CN117912740A - 一种用于核军控核查的中子源慢化装置 - Google Patents

一种用于核军控核查的中子源慢化装置 Download PDF

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CN117912740A
CN117912740A CN202410064283.XA CN202410064283A CN117912740A CN 117912740 A CN117912740 A CN 117912740A CN 202410064283 A CN202410064283 A CN 202410064283A CN 117912740 A CN117912740 A CN 117912740A
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何小锁
何庆华
戴耀东
窦小敏
王翔宇
夏李倩
毛钰丰
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Nanjing University of Aeronautics and Astronautics
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    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21KTECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01TMEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/29Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01TMEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/36Measuring spectral distribution of X-rays or of nuclear radiation spectrometry
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01TMEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T7/00Details of radiation-measuring instruments
    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21KTECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/10Scattering devices; Absorbing devices; Ionising radiation filters

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Abstract

本发明提供一种基于加速器中子源的中子慢化装置,应用于核军控核查。装置包括三个部分:慢化层、中子吸收层及伽马射线屏蔽层。该装置中的慢化层由半径为5cm、厚度为6cm的高密度聚乙烯和半径为5cm、厚度为1cm的金属铅两种材料相间构成,够有效地慢化快中子。中子吸收层由长35cm、内半径5cm、外半径105cm的圆筒构成,选择5%含B聚乙烯作为中子吸收材料。在慢化装置的最外层包裹了厚度为10cm的伽马射线屏蔽层,采用金属铅作为伽马射线屏蔽材料,屏蔽吸收层完全满足本发明中的射线防护要求。在基于中子活化分析的军控条约核查领域中,该中子慢化装置能够提供一种能量匹配、产额适中、束流均匀的中子源,能够高效完成军控条约项目的射线检测任务。

Description

一种用于核军控核查的中子源慢化装置
技术领域:
本发明涉及射线检测领域,具体为一种用于核军控核查的中子源慢化装置。
背景技术:
中子活化分析作为射线检测的一种重要方法,具备灵敏度高、准确性好等优点,广泛应用于工业生产等领域中。传统理论研究表明,结合特定的加密方法,中子活化分析能够高效完成军控条约项目的核查,但是较低能量(~0.025eV)的优质中子束流难以获取,导致基于中子活化分析的军控核查难以在实验上重现。故本发明提出一种可用于基于中子活化分析的军控核查的中子源慢化装置,该装置能提供相应能量、产额适中、束流均匀、安全的热中子束流,完全满足基于中子活化分析的军控核查需求。
发明内容:
为了提供一种可用于基于中子活化分析的核军控核查的热中子源,本发明设计了一种中子源慢化装置,可提供符合要求的优质中子束流。该慢化装置在基于7Li(d,n)7Be核反应的加速器中子源的基础上设计,上述核反应可产生0.12MeV的单能中子,有利于军控所需热中子的获取。发明所提出的慢化装置如图1所示,具体包括慢化层、中子吸收层以及伽马射线屏蔽层。
慢化层由半径为5cm、厚度为6cm的高密度聚乙烯和半径为5cm、厚度为1cm的材料铅组成,如图1最内层所示,其具体由三部分组成:1cm厚的高密度聚乙烯,1cm厚的铅以及5cm厚的高密度聚乙烯依次紧密排列。金属铅具有较大的[n,n],[n,n’]以及[n,2n]反应截面,能够将快中子降到1MeV以下,并有一定的增值作用,考虑到0.12MeV的中子入射能量,采用1cm厚度的铅较为合适。能量在1MeV以下的中子与物质主要发生弹性散射,氢核为最有效的减速材料,而高密度聚乙烯是慢化几个MeV中子的最佳材料,在本发明中6cm厚的高密度聚乙烯有助于增大所需热中子的产额。因此,本发明采用金属铅和高密度聚乙烯组合的结构慢化基于加速器中子源的中子。
因为B元素对热中子的俘获截面高于氢元素,而5%含B聚乙烯的吸收效果较好,所以中子吸收层材料选择掺5%B元素的聚乙烯,中子吸收层的几何形状是内半径为5cm、外半径为105cm、长度为35cm的圆筒,100cm的厚度在本发明中完全满足中子屏蔽要求。在该中子源慢化装置的最外层是厚度为10cm、长度为35cm的伽马射线屏蔽层,采取最常见的铅作为屏蔽材料,经论证10cm厚的铅材料在本发明中能够满足防护要求。
借助蒙卡工具Geant4,以一次发射1×108粒子为例,我们对比了本发明中金属铅和高密度聚乙烯相间的慢化层和单纯6cm厚度的高密度聚乙烯这两种结构,结果如表1所示。
慢化层结构 能峰总占比 低高能积分比 低能峰值位置(eV)
6cm厚高密度聚乙烯 66.42% 3.96∶1 0.0238
6cm厚高密度聚乙烯+1cm厚铅 66.19% 4.69∶1 0.0273
表1不同结构慢化层的慢化效果
从表1可以看出,两种慢化结构的能峰总占比以及低能中子峰值位置相当,但是金属铅和高密度聚乙烯相间结构的慢化层慢化的低能中子占比更多,慢化效果更好。此外,图2展示了本发明提出的中子源慢化装置的慢化后能谱。
附图说明:
附图用来提供对本发明的进一步理解,并构成说明书的一部分,用于解释本发明,并不构成对本发明的限制。
图1为用于军控核查的中子源慢化装置。
图2为用于军控核查的中子源慢化装置慢化能谱。
具体实施方式:
本发明为解决基于中子活化分析的核军控核查技术的切实需求,提出了一种中子源慢化装置,其具体实施方案如下:
1.选取一个基于7Li(d,n)7Be核反应的加速器中子源,将其发射角度以及位置与本发明提出的慢化装置的入射孔匹配,使其在入射孔范围内均匀发射中子。
2.将被测项目放置在慢化装置出射孔的方向上,使其接受慢化中子的辐照检测。
3.核查双方使用可信的设备在慢化装置出射孔来监测慢化后中子的通量,在达到事先商定好的时间后,停止测量,并分析收集的特征伽马信息,以鉴定核武器的真实性。

Claims (1)

1.一种用于核军控核查的中子源慢化装置,其特征在于:装置包括三个部分:慢化层、中子吸收层以及伽马射线屏蔽层;所述慢化层位于装置的最内侧,由半径为5cm、厚度为6cm的高密度聚乙烯和半径为5cm、厚度为1cm的材料铅组成,其具体由三部分组成:1cm厚的高密度聚乙烯,1cm厚的铅以及5cm厚的高密度聚乙烯依次紧密排列;所述中子吸收层材料选择掺5%B元素的聚乙烯,位于装置的中层,中子吸收层的几何形状是内半径为5cm、外半径为105cm、长度为35cm的圆筒,厚度为100cm;所述的伽马射线屏蔽层在该中子源慢化装置的最外层,厚度为10cm、长度为35cm,采取铅作为屏蔽材料。
CN202410064283.XA 2024-01-16 2024-01-16 一种用于核军控核查的中子源慢化装置 Pending CN117912740A (zh)

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