A method for estimating the age of spontaneous fission sources

Abstract

The embodiment of the present application provides a method for estimating the age of a spontaneous fission source, which relates to the field of nuclear technology and is used to solve the problem that the estimation process of the age of a spontaneous fission source is relatively difficult. The method for estimating the age of a spontaneous fission source provided in the embodiment of the present application includes: obtaining the radioactivity A of the sum of the first nuclides in the spontaneous fission source; 11 ; According to the radioactivity A of the sum of the first nuclides produced by spontaneous fission of at least one nuclide in the spontaneous fission source 21 and the first estimated age t1 of the spontaneous fission source, and let A 21 =A 11 , calculate t1; wherein the at least one nuclide includes the main nuclide of the spontaneous fission source. The embodiment of the present application provides a method for estimating the age of a spontaneous fission source for estimating the age of the spontaneous fission source.

Description

Technical Field

[0001] The present application relates to the field of nuclear technology, and in particular to a method for estimating the age of a spontaneous fission source. Background Art

[0002] Spontaneous fission sources have a wide range of applications in medicine, scientific research, industry, nuclear science education and many other fields, such as: they can be used for human nuclide analysis, instrument calibration, characterization of detector efficiency, neutron imaging, nuclear reactor start-up sources, nuclear fuels and explosives, etc. Estimating the age of spontaneous fission sources is of great significance and practical application value, for example: spontaneous fission sources can be traced, their origins and production dates can be tracked, etc.; the neutron intensity of spontaneous fission sources can also be accurately determined, so that related instruments can obtain higher accuracy when using spontaneous fission sources for calibration.

[0003] The main nuclides in spontaneous fission sources often either do not emit gamma rays or the gamma rays they emit are difficult to measure, making it difficult for researchers to measure them using gamma spectroscopy. 252 The age of spontaneous fission sources can be estimated by measuring the amount of Cf, but the estimation of the age of spontaneous fission sources is more difficult. Summary of the invention

[0004] In view of this, an embodiment of the present application provides a method for estimating the age of a spontaneous fission source to solve the problem that the estimation process of the age of a spontaneous fission source is relatively difficult.

[0005] To achieve the above object, the present invention provides a method for estimating the age of a spontaneous fission source, comprising: obtaining the radioactivity A of the sum of the first nuclides in the spontaneous fission source 11 ; According to the radioactivity A of the sum of the first nuclides produced by spontaneous fission of at least one nuclide in the spontaneous fission source 21 and the first estimated age t1 of the spontaneous fission source, and let A 21 =A 11 , calculate t1; wherein at least one nuclide includes the main nuclide of the spontaneous fission source; the radioactivity of the sum of the fission products produced by the spontaneous fission of any one of the at least one nuclide in the spontaneous fission source The relationship between it and t1 is:

[0006]

[0007] In the formula, is the decay constant of the fission parent of this fission product, is the radioactivity of the total fission precursor in the spontaneous fission source, is the spontaneous fission branching ratio of the fission matrix, is the cumulative yield of such fission product; is the decay constant of the fission product.

[0008] In some optional embodiments of the present application, the at least one nuclide further comprises at least one decay product of the nuclide in the spontaneous fission source, and the radioactivity of the sum of the decay products is The relationship with t1 is:

[0009]

[0010] In the formula, is the number of nuclei that are the sum of one decay product, is the decay constant of the decay product, is the decay constant of the decay parent of this decay product, The number of nuclei of the decay parent in the spontaneous fission source, is the spontaneous fission branching ratio of the decay parent.

[0011] In some optional embodiments of the present application, the method for estimating the age of a spontaneous fission source further includes: obtaining the radioactivity A of the sum of the second nuclides in the spontaneous fission source. 12 According to A 21 The relationship between t1 and A 21 =A 11 , calculate t1, as: According to A 21 The relationship between t1 and the sum of the radioactivity A of the second nuclides produced by the spontaneous fission of at least one nuclide in the spontaneous fission source 22 The relationship between t1 and A 21 =A 11 , A 22 =A 12 , calculate t1.

[0012] In some optional embodiments of the present application, any one of the at least one nuclide has a long-lived fission product of the same type as the first nuclide, and any one of the at least one nuclide has a short-lived fission product of the same type as the second nuclide.

[0013] In some optional embodiments of the present application, according to A 21 The relationship between t1 and A 22 The relationship between t1 and A 21 =A 11 , A 22 =A 12 , calculate t1 as: calculate A 11 With A 12 The ratio R1 between them, calculate A 21 With A22 The ratio R2 between them, according to the relationship between R2 and t1, and let R 2＝ R1, calculate t1.

[0014] In some optional embodiments of the present application, the method for estimating the age of a spontaneous fission source further includes: obtaining the radioactivity A of the sum of the third nuclides in the spontaneous fission source. 13 According to A 21 The relationship between the second estimated age value t2 of the spontaneous fission source and the radioactivity A of the sum of the third nuclides produced by the spontaneous fission of at least one nuclide in the spontaneous fission source 23 The relationship between t2 and A 21 =A 11 , A 23 =A 13 , calculate t2; calculate the average of t1 and t2; wherein any one of the at least one nuclides has a fission product of the same type as that of the third nuclide.

[0015] In some optional embodiments of the present application, the main nuclide is 252 Cf, the first nuclide is 137 Cs.

[0016] In some optional implementations of the present application, obtaining A 11 Includes: Determination of spontaneous fission sources 137 The peak net count rate I(E1) of the characteristic γ energy peak of Cs with energy of 661.66keV; using A 11 Calculate the relationship between A and I(E1) 11 Among them, A 11 The relationship between it and I(E1) is:

[0017] I(E1)=A 11 ×Br(E1)×η(E1)

[0018] Where η(E1) is the spontaneous fission source 137 The detection efficiency of the full energy peak of Cs with an energy of 661.66 keV, Br(E1) in the spontaneous fission source 137 The energy of Cs is 661.66keV, which is the branching ratio of the characteristic γ energy peak.

[0019] In some optional embodiments of the present application, the second nuclide is 132 I.

[0020] In some optional implementations of the present application, obtaining A 12 Includes: Determination of spontaneous fission sources 132The energy of I is the peak net count rate I(E2) of the characteristic γ energy peak of 667.72keV; using A 12 Calculate the relationship between A and I(E2) 12 Among them, A 12 The relationship between it and I(E2) is:

[0021] I(E2)=A 12 ×Br(E2)×η(E2)

[0022] Where η(E2) is the spontaneous fission source 132 The detection efficiency of the full energy peak of I with an energy of 667.72 keV, Br(E2) in the spontaneous fission source 132 The energy of I is the branching ratio of the characteristic γ energy peak at 667.72 keV.

[0023] The method for estimating the age of a spontaneous fission source provided in the embodiment of the present application indirectly estimates the age of a spontaneous fission source by using the relationship between the activity of a spontaneous fission product of a main element in the spontaneous fission source and the age of the spontaneous fission source. It is not necessary to directly measure the amount of the main element in the spontaneous fission source, and it is relatively easy to obtain the activity of the spontaneous fission product of the main element in the spontaneous fission source, which can make the estimation process of the age of the spontaneous fission source relatively simple. Specifically, the main element will undergo spontaneous fission, and in the age of the spontaneous fission source, the amount of the spontaneous fission product of the main element will change with the age of the spontaneous fission source, that is, the amount of the spontaneous fission product of the main element in the age of the spontaneous fission source is related to the age of the spontaneous fission source. Therefore, the current age of the spontaneous fission source can be estimated based on the amount of the spontaneous fission product of the main element in the current spontaneous fission source, and the process is relatively convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is one of the flow charts of the method for estimating the age of a spontaneous fission source in some embodiments of the present application;

[0025] Figure 2 The second flow chart of the method for estimating the age of a spontaneous fission source in some embodiments of the present application;

[0026] Figure 3 The third flow chart of the method for estimating the age of a spontaneous fission source in some embodiments of the present application;

[0027] Figure 4 FIG4 is a flow chart of a method for estimating the age of a spontaneous fission source in some embodiments of the present application;

[0028] Figure 5 For obtaining the spontaneous fission source in some embodiments of the present application 137 Schematic diagram of the flow chart of the total radioactivity of Cs;

[0029] Figure 6 For obtaining the spontaneous fission source in some embodiments of the present application 132 Schematic diagram of the total radioactivity of I;

[0030] Figure 7 In some embodiments of this application 252 Schematic diagram of the flow chart of the Cf source age estimation method. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0032] In the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more.

[0033] In addition, in the embodiments of the present application, directional terms such as "up", "down", "left" and "right" are defined relative to the orientation of the components in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they may change accordingly according to the changes in the orientation of the components in the drawings.

[0034] In the embodiments of the present application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0035] In the embodiments of the present application, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0036] In the embodiments of the present application, words such as "exemplarily" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplarily" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplarily" or "for example" is intended to present related concepts in a specific way.

[0037] The present application provides a method for estimating the age of a spontaneous fission source, wherein the type of the spontaneous fission source is not limited, as long as the main nuclide of the spontaneous fission source is a heavy nuclide that can undergo spontaneous fission. For example, a spontaneous fission source can be 252 Cf source, 250 Cf source, 244 Pu source or 248 Cm source, etc. The age of the spontaneous fission source, that is, the time since the spontaneous fission source was separated and purified for the last time.

[0038] The present application provides a method for estimating the age of a spontaneous fission source, comprising: obtaining the radioactivity A of the sum of the first nuclides in the spontaneous fission source; 11 ; According to the radioactivity A of the sum of the first nuclides produced by spontaneous fission of at least one nuclide in the spontaneous fission source 21 and the first estimated age t1 of the spontaneous fission source, and let A 21 =A 11 , calculate t1; wherein at least one nuclide includes the main nuclide of the spontaneous fission source; the radioactivity of the sum of the fission products produced by the spontaneous fission of any one of the at least one nuclide in the spontaneous fission source The relationship between it and t1 is:

[0039]

[0040] In the formula, is the decay constant of the fission parent of this fission product, is the radioactivity of the total fission precursor in the spontaneous fission source, is the spontaneous fission branching ratio of the fission matrix, is the cumulative yield of such fission product; is the decay constant of the fission product.

[0041] That is, please refer to Figure 1 The method for estimating the age of a spontaneous fission source provided in the embodiment of the present application comprises the following steps:

[0042] S101, get A 11 ;

[0043] S102, according to A21 The relationship between t1 and A 21 =A 11 , calculate t1.

[0044] The method for estimating the age of a spontaneous fission source provided in the embodiment of the present application indirectly estimates the age of a spontaneous fission source by using the relationship between the activity of a spontaneous fission product of a main element in the spontaneous fission source and the age of the spontaneous fission source. It is not necessary to directly measure the amount of the main element in the spontaneous fission source, and it is relatively easy to obtain the activity of the spontaneous fission product of the main element in the spontaneous fission source, which can make the estimation process of the age of the spontaneous fission source relatively simple. Specifically, the main element will undergo spontaneous fission, and in the age of the spontaneous fission source, the amount of the spontaneous fission product of the main element will change with the age of the spontaneous fission source, that is, the amount of the spontaneous fission product of the main element in the age of the spontaneous fission source is related to the age of the spontaneous fission source. Therefore, the current age of the spontaneous fission source can be estimated based on the amount of the spontaneous fission product of the main element in the current spontaneous fission source, and the process is relatively convenient.

[0045] It needs to be explained that the first nuclide refers to a certain nuclide in the spontaneous fission source and cannot include multiple nuclides.

[0046] It should be explained that the total radioactivity A of the first nuclide in the spontaneous fission source is obtained. 11 It refers to obtaining the radioactivity of the sum of the first nuclides existing in the spontaneous fission source at the current moment, and the same applies to the second and third nuclides. In addition, the sum of the first nuclides produced by the spontaneous fission of at least one nuclide in the spontaneous fission source refers to the sum of all the first nuclides produced by the fission of at least one nuclide from the initial moment to the current moment, and the first nuclides still existing in the spontaneous fission source at the current moment, and each nuclide in at least one nuclide will spontaneously fission to produce the first nuclide. The same applies to the second and third nuclides. In addition, the initial moment refers to the moment when the age of the spontaneous fission source is zero.

[0047] It should be explained that the main nuclide of the spontaneous fission source refers to the nuclide with the highest content in the spontaneous fission source at the initial moment. For example, 252 The main nuclides of Cf sources are 252 Cf.

[0048] Optionally, in some embodiments of the present application, the first nuclide may be a long-lived fission product of the main nuclide. Long-lived fission products accumulate over time, and using long-lived fission products to estimate the lifetime is more accurate.

[0049] It should be explained that the long-lived fission product of a certain nuclide refers to the fission product of the nuclide with a longer half-life, which is not easy to decay into other nuclides and will accumulate as the parent nuclide continues to spontaneously fission. The short-lived fission product of a certain nuclide refers to the fission product of the nuclide with a shorter half-life, which is easy to decay into other nuclides. In the embodiment of the present application, the short-lived fission product can be defined as follows: in the process of spontaneous fission of the parent nuclide, a short-lived fission product of the parent nuclide and the parent nuclide will gradually reach a radioactive equilibrium state and last until the end. The long-lived fission product can be defined as follows: all other spontaneous fission products of the parent nuclide except the short-lived fission product can be used as long-lived fission products.

[0050] The first nuclide, the second nuclide and the third nuclide in the spontaneous fission source may not be completely produced by the fission of the main element. The impurity nuclides in the spontaneous fission source, the various decay products in the decay chain of the main nuclides and the various decay products in the decay chain of the impurity nuclides may all spontaneously fission to produce the first nuclide, the second nuclide and the third nuclide. For example, 252 In the Cf source, not only 252 Cf will fission to produce 137 Cs and 132 I etc. 252 The decay chain of Cf contains multiple decay daughters such as 248 Cm and 244 Pu, 252 Impurities in Cf Source 250 Cf, and 250 Cf decay produces 246 Cm and others will also produce more 137 Cs and 132 I etc.

[0051] Therefore, in some optional embodiments of the present application, at least one nuclide further includes any one or more of an impurity nuclide of a spontaneous fission source, at least one decay daughter on a decay chain of a main nuclide, and at least one decay daughter on a decay chain of an impurity nuclide. It can be understood that the first nuclide, the second nuclide, the third nuclide, etc. are mostly produced by spontaneous fission of the main nuclide, but the more nuclides included in the at least one nuclide, the more accurate the estimation of the age of the spontaneous fission source.

[0052] It needs to be explained that 252 The impurity nuclide of the Cf source refers to the initial moment, i.e. 252 When the age of the Cf source is zero 252 Other nuclides in Cf sources other than the main nuclides are not included in 252 As the Cf source ages, 252 Decay products of various nuclides in the Cf source.

[0053] It can be understood that if at least one nuclide includes only the main nuclide, then formula 1 can be used to obtain: A 21 The relationship between t1 and If at least one nuclide includes multiple nuclides, then A can be obtained by adding the sum of the radioactive activities of the first nuclides produced by spontaneous fission of multiple nuclides using formula 1. 21 , the same applies to the second and third nuclides.

[0054] In addition, it should be explained that if Formula 1 is used to obtain the radioactivity of the sum of the fission products produced by the spontaneous fission of the main nuclide in the spontaneous fission source The relationship between and t1, then in formula 1,

[0055]

[0056] In the formula, is the activity of the main nuclide in the spontaneous fission source at the initial moment.

[0057] That is, if formula 1 is used to obtain the total radioactivity of a fission product produced by spontaneous fission of the main nuclide in the spontaneous fission source The relationship between t1 and equation 1 can be expressed as follows:

[0058]

[0059] From formula 3, we can see that and In this case, t1 can be obtained by applying Formula 3.

[0060] In some optional embodiments of the present application, the at least one nuclide further comprises at least one decay product of the nuclide in the spontaneous fission source, and the radioactivity of the sum of the decay products is The relationship with t1 is:

[0061]

[0062] In the formula, is the number of nuclei that are the sum of one decay product, is the decay constant of the decay product, is the decay constant of the decay parent of this decay product, The number of nuclei of the decay parent in the spontaneous fission source, is the spontaneous fission branching ratio of the decay parent.

[0063] By combining Formula 1 with Formula 4, we can obtain the relationship between t1 and the sum of the first nuclide, the second nuclide, or the third nuclide produced by the spontaneous fission of the decay products of one nuclide in the spontaneous fission source.

[0064] It should be explained that the decay products of the nuclides in the spontaneous fission source still exist in all the decay products produced by the decay of the nuclides in the spontaneous fission source from the initial moment to the current moment. One decay product only includes one nuclide and cannot include multiple nuclides.

[0065] It is understandable that if a nuclide can decay continuously, the relationship between the activity of the sum of any decay daughters of the nuclide in the spontaneous fission source and t1 can be obtained using Formula 4. For example, 252 Cf will decay to produce 248 Cm, 248 Cm will decay to produce 244 Pu, can be obtained by using formula 4 in the spontaneous fission source. 252 Cf produced 244 The relationship between the activity of the total Pu and t1. Specifically, first use formula 4 to obtain the spontaneous fission source composed of 252 Cf decay produces 248 The relationship between the total activity of Cm and t1, and then use formula 4 to obtain the spontaneous fission source 252 Cf decay produces 248 Cm decay 244 The relationship between the total activity of Pu and t1 can be expressed as follows:

[0066]

[0067] Where N Cm248 (t1) is the spontaneous fission source 252 Cf decay produces 248 The number of Cm nuclei, For spontaneous fission sources 252 Cf decay produces 244 The number of Pu nuclei, N Cf252 (t1), is the spontaneous fission source 252 The number of nuclei of Cf, λ Cf252 for 252 Decay constant of Cf, λ Cm248 for 248 Decay constant of Cm, λ Pu244 for 244 The decay constant of Pu, S Cf252 for 252 Spontaneous fission branching ratio of Cf, S Cm248 for 248Spontaneous fission branching ratio of Cm.

[0068] In addition, in Formula 5,

[0069]

[0070] Where N Cf252 (0) is the spontaneous fission source at the initial moment 252 The number of nuclei of Cf.

[0071] Furthermore, in some optional embodiments of the present application, the method for estimating the age of the spontaneous fission source further includes: obtaining the radioactivity A of the sum of the second nuclides in the spontaneous fission source. 12 According to A 21 The relationship between t1 and A 21 =A 11 , calculate t1, as: According to A 21 The relationship between t1 and the sum of the radioactivity A of the second nuclides produced by the spontaneous fission of at least one nuclide in the spontaneous fission source 22 The relationship between t1 and A 21 =A 11 , A 22 =A 12 , calculate t1. That is, please refer to Figure 2 In this embodiment, the method for estimating the age of the spontaneous fission source includes:

[0072] Step S201, obtain A 11 With A 12 ;

[0073] Step S202, according to A 21 The relationship between t1 and A 22 The relationship between t1 and A 21 =A 11 , A 22 =A 12 , calculate t1.

[0074] In the process of estimating the age of a spontaneous fission source, the amount of the main element in the age of the spontaneous fission source at the initial moment is usually unknown, so it may be difficult to directly calculate using Formula 3. However, a variety of fission products will be produced during the spontaneous fission of the main element, and the relationship between the activities of the various spontaneous fission products of the main element in the age of the spontaneous fission source and the age of the spontaneous fission source can be combined, so that the age of the spontaneous fission source can be estimated without obtaining the amount of the main element in the spontaneous fission source at the initial moment.

[0075] A can be converted into 21 The relationship between t1 and A 22In some optional embodiments of the present application, according to A 21 The relationship between t1 and A 22 The relationship between t1 and A 21 =A 11 , A 22 =A 12 , calculate t1 as: calculate A 11 With A 12 The ratio R1 between them, calculate A 21 With A 22 The ratio R2 between them, according to the relationship between R2 and t1, and let R2 = R1, calculate t1, that is, please refer to Figure 3 In this embodiment, the method for estimating the age of the spontaneous fission source includes:

[0076] Step S301, obtain A 11 With A 12 ;

[0077] Step S302, calculate A 11 With A 12 The ratio R1 between them, calculate A 21 With A 22 The ratio between them is R2;

[0078] Step S303, according to the relationship between R2 and t1, and setting R2=R1, calculate t1.

[0079] So, calculate A 21 With A 22 In the process of calculating the ratio R2 between them, the amount of main elements in the age of spontaneous fission source at the initial moment will be reduced, that is, R2 is determined, t1 can be determined, so the age of spontaneous fission source can be estimated without obtaining the amount of main elements in the age of spontaneous fission source at the initial moment.

[0080] It is understandable that Formula A 21 The relationship between t1 and A 22 The relationship between and t1 can be obtained using Formula 1.

[0081] In some optional embodiments of the present application, any one of the at least one nuclide has a long-lived fission product of the same type as the first nuclide, and any one of the at least one nuclide has a short-lived fission product of the same type as the second nuclide. In this way, by combining the relationship between the activity of the long-lived fission product and the age of the spontaneous fission source, and the relationship between the activity of the short-lived fission product and the age of the spontaneous fission source, the age can be estimated without knowing the initial activity of the main elements in the spontaneous fission source, and the estimated result is relatively accurate. Exemplarily, if the estimation is performed by calculating R2, the first nuclide is a long-lived fission product, and the second nuclide is a short-lived fission product, the calculated R2 will have a linear relationship with t1, and R2 is more sensitive to changes in t1, which is conducive to making the calculation result accurate.

[0082] On this basis, in some optional embodiments, if Formula 1 is used to obtain the radioactivity of the sum of the second nuclides produced by spontaneous fission of any one of at least one nuclide in the spontaneous fission source, The relationship between t1 and

[0083] Formula 1 can be simplified to the following form:

[0084]

[0085] In some optional embodiments of the present application, the method for estimating the age of a spontaneous fission source further includes: obtaining the radioactivity A of the sum of the third nuclides in the spontaneous fission source. 13 According to A 21 The relationship between the second estimated age value t2 of the spontaneous fission source and the radioactivity A of the sum of the third nuclides produced by the spontaneous fission of at least one nuclide in the spontaneous fission source 23 The relationship between t2 and A 21 =A 11 , A 23 =A 13 , calculate t2; calculate the average of t1 and t2; wherein any one of at least one of the nuclides has a fission product of the same type as the third nuclide, that is, please refer to Figure 4 In this embodiment, the method for estimating the age of the spontaneous fission source includes:

[0086] Step S401, obtain A 11 , A 12 With A 13 ;

[0087] Step S402: According to A 21 The relationship between t1 and A 22 The relationship between t1 and A21 =A 11 , A 22 =A 12 , calculate t1; according to A 21 The relationship between t2 and A 23 The relationship between t2 and A 21 =A 11 , A 23 =A 13 , calculate t2;

[0088] Step S403, calculating the average value of t1 and t2.

[0089] In this way, multiple estimated age values ​​of the spontaneous fission source are obtained by using multiple nuclides produced by spontaneous fission of at least one nuclide in the spontaneous fission source, and the average value of the multiple estimated age values ​​is calculated, which is conducive to making the estimation of the age of the spontaneous fission source more accurate.

[0090] Furthermore, obtaining A 11 With A 12 There are many methods, for example, it can be an absolute measurement method of radioactivity or a relative measurement method of radioactivity. In some optional embodiments of the present application, the peak net count rate of the characteristic γ energy peak of the nuclide to be measured with the energy E is obtained by using the gamma energy spectrum to obtain A 11 With A 12 .

[0091] In some optional embodiments of the present application, the main nuclide is 252 Cf, the first nuclide is 137 Cs. Experiments have shown that selecting this nuclide as the first nuclide for age estimation is more accurate. On this basis, in some optional implementations of this application, please refer to Figure 5 , get A 11 include:

[0092] Step S501, determining the spontaneous fission source 137 The peak net count rate I(E1) of the characteristic γ energy peak of Cs with an energy of 661.66keV;

[0093] Step S502, use A 11 Calculate the relationship between A and I(E1) 11 .

[0094] Among them, A 11 The relationship between it and I(E1) is:

[0095] I(E1)=A 11 ×Br(E1)×η(E1)

[0096] Where η(E1) is the spontaneous fission source 137 The detection efficiency of the full energy peak of Cs with an energy of 661.66 keV, Br(E1) in the spontaneous fission source 137 The energy of Cs is 661.66keV, which is the branching ratio of the characteristic γ energy peak.

[0097] In some optional embodiments of the present application, the second nuclide is 132 I. On this basis, in some optional implementations of this application, please refer to Figure 6 , get A 12 include:

[0098] Step S601, determining the spontaneous fission source 132 The energy of I is the peak net count rate of the characteristic γ energy peak of 667.72keV I(E2);

[0099] Step S602, use A 12 Calculate the relationship between A and I(E2) 12 .

[0100] Among them, A 12 The relationship between it and I(E2) is:

[0101] I(E2)=A 12 ×Br(E2)×η(E2)

[0102] Where η(E2) is the spontaneous fission source 132 The detection efficiency of the full energy peak of I with an energy of 667.72 keV, Br(E2) in the spontaneous fission source 132 The energy of I is the branching ratio of the characteristic γ energy peak at 667.72 keV.

[0103] In this way, the spontaneous fission source does not need to be destroyed to determine I(E1) and I(E2), and the spontaneous fission source can continue to be used, and the whole acquisition of A can be achieved. 11 With A 12 The process is relatively simple, efficient and easy to operate.

[0104] The following is an elaboration of the method for estimating the age of a spontaneous fission source provided by the present application in conjunction with a specific embodiment. The spontaneous fission source is 252 Cf source, 252 Impurities in Cf source include 250 Cf, please refer to Figure 7 ,Should 252 The estimation method of Cf source age mainly includes the following steps:

[0105] Step S701, select 137The peak net count rate of the characteristic γ energy peak of Cs with an energy of 661.66 keV is 132 The peak net count rate of the characteristic γ energy peak with energy of 667.72keV is taken as the parameter to be measured;

[0106] Step S702, setting a high energy germanium detector according to the selected parameters to be measured;

[0107] Step S703, performing energy calibration, efficiency calibration and background measurement on the high energy germanium detector;

[0108] Step S704: 252 The Cf source is placed at a preset position on the center line of the high-energy germanium detector, and then gamma spectrum measurement in the range of 0 to 2.6 MeV is performed;

[0109] Step S705, calculate the obtained measured parameter mathematical model 252 Age of the Cf source.

[0110] The mathematical model is as follows:

[0111]

[0112] Where R is the measured 137 The peak net count rate of the characteristic γ energy peak of Cs with an energy of 661.66keV is similar to the measured 132 The energy of I is the ratio of the peak net count rate of the characteristic γ energy peak of 667.72 keV, I Cf252 (y1), I Cf250 (y1), I Cm248 (y1), I Cm246 (y1) and I Pu244 (y1) are produced by spontaneous fission of various nuclides 137 The time expression of the peak net count rate of the characteristic gamma energy peak of Cs with an energy of 661.66keV, multiple nuclides including 252 Cf 250 Cf 252 Cf decay produces 248 Cm, 250 Cf decay produces 246 Cm and 252 Cf decay produces 244 Pu. I Cf252 (y2), I Cf250 (y2), I Cm248 (y2), I Cm246 (y2) and I Pu244 (y2) are produced by spontaneous fission of various nuclides 132 The time expression of the peak net count rate of the characteristic gamma energy peak of I with an energy of 667.72keV, multiple nuclides including252 Cf 250 Cf 252 Cf decay produces 248 Cm, 250 Cf decay produces 246 Cm and 252 Cf decay produces 244 Pu.

[0113] The final estimated 252 The age of the Cf source is 25.7 years, and the certified age of the neutron source is 26.2 years, and the estimated results are relatively accurate.

[0114] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for estimating the age of a spontaneous fission source, characterized in that: include: Obtaining the total radioactivity A of the first nuclide in the spontaneous fission source 11 ; According to the radioactivity A of the sum of the first nuclides produced by spontaneous fission of at least one nuclide in the spontaneous fission source 21 and the first estimated age value t1 of the spontaneous fission source, and let A 21 =A 11 , calculate t1; wherein the at least one nuclide comprises a major nuclide of the spontaneous fission source; The radioactivity of the sum of the fission products produced by the spontaneous fission of any one of the at least one nuclides in the spontaneous fission source The relationship between it and t1 is: In the formula, is the decay constant of the fission parent of this fission product, is the radioactivity of the total fission precursor in the spontaneous fission source, is the spontaneous fission branching ratio of the fission matrix, is the cumulative yield of such fission product; is the decay constant of the fission product; Obtaining the total radioactivity A of the second nuclide in the spontaneous fission source 12 ; According to A 21 The relationship between t1 and A 21 =A 11 , calculate t1, as: According to A 21 The relationship between t1 and the radioactivity A of the sum of the second nuclides produced by the spontaneous fission of the at least one nuclide in the spontaneous fission source 22 The relationship between t1 and A 21 =A 11 , A 22 =A 12 , calculate t1; According to A 21 The relationship between t1 and A 22 The relationship between t1 and A 21 =A 11 , A 22 =A 12 , calculate t1 as: calculate A 11 With A 12 The ratio R1 between them, calculate A 21 With A 22 The ratio R2 between them, according to the relationship between R2 and t1, and let R 2＝ R1, calculate t1.

2. The method for estimating the age of a spontaneous fission source according to claim 1, characterized in that: The at least one nuclide further comprises at least one decay product of the nuclide in the spontaneous fission source, the radioactivity of the total of the decay products being The relationship with t1 is: In the formula, is the number of nuclei that are the sum of one decay product, is the decay constant of the decay product, is the decay constant of the decay parent of this decay product, The number of atomic nuclei of the decay parent in the spontaneous fission source, is the spontaneous fission branching ratio of the decay parent.

3. The method for estimating the age of a spontaneous fission source according to claim 1, characterized in that: Any one of the at least one nuclide has a long-lived fission product of the same type as the first nuclide, and any one of the at least one nuclide has a short-lived fission product of the same type as the second nuclide.

4. The method for estimating the age of a spontaneous fission source according to claim 1, characterized in that: Also includes: Obtain the total radioactivity A of the third nuclide in the spontaneous fission source 13 ; According to A 21 and the relationship between the second estimated age value t2 of the spontaneous fission source and the radioactivity A of the sum of the third nuclides produced by the spontaneous fission of the at least one nuclide in the spontaneous fission source. 23 The relationship between t2 and A 21 =A 11 , A 23 =A 13 , calculate t2; Calculate the average of t1 and t2.

5. The method for estimating the age of a spontaneous fission source according to any one of claims 1 to 4, characterized in that: The main nuclides are 252 Cf, the first nuclide is 137 Cs.

6. The method for estimating the age of a spontaneous fission source according to claim 5, characterized in that: The acquisition A 11 include: Determine the spontaneous fission source 137 The peak net count rate I(E1) of the characteristic γ energy peak of Cs with an energy of 661.66keV; Use A 11 Calculate the relationship between A and I(E1) 11 ; Among them, A 11 The relationship between it and I(E1) is: I(E1)=A 11 ×Br(E1)×η(E1) Wherein, η(E1) is the spontaneous fission source 137 The energy of Cs is 661.66 keV, and the detection efficiency of Br(E1) is the total energy peak of the spontaneous fission source. 137 The energy of Cs is 661.66keV, which is the branching ratio of the characteristic γ energy peak.

7. The method for estimating the age of a spontaneous fission source according to claim 5, characterized in that: The second nuclide is 132 I.

8. The method for estimating the age of a spontaneous fission source according to claim 7, characterized in that: The acquisition A 12 include: Determine the spontaneous fission source 132 The energy of I is the peak net count rate of the characteristic γ energy peak of 667.72keV I(E2); Use A 12 Calculate the relationship between A and I(E2) 12 ; Among them, A 12 The relationship between it and I(E2) is: I(E2)=A 12 ×Br(E2)×η(E2) Wherein, η(E2) is the spontaneous fission source 132 The energy of I is 667.72 keV, and Br(E2) is the detection efficiency of the total energy peak in the spontaneous fission source. 132 The energy of I is the branching ratio of the characteristic γ energy peak at 667.72 keV.

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