双探头SPECT质控回顾性分析

根据NEMA标准对一台SPECT进行固有均匀性、旋转中心校正、四象限铅栅模型、Jaszczak系统模型、Hoffman脑3D模型测试.2003-2010年质控数据分析结果显示,有效视野(UFOV)固有积分均匀性与旋转中心均无明显差异(p＞0.05),中心视野(CFOV)固有积分均匀性从2007年开始有明显差异(p＜0....     

单点源,双探头新型液位计的研究与应用

研制了单点源、双探头核辐射液位计，其测量范围为０—１４０ｇ／ｃｍ２，比单点源、单探头液位计的测量范围扩大１倍，使用效果良好     

双探头符合图像中冷灶的部分容积效应

部分容积效应是影响图像质量的重要因素,它使图像的像素值与实际值产生偏差.本文探讨部分容积效应对双探头符合图像中冷灶的影响.采用GE.Hawkeye符合成像设备及东芝AZ-618 ECT模型.18F-FDG的总活度从15.15 MBq到204.33 MBq分18次扫描.图像重建采用OSEM算法,Hanning后滤波.由重建数据确定冷灶的恢复系数,分析部分容积效应.结果显示,冷灶恢复系数随其背景实际放射性浓度的增高而增大,并随冷灶尺寸的增加而减小.说明部分容积效应不仅随病灶尺寸的减小而增强,且随本底活度的增加而加剧.     

双探头SPECT对向平面显像放射性活度定量的模型研究

放射性核素体内吸收剂量估测是评价辐射危害和内照射治疗价值的重要指标.器官组织的绝对活度定量是吸收剂量估算的必要步骤.本研究采用双探头单光子发射型计算机断层显像术（Single photon emission computed tomography,SPECT）对向测定对模拟的^99Tc^m源器官进行了活度定量的模型实验.结果表明：双探头SPECT对向平面显像放射性活度定量不受放射源在体模内深度的影响,并且在放射源直径≤2cm时活度定量最准确;Buijs法提供了最准确且最稳定的本底校正方法.     

基于双腔探头的流强精确测量

上海同步辐射光源(Shanghai Synchrotron Radiation Facility,SSRF,简称上海光源)作为中国第三代同步辐射装置,在为用户提供研究平台的同时,也在不断优化top-up运行模式,包括研究多束团注入以及注入效率优化等。而注入效率的优化需要精确测定注入束团的电荷量。由于ICT(Integrating Current Transformer)信号易受噪声干扰,分辨率不足1%,尤其在低电荷量注入时,分辨率将进一步降低,因此本文提出利用腔式探头分辨率高的特性,使用双腔探头检测注入流强的方案,并着重研究探头信号的采集处理方法。在上海光源高能输运线上完成的初步束流实验结果表明:注入流强的相对测量精度最好可以达到0.03%,满足储存环注入效率精确测量的要求。     

双探头符合成像系统的分辨率及其影响因素

研究双探头符合成像系统的分辨率及其影响因素。采用Hawkeye双探头符合成像设备,对Toshiba椭圆柱分辨率模型成像。用X线透射扫描进行衰减校正,在不同的活度下做18次扫描。OS-EM算法选择4种后滤波截止频率重建图像。计算线源横断层面上扩展函数的半高宽（FWHM）。在视野中活度较低时（〈101．00MBq）,FWHM基本不随活度变化;但在较高的活度区,FWHM随视野中活度的增加而缓慢增加;在视野中心至横向12cm范围内,视野中心区径向FWHMx最大,越靠边缘越小,而切向FWH嗨基本不随位置变化;FWHM随重建算法中后滤波截止频率的增加而减小。结论是视野中的总活度、位置及重建算法均影响双探头符合成像系统的分辨率。     

基于腔式探头的高分辨率束团电荷量测量方法研究

束团电荷量是粒子束流最基本的特征参数,精确的电荷量测量和控制对于装置的运行以及束损的监测和安全联锁具有非常重要的作用.上海软X射线自由电子激光装置(Shanghai Soft X-ray Free Electron Laser Device,SXFEL)中加入了电荷量反馈环路,以期实现束团电荷量的精确控制并满足单束团实...     

便携式γ能谱仪闪烁探头改进设计及性能研究

为满足当前便携式γ能谱仪对高性能闪烁探头的需要,本文提出了采用CsI(Tl)晶体耦合雪崩光电二极管的方式代替NaI(Tl)晶体耦合光电倍增管以构成新的闪烁探测器,并设计了低噪声电荷灵敏放大器作为探测器读出电路。根据唯一变量原则分别测试了能量分辨率随温度与偏压的变化规律,并对多种放射源的γ射线进行能谱响应实验。实验结果表明：当温度为23 ℃且偏压为370 V时,该闪烁探头对¹³⁷Cs、²²⁶Ra、⁶⁰Co和¹⁵²Eu源的γ射线具备优异的能谱响应特性,其中,对¹³⁷Cs源的γ射线能量分辨率可达4.98%,输出信号信噪比可达21∶1,上升时间为80 ns。可见,改进后的闪烁探头的性能有大幅提升,具备能量分辨率更佳、体积更小、抗机械性能与适用性更强等优点。     

含磷硫双功能团萃取剂的合成及其萃取性能的研究

合成了９种烷硫基烷撑二烷基膦酸酯（Ｒ＇Ｏ）２Ｐ（Ｏ）（ＣＨ２）ｎＳＲ＇＇，研究了它们从盐酸和硝酸溶液中对几种软、硬酸金属离子的萃取及取代基对萃取性能的影响，结果表明，这类萃取剂对软酸和硬酸金属离子如Ｐｄ（Ⅱ）和Ｕ（Ⅵ）均有良好的萃取能力，而对交界酸金属离子如Ｒｈ（Ⅲ）Ｃｄ（Ⅱ）等几乎不萃取。萃取剂分子中，烷撑基（ＣＨ２）ｎ）中的碳原子数ｎ是影响其萃取能力的主要因素，而取代基Ｒ＇和Ｒ＇＇的大小，对其     

串列加速器358型双等离子体离子源改进及性能研究

为提高北京师范大学GIC4117型串列加速器358型双等离子体离子源束流强度及灯丝使用寿命,改进了离子源灯丝涂覆材料中Ba、Sr、Ca元素的占比、灯丝涂覆方法及离子源保护措施。讨论了在不同灯丝电流下,进气量、弧流、约束磁铁电流对离子源输出束流强度的影响。灯丝累积使用寿命达到200 h以上,靶室束流强度较原来采用860A溅射源提高约500倍。同时本文对358型双等离子体离子源调试过程中的异常断弧情况进行了分析和改进。     

基于双GM计数管设计的宽量程伽马剂量计性能初步测试

为在核事故中使用机器人定位和抓取丢失的伽马放射源,本文初步设计了一款基于双GM（Geiger Müller）计数管（ZP1321,ZP1301）的宽量程伽马剂量计。设计了用于探测器信号处理的前端模拟电路和基于微控制器的数据处理和传输程序等,并使用137Cs伽马放射源对设计的系统进行了初步测试。测量并分析了影响剂量计输出信号的主要因素。初步实验结果表明,所设计的无屏蔽壳的伽马剂量计可成功地在线检测伽马放射源。     

Measurement of Gamma Photon Distribution from Narrow Slit

Deposition profiles of corrosion products on fuel surfaces and products chemical compositions were determined at Shimane Nuclear Power Plant, a low-crud BWR. The deposited amounts were expressed as functions of crud concentration in the reactor water, fuel burnup and flow velocity in a fuel channel. The results could be predicted satisfactorily by the crud deposition model based on microlayer evaporation and drying out phenomena. The amount depositing at high flow velocity gave saturated values which were inversely proportional to the flow velocity (∝ 1/v), while those at low velocity did not reach saturated values, but rather were proportional to 1/v ³. The depositing corrosion products could be divided into two layers, inner and outer, with more Co ions being taken into the former layer.     

Local Gamma-Ray Counting Efficiency of Halogen Counter with Thick Anode

A substance for solidifying waste containing ¹²⁹I is sought that effectively sorbs iodine to inhibit its release from repository into the environment. Three candidate media—commercial alumina cement mixed with calcium sulfate and/or calcium hydroxide—were investigated. The criterion applied for evaluating iodine sorption performance was the distribution coefficient Kd of iodine between solid and solution in an emulsion of sodium iodide solution and powder prepared from the alumina cement/calcium compound mixture, which was molded, cured and ground. Batch sorption experiments were performed on different combinations of the above-mentioned calcium compounds added to alumina cement. The solidified substance was also examined for mechanical strength. The highest iodine sorption performance was obtained with calcium sulfate added to alumina cement to a SC₄/Ca mole ratio of 0.16, which ensured a Kd value raised to a level of not lower than 0.2 m³/kg from the (1.8–3.2)x10^-3 m³/kg obtainable with alumina cement before calcium compound addition. The enhancement of iodine sorption with addition of calcium sulfate is attributed to formation in the substance of monosulfate (3CaO·Al₂O₃·CaSO₄12H₂O) or tetracalcium aluminate hydrate (4CaO·Al₂O3·XH₂O (X=13 to 19)).     

New Chair Type Whole-Body Counter

Abstract

A new chair type whole-body counter has been developed for rapid mass monitoring of workers for internal exposure, to be used in projects involving work risking radiation exposure by a large force of workers, such as the reconstruction and decommissioning of reactors at the Japan Atomic Energy Research Institute (JAERI). The new counter is capable of discerning from 2-min count a body burden corresponding to a recording level of internal dose equivalent to 0.2 mSv committed dose for nuclides commonly encountered in projects such as cited above. The counter incorporates two NaI(Tl) detectors (20 cm dia. × 10 cm) housed in a collimator. The upper detector covers in its field the lower half of the head and chest, and the lower detector the trunk. The chair is installed in a shielding cubicle of 5 cm thick lead in the main part and open toward ceiling and at entrance. Data processing is completely computer-automated Calibration experiments using plastic phantom containing homogeneous radioactive solution have proved the counter to be capable of descerning in 2-min counting time a ⁶⁰Co activity of 80 Bq contained in the trunk, distinguishing it above 3 times standard deviation of background count rate.     

分层γ扫描层间串扰影响研究

分层γ扫描(SGS)测量分析方法是核废料与放射性废物定量测量分析的重要手段。其中,由于分层形成的临近层对当前层测量的干扰（层间串扰）是分析结果误差的来源之一。本工作研究了串扰及测量和计算误差对串扰方程组解的影响,并通过实验测量和Monte-Carlo模拟计算予以印证。结果表明：在测量和计算误差存在的条件下,适当的串扰对样品中物料总含量分析结果的影响较小。如果希望得到每一分层中物料含量的准确数据,则需对串扰及测量和计算误差有更严格的要求。     

分层γ扫描定量分析中层内放射性非均匀分布影响分析

分层γ扫描(SGS)测量分析方法是核废料与放射性废物定量测量的重要手段,被测样品层内放射性均匀分布是SGS分析方法的基本假设之一。本文采用蒙特卡罗方法模拟计算与实验验证相结合,研究了样品层内放射性非均匀分布对SGS测量分析误差的影响趋势和影响程度。研究表明,当实际样品的层内放射性分布偏离均匀假设时,会导致SGS分析结果偏离实际含量。这一结论与实际测量结果一致。     

GM计数管的线性化

本文给出一种适合于所有GM计数数线性化的电路及测试结果。文中给出适于几种GM计数管死时间τ和计数率n之间关系的表达式,因而提供一个通过微机使GM计数管线性化的方法。     

计数率测量仪死时间的确定方法

采用反应堆不同的运行功率和缓发中子不同时刻的衰减作为模拟源,测量出两套计数率测量仪的死时间分别为3.65和5.18μs,并提出利用反应堆的功率周期上升测量计数率测量仪死时间的方法。     

Dependence of Position Signal on Pressure of Counting Gas in Charge Division Type Position-Sensitive Proportional Counter

In the absolute radioactivity measurement of radioisotope gaseous samples with newly developed position-sensitive proportional counter (PSPC) method, it is necessary to change the counting gas pressure for the correction of the wall effect. The position signal was found to drift depending on the pressure. Theoretical explanation was given for this drift. Rise time of output pulses varies with gas pressure, which leads to a change of ballistic deficit. Consequently, the ballistic deficit differs between pulses from both the ends of the PSPC, which causes the change of position signals. Increasing the pressure of the counting gas from 0.5×10⁵Pa to 4×10⁵Pa, the range of position signals for two position calibration sources became narrower by about 8% under 6 μs shaping time.     

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。