is used to delay the pulse signal, and a counter is used to record the pulses within the time window of the delay queue. Each time a pulse arrives, a trigger is achieved. The number and frequency of pulses within the R+A and A time windows at the trigger time are recorded, and finally, the coincidence count and multiplicity distribution can be obtained.

[0033] Based on the above principles, this invention provides an algorithm for reducing the relative standard deviation of neutron multiplicity measurements. Figure 1 The flowchart of the algorithm is shown, including the following steps:

[0034] S1. When the neutron pulse arrives at the detection system, the neutron pulse signal is pre-delayed.

[0035] The pre-delay time is adjustable within the range of 0-7.5 microseconds. Specifically, a delay queue can be used to achieve the pre-delay of the neutron pulse signal.

[0036] S2. After the pre-delay, the neutron pulse enters the true coincidence pulse window. The number of pulses in the true coincidence pulse window is recorded to obtain the true multiple coincidence neutron pulse count R+A, which is superimposed with the accidental multiple coincidence neutron pulse.

[0037] The gate width time of the true coincidence pulse window is adjustable within the range of 10-256 microseconds. Specifically, a pulse counter can be used to count the pulses within the delay queue time window by recording the number of pulses entering and leaving the true coincidence pulse window, and the counter is triggered every time a pulse arrives.

[0038] S3. The neutron pulse passes through a long delay queue and then enters the accidental coincidence pulse window. The number of pulses in the accidental coincidence pulse window is recorded to obtain the accidental multiple coincidence neutron pulse count A.

[0039] This invention calculates the count of accidental multiple coincidence neutron pulses by opening three windows for detecting accidental coincidence neutron pulses and taking the median value of these three windows. The method specifically includes the following steps:

[0040] S31. After the neutron pulse passes through the first long delay queue, it enters the first accidental coincidence pulse window. The number of pulses in the first accidental coincidence pulse window is recorded as C1.

[0041] S32. After passing through the second long delay queue, the neutron pulse enters the second accidental coincidence pulse window. The number of pulses in the second accidental coincidence pulse window is recorded as C2.

[0042] S33. After passing through the third long delay queue, the neutron pulse enters the third accidental coincidence pulse window. The number of pulses in the third accidental coincidence pulse window is recorded as C3.

[0043] The gate width of the first long delay queue is adjustable within the range of 3072-4096 microseconds, while the gate widths of the second and third long delay queues are adjustable within the range of 10-512 microseconds. The gate widths of the three accidental coincidence pulse windows are adjustable within the range of 10-256 microseconds and must be the same as the gate width of the true coincidence pulse window. Specifically, a pulse counter can be used to count the pulses within the delay queue time window by recording the number of pulses entering and leaving the accidental coincidence pulse window, triggering the counter each time a pulse arrives.

[0044] S34. Take the middle value of the counts of C1, C2, and C3, which is the accidental multiple coincidence neutron pulse count A.

[0045] S4. When each neutron pulse arrives, the method described in steps S1-S3 is executed to perform multivariate statistical analysis on the R+A and A values ​​corresponding to each pulse, and to obtain multichannel statistical graphs of R+A and A.

[0046] The multiplicity analysis provided by this invention specifically involves using the values ​​of R+A and A as addresses. R+A and A each have N channels, for example, 256 channels. If the number of recorded pulses is between 1 and 254, it is recorded in the corresponding channel. If the number of recorded pulses is greater than or equal to 255, all pulses are recorded in channel 255, thus obtaining a multichannel statistical chart of R+A and A. For example, if R+A = 5 when a neutron pulse arrives, then the count value in channel 5 is incremented by 1. In software, this is actually achieved by creating two arrays, using the number of pulses within the gate width when each trigger pulse arrives as an address, and incrementing the content at that address by 1.

[0047] S5. After the predetermined time is reached, the pulse count R+A in the true coincidence pulse window and the pulse count A in the random coincidence pulse window are subtracted to obtain the true multiple coincidence neutron pulse count R distribution.

[0048] After completing the multiplicity analysis of all pulses, subtracting A from R+A yields the true multiple coincidence neutron pulse count R distribution of the neutron pulses.

[0049] Example 1

[0050] Figure 3This illustrates a specific embodiment of the neutron pulse signal multiplicity analysis algorithm provided by the present invention, showing a timing diagram. When the neutron pulse reaches the detection system ( Figure 3 At time t=0, the system first delays by 3 microseconds (this time is called the pre-delay, adjustable from 0-7.5 microseconds). The number of pulses within the following 64 microseconds (this time is called the gate width, adjustable from 0-256 microseconds) is recorded as R+A. Then, after a further delay of 3072 microseconds, the number of pulses within the following 64 microseconds (gate width, adjustable from 0-256 microseconds) is the first coincidence window count C1. After another delay of 512 microseconds, the number of pulses within the following 64 microseconds (gate width, adjustable from 0-256 microseconds) is the second coincidence window count C2. After another 512 microseconds, the number of pulses within the following 64 microseconds (gate width, adjustable from 0-256 microseconds) is the third coincidence window count C3. The median value of the counts C1, C2, and C3 is then taken as A. For each pulse arrival, R+A and A are calculated and accumulated. After completing the pulse analysis as described above, the next pulse is analyzed in the same way until all pulses have been analyzed. After a preset time (e.g., 1000 seconds), the system subtracts the number of pulses A from the number of pulses R+A to obtain the value of R.

[0051] Example 2

[0052] Figure 4 The diagram illustrates the neutron multiplicity pulse counting algorithm provided by this invention. First, a pulse queue is used to pre-delay the neutron signal pulse. Then, the neutron pulse enters the true coincidence pulse recording window. The number of pulses entering and leaving the window is recorded to achieve a pulse count equal to C0. After passing through a long-delay queue, the pulse enters the first accidental coincidence window. The number of pulses in the window is recorded as C1. This process is repeated twice, and the number of pulses in the window is recorded as C2 and C3, respectively. Finally, the true coincidence pulse window count R+A equals C0, and the accidental coincidence pulse window count A equals the intermediate value of the counts of C1, C2, and C3.

[0053] The values ​​of R+A and A are used as addresses, with 256 channels for each. If the number of recorded pulses is between 1 and 254, it is recorded in each channel; if the number of pulses is greater than or equal to 255, all pulses are recorded in channel 255. After a predetermined time, the system sends the statistical results of R+A and A during this period to the computer.

[0054] The algorithm for reducing the relative standard deviation of neutron multiplicity measurements provided by this invention rapidly analyzes and processes neutron pulse signals to statistically determine the distribution of neutron pulse signals over time, providing the distribution results of the total neutron count, coincidence count, and multiplicity per unit time. Compared to other technical solutions, the ingenuity of this invention lies in the method of opening three windows for detecting accidental coincidence neutron pulses and taking the median value of these three values. This effectively reduces the probability of true coincidence pulses falling within the accidental coincidence neutron pulse window, thereby reducing the fluctuation of the measurement results, decreasing the relative standard deviation of the measurement results, and improving the measurement accuracy of the measuring equipment.

[0055] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. An algorithm for reducing the relative standard deviation of neutron multiplicity measurements, comprising the following steps: S1. After the neutron pulse arrives at the detection system, the neutron pulse signal is pre-delayed; S2. After the pre-delay, the neutron pulse enters the true coincidence pulse window. The number of pulses in the true coincidence pulse window is recorded to obtain the true multiple coincidence neutron pulse count R+A, which is superimposed with the accidental multiple coincidence neutron pulse. S3. The neutron pulse passes through a long delay queue and then enters the accidental coincidence pulse window. The number of pulses in the accidental coincidence pulse window is recorded to obtain the accidental multiple coincidence neutron pulse count A. S4. When each neutron pulse arrives, execute steps S1-S3 to perform multivariability statistical analysis on the R+A and A values ​​corresponding to each pulse, and obtain multichannel statistical graphs of R+A and A. S5. After the predetermined time is reached, the pulse count R+A in the true coincidence pulse window and the pulse count A in the random coincidence pulse window are subtracted to obtain the distribution of the true multiple coincidence neutron pulse count R. Step S3 specifically involves: S31. After the neutron pulse passes through the first long delay queue, it enters the first accidental coincidence pulse window. The number of pulses C1 in the first accidental coincidence pulse window is recorded. The gate width time of the first long delay queue is adjustable in the range of 3072-4096 microseconds. S32. After the neutron pulse passes through the second long delay queue, it enters the second accidental coincidence pulse window. The number of pulses C2 in the second accidental coincidence pulse window is recorded. The gate width time of the second long delay queue and the third long delay queue is adjustable in the range of 10-512 microseconds. S33. After the neutron pulse passes through the third long delay queue, it enters the third accidental coincidence pulse window. The number of pulses C3 in the third accidental coincidence pulse window is recorded. S34. Take the middle value of the counts of C1, C2, and C3, which is the accidental multiple coincidence neutron pulse count A.

2. The algorithm for reducing the relative standard deviation of neutron multiplicity measurements according to claim 1, characterized in that, In step S1, a delay queue is used to pre-delay the neutron pulse signal, and the pre-delay time is adjustable in the range of 0-7.5 microseconds.

3. The algorithm for reducing the relative standard deviation of neutron multiplicity measurements according to claim 2, characterized in that, In step S2, a pulse counter is used to count the pulses in the delay queue time window by recording the number of pulses entering and leaving the true coincidence pulse window. The gate width time of the true coincidence pulse window is adjustable in the range of 10-256 microseconds.

4. The algorithm for reducing the relative standard deviation of neutron multiplicity measurements according to claim 1, characterized in that, In step S3, the gate width time of the first accidental coincidence pulse window, the second accidental coincidence pulse window, and the third accidental coincidence pulse window is adjustable in the range of 10-256 microseconds, and is the same as the gate width time of the true coincidence pulse window.

5. The algorithm for reducing the relative standard deviation of neutron multiplicity measurements according to any one of claims 2-4, characterized in that, In step S3, a pulse counter is used to count the pulses within the time window of the delay queue by recording the number of pulses entering and exiting the three coincident pulse windows.

6. The algorithm for reducing the relative standard deviation of neutron multiplicity measurements according to claim 1, characterized in that, The multiplicity statistical analysis described in step S4 is as follows: the values ​​of R+A and A are used as addresses, and R+A and A each have N channels, defined as channels 0 to N-1. If the number of recorded pulses is between 1 and (N-2), it is recorded in the corresponding channel; if the number of recorded pulses is greater than or equal to N-1, all of them are recorded in channel N-1, thus obtaining the multichannel statistical charts of R+A and A.

7. The algorithm for reducing the relative standard deviation of neutron multiplicity measurements according to claim 6, characterized in that, R+A and A each have 256 channels. If the number of pulses recorded is between 1 and 254, it is recorded in the corresponding channel; if the number of pulses recorded is greater than or equal to 255, it is all recorded in channel 255.

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