阅读说明：本技术 扣除其它核反应生成物对目标核反应截面测量影响的方法 (Method for deducting influence of other nuclear reaction products on measurement of target nuclear reaction cross section ) 是由 周丰群 宋月丽 李勇 袁书卿 于 2020-12-30 设计创作，主要内容包括：本发明提供一种扣除其它核反应生成物对目标核反应截面测量影响的方法。在核反应截面测量中,如果其它核反应产物的半衰期远大于目标核反应产物的半衰期,则可用以下方法扣除其它反应产物对目标核反应截面测量的影响：对目标核反应的特征伽马射线测量两次,第一次测量不同反应产物衰变到目标反应产物的伽马射线全能峰面积C-(11)与第二次测量的伽马射线全能峰面积C-(12)的关系为在用核反应截面一般计算公式测量目标核反应截面时,其中的伽马射线全能峰面积C-x应为第一次实测的目标核反应产物的伽马射线全能峰面积减去C-(11),而C-(11)可由与C-(12)的上述关系式得到。(The invention provides a method for deducting the influence of other nuclear reaction products on the measurement of a target nuclear reaction section. In the nuclear reaction cross-section measurement, if the half-life of other nuclear reaction products is much greater than that of the target nuclear reaction product, the influence of the other reaction products on the target nuclear reaction cross-section measurement can be deducted by the following method: measuring the characteristic gamma ray of target nuclear reaction twice, measuring the gamma ray full energy peak area C of different reaction products decaying to target reaction product for the first time 11 With the second measurement of the gamma ray total energy peak area C 12 In a relationship of General calculation formula of nuclear reaction section When measuring the nuclear reaction cross section of the target, the gamma ray all-round peak area C therein x Should be the first measurementC minus the gamma ray energy peak area of the target nuclear reaction product 11 And C is 11 Can be formed by 12 The above-mentioned relational expression of (a) is obtained.)

1. A method for deducting the influence of other nuclear reaction products on the measurement of a target nuclear reaction section is characterized in that: in the actual nuclear reaction section measurement, a general calculation formula based on the nuclear reaction section is usedWhen the nuclear reaction section to be researched is measured and calculated, if the half-life period of other different nuclear reaction products is far larger than that of the target nuclear reaction product, the influence of the other different nuclear reaction products on the nuclear reaction product to be tested can be deducted by the following method: measuring the characteristic gamma ray of the target nuclear reaction twice, wherein the first measurement is scheduled to be carried out in a time period that the cooling time of the sample is less than 7 times of the half-life period of the target nuclear reaction product; the second measurement is arranged at a sample cooling time greater than the target nuclear reactionAfter 7 times the half-life of the product, the total energy peak area C of the characteristic gamma ray from other different reaction products decaying to the target reaction product is measured twice₁₁And C₁₂The relationship of (a) to (b) is as follows:

in which the subscripts "q" and "m" denote the value corresponding to the target nuclear reaction and the values corresponding to the other different nuclear reactions, respectively, lambda_qIs the decay constant of the target nuclear reaction product,growth factor, T, being a product of a targeted nuclear reaction₁The total irradiation time is the sum of the irradiation times,for measuring the collection factor, T_2qAnd T_3qRespectively the cooling time and the measuring time of the sample before the characteristic gamma ray of the target nuclear reaction product is measured,a neutron fluence rate fluctuation correction factor for the targeted nuclear reaction, n being the number of segments into which the irradiation time is divided, T_iIs the ith time interval, t_iFor the time interval between the end of the i-th segment and the end of the total irradiation, phi_iIs at T_iAverage neutron flux incident on the sample over time, phi being at T₁Average neutron flux, λ, incident on the sample over the total irradiation time_m，Respectively, the meaning of the corresponding amount of other different nuclear reaction products, T_3q1is the first measurement of time and T_2q1Is the cooling time; t is_3q2Is the second measurement time and T_2q2Is the cooling time.

2. The method of claim 1 for subtracting the effect of other nuclear reaction products on the measurement of the cross-section of the target nuclear reaction, wherein: in the actual measurement of nuclear reaction section, the general calculation formula of nuclear reaction section is usedWhen measuring and calculating the reaction cross section of the target nucleus, C in the formula_xThe first measurement should be taken of the total energy peak area of the gamma ray characteristic of the target nuclear reaction product minus C₁₁And C is₁₁Can be formed by₁₂Is a relational expression ofThus obtaining the product.

Technical Field

The invention belongs to the technical field of nuclear energy development, and particularly relates to a method for deducting the influence of other nuclear reaction products on the measurement of a target nuclear reaction section.

Background

With the continuous development of national defense construction and nuclear energy application in new period, nuclear technology development represented by the research and development of a new generation of nuclear energy system and nuclear device puts higher-level requirements on the quality, quantity, variety and the like of nuclear data. The accurate and reliable nuclear reaction section experimental value has very important significance for verifying the accuracy of a nuclear theoretical model for calculating the nuclear reaction section, the application of nuclear technology, the development and the utilization of nuclear energy and the like. In the actual measurement of the nuclear reaction cross section, many problems need to be reasonably solved to obtain accurate and reliable experimental values of the nuclear reaction cross section, such as medium wave dynamic correction, self-absorption correction of gamma rays in a sample, coincidence addition effect correction of cascade gamma rays, geometric correction of the sample, mutual influence of gamma rays with similar energy, influence of excited state of generated nuclei on ground state, mutual influence of all possible nuclear reactions and the like.

The problem of interaction of all possible nuclear reactions can be solved by isotopic separation enrichment or by cooling the sample for different times after it has been irradiated, depending on the half-life of the nuclei produced. However, in the case where an isotope separation enrichment method is not available and a natural sample containing a plurality of stable isotopes is used in an experiment, it is sometimes difficult to avoid the influence of decay of other different nuclear reaction products on the measurement of the reaction cross section of the target nucleus. For example, in the above case, the objective nuclear reaction shown in FIG. 1⁹¹Zr(n,p)^91mY will be subject to reactions from other differences⁹⁴Zr(n,a)⁹¹Sr (strontium) products⁹¹Sr decays to^91mThe influence of Y. In this case, in order to obtain accuracy and reliability⁹¹Zr(n,p)^91mExperimental cross-section values of Y-nuclear reactions, other different nuclear reactions⁹⁴Zr(n,a)⁹¹Product of Sr⁹¹Sr decays to^91mY, thus reacting to the target nucleus⁹¹Zr(n,p)^91mThe cross-sectional measurement effect of Y must be subtracted or otherwise cause large errors. However, up to now, for deducting different nuclear reactantsThe method of influence of decay on measurement of target nuclear reaction cross section is only disclosed in the literature [1-2]]Mention is made of and a formula for subtracting the effect is given. However, the formula given is limited to solving the situation when the branching ratio of the other different nuclear reaction products decaying to the target nuclear reaction product is known and the cross section of the other different nuclear reactions is known. Under the condition that other different nuclear reaction product decay branch ratios are unknown, a method for deducting the influence of different nuclear reaction product decays on the measurement of a target nuclear reaction section is not reported so far. The invention provides a method for deducting the influence of decay of other different nuclear reaction products on measurement of a target nuclear reaction section under the condition that the total branching ratio of the other different nuclear reaction products to decay to the target nuclear reaction product is unknown (or known), and the half-life periods of the other different nuclear reaction products are far larger than that of the target reaction product, and the method can be widely applied to solving the problem that the influence of decay of the other different nuclear reaction products on measurement of the target nuclear reaction section is deducted under the condition in the nuclear reaction section measurement.

[1]Junhua Luo,FeiTuo,Xiangzhong Kong,Rong Liu,and Li Jiang,Measurements of activation cross-sections for the ⁹⁶Ru(n,d*)^95gTc reaction for neutrons with energies between 13.3and 15.0MeV.Appl.Radiat.Isot.

66,1920-1924(2008)。

[2]Junhua Luo,Jiuning Han,FeiTuo,Xiangzhong Kong,Rong Liu,and Li Jiang，Cross-sections for formation of ^99mTc through ^natRu(n,x)^99mTc reaction induced by neutrons at 13.5and 14.8MeV.Radiat.Phys.Chem.81,495-498(2012)。

Disclosure of Invention

The invention aims to provide a method for deducting the influence of other nuclear reaction products on the measurement of a target nuclear reaction cross section against the defects of the prior art, and the specific scheme is as follows:

a method for deducting the influence of other nuclear reaction products on the measurement of target nuclear reaction cross section features that in the actual measurement of nuclear reaction cross section, the general calculation formula of nuclear reaction cross section is usedWhen the nuclear reaction section to be researched is measured and calculated, if the half-life period of other different nuclear reaction products is far larger than that of the target nuclear reaction product, the influence of the other different nuclear reaction products on the nuclear reaction product to be tested can be deducted by the following method: measuring the characteristic gamma ray of the target nuclear reaction twice, wherein the first measurement is scheduled to be carried out in a time period that the cooling time of the sample is less than 7 times of the half-life period of the target nuclear reaction product; the second measurement is carried out after the sample is cooled for a time longer than 7 times of the half-life of the target nuclear reaction product, and the total energy peak area C of the characteristic gamma ray decayed to the target reaction product from other different reaction products is measured twice₁₁And C₁₂The relationship of (a) to (b) is as follows:

in which the subscripts "q" and "m" denote the value corresponding to the target nuclear reaction and the values corresponding to the other different nuclear reactions, respectively, lambda_qIs the decay constant of the target nuclear reaction product,growth factor, T, being a product of a targeted nuclear reaction₁The total irradiation time is the sum of the irradiation times,for measuring the collection factor, T_2qAnd T_3qRespectively the cooling time and the measuring time of the sample before the characteristic gamma ray of the target nuclear reaction product is measured,a neutron fluence rate fluctuation correction factor for the targeted nuclear reaction, n being the number of segments into which the irradiation time is divided, T_iIs the ith time interval, t_iFor the time interval between the end of the i-th segment and the end of the total irradiation, phi_iIs at T_iAverage neutron flux incident on the sample over time, phi being at T₁Incident on the sample for the total irradiation timeAverage neutron flux, λ_m，Respectively, the meaning of the corresponding amount of other different nuclear reaction products, T_3q1is the first measurement of time and T_2q1Is the cooling time; t is_3q2Is the second measurement time and T_2q2Is the cooling time.

Based on the above, in the actual measurement of the nuclear reaction cross section, the general calculation formula of the nuclear reaction cross section is usedWhen measuring and calculating the reaction cross section of the target nucleus, C in the formula_xThe first measurement should be taken of the total energy peak area of the gamma ray characteristic of the target nuclear reaction product minus C₁₁And C is₁₁Can be formed by₁₂Is a relational expression ofThus obtaining the product.

Compared with the prior art, the invention has outstanding substantive characteristics and remarkable progress, and particularly has the following advantages:

1. the method provided by the invention can be suitable for deducting the influence of other different reaction products on the nuclear reaction product to be detected no matter the total branching ratio of the other different reaction products decayed to the target reaction product is known or unknown if the half-life period of the other different nuclear reaction products is far larger than that of the target nuclear reaction product. (the methods mentioned in the references [1-2] are applicable only to cases where the total branching ratio of other different reaction products to decay to the target reaction product is known)

2. The proposed method only requires that the half-life of the other different nuclear reaction products is much larger than the half-life of the target reaction product, and does not require that the cross-section of the other different nuclear reactions be known.

Drawings

FIG. 1 is a view of the background art of the present invention⁹¹Sr and⁹¹simplified decay schematic for Y.

Detailed Description

The technical solution of the present invention is further described in detail by the following embodiments.

Examples

As shown in FIG. 1, the present invention provides a method for deducting the influence of other nuclear reaction products on the measurement of a target nuclear reaction cross section, and the general calculation formula based on the measurement of the nuclear reaction cross section by a relative method is as follows:

subscripts 'x' and '0' in the formula (1) respectively represent values of a sample to be measured and a monitoring sheet, wherein epsilon is the full energy peak efficiency of the measured characteristic gamma ray; i is_γIs the intensity of the characteristic gamma ray; eta is the natural abundance of the nuclide to be detected; m is the sample mass;collecting factors (t) for measurement₁Is the time interval from the end of the irradiation to the start of the measurement, t₂Is the time interval from the end of irradiation to the end of measurement); a is the atomic weight of the sample element; c is the measured characteristic gamma ray all-around peak area of the target nuclear reaction product; λ is the decay constant; f is the total gamma ray activity correction factor: f ═ F_s×f_c×f_gWherein f is_s、f_c、f_gSelf-absorption correction factors, cascade gamma ray coincidence effect correction factors and geometric correction factors of gamma rays in a sample are respectively; k is a neutron fluence rate fluctuation correction factor and has an expression ofWhere L is the number of segments into which the irradiation time is divided, Δ t_iIs the time interval of the i-th segment,_Tithe time interval from the end of the ith section to the end of all irradiation; phi_iIs at Δ t_iAverage neutron flux incident on the sample over time, [ phi ] is the average neutron flux incident on the sample over time T (total exposure time), and S-1-e^-λTIndicating the growth factor of the remaining nuclei.

As described in the background, in the actual measurement of nuclear reaction cross section, if the isotope separation enrichment method is not available and a natural sample containing a plurality of stable isotopes is used in the experiment, the influence of decay of other different nuclear reaction products on the measurement of the nuclear reaction cross section of the target is often encountered, as in the example of FIG. 1, described above⁹¹Zr(n,p)^91mY will be subject to reactions from other differences⁹⁴Zr(n,a)⁹¹Product of Sr⁹¹Sr decays to^91mThe influence of Y. In this regard, if the half-life of the other different nuclear reaction products is much greater than the half-life of the target nuclear reaction product, the effect of the other different nuclear reaction products on the nuclear reaction product can be subtracted by the following method, and the gamma ray characteristic of the target nuclear reaction can be measured twice: the first measurement is scheduled to be made in less than 7 times the half-life of the target nuclear reaction product (if there is no other reason, the earlier the first measurement is, the better); the second measurement is scheduled to be taken after the sample has been cooled for a time greater than 7 times the half-life of the target nuclear reaction product (the later the second measurement is, the better if the counting statistics allow); the first measurement of the total energy peak area C of the characteristic gamma rays from other different reaction products decaying to the target reaction product₁₁The full energy peak area C of the gamma ray which is characteristic of decaying from other different reaction products to the target reaction product is measured for the second time₁₂The relationship of (a) to (b) is as follows:

in formula (2), the subscripts "q" and "m' represents the value corresponding to the target nuclear reaction and the values corresponding to other different nuclear reactions, lambda_qIs the decay constant of the target nuclear reaction product,growth factor, T, being a product of a targeted nuclear reaction₁The total irradiation time is the sum of the irradiation times,for measuring the collection factor, T_2qAnd T_3qRespectively the cooling time and the measuring time of the sample before the characteristic gamma ray of the target nuclear reaction product is measured,a neutron fluence rate fluctuation correction factor for the targeted nuclear reaction, n being the number of segments into which the irradiation time is divided, T_iIs the ith time interval, t_iFor the time interval between the end of the i-th segment and the end of the total irradiation, phi_iIs at T_iAverage neutron flux incident on the sample over time, phi being at T₁Average neutron flux, λ, incident on the sample over the total irradiation time_m，Respectively, the meaning of the corresponding amount of other different nuclear reaction products, T_3q1is the first measurement of time and T_2q1Is the cooling time; t is_3q2Is the second measurement time and T_2q2Is the cooling time.

In the actual measurement of the nuclear reaction cross section, when the target nuclear reaction cross section is measured and calculated by the formula (1), C in the formula (1)_xShould be the firstSubtracting the total energy peak area C of the gamma ray from other different nuclear reaction products to the target reaction product from the total energy peak area C of the gamma ray characteristic of the target nuclear reaction product measured at one time₁₁And C is₁₁The total energy peak area C of the gamma ray characteristic of the target nuclear reaction product measured by the second time₁₂And formula (2).

In summary, the method of the present invention is applicable to other cases where the total branching ratio of different nuclear reaction products to decay to the target nuclear reaction product is unknown or known.

The proposed method only requires that the half-life of the other different nuclear reaction products is much larger than the half-life of the target reaction product, and does not require that the cross-section of the other different nuclear reactions be known.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.