﻿ 航天员受银河宇宙线辐射的剂量计算
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Calculation of the astronauts' radiation dose from galactic cosmic ray
ZHANG Binquan, YU Qinglong, LIANG Jinbao, SUN Yueqiang, YANG Chuibai, ZHANG Shenyi
National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
Abstract: Radiation risk of astronauts during the flight in low earth orbit (LEO) and deep space exploration is mainly from the exposure of galactic cosmic ray (GCR). The radiation dose from GCR is the basis for the assessment of astronauts' radiation risk. In 2013, a new estimation method for the assessment of astronauts' radiation dose was presented by the International Committee on Radiological Protection (ICRP), so as to improve the assessment's accuracy of the radiation dose from heavy ions in space. Based on this method, a Monte Carlo program was developed for simulation of the particle transportation in materials and a voxel phantom of Chinese adult male was realized in this program to represent the astronaut. With this program, the fluence to dose conversion coefficients for the organs of astronauts were calculated for the isotropic exposure by particles with the atomic number from 1 to 92. The radiation dose to astronauts in LEO from GCR was also estimated.
Key words: space radiation     galactic cosmic ray (GCR)     astronaut     radiation dose     Monte Carlo

2013年,ICRP发布了第123号出版物——《航天员空间辐射照射的评价》[6].该出版物在大量重离子生物学效应研究的基础上,提出了新的用于航天员辐射剂量计算的辐射品质因数.该因数不再仅是LET的函数,而是与辐射粒子原子序数、能量和辐射效应类型有关,更真实反映粒子辐射的生物效应.有必要研究与ICRP 123号出版物相适应的航天员辐射剂量监测评估方法.

1 模型和方法 1.1 人体数字模型

1.2 剂量计算方法

 图 1 航天员器官剂量计算流程 Fig. 1 Process to calculate astronauts'organ dose

 图 2 不同粒子在水中的质量阻止本领 Fig. 2 Stopping powers of various particles in water

 图 3 ICRP 123与ICRP 60出版物的辐射品质因数 Fig. 3 Radiation quality factor from ICRP 60 and ICRP 123 publications

1.3 银河宇宙线模型

 图 4 国际空间站轨道银河宇宙线粒子(1H、4He、12C、40Ar、56Fe和238U)的能谱 Fig. 4 Energy spectra of GCR particles (1H,4He,12C,40Ar,56Fe and 238U) in ISS orbit

2 结果与分析 2.1 剂量转换因数

 图 5 受1H、4He、12C、56Fe和238U粒子照射时通量-器官吸收剂量转换因数和通量-器官剂量当量转换因数 Fig. 5 Fluence to organ absorbed dose conversion coefficients and organ dose equivalent conversion coefficients for exposure by 1H,4He,12C,56Fe and 238U

 图 6 不同屏蔽厚度下56Fe粒子照射时的通量-器官吸收剂量转换因数和通量-器官剂量当量转换因数 Fig. 6 Fluence to organ absorbed dose conversion coefficients and organ dose equivalent conversion coefficients for exposure by 56Fe with various shielding thicknesses

 图 7 计算的通量-器官吸收剂量转换因数和通量-器官剂量当量转换因数与ICRP 123结果的比较 Fig. 7 Comparisons of fluence to organ absorbed dose conversion coefficients and organ dose equivalent conversion coefficients calculated with results from ICRP 123

2.2 近地轨道航天员的辐射剂量

 图 8 国际空间站轨道不同屏蔽厚度下航天员受银河宇宙线照射时的器官吸收剂量率和器官剂量当量率 Fig. 8 Astronauts'organ absorbed dose rates and organ dose equivalent rates from exposure by GCR in ISS orbit with various shielding thicknesses

 图 9 银河宇宙线不同粒子造成的皮肤吸收剂量率和皮肤剂量当量率 Fig. 9 Skin absorbed dose rates and skin dose equivalent rates from various particles of GCR

 图 10 计算的航天员受银河宇宙线照射的器官吸收剂量率与PHITS计算结果比较 Fig. 10 Comparisons of the calculated astronauts’ organ absorbed dose rates from exposure by GCR with those from PHITS simulation

3 结 论

1) 根据ICRP 123号出版物对航天员辐射剂量评价的建议,采用中国人体数字模型和粒子输运程序获取了航天员受空间粒子(Z=1~92)辐射时器官的通量-吸收剂量转换因数和通量-剂量当量转换因数.由于人体模型和计算程序的不同,获得的转换因数与ICRP 123号出版物的差别可达数十倍.

2) 计算出航天员在国际空间站轨道受银河宇宙线照射时不同屏蔽厚度下器官的吸收剂量和剂量当量.器官的吸收剂量在40μGy/d左右,剂量当量约200μSv/d.宇宙线照射的剂量主要来自于原子序数小于29的粒子.随屏蔽厚度增加,剂量并不是单调递减.

文章信息

ZHANG Binquan, YU Qinglong, LIANG Jinbao, SUN Yueqiang, YANG Chuibai, ZHANG Shenyi

Calculation of the astronauts' radiation dose from galactic cosmic ray

Journal of Beijing University of Aeronautics and Astronsutics, 2015, 41(11): 2044-2051.
http://dx.doi.org/10.13700/j.bh.1001-5965.2014.0712