KR20100079602A - Method and apparatus for determining nuclide in nuclear material composed of only one nuclide, and for determining nuclide composition ratio in nuclear material composed of several nuclides - Google Patents

Abstract

The present invention calculates the multiplier distribution from neutrons released during nuclear fission, and compares it with the reference distribution to determine the nuclide of a single nuclide nuclide or to determine the nuclide component ratio of a multinuclear nucleus. A method and an apparatus for determining each are provided.

Description

METHOD AND APPARATUS FOR DETERMINING NUCLIDE IN NUCLEAR MATERIAL COMPOSED OF ONLY NUCLIDE, AND FOR DETERMINING NUCLIDE COMPOSITION RATIO IN NUCLEAR MATERIAL COMPOSED OF SEVERAL NUCLIDES}

The present invention relates to a method and apparatus for determining nuclide species of neutron generators (also called 'sources') or determining component ratios between nuclides in the case of multinuclides by measuring neutrons emitted during nuclear fission of nuclear material.

In general, after a natural nuclear fuel such as uranium reacts in a technically controlled state to generate energy (nuclear power generation), not only uranium but also plutonium and the like are present in combination, which is called spent fuel. Among the spent fuels, uranium and plutonium are classified as Special Nuclear Material (SNM), reported to and managed by the International Atomic Energy Agency.

For such reporting or process-specific management during nuclear power generation, it is necessary to know the existence of a particular nuclide in the fuel or to determine the composition of the nuclide.

Nuclear fuel samples may be obtained and subjected to chemical tests to determine the nuclide or determine the composition ratio. However, this method has a problem that requires a lot of time for analysis.

Other non-destructive methods include measuring gamma rays or detecting neutrons to determine gastric nuclides.

The neutron detection method is difficult to measure the neutron spectrum, there is no simple equipment for measuring it, and it is not easy to miniaturize the device. In addition, in the case of multinuclide nuclear material, it is not easy to identify which source of neutron generation.

In particular, in the case of spent nuclear fuel, which is a multinuclear material, after measuring Cm-244, the main source, information on the degree of combustion (provided by the power plant or gamma ray measurement as the degree of combustion of the fuel), and the ORIGEN (combustion degree) And the Cm ratio (U-235 / Cm-244 or Pu / Cm-244) (nuclide component ratio) to determine the amount of U-235 and Pu. At this time, since the error of the combustion degree measurement error and the computer code is accumulated in the final result value, the measurement error and the uncertainty are large.

One object of the present invention is to provide a method and apparatus for determining a nuclide or component ratio different from the conventional one.

Another object of the present invention is to use a conventional neutron measuring device to easily determine the nuclide or nucleus component ratio of the nuclear material.

Nuclear species identification method of a single nuclide nuclear material according to an embodiment of the present invention for realizing the above object is to detect the neutrons released during nuclear fission in the nuclear material sample, and within a predetermined time interval of the detected neutrons Counting the number of neutrons continuously detected by the number of cluster signals, calculating the number of neutron multiplications by converting the number of counts of the number of cluster signals, and comparing the distribution of the neutron multiplications with a reference distribution of the sample. Determining the nuclide.

Nuclide discrimination apparatus of a single nuclide nuclear material according to another embodiment of the present invention is a neutron detector for detecting neutrons released during nuclear fission in a nuclear material sample, and the neutron detector is electrically connected to the neutron detector is a constant of the detected neutrons A signal converter for counting the number of neutrons clustered continuously within a time interval for each number of cluster signals, a calculator electrically connected to the signal converter for converting coefficient values for the number of cluster signals to calculate neutron multiplications, and And a determiner electrically connected to determine the nuclide of the sample by comparing the distribution of the neutron multiplier with a reference distribution.

In accordance with another aspect of the present invention, a method for determining a nuclear species component ratio of a multinuclide nuclear material includes combining a multiplication factor distribution of each of a plurality of nuclides to calculate a mixed reference distribution, and a nuclear material mixed with a plurality of nuclides. Detecting neutrons emitted during nuclear fission from a sample, counting neutrons of the clusters continuously detected within a predetermined time interval among the detected neutrons by the number of cluster signals, and converting the coefficient values by the number of cluster signals Calculating a mixed multiplier of neutrons and comparing the distribution of the neutron mixed multiplier with the mixed reference distribution to determine a component ratio of each nuclide.

According to another embodiment of the present invention, an apparatus for determining a nuclear species component ratio of a multinuclide nucleus material includes a neutron detector for detecting neutrons emitted during fission from a nuclear material sample containing a plurality of nuclides mixed with the neutron detector. A signal converter that is connected to count the number of neutrons of the clusters that are continuously detected within a predetermined time interval among the detected neutrons by the number of cluster signals, and is electrically connected to the signal converter to convert the coefficient values for the number of cluster signals to mix neutrons A calculator for calculating the multiplied multiplier and a discriminator for comparing the distribution of the mixed reference distribution calculated by combining the multiplier distribution of each of the plurality of nuclides and the distribution of the neutron mixed multiplier to determine the component ratio for each nuclide.

Nuclear species determination method and apparatus of a single nuclide nuclear material, and nucleus component ratio determination method of a multinuclear nucleus material according to the present invention configured as described above is a neutron multiplier from the neutron number of the cluster using a conventional neutron measuring device As it is configured to calculate and compare with the reference multiplier distribution, the process necessary for nuclide identification is simplified and the cumulative error of the error can be eliminated to more accurately determine the nuclide or component ratio of each nuclide.

Hereinafter, a method and apparatus for determining a nuclide of a single nuclide nuclear material according to a preferred embodiment of the present invention, and a method and apparatus for determining the nuclide component ratio of a multinuclide nuclear material will be described in detail with reference to the accompanying drawings. In the present specification, the same or similar reference numerals are assigned to the same or similar configurations in different embodiments, and the description thereof is replaced with the first description.

1 is a conceptual diagram illustrating a neutron measuring system 100 according to an embodiment of the present invention.

Referring to this figure, the neutron measurement system 100 includes a neutron detector 110, a signal converter 120, and a calculator 130.

The neutron detector 110 includes a tube 111 for detecting neutrons emitted from the sample O and a moderator 113 in which the tube 111 is embedded. Mechanisms for the tube 111 to detect neutrons vary, but a ³ He tube gas detector is typically used for thermal neutron detection. The moderator 113 is a material that lowers the speed of the neutron, and also serves as a structure. As the moderator 113, a hydrogen-based material such as polyethylene may be used.

The signal converter 120 is electrically connected to the neutron detector 110 to separate and output a signal by the neutron emitted within a predetermined time from the neutron signals detected by the neutron detector 110. These neutrons are called clustered neutrons. The signal converter 120 outputs a value calculated for each number of cluster signals for the neutrons of the cluster. The operating principle of the signal converter 120 will be described with reference to FIG. 2.

The calculator 130 is electrically connected to the signal converter 120 to receive the count values for the number of cluster signals. By converting the above coefficient values, the neutron multiplier is calculated, which is expressed as the neutron multiplication distribution. The discriminator 135 determines the nuclide of the nuclear material by comparing the distribution of the multiplier with the distribution of the standard multiplier by nuclide. The discriminator 135 may be classified in the form of a separate calculator, but if the calculator 130 is a conventional computer, it may form part of its processor. In this case, the discriminator 135 is shown as part of the calculator 130.

Ancillary equipment such as an amplifier and / or a multi-wavelength analyzer may be connected between the neutron detector 110 and the signal converter 120. An amplifier amplifies the neutron detection signal, and a multi-wavelength analyzer can separate the detection signal from noise.

FIG. 2 is a conceptual diagram for describing a method of calculating a clustered neutron number output by the signal converter 120 from the neutron signal detected by the neutron detector 110 of FIG. 1.

Referring to this figure, neutrons are detected in a cluster within a specific time range over time. These clustered neutrons, as mentioned earlier, are called clustered neutrons. In this example, the neutron communities are divided into four clusters (A to D). If the quantity of nuclear material is small, there is little redundancy between adjacent communities.

The signal converter 120 counts the number of neutrons for a certain time interval (G). At this time, for each neutron, the number of neutron detections during the interval G is counted from the time when the neutrons are detected.

Specifically, the signal converter 120 outputs event values at the R + A gate and the A gate, respectively. R stands for Real event, A stands for Accidental event, and the value to know for multiplication distribution measurement is related to R. The outputs from the two gates are related to each other so that R can be solved by using known mathematical methods, rather than simply subtracting A from R + A. Based on this, the distribution measure of the multiplication factor is counted. Although it is preferable to measure the multiplier distribution through the R value, an ideal experimental condition with a small amount of sample and an external factor is very small, so the value of A is very small. none.

Referring back to FIG. 2, for cluster A, the coefficient value for the first neutron is two. The coefficient value for the second neutron is one. Since the neutron is not detected during the interval G from the third neutron, the coefficient value becomes O.

In the same way, the signal converter 120 outputs 3, 2, 1, 0 values for the B group, and 1,0 for the C group. The signal converter 120 outputs 5, 4, 3, 2, 1, 0 values for the D group. This is summarized in Table 1 below.

Cluster signal Signal converter 120 output value 0 4 One 4 2 3 3 2 4 One 5 One

In the above table, the output value of the signal converter 120 represents the number of occurrences of the number of cluster signals.

The signal converter 120 output value above is converted to obtain a neutron multiplier. This conversion is performed in such a manner that the number of cluster signals is arranged in order from the largest to the smallest, so that the output value of the signal converter 120 is exhausted from the number of cluster signals.

According to this scheme, from Table 1 above, the group of (5,4,3,2,1,0), the group of (3,2,1,0), the group of (2,1,0), and A group of (1, 0) is calculated. From each group, it can be seen that six, four, three, and two neutrons occurred in clusters, respectively. This clustering of neutron distribution is understood as neutron multiplication.

3 is a graph showing a reference distribution of neutron multipliers by nuclide.

Referring to the figure, for example, the probability that U-235 does not emit neutrons by one nuclear fission is about 0.03, and the probability of emitting one to eight is 0.18, 0.34, 0.31, 0.13, 0.03, 0.01, 0, 0. In other words, U-235 will release mainly two or three neutrons in one fission.

Cm-244 is most likely to emit three neutrons, while Cf-252 is most likely to emit four neutrons. Pu-239 is a nuclide that is likely to emit three neutrons. The distribution of neutron emission characteristics by nuclide forms a unique multiplier distribution by nuclide. Here, multiplicity refers to the number of neutrons released by one spontaneous fission or induced fission of a specific nuclide. Since neutrons released by fission are released in clusters, the number of neutrons in a cluster can be determined by the probability by the doubling distribution.

The reference distribution of the neutron multiplication factor may be used for comparison with the multiplication factor distribution obtained through the conversion of the calculated value by the signal converter 120 as previously obtained in FIG.

For example, if the probability of neutron emission for neutron number / nuclear fission from 0 to 8 in the transformed multiplier distribution is close to 0.03, 0.18, 0.34, 0.31, 0.13, 0.03, 0.01, 0, 0, the fission source May be determined as U-235.

4 is a conceptual diagram illustrating a method for determining the composition ratio of nuclear species by multinuclide nuclear material according to another embodiment of the present invention.

Referring to this figure, the manner of obtaining the nuclides and their nuclide component ratios in the multinuclide nuclear material can be described by way of example for a nuclear material in which two nuclides are mixed.

For each of the two individual nuclides, the true neutron multiplication distribution is true. This is obtained by converting the measured value of the signal converter 120 for the neutron signal detected by the neutron detector 110 into the calculator 130 as described above. This process accumulates data, analyzes the link between measured and true values, and enables them to be more seamlessly linked.

A mixed reference distribution is calculated by combining the multiplication distribution of each of the two nuclides that are closer to the true value as above. The mixed reference distribution is calculated by combining the multiplication distribution corresponding to the ratio of the nuclides. This makes it possible to generate data on various mixed reference distributions according to the ratio of two nuclides.

With respect to the above mixed reference distribution, the mixed multipliers of the neutrons obtained by converting the coefficient values for the number of cluster signals of the neutrons of the clusters emitted from the mixed nuclear materials of the two nuclides are compared. From the above comparison, the mixed reference distribution most similar to the mixed multiplier can be found, and the composition ratio of each nuclide can be determined from the characteristics of the reference distribution (mixing ratio of two nuclide materials).

Such a method and apparatus for determining a nuclide of a single nuclide nuclear material, and a method and apparatus for determining a nuclear species component ratio of a multinuclide nuclear material are not limited to the configuration and operation of the embodiments described above. The above embodiments may be configured such that various modifications may be made by selectively combining all or part of the embodiments.

1 is a conceptual diagram illustrating a neutron measuring system according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram illustrating a method of counting the number of neutrons in a cluster output by a signal converter from a neutron signal detected by the neutron detector of FIG. 1; FIG.

3 is a graph showing a reference distribution of neutron multipliers by nuclide.

4 is a conceptual diagram illustrating a method for determining the nuclear species component ratio of multinuclide nuclear material according to another embodiment of the present invention.

Claims (9)

(a) detecting neutrons released upon nuclear fission in a nuclear material sample; (b) counting the number of neutrons in the cluster continuously detected within a predetermined time interval among the detected neutrons for each cluster signal number; (c) counting neutron multiplications by converting the coefficient values for the number of cluster signals; And (d) comparing the distribution of the neutron multiplier with a reference distribution to determine the nuclide of the sample. The method of claim 1, In the step (b), the nuclide discrimination method of a single nuclide nuclear material, characterized in that the number of neutrons of the cluster detected within the same time interval based on each detected neutrons. A neutron detector for detecting neutrons released during nuclear fission from a nuclear material sample; A signal converter electrically connected to the neutron detector and counting the number of neutrons of the clusters continuously detected within a predetermined time interval among the detected neutrons by the number of cluster signals; A calculator which is electrically connected to the signal converter and calculates a neutron multiplication number by converting a coefficient value for each cluster signal number; And And a discriminator electrically connected with the calculator, the discriminator for discriminating a nuclide of the sample by comparing the distribution of the neutron multiplications with a reference distribution. The method of claim 3, The neutron detector is a nuclide discrimination device of a single nuclide nuclear material, characterized in that it comprises a ³ He tube inserted into the hydrogen-based moderator. The method of claim 3, An apparatus for determining a nuclide of a single nuclide nuclear material, characterized in that an amplifier and / or a multi-wavelength analyzer are connected between the neutron detector and the signal converter. (a) combining a multiplication factor distribution of each of the plurality of nuclides to produce a mixed reference distribution; (b) detecting neutrons released upon nuclear fission in a sample of nuclear material mixed with a plurality of nuclides; (c) counting the number of neutrons in the cluster continuously detected within a predetermined time interval among the detected neutrons for each cluster signal number; (d) calculating mixed multipliers of neutrons by converting the coefficient values for the number of cluster signals; And (e) comparing the distribution of the neutron mixed multiplier with the mixed reference distribution to determine the composition ratio of the nuclear species. The method of claim 6, In the step (a), the nucleus component ratio determination method of the multinuclide nuclear material, characterized in that to calculate the mixed reference distribution by combining the multiplication distribution corresponding to the ratio of the nuclides. A neutron detector for detecting neutrons emitted during nuclear fission from a sample of nuclear material mixed with a plurality of nuclides; A signal converter electrically connected to the neutron detector and counting the number of neutrons of the clusters continuously detected within a predetermined time interval among the detected neutrons by the number of cluster signals; A calculator electrically connected to the signal converter for converting coefficient values for the number of cluster signals to calculate mixed multipliers of neutrons; And Apparatus for determining the nuclear component ratio of the multinuclide nuclear material comprising a discriminator for determining the component ratio of each nuclide by comparing the distribution of the mixed reference distribution calculated by combining the multiplier distribution of each of the plurality of nuclides and the distribution of the neutron mixed multiplier . The method of claim 8, Wherein said mixed reference distribution is calculated by combining said multiplication factor distribution corresponding to the ratio of said nuclides.

Images