12 MeV无损检测用电子直线加速器研制

正近年来,无损检测用电子直线加速器能量有了更高的需求,2017年我院直线加速器研究室(62室)成功中标一重集团大连石化装备有限公司2台12 MeV无损检测用电子直线加速器,2017年先交付1台。加速器主要技术指标要求如下:1)等效钢铁检测厚度范围为76～420 mm;2)X射线能量,12MeV/9MeV;3)X射线束剂量率,≥5 000cGy/min@12MeV,≥3 000cGy/min@9MeV;4)X射线束斑焦点,≤3mm。加速器采用12 MeV驻波加速器结构,电子     

能量可切换的加速器性能测试

能量可切换的探伤加速器性能测试包括电子束能量、X射线剂量率、X射线均匀度、X射线不对称度、泄漏剂量、电离室校准、频率与剂量率的关系、X射线照相灵敏度、X射线束斑焦点、运行考验等。该探伤加速器的性能均达到国家标准GB-T20129--2006《无损检测用电子直线加速器》的要求。其中，灵敏度测试及焦点测试使用多组铜增感屏，取得更好的射线照相的胶片图像质量。     

X波段电子直线加速管转换靶设计

<正>X波段电子直线加速管以其结构紧凑、占用空间小和使用方便等优势,逐渐在机场和海关等安检领域被人们所关注,转换靶是加速管中用于高速电子轰击产生X射线的重要部件之一,转换靶的设计关系到加速管产生X射线的能谱分布、剂量率等。为满足X波段电子直线加速管高能量、高剂量率和多能量可调节的需求,本文针对其产生的4、6和9MeV高能电子束轰击转换靶的相     

9MeV电子束与复合靶作用的模拟研究

电子束与复合靶作用发生韧致辐射是一个复杂的过程,为优化产生X射线的品质,需要详细研究不同条件下电子束与复合靶的作用规律,本文从粒子与物质相互作用理论出发,应用蒙特卡罗模拟程序Fluka研究9 MeV加速器X射线转换靶的设计问题。结合9 MeV电子直线加速器转换靶的实际设计参数,设计高、低原子序数不同组合顺序的复合靶,并模拟分析9 MeV电子束与复合靶作用的剂量场分布、能谱分布、角分布以及漏电子情况等,通过对电子束与不同组合顺序复合靶作用研究,给出不同组合顺序与剂量场分布、能谱分布、角分布及漏电子等的关系与规律,并对能谱的硬化效果进一步分析。同时对部分模拟结果进行了实验验证。结果表明,复合靶中不同靶材的组合顺序对产生光子的能谱、电子能量漏率和角分布等都有一定影响,是复合靶设计时需要考虑的因素之一。     

强激光与固体靶相互作用所致硬X射线剂量的蒙特卡罗模拟

本文利用蒙特卡罗程序FLUKA建立了强激光与固体靶相互作用所致硬X射线剂量估算模型,通过与文献结果进行比较,对计算模型进行了验证。利用该计算模型研究了不同电子温度、不同靶材料(包括金、铜和聚乙烯3种常见靶材)和厚度对X射线剂量的影响。计算结果表明,X射线剂量与电子温度密切相关,并会受到靶参数的影响。相同靶厚情形下,Au靶产生的X射线剂量约为Cu靶产生的X射线剂量的1.2倍,约为PE(聚乙烯)产生的X射线剂量的5倍。另外,相较于其他靶厚,当选取电子的平均射程为靶厚时,产生的X射线剂量较大。这些计算结果将为强激光装置中电离辐射剂量的评估提供相关参考。     

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。     

轫致辐射X光源初步研究

对高能电子打薄靶和低能电子打厚靶两种不同轫致辐射方式的微型轫致辐射光源进行了研究.推导并比较了两种方式的单位电子光子产生率,给出了提高光子产额的方法.以BFEL直线加速器为平台,利用高能电子薄靶的轫致辐射光进行X光成像实验,研究薄靶对电子束流参数的影响,并对轫致辐射微型X光源的特性进行了讨论.     

首台出口无损检测用电子直线加速器的研制

正2018年,核技术应用研究所直线加速器研究室完成了一台无损检测用电子直线加速器的研制任务,实现了中国核工业集团有限公司出口加速器零的突破。1主要技术指标本台加速器用于无损检测,其技术指标满足IEC 62976—2017《工业无损检测装置-电子直线加速器》国际标准,主要技术指标如下:加速器类型,驻     

S波段轴耦合驻波加速结构优化计算

正电子直线加速器的加速结构主要包括行波结构和驻波结构,其中行波结构主要应用于科研用高能电子直线加速器及工业用高能电子束辐照等领域,驻波结构主要应用于医疗和无损检测等领域。中国原子能科学研究院开发的基于电子直线加速器的无损检测设备已形成系列产品,涵盖1/2、2/4、4/6、6/9、9/12 MeV双能无损检测加速     

9MeV电子直线探伤加速器性能测试

核技术所62室生产的9 MeV电子直线探伤加速器性能测试完成,满足了合同的要求,成为我室生产的第一台9 MeV探伤加速器。 将剂量率仪探头放在X射线中心轴线上距靶点2 m处,重复频率为240 Hz时,测得它的最大剂量率已达到3 000 rad/min。将剂量率仪探头放在X射线中心轴线上距靶1 m处,     

γ射线测距中散射光子影响因素的蒙特卡罗模拟

基于散射光子的γ射线测距技术,具有测距精度高、响应速度快、可靠性高、体积小、重量轻等特点,适用于在苛刻空间环境中实现近距离高精度的高度测量。本文采用蒙特卡罗程序MCNP建立模型,模拟不同条件下散射光子的能量、强度的变化规律,分析了探测距离、源 探距离、γ射线能量、靶目标厚度以及靶目标材料的变化对反散射峰光子能量与强度的影响,得出以下结论：反散射峰光子能量与靶目标厚度（>7 cm）、靶目标材料无关,与γ射线能量、源 探距离正相关,与探测距离负相关;反散射峰光子强度与靶目标厚度（>7 cm）无关,与探测距离正相关,与γ射线能量、源 探距离、靶目标材料负相关。对于不同靶目标材料,模拟计算的反散射峰光子能量分布区间与理论计算结果一致,证实本文γ射线散射光子测距技术的仿真方法可行、结果可信。     

ORE Assessment Due to ACP in the PHTS of the Point Design Phase of the ITER Project

The work presented here dealt with the revision and the updating of the ORE (Occupational Radiation Exposure) assessment for the ITER PHTS (Primary Heat Transfer System). The data used come from the Point Design Documents and refers to the ITER design of the first half of 1996. The MCNP computer code was adopted to perform the shielding calculation. In addition, an accurate approach to evaluate the photon flux during maintenance and inspection activities was followed and recently published photon-flux-to-dose-rate conversion factors were applied to obtain the corresponding dose rate. The ACP inventory was taken from the relevant calculation performed with the PACTOLE code for the Point Design. A special ACP calculation was performed for each PHTS circuit and the related results are used in the respective dose rate calculations. The collective dose for the main activities performed to maintain the PHTS components is reported. The dose result for each activity type is shown and the comparison with a reference fission plant is discussed.     

15 MeV～3 GeV电子加速器90°方向光子源项研究

韧致辐射光子是电子加速器屏蔽设计中的重要源项。为研究90°方向光子源项特征以及靶体半径和厚度对90°方向光子源项的影响,采用蒙特卡罗程序MCNPX27对15 MeV～3 GeV电子束轰击铁靶后的辐射源项进行计算。分析了90°方向光子辐射剂量、光子能谱等源项随靶厚度和半径的变化。通过与0°方向光子源项以及靶体内级联电子沉积能量进行对比,进一步分析了90°方向的光子源项特点。结果表明,90°方向光子能量主要集中在10 MeV以内,光子能谱形状与入射电子能量关系较小。受级联电子在靶内能量沉积程度及靶体对光子自吸收的共同影响,靶体半径和厚度是影响90°方向光子源项的重要因素。在电子加速器的屏蔽设计中应考虑靶体尺寸差异所带来的影响,同时建议针对束流90°方向和0°方向光子源项的差异,对加速器辐射屏蔽和防护进行优化设计。     

Shielding Design for Activated First Wall Transferring in ITER Hot Cell Building

The hot cell building is a part of the hot cell complex which is located to the north of the main ITER tokamak building. It would provide a controlled area for the preparation, transfer and repair-refurbishment of the in-vessel parts of the tokamak machine. During transfer of the activated parts and plasma operation, high radiation would be produced. For safe operation and maintenance of nuclear devices, it is very important to predict the dose rate distribution caused by transferring the components. This paper describes the study of the dose distribution in the hot cell building. A whole calculation model based on existing MCNP calculation models was built by multi-physics coupling analysis modeling program and then used to calculate the dose map using MCNP with sources defined according to previous calculation results. The thickness of shielding doors was then optimized according to the gamma dose before the doors and gamma dose attenuation within a concrete door.     

A comparison of dose rate calculations for a spent fuel storage cask by using MCNP and SAS4

This paper presents a detailed comparison of the surface dose rate calculations for the NAC-UMS spent fuel storage cask by using MCNP and SAS4 computer codes. Their accuracy and computation efficiencies are compared. For such a real world deep penetration and streaming problem, effective variance reduction techniques are indispensable for a Monte Carlo simulation to obtain results of small statistic errors within reasonable computing time. The TORT-coupled MCNP calculation based on the CADIS methodology has been used in this study. The main differences between MCNP and SAS4 calculations are the underlying cross-section libraries and the adjoint functions used for variance reduction in Monte Carlo simulations. The cross-section libraries and their formats should be the root cause for some significant discrepancies between the MCNP and SAS4 results. In addition, limited by the 1D adjoint biasing scheme, SAS4 is inefficient in calculating the dose rates near inlet/outlet apertures. Considering all the computer time spent and the statistical errors of results obtained, the overall computation efficiency by using the TORT-coupled MCNP is better than SAS4 in the shielding calculations of spent fuel storage casks. More specifically, although the SAS4 efficiency is better when the cask side calculation is the only concern, the TORT-coupled MCNP technique is more efficient for the gamma-ray transport in cask top configurations and almost all the vent-streaming problems.     

~(60)Coγ辐照加工产品剂量分布的蒙特卡罗模拟

对上海金鹏源(SHJPY)~(60)Coγ辐照装置进行数学建模,运用蒙特卡罗方法(MCNP),模拟计算辐照装置在装载0.1g/cm3的均匀产品情况下的剂量分布,软件模拟计算结果的统计误差控制在5%以内,模拟计算结果与实际0.1g/cm3产品剂量分布测试结果比较,发现偏差的绝对值在15%(多数在8%以下)以内,模拟计算与测量数据基本吻合,计算结果可以反应产品吸收剂量的分布规律。     

长中子计数管探测效率的模拟

为获得较高的探测效率且在较大范围内对中子有比较平坦的能量响应曲线,用蒙特卡罗程序研究了聚乙烯慢化体结构对BF3长正比计数管的中子探测效率的影响。模拟结果表明,增大慢化体半径可增加计数管探测效率,调节计数管前端慢化体厚度可改善能量响应曲线高能部分的平坦度。另外,利用建立的模型计算了1套现有的长硼计数器对D-D(2.4MeV)及D-T(14.1MeV)中子的相对探测效率。模拟结果为探测系统对D-D中子的探测效率为对D-T中子的75％,而加速器标定的实验结果为61％。两者可认为是近似一致的,这从实验上验证了模拟模型的可靠性。     

基于MCNP对γ辐射积累因子不同影响因素的研究

通过蒙特卡罗程序来模拟计算γ辐射积累因子,以找出不同条件下积累因子受各因素的影响,为屏蔽研究提供一定的数据参考。就γ辐射积累因子的影响因素:γ光子能量,源的几何尺寸,辐射角和屏蔽层厚度,通过MCNP程序进行了模拟计算。初步结论为:轻元素和中等元素构成的介质在厚度一定的情况下,积累因子随着γ光子初始能量的减小而增大;相对于轻材料,重材料的积累因子较小;随着源的线度增大而增大;随着准直角进一步增大而增大,源的各向同性程度增高会导致积累因子增加;随着源与探测器之间介质厚度的增加,积累因子增大,对于高能辐射源和具有中偏低原子序数Z的元素,积累因子增长速率接近于线性。     

Photon and positron production by ultrahigh-intensity laser interaction with various plasma foils

The generation of γ photons and positrons using an ultrahigh-intensity laser pulse interacting with various plasma solid foils is investigated with a series of quantum electrodynamic particlein-cell(PIC) simulations. When ultrahigh-intensity lasers interact with plasma foils, a large amount of the laser energy is converted into γ photon energy. The simulation results indicate that for a fixed laser intensity with different foil densities, the conversion efficiency of the laser to γphotons and the number of produced photons are highly related to the foil density. We determine the optimal foil density by PIC simulations for high conversion efficiencies as approximately 250 times the critical plasma density, and this result agrees very well with our theoretical assumptions. Four different foil thicknesses are simulated and the effects of foil thickness on γ photon emission and positron production are discussed. The results indicate that optimal foil thickness plays an important role in obtaining the desired γ photon and positron production according to the foil density and laser intensity. Further, a relation between the laser intensity and conversion efficiency is present for the optimal foil density and thickness.     

Benchmarking of the 3-D CAD-based Discrete Ordinates code “ATTILA” for dose rate calculations against experiments and Monte Carlo calculations

Shutdown dose rate (SDDR) inside and around the diagnostics ports of ITER is performed at PPPL/UCLA using the 3-D, FEM, Discrete Ordinates code, ATTILA, along with its updated FORNAX transmutation/decay gamma library. Other ITER partners assess SDDR using codes based on the Monte Carlo (MC) approach (e.g. MCNP code) for transport calculation and the radioactivity inventory code FISPACT or other equivalent decay data libraries for dose rate assessment. To reveal the range of discrepancies in the results obtained by various analysts, an extensive experimental and calculation benchmarking effort has been undertaken to validate the capability of ATTILA for dose rate assessment. On the experimental validation front, the comparison was performed using the measured data from two SDDR experiments performed at the FNG facility, Italy. Comparison was made to the experimental data and to MC results obtained by other analysts. On the calculation validation front, the ATTILA's predictions were compared to other results at key locations inside a calculation benchmark whose configuration duplicates an upper diagnostics port plug (UPP) in ITER. Both serial and parallel version of ATTILA-7.1.0 are used in the PPPL/UCLA analysis performed with FENDL-2.1/FORNAX databases. In the FNG 1st experimental, it was shown that ATTILA's dose rates are largely over estimated (by ～30–60%) with the ANSI/ANS-6.1.1 flux-to-dose factors whereas the ICRP-74 factors give better agreement (10–20%) with the experimental data and with the MC results at all cooling times. In the 2nd experiment, there is an under estimation in SDDR calculated by both MCNP and ATTILA based on ANSI/ANS-6.1.1 for cooling times up to ～4 days after irradiation. Thereafter, an over estimation is observed (～5–10% with MCNP and ～10–15% with ATTILA). As for the calculation benchmark, the agreement is much better based on ICRP-74 1996 data. The divergence among all dose rate results at ～11 days cooling time is no more than 15% among all participants.