点核积分计算6711型~(125)I籽粒源剂量参数

使用点核积分方法计算6711型~(125)I籽粒源参数,根据美国医学物理学家协会(American Association of Physicists in Medicine,AAPM)TG-43U1号报告推荐的剂量参数计算公式,可以获得6711型~(125)I籽粒源各参数。与AAPM TG-43U1推荐值比较,剂量常数相差6.76%,径向剂量函数值(不包括0.1 cm、0.15 cm、0.25 cm)最大相差2.27%,最小相差0.02%;与MCNP5(A General N-Particle Transport Code,Version 5)方法计算结果比较,剂量常数相差6.19%,径向剂量函数值(不包括0.1 cm、0.15 cm、0.25 cm)最大相差6.65%,最小相差0.06%。结果与推荐值符合较好,证明点核积分能够应用于籽粒源剂量参数计算。     

Evaluation of dosimetric functions for Ir-192 source using radiochromic film

Ir-192 source is widely used in high dose rate brachytherapy. The aim of this study was to derive the brachytherapy dosimetric functions described in AAPM TG-43 to characterize the dosimetric properties of commercially available microselectron HDR Ir-192 source. All the measurements were carried out with GAFCHROMIC EBT radiochromic film in water equivalent solid phantom and the grey values were analyzed using Omnipro IMRT film dosimetry software with Vidar VXR-16 scanner. Optical density of the film was converted to dose using calibration film established in this study. Measurements were carried out by measuring the dose at radial distances from 0.5 cm to 5.0 cm with interval of 0.5 cm and at polar angle 0°-180° in 10° intervals. Dosimetric functions such as dose rate constant, radial dose functions and anisotropy of the dose distribution were found to be in good agreement with Monte Carlo calculations. This study confirms the feasibility of radiochromic EBT film dosimetry in characterization of the TG-43 parameters for Ir-192 HDR source.     

Monte-Carlo方法确定CS-1型131Cs近距离放射治疗源剂量计算参数

针对当前CS-1型¹³¹Cs近距离治疗源剂量计算参数的不一致，根据源的组成和结构，用Monte-Carlo方法（MCNP）计算剂量率常数、径向剂量函数和各向异性函数。其中，剂量率常数计算结果为1.055cGy•h^-1•U^-1，验证了Chen等的γ光谱法实测值（1.066cGy•h^-1•U^-1）和TLD实测值（1.058cGy•h^-1•U^-1）。按AAPMTG43U1的推荐，采用最新的光子截面库（EPDL97）在0.1～10.0cm范围内补充和更新了已报道的径向剂量函数数值，在1.0～7.0cm、0°～90°范围内补充和更新了各向异性函数的相关数值。并对径向剂量函数和各向异性函数进行拟合，得到了实用性较强的经验公式。     

HIMM治疗室的辐射屏蔽设计

为了保证医用重离子加速器（HIMM）运行时的辐射安全，利用FLUKA计算了治疗时产生的瞬发中子源项，并对次级中子、γ辐射对屏蔽的影响进行了分析。用半经验公式及FLUKA计算了屏蔽厚度，给出了HIMM治疗室的屏蔽设计。在HIMM最大负载运行时，测量了屏蔽外中子剂量率，测量结果与模拟计算结果相符合。结果表明，本文选用的屏蔽设计方法是合理的，HIMM治疗室屏蔽设计方案满足国家标准要求。     

用蒙特卡罗方法确定81-02型198Au短程治疗源剂量计算参数

针对81-02型¹⁹⁸Au短程治疗源的临床应用，用蒙特卡罗方法计算了在一半径为30cm的理论球体模型中，AAPMTG43U1所推荐剂量计算参数的数值，包括剂量率常数、径向剂量函数和各向异性函数。所得单个81-02型¹⁹⁸Au短程治疗源的剂量率常数为1.113 cGy·h^-1·U^-1，与Dauffy等的理论计算值和TLD实测值分别相差0.18%和1.62％。在源中垂轴0.1～10.0cm距离范围内计算径向剂量函数的数值，在角度0°～90°（10°间隔）、距离0.5～9.0cm（1cm间隔）范围内计算各向异性函数的数值，最后对径向剂量函数和各向异性函数进行拟合，得到实用性较强的经验公式。     

6711型125I种子源剂量参数的蒙特卡罗研究

使用蒙特卡罗方法计算6711型125I种子源参数,采用新的种子源几何模型和新的光子截面数据(mcplib04),根据AAPM TG-43U1推荐的剂量参数计算公式,可以获得6711型125I种子源各参数。与AAPMTG-43U1推荐值比较,剂量常数相差0.62%,径向剂量函数值最大相差5.12%,最小相差0.15%。     

具有长期放射平衡子体的母体核素各向同性点源的总剂量学常数

本文报道了对ＩＡＥＡ１１５号安全丛书列出的具有长期放射平衡子体的３３种母体核素各向同性点源总剂量学常数值的计算结果,其中含空气比释放动能率常数、照射量率常数、周围剂量当量率常数和定向剂量当量率常数;提出了未经化学分离的天然铀定义,并计算了相应的剂量学常数值;此外,还对某些核素的衰变链作了适当讨论。     

Dose rate distribution of photoneutrons in an ID beamline of SSRF: simulations and measurements

Photoneutrons, emitted by means of photonuclear interactions when gas bremsstrahlung interacts with beam- line components, can be another potential radiation source needed to be considered for shielding design and dose assessment of beamline. In this paper, simulations and measurements of photoneutrons dose rate at beam- line BL09U are carried out when Shanghai Synchrotron Radiation Facility （SSRF） running at Top-up mode （3.5 GeV, 235 mA）. A geometry model is constructed for the beamline BL09U with considerations of the scattering process of the major optical components. The model is compiled into Monte Carlo simulation code FLUKA to calculate photoneutron dose distribution. Measurements of the photoneutrons dose rate were per- formed by using Environmental Neutron Monitor （ENM）. Observation points were arranged uniformly along the inside and outside of the optical enclosure （OE） of BL09U. The calculation results agree with experiments within the measurements uncertainties. It is verified that photoneutrons dose simulation is reliable. The simula- tion and measurement methods can be applied to evaluate the neutron dose level of other beamline stations, and provide references for the shielding design of the beamlines at SSRF in the near future.     

Measurement and Simulation of TEPC Microdosimetric Spectra in Gamma Radiation Field

According to the different characteristics of microdosimetric spectra measured by tissue equivalent proportional counter (TEPC), the neutron dose equivalent and γ dose equivalent could be distinguished in a unknown neutron and γ mixed radiation field. In order to discriminate the γ radiation dose equivalent from the total value,the pure γ microdosimetric spectra was measured in ⁶⁰Co、¹³⁷Cs radionuclide radiation field with TEPC. TEPC microdosimetric spectra in a series of monoenergy γ radiation field were simulated by FLUKA code. All the γ radiation microdosimetric spectra, including measured spectrum in ⁶⁰Co、¹³⁷Cs radiation field and that of simulation spectrum by FLUKA code, reveal a trait that the linear energy of γ radiation is basically lower than 10 keV/μm. This trait is the very foundation to discriminate the γ radiation from the mixed radiation.     

Monte Carlo Simulation of Dosimetric Parameters for Hybrid PdI Source in Brachytherapy

According to dose calculation formula recommended by AAPM TG-43U1,dose rate constant of Model 6711 ¹²⁵I brachytherapy source was calculated by Monte Carlo method. The calculation results were in good agreement with TG-43U1. Then, dose rate constant,radial dose function and anisotropy function of new hybrid PdI source were calculated by Monte Carlo method．Empiric equations were obtained for radial dose function．     

西门子直线加速器均整和未均整射束的光子束剂量学特性

利用BEAMnrc和DOSXYZnrc蒙特卡罗程序研究西门子直线加速器6 MV能量均整和未均整光子束的剂量学特点。比较两种射束的深度剂量分布、离轴比剂量分布、中心轴剂量率和总散射因子。结果表明,未均整射束各射野的百分深度剂量均比均整射束的低;中心轴剂量率比均整射束大,且两种射束中心轴剂量率比值随射野和深度的增加逐渐下降;除此之外,未均整射束的半影宽度及总散射因子随深度的变化趋势均比均整射束小。未均整射束的剂量学优势可用于临床应用。     

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.     

基于MELCOR与MCNP程序的安全壳剂量率计算方法

严重事故条件下,评估安全壳内的放射性剂量率水平对核电厂严重事故管理、应急响应等环节具有重要指导意义。本工作利用MELCOR程序模拟严重事故序列,计算不同核素组释放进入安全壳内的质量;利用ORIGEN2程序计算不同核素组的堆芯积存量及核素的γ源强;利用MCNP程序计算每组核素100%释放进入安全壳所产生的剂量率水平;最后根据拟合公式求解安全壳剂量率。中核核电运行管理有限公司30万千瓦机组安全壳剂量率的计算结果说明该方法切实可行。     

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。     

Fuel Pin and Subassembly Heterogeneity Effect on Neutronics Properties of Fast Power Reactor

The PALLAS (discrete ordinates-integral transport) code was improved to include secondary sources, such as bremsstrahlung and fluorescence, to assure accurate and reliable results. The point buildup factors for high-Z materials were calculated with this code in the energy range of 0.015~15 MeV up to 40 mean free paths. The buildup factors for low-Z materials in the low energy range, which are most difficult to calculate, were calculated with PALLAS and were validated by comparison with the results of the EGS4 (point Monte Carlo), and ANISN codes.

A function to calculate coherent scattering was added to the EGS4 code. It was suggested that neglecting coherent scattering and assuming free-electron Compton scattering can result in an error in the buildup factor.

A fitting formula, the geometric progression (G-P) form, was developed to reproduce the data in codes used for shielding design. This formula can reproduce the data over the full range of distance, energy and atomic number within a few percent.

The above cited buildup factor data and the G-P formula have been adopted for proposed standard ANS-6.4.3 “Gamma Ray Attenuation Coefficient and Buildup Factors for Engineering Materials”. The G-P fitting function has been implemented in the CCC-493/QAD-CGGP and CCC-494/G33-GP codes available from the Radiation Shielding Information Center (RSIC) at Oak Ridge National Laboratory. These are used for γ-ray shielding calculations throughout the world.

Also, the data and the method of evaluation for 1 cm dose equivalent, introduced into the Japanese law according to ICRP recommendations, have been offered by this team.     

XG-Ⅲ装置ps激光束线所致感生放射性评估研究

利用PIC与蒙特卡罗模拟方法对XG-Ⅲ装置在ps激光束线驱动的X射线源和中子源等多种工作模式下进行了剂量学评估,使用PIC模拟确定了高能电子源项后,将其作为蒙特卡罗软件FLUKA的输入数据,通过模拟计算得到了不同靶材在实验结束后不同时刻的感生放射性核素活度及在靶周围所致的剂量。模拟结果表明,对于激光驱动的轫致辐射X射线源,在每次打靶完成并冷却10 min后,在距靶表面1 cm处的感生放射性剂量率约为4 mSv/h,而在距靶表面30 cm处的感生放射性剂量率则已降低到15 μSv/h。对于激光驱动的光核反应产生的光中子源,冷却10 min后在距靶表面1 cm处的感生放射性剂量率小于10 μSv/h。除了靶的材料,靶厚度也会对靶周围的感生放射性剂量率变化情况产生影响,因此有必要在不同的照射环境下,针对不同的靶材及靶厚采取不同的辐射防护方案。本文研究结果可为超短超强激光设施的辐射风险分析及辐射防护工作提供相关参考。     

Radiation Dosimeters for High Dose by Commercial PMOS Transistors Using Normalized Drain Current as Dosimetric Parameter

A PMOS transistor that is commercially available device can function as a practical radiation dosimeter for high dose. A new dosimetric parameter, that is shift rate of drain current, is proposed and demonstrated to reduce the possible errors of measurement. The calibration curve of dosimetric parameter vs. radiation dose shows a very linear characteristic. Some modifications were suggested to compensate the room temperature effects. The gate bias can be applied to further increase the dosimetric sensitivity and extend the dose of radiation measurement to a lower range.     

我国南方某核厂址蟾蜍剂量率评估的比较研究

选择我国南方某核厂址两栖动物——蟾蜍作为参考生物,建立了蟾蜍的生物解剖学模型和外照射环境模型。采用蒙特卡罗模拟技术计算源介质中放射性核素¹³⁷Cs、⁹⁰Sr和²³⁹Pu对靶组织/器官的辐射剂量率,由此计算蟾蜍整体的辐射剂量率。采用ERICA程序和RESRAD-BIOTA程序计算蟾蜍的剂量率,并与解剖学模型进行比较。结果表明:三种方法计算的蟾蜍内照射剂量率基本一致;由于外照射环境模型的不同,外照射剂量率估算结果并不相同,ERICA程序与解剖学模型计算的外照射剂量率结果更接近;解剖学模型关注生物组织/器官的辐射剂量,对于核素分布不均匀的生物个体研究具有重要的意义。     

西安脉冲堆1#径向孔道等效平面源的模拟计算

采用反应堆孔道深穿透屏蔽计算的点探测器、DXTRAN球抽样方法，计算了西安脉冲堆径向孔道出口处中子、光子的注量率空间分布、能谱分布和角分布等重要参数，并利用相应的实验测量值，验证了理论计算的准确性，为该实验孔道应用及建立该孔道出口处平面等效源提供了理论依据。