γ射线外照射条件下体模红骨髓剂量及剂量深度分布的蒙特卡罗计算

用蒙特卡罗方法,对0.025、0.05、0.11、0.30、0.661、1.25、3.0和6.OMeV等八种能量的平行宽束γ射线沿垂直于体模中心轴线方向的旋转照射,位于体模躯干下端离体模中心轴线的距离分别为50、100和200cm的1.25MeVγ点源对体模正面照射,1.25MeV平行宽束γ射线对体模正面、背面和侧面方向的垂直照射,以及当体模处于年龄为22.5小时的落下灰γ辐射场中时,计算了体模的红骨髓平均剂量D_m、干细胞活存率计权等效剂量D_(sw)和组织吸收剂量的深度分布。计算结果,除低能(<0.05MeV)γ射线和近距离(距体模中心2m以内)点源照射条件之外,D_m和D_(sw)在2％以内相符。对于在落下灰γ辐射场中测量人体红骨髓平均剂量的仪器,可用1.25MeVγ射线平行宽束旋转照射条件进行刻度。     

X,γ射线外照射有效剂量当量

国际放射防护委员会(ICRP)提出在辐射防护中采用有效剂量当量,本文对能量在62keV 至10MeV 范围内的 X、γ射线,在不同的照射几何条件下,计算了有效剂量当量与自由空气场照射量或个人剂量仪读数的比值,并讨论了有关的应用问题。     

关于γ浸没外照射短期大气弥散因子的计算方法

关于γ浸没外照射短期大气弥散因子，以前通常使用半无限体源作近似计算，由于高源近距离的计算不合适，故本文对新的计算模式在烟羽轴线上给出它的计算方法。     

~(60)Coγ射线外照射的有效剂量当量

由国际放射防护委员会(ICRP)提出,为辐射防护剂量学所用的有效剂量当量(H_E)概念,在目前,它的应用仍有困难。为简化确定 H_E,本文分别计算了~(60)Coγ射线外照射的器官剂量、H_E 与个人剂量仪佩带处吸收剂量的比值(DROP),同时也计算了与人体中心自由空气中照射量的比值。当放射源离人体中心的距离不同时,DROP 也随之改变。3m 远条件下算得的结果与 Maruya-ma 给出的平行线束结果符合得很好。     

外照射的转换系数

本文介绍了ＩＣＲＰ既将出版的新的报告中关于外照射剂量测量的实用量，并结合ＩＣＲＰ６０号出版物对此进行了简要讨论。     

舱室内γ外照射剂量快速估算方法的比较

舱室内γ外照射剂量的快速估算对于核动力船舶核事故后果评价、核应急决策等具有重要意义,但是目前对于舱室内γ外照射剂量的快速估算尚无明确的标准或统一公式。采用MCNP程序计算结果作为基准,对烟羽浸没公式和点核积分公式这2种快速估算方法进行了评估,详细分析了这2种估算方法在不同形状、不同体积舱室情况下的估算结果误差及原因。结果表明,舱室的形状越偏离半球体形状、体积越大,公式估算结果与MCNP程序计算结果偏差越大:有限烟羽浸没公式的误差约为30%,点核积分公式的误差约为10%。因此,在实际工程应用时,点核积分公式可提供更为准确和快速的估算结果。      

快速估算γ射线外照射事故个人剂量的实验研究

本文报道了γ射线外照射个人剂量估算的体模实验结果,给出了不同照射几何条件下的器官剂量,有效剂量当量与个人剂量计吸收剂量或人体中心自由空气场照射量的比值(DROP、DROT),对事故剂量的几种表达方式作了比较,并讨论了事故剂量估算的应用问题。     

铅玻璃对核材料操作人员γ射线屏蔽作用的MC模拟

核材料产生的γ射线对操作人员有较强的辐射影响，实际工作中多用铅玻璃对其进行屏蔽。本文以人体甲状腺为研究对象，应用蒙特卡罗方法通用软件MCNP4B，模拟计算了人员在操作核部件时，在不同厚度铅玻璃条件下人员甲状腺所受的剂量。     

一起小剂量γ外照射事故剂量估算

本文叙述了一起小剂量γ外照射事故的情况。对受照射的六名男性儿童(9—12岁)给出了性腺剂量(9.5×10~(-3)—1.4mGy)和躯干中线平均剂量(2.6×10~(-2)—10×10~(-2)mGy。)     

γ外照射皮肤剂量的测量与计算

人体所遭受的辐射危害，常常以吸收剂量来表示。由于吸收和散射现象的同时存在，使得人体不同深度处受到的照射情况不同。高能γ射线对人体的照射多用于医疗照射，考虑的均为较远距离的照射（即源皮距大于８０～１００ｃｍ的医疗照射）。实际上剂量梯度（在源皮距越小时）...     

利用MCNP模拟气体裂变产物混合源的γ剂量率

西安脉冲反应堆辐照铀靶后,抽取Kr、Xe裂变气体,通过活性炭吸附于气体源盒内。HPGe γ谱仪测量源盒内混合气体活度,塑料闪烁探测器测量γ剂量率。将源盒、塑料闪烁探测器的几何结构、材料作为蒙特卡罗程序（MCNP）输入信息,模拟塑料闪烁探测器对源盒中核素活度与其γ剂量率对应关系,结合HPGe γ谱仪所测活度得到剂量率模拟值,结果与实测值偏差小于6%。该工作说明在已知放射源空间结构、放射性核素种类和活度的情况下,采用MCNP模拟计算复杂气体放射源γ剂量率的方法是可行的。     

我国职业外照射个人剂量监测的回顾与思考

简要回顾了我国职业外照射个人剂量监测的监测对象和人数、监测方法、监测体制和模式的有关内容。提出了提高监测水平的几点建议：明确个人剂量监测的目的;理顺个人剂量监管体制;加强对商业性监测的管理;建立个人剂量监测的质量保障体系;放射性工作业主和放射性工作人员要主动接受完整的个人剂量监测。     

中国女性参考人曲面模型的光子有效剂量转换系数计算

本文基于人体断层解剖图像,根据所建立的中国女性参考人曲面模型和体素模型,采用MCNP计算了6种标准照射方式下光子在0.01~10MeV能量范围内20个能量点的光子有效剂量转换系数,并对曲面模型和体素模型的计算结果进行了比较。结果表明:在不同照射方式下曲面模型和体素模型的光子有效剂量转换系数的变化趋势基本一致,大部分能量点其差异在10%之内。光子有效剂量转换系数的差异主要是由于模型器官的位置和质量对剂量有一定影响,在低能级下差异较为明显。     

External Gamma Exposure to Radon Progeny in Indoor Air

The external γ-exposure from radon progeny uniformly distributed in indoor air was estimated by a computer program that was developed. This program can calculate the fluence rate, exposure rate and average energy for any given point in a room of any given size. As numerical example, the exposure rate normalized to unit airborne activity is presented, together with the fluence-weighted and exposure-weighted average photon energies, for a room of representative geometry containing radon progeny in equilibrium. To cover other conditions encountered in practice, quantitative evaluations are additionally presented of the effect on the exposure brought by changes in certain parameters, such as equilibrium factor, wall thickness, room size and receptor position. The study has quantitatively substantiated the prevailing postulate that the effective dose equivalent due to external exposure resulting from normal indoor concentrations of airborne radon progeny in the room of representative geometry should only amount to 0.04% of that from the internal exposure from the same sources, and that it should be of similarly negligible order compared with internal exposure also in the case of other room geometries.     

Dose Conversion Coefficients for External Photons Based on ICRP 1990 Recommendations

Monte Carlo calculations were performed to estimate the effective doses E for external photons based on the recent proposals in the ICRP 1990 Recommendations. Twelve photon energies between 17 keV and 8.5 MeV and eleven irradiation geometries were selected to be applicable to many exposure conditions encountered in the working and living environment. A MIRD-based unisex phantom was used in conjunction with the Monte Carlo transport code MORSE-CG. The results were presented as a form of dose conversion coefficients transforming the air kerma or fluence in free air to the effective dose. These coefficients were given in graphical and tabular forms. Analyses of organs' fractional contribution to E showed that the gonadal exposure has generally a great contribution for all the geometries except the incidence from above. A comparison of conversion coefficients with other results gave a reasonably satisfactory agreement. Finally, the ambient dose equivalent H ^*(10), one of the operational quantities proposed by the ICRU, was found to give conservative estimates of E for most of the irradiation geometries considered, but it gives a considerable overestimate of E at the incidences from above and below.     

Monte Carlo Simulation of Dose Calculation Parameter of Radioactive 125I Brachytherapy Source

The end of silver rod of the domestic ¹²⁵I brachytherapy source is right angle type, which is slightly different from the typical model of 6711 ¹²⁵I brachytherapy source. And it can have influence on the dose calculation parameters. Based on the structure of domestic ¹²⁵I brachytherapy source, dose calculation parameters which are recommended by AAPM TG43-U1 were calculated by Monte Carlo method. The influence of the end of silver rod on the dose calculation parameters was studied. The simulation result of dose rate constant is 0.955 cGy·h-1·U-1 when the air kerma strength was calculated by the point detector, and the difference with the result of the TG43-U1 is within 1.03%. The radial dose function g(r) in the range of 0.05-10 cm at the transverse axis was calculated precisely. Then empiric equation was acquired by curve fitting. 2D anisotropy function F(r,θ) was calculated in 0°-90° and 0.25-7 cm. The source of the right angle structure of the end of the silver rod would cause a hump area of 2D anisotropy function when r equals 0.25 cm.     

非人类物种辐射剂量估算中剂量转换因子分析

剂量转换因子是辐射剂量估算中的基础和重要部分之一.本文介绍了非人类物种剂量转换因子计算的剂量学模型、主要假设条件和计算方法,并对辐射剂量估算的整体模型和简化解剖学模型中剂量转换因子进行了比较和实用性分析.     

125I粒子源剂量计算参数模拟研究

国产125I粒子源的银棒末端结构为直角型,与典型的6711型粒子源结构略有不同,结构不同会对剂量计算参数产生一定影响。本文针对国产粒子源结构,利用蒙特卡罗方法计算美国医学物理学家协会（AAPM）在TG43-U1报告中推荐的剂量计算参数,并分析研究银棒末端结构对剂量计算参数的影响。模拟得到国产¹²⁵I粒子源剂量率常数为0.955 cGy·h^-1·U^-1（空气比释动能强度基于点探测器计算得到）,与TG43-U1推荐值较接近,两者仅相差1.03%,更加精细地计算了在源中垂线0.05~10 cm（1 cm间隔）范围内的径向剂量函数,拟合得到较好的经验公式,得到在0°~90°（5°间隔）、距源中心0.25~7 cm（2 cm间隔）范围内的二维各向异性函数,通过对比分析得到银棒末端为直角型结构时的二维各向异性函数在r=0.25 cm处会引起驼峰区。     

MCNP计算含肿瘤Snyder修正头部模型的硼中子俘获治疗剂量

为得出硼中子俘获治疗(BNCT)中不同能量中子在含肿瘤Snyder修正头部模型内的深度-剂量曲线,籍以进一步理解BNCT原理,优化BNCT治疗中子源的能谱分布,本文利用MCNP模拟计算0.025 3 eV、1 eV、1 keV、10 keV、100 keV、1 MeV和混合能量的超热中子源在含肿瘤Snyder修正头部模型内的硼剂量、热中子剂量、超热和快中子剂量以及次级光子剂量组分的深度-剂量分布,并在此基础上得到总的相对生物学剂量的深度-剂量分布,以判断不同能量组中子源在BNCT中的优劣。结果表明,热中子头皮浅表处硼剂量高于肿瘤区硼剂量;快中子源硼剂量小,但其剂量组分中超热和快中子剂量过大;超热中子具有一定的穿透性,在脑深部肿瘤区形成了较高的硼剂量和总的相对生物学剂量。说明超热中子具有良好的BNCT治疗效果,热中子和快中子不适宜用于脑部BNCT治疗。     

Calculations of Effective Dose and Ambient Dose Equivalent Conversion Coefficients for High Energy Photons

The conversion coefficients from photon fluence to ambient dose equivalent, H* (10) and effective doses were calculated for photons up to 10 GeV. A Monte Carlo code EGS4 was used for these calculations and secondary particle transports were considered. The calculated ambient dose equivalents were compared to the calculated effective doses. The comparison shows that the ambient dose equivalents at 1 cm depth, H* (10) underestimate the effective doses at the energy above 5MeV. H* (10) is not suitable operational quantity since it does not provide reasonable estimation of effective dose. It is difficult to define the operational quantity which can be consistently used for photons from low energy to high energy above 10 MeV. Instead of operational quantities, the maximum effective dose in various irradiation geometries can be used for shielding design calculations.