强脉冲中子的地面感生放射性环境研究

魏铭言; 商鹏; 牛胜利; 卓俊; 左应红

doi:10.11884/HPLPB202638.250344

强脉冲中子的地面感生放射性环境研究

doi: 10.11884/HPLPB202638.250344

魏铭言^{1, 2,},
商鹏^{1, 2},
牛胜利^{1, 2},
卓俊^{1, 2, ,},
左应红^{1, 2}

1.
强脉冲辐射环境模拟与效应全国重点实验室，西安 710024
2.
西北核技术研究所，西安 710024

详细信息

作者简介:
魏铭言，weimingyan@nint.ac.cn

通讯作者:
卓　俊，zhuojun@nint.ac.cn。

中图分类号: O571;TL91
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- 文章访问数: 50
- HTML全文浏览量: 21
- PDF下载量: 13
- 被引次数: 0
出版历程
- 收稿日期: 2025-10-13
- 修回日期: 2026-02-13
- 录用日期: 2026-01-09
- 网络出版日期: 2026-03-28

Study of the Ground-Induced Radioactive Environment Caused by Intense Pulsed Neutrons

Wei Mingyan^{1, 2
,},
Shang Peng^{1, 2},
Niu Shengli^{1, 2},
Zhuo Jun^{1, 2
, ,},
Zuo Yinghong^{1, 2}

1.
National Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Xi’an 710024, China
2.
Northwest Institute of Nuclear Technology, Xi’an 710024, China

摘要

摘要: 强脉冲中子在地面产生的感生放射性γ辐射场受到源位置、地面介质组分的影响，呈现不同的分布特点，进而对人员造成不同程度的辐射危害。为评估不同场景（包括源位置与地面介质组成）下的感生放射性γ辐射环境水平，支撑强脉冲辐射环境研究与相关人员防护策略制定，基于大气分层模型，通过基于蒙卡的地面感生放射性两步计算方法计算了不同土壤条件下，感生放射性的剂量分布及典型位置剂量率随时间的变化规律，拟合给出了不同核素剂量贡献公式。通过对三种典型土壤的模拟计算，给出了核素活化系数以快速评估土壤中原子活化数，并通过单位质量剂量贡献评估了土壤中各种核素的平均剂量贡献；提出了土壤的安全驻留指数与安全驻留距离两个指标以在不同时间尺度下评价不同土壤条件下的强脉冲中子感生放射性环境的安全性。结果表明，源高度1000 m以下，剂量随源高度呈指数变化规律，且活化系数随水平投影距变化明显；单位质量Mn元素具有最高的剂量贡献，低Al土壤的土壤安全驻留指数更高，且Mn、Na元素含量高的土壤安全驻留距离更短。基于以上结果，计算了用于评价感生放射性在不同时间尺度对人员的安全影响的土壤安全指数与安全驻留距离参数，为后续差异化的安全策略提供数据支持。
- 蒙特卡罗 /
- 感生放射性 /
- 中子活化 /
- 辐射防护
Abstract: Background
The spatial distribution of the neutron-induced gamma radiation field generated within the ground medium by intense pulsed neutrons is critically dependent on the neutron source location and the chemical composition of the soil. These distributional variations give rise to differential radiological hazards for personnel.
Purpose
The objective of this study is to quantitatively assess the environmental levels of neutron-induced gamma radiation across diverse scenarios—specifically incorporating variations in neutron source location and ground medium composition—to facilitate research on intense pulsed neutron radiation environments and to inform evidence-based development of radiation protection protocols for personnel.
Methods
Based on an atmospheric stratification model, a two-step Monte Carlo simulation methodology was implemented to quantify the dose distribution of neutron-induced radioactivity within the ground medium and the temporal evolution of dose rates at representative locations across diverse soil compositions. Subsequently, empirical formulas characterizing the dose contributions of individual radionuclides were derived through curve-fitting analysis. Numerical simulations were performed for three representative soil compositions to derive nuclide-specific activation coefficients, facilitating rapid estimation of activated atom populations within the soil matrix. The average dose contributions of individual radionuclides were quantitatively evaluated based on dose contribution per unit mass. Furthermore, two novel safety metrics—the Soil Safety Residence Index and Safety Residence Distance —were proposed to systematically assess the safety of the induced radioactivity environment caused by intense pulsed neutron under varying soil conditions across multiple temporal scales.
Results
Results demonstrate that, for neutron source heights below 1000 m, the dose exhibits an exponential dependence on source altitude, while the activation coefficient shows pronounced variation with horizontal projection distance. Manganese (Mn) was identified as the element contributing the highest dose per unit mass. Soils with low aluminum (Al) content yielded a higher Soil Safety Residence Index, whereas soils enriched in manganese (Mn) and sodium (Na) exhibited shorter Safety Residence Distances, indicating elevated radiological risk under equivalent exposure conditions.
Conclusions
This study confirms that the spatial distribution and temporal evolution of the gamma radiation field generated by intense pulsed neutrons are governed by source geometry and the chemical composition of the soil medium. Manganese (Mn) is identified as the predominant radionuclide contributing to dose per unit mass, underscoring the imperative for enhanced radiological protection protocols in manganese-enriched soil environments. Moreover, the Soil Safety Residence Index and Residence Distance serve as rapid, quantitative metrics to inform appropriate radiation protection strategies for personnel across diverse soil conditions.
- Monte-Carlo /
- Induced radioactivity /
- Neutron activation /
- Radiation protection

HTML全文

图 1 地面感生放射性两步法计算流程图

Figure 1. Flow chart of two-step method for induced radioactivity on the ground

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图 2 中子输运模型示意图

Figure 2. Schematic diagram of the neutron transport model

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图 3 分层体源模型示意图

Figure 3. Diagram of layered-radiator source model

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图 4 土壤1中，总剂量与各元素剂量贡献随源高度的变化

Figure 4. Variation of total dose and contribution of each element dose with source height in soil 1

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图 5 土壤1中，活化原子数与中子注量随源高度的变化

Figure 5. Variation of activation atom number and neutron fluence with source height in Soil 1

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图 6 活化系数随源高度变化的曲线

Figure 6. Curves showing the variation of activation coefficients with source height

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图 7 土壤1中，总剂量随水平投影距的变化

Figure 7. Total dose as a function of horizontal projection distance in Soil 1

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图 8 四种元素活化系数随水平投影距的变化

Figure 8. Variation of activation coefficients of four elements with horizontal projection distance

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图 9 三种土壤中感生放射性剂量随水平投影距的变化

Figure 9. Variation of induced radioactive dose with horizontal projection distance in three soil types

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图 10 四种元素在不同水平投影距处的剂量贡献

Figure 10. Dose contributions of four elements at different horizontal projection distances

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图 11 单位质量核素在土壤中的平均剂量贡献

Figure 11. Average dose contribution per unit mass of radionuclides in soil

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图 12 源高度100m时，脉冲中子产生1h后剂量率随水平投影距的变化

Figure 12. Variation of dose rate with ground zero projection distance at 1 hour after the pulse neutron emission, for a source height of 100 m

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图 13 中子发生后各元素剂量率贡献随时间的变化

Figure 13. Variation of dose rate contributions from individual elements over time following the neutron pulse

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图 14 源高度100m，中子发生后土壤1不同水平距离处达到安全阈值所需要的时间

Figure 14. Time required for Soil 1 at different horizontal distances from the ground zero to reach the safety threshold after the neutron pulse, with a source height of 100 m

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表 1 土壤成分的核素性质

Table 1. The nuclide properties of soil components

Target nucleus element	Activated element	Atomic weight A	Abundance a/10⁻²
²⁷Al	²⁸Al	27	100
⁵⁵Mn	⁵⁶Mn	55	100
²³Na	²⁴Na	23	100
⁵⁸Fe	⁵⁹Fe	58	0.31

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表 2 土壤中核素的衰变γ射线参数^{[5, 13]}

Table 2. The decay γ-ray parameters of nuclides in soil

Nuclide	Half-life/h	Decay constantλ/h⁻¹	Energy/MeV	Yield
²⁸Al	0.038	18.3	1.78	1.000
⁵⁶Mn	2.579	0.269	1.68	1.404
²⁴Na	15.03	0.046	4.12	1.998
⁵⁹Fe	1068	6.4×10⁻⁴	1.19	0.997

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表 3 不同土壤类型的物质组分

Table 3. Composition of different soil types

soil type	composition
soil type	Mn×10⁻²	Na₂O×10⁻²	Al₂O₃×10⁻²	TFe₂O₃×10⁻²	FeO×10⁻²
Soil 1	0.092	2.67	11.70	4.22	0.78
Soil 2	0.051	0.1	16.88	9.80	0.19
Soil 3	0.19	0.1	27.39	18.03	1.46

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表 4 不同土壤类型的元素占比

Table 4. The proportion of elements in different soils

Soil Type	Element
Soil Type	Al(%)	Mn(%)	Na(%)	Fe(%)
Soil 1	6.190	0.092	1.981	3.561
Soil 2	8.936	0.051	0.074	7.007
Soil 3	14.501	0.19	0.074	13.757

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表 5 总剂量与各元素剂量贡献的系数

Table 5. Coefficients of total dose and dose contributions from individual elements

	total dose	dose contribution-Al	dose contribution-Mn	dose contribution-Na	dose contribution-Fe
a	3410.78	983.39	413.91	2009.92	3.622
b	93.92	94.03	93.04	94.06	88.30

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表 6 不同元素的活化系数参数

Table 6. Activation coefficient parameters for different elements

Index	element in soil
Index	Al	Mn	Na	Fe
A₀	3.62E-5	1.88E-5	3.07E-5	2.38E-7
λ	5.76E-5	2.46E-5	4.96E-5	2.43E-7
D	468.41	482.95	481.18	390.58

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表 7 不同土壤的安全驻留指数

Table 7. Safety indices for different soil types

	soil 1	soil 2	soil 3
soil safety residence index k	0.67	0.19	0.15

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表 8 不同土壤在不同源强度下的安全驻留距离

Table 8. Safe standoff distances for different soil types under various source intensities

source intensity	safety residence distance/m
source intensity	soil 1	soil 2	soil 3
0.3	700	600	650
1	850	750	850
1.5	950	850	900

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