吸入性氚化粒子在人体肺部组织中吸收剂量的研究
Simulation Investigations on the Absorbed Dose in Lung Tissue from Inhaled Tritiated Particles
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摘要: 涉氚核设施在检修及退役时，其产生的氚化粒子容易被工作人员误吸入，并在呼吸系统的不同部位停留，部分尺寸较小的粒子可能在肺泡间质区(AI 区) 停留超过1 年的时间。氚粒子通过 衰变释放电子，在释放电子的同时以及释放的电子与周围原子相互作用还会分别产生出内、外轫致辐射，这些都会对人体肺部组织造成辐射损伤。本文采用蒙特卡罗程序PENELOPE 对多种氚化粒子在人体肺部组织中的吸收剂量进行了模拟计算，特别是讨论了氚 衰变的内轫致辐射的贡献。研究发现，电子辐射对人体肺泡产生的吸收剂量大于外、内轫致辐射，但后两者作用距离较长，对人体造成的影响重要；电子辐射吸收剂量随着粒子尺寸的增大以及金属原子序数的增大而减小；外轫致辐射吸收剂量随着粒子尺寸的增大而减小，随着金属原子序数的增大而增大；内轫致辐射吸收剂量随着粒子尺寸的增大以及金属原子序数的增大而减小。Some tritium relevant nuclear facilities, such as Tokamak, can produce tritiated particles. There is the possibility for the staffs to inhale the tritiated particles by accident in the process of maintenance or decommission of these facilities. Tritium decays to 3He, during which the beta electron and the internal bremsstrahlung are released. Meanwhile, the released electrons will interact with the surrounding atoms, and the external bremsstrahlung will be generated. All the electrons, internal bremsstrahlung and external bremsstrahlung will deposit the radiation energies to lung tissues and generate the radiation damage. In this paper we studied the radiation doses by inhaled tritiated particles in lung tissues by Monte Carlo code PENELOPE, in particular, internal bremsstrahlung contribution was included. Our results demonstrated that (1) the dose caused by electron radiation is far higher than those of external and internal bremsstrahlung, which however shall not be negligible due to their long-distance effects; (2) the dose caused by electron radiation decreases as the particle size and metal atomic number Z increase; (3) the dose caused by external bremsstrahlung decreases as the particle size increases, but increases as the metal Z increases; (4) the dose caused by internal bremsstrahlung decreases as the particle size and metal Z increase.Abstract: Some tritium relevant nuclear facilities, such as Tokamak, can produce tritiated particles. There is the possibility for the staffs to inhale the tritiated particles by accident in the process of maintenance or decommission of these facilities. Tritium decays to 3He, during which the beta electron and the internal bremsstrahlung are released. Meanwhile, the released electrons will interact with the surrounding atoms, and the external bremsstrahlung will be generated. All the electrons, internal bremsstrahlung and external bremsstrahlung will deposit the radiation energies to lung tissues and generate the radiation damage. In this paper we studied the radiation doses by inhaled tritiated particles in lung tissues by Monte Carlo code PENELOPE, in particular, internal bremsstrahlung contribution was included. Our results demonstrated that (1) the dose caused by electron radiation is far higher than those of external and internal bremsstrahlung, which however shall not be negligible due to their long-distance effects; (2) the dose caused by electron radiation decreases as the particle size and metal atomic number Z increase; (3) the dose caused by external bremsstrahlung decreases as the particle size increases, but increases as the metal Z increases; (4) the dose caused by internal bremsstrahlung decreases as the particle size and metal Z increase.
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