The role of high-energy computed radiography （CR） in radiotherapy

Computed radiography (CR) imaging has high irradiation tolerance and it is easy to archive CR images along with other image information by Digital Imaging and Communications in Medicine (DICOM) format,and to process them.CR can be used in radiation Quality Control (QC) task and verification of treatment setting-up.In this paper,the role of high-energy CR in radiation oncology is studied.The patients were imaged by CR system and EPID before radiotherapy.All verification images were acquired with 1-2 MU (Monitor Unit) using 6 MV X-rays.QC for a tinac was done with film and high-energy CR to collect the data on daily,weekly and monthly basis.The QC included Multileaf Collimators (MLC) calibration and mechanical iso-centre check.CR was also adapted to verify patient position,the film was used to compare with digitally reconstructed radiographs (DRR) and portal image from EPID.Treatment setting-up was verified based on the result of comparison.High quality verification images cou ld beacquired by the CR system.Comparing to EPID,the results showed that the system was suitable for practical use to acquire daffy verification images,and it was useful to fulfill part of quality assurance (QA) in radiation oncology.The quality of image acquired by the high-energy CR system is comparable or even better than DRRs and portal images.The final treatment set-up for the patients could be verified more accurately with the CR system.     

反应堆吊篮在泵致脉动压力载荷下的响应研究

反应堆结构的流致振动问题一直受到核工程界的广泛关注。主泵的泵致脉动压力是一个重要激励源,其将导致反应堆吊篮等部件周期性振动,长期运行会导致结构的疲劳损坏。为研究新设计的“华龙一号”反应堆吊篮在泵致脉动压力作用下的振动响应,本文首先分析反应堆吊篮所受的泵致脉动压力,而后建立吊篮有限元模型,对其在泵致脉动压力载荷下的动力学响应进行研究,并综合考虑湍流激励,评价吊篮在堆内构件流体作用下的整体影响。应力分析表明,吊篮各位置流致振动的最大应力强度小于疲劳应力限值,结构是安全的。但对于新设计的反应堆,或反应堆冷却剂系统更换新的主泵,则反应堆吊篮及堆内构件的泵致振动需受到重视。     

Manufacturing of JT-60SA Cryostat Base

JT-60SA is a superconducting tokamak to be assembled and operated at the JAEA laboratories in Naka (Japan) [1]. The tokamak has been designed to prepare, support and complement the ITER experimental programme and will be manufactured and operated under the funding of the Broader Approach Agreement (between the government of Japan and the European Commission) and of the Japan Fusion National Programme. Within the European contribution to JT-60SA, Spain has to provide the cryostat. Due to functional purposes, the cryostat has been divided in two large assemblies: the Cryostat Base (CB) and the Cryostat Vessel Body the latter subdivided into Cryostat Vessel Body Cylindrical Section (CVBCS) and the Top Lid. Spain is committed to provide the design and subsequent manufacturing of the CB and CVBCS (excluding the Top Lid) through the National Laboratory of Fusion at Ciemat. The design of both components has been concluded and the CB is currently being manufactured by a Spanish company, IDESA. This paper aims to present the status of the manufacturing and pre-assembly at the factory of the CB that has to be delivered in November 2012.     

聚乙烯/碳黑复合导电材料的正电子谱学研究

在高密度聚乙烯（HDPE）中掺入碳黑（CB）可以显著提高其导电性能,而且碳黑含量的变化对导电性有很在影响。本文用正电子湮没技术研究了这种复合体系中自由体积随碳黑含量的变化规律,证实了碳黑颗粒处于非晶区的观点,并结合电阻率测量和差热分析的实验结果探讨了渗流阈值以及结晶度等问题。     

辐射交联CB/EVA导电复合物热氧稳定研究

研究CB／EVA半导电聚合物复合物电阻的热氧稳定性与辐照剂量的关系，并对辐照样品作了DSC，IR等分析。结果表明，合适的辐照剂量和复合热氧稳定剂体系能有效地提高半导电CB／EVA复合物电阻的热氧稳定性。     

Semi-automated synthesis, validation and microPET imaging of 18F-FP-DTBZ as a vesicular monoamine transporter ligand

This work was to develop a semi-automated synthesis of 18F-9-fluoropropyl-9-desmethyl-DTBZ (18F-FP-DTBZ) and validate its potential as a vesicular monoamine transporter 2 (VMAT2) ligand.18F-FP-DTBZ was synthesized by a semi-automated procedure in a 21-35% yield without decay correction and with a radiochemical purity of >98%.Bioistribution in rats exhibited a favorable brain uptakes of the ligand (0.31±0.04 ID% at 60min post injection,n=8).The highest radioactivity located in VMAT2 enriched striatal tissue.The target-to-nontarget ratio (striatum/cerebellum,ST/CB) was 4.81±0.84.Blocking studies implied that striatum uptake could be blocked by DTBZ (a VMAT2 inhibitor) but could not by CFT (a dopamine transporter inhibitor).MicroPET imaging with 18F-FP-DTBZ in normal rats gave high quality images in which high radioactivity were observed in the striatal tissue.Time-and-activity curves revealed good retention in the target (striatum) and rapid clearance in the background (cerebellum),which resulted in a maximum ST/CB ratio of 5.08±0.81 (n=3) in 80-120min.By contrast,the 6-hydroxydopamine unilateral lesioned rats gave asymmetrical striata images with higher 18F-FP-DTBZ concentration on the unlesioned side (unlesioned-ST/CB=5.21±0.38,n=3) than the lesioned (lesioned-ST/CB=2.34±0.51).The results validated that 18F-FP-DTBZ is a favorable PET ligand binding to VMAT2.     

CSR1000控制棒落入堆芯三维瞬态分析

针对超临界水堆(SCWR)控制棒落入堆芯事件特点,采用堆芯三维瞬态性能分析方法,利用开发的SCWR堆芯三维瞬态物理-热工水力耦合程序STTA,建立SCWR堆芯落棒瞬态三维计算模型和分析流程,研究分析超临界水堆CSR1000在控制棒落入堆芯瞬态过程中的堆芯性能,分析评价落棒瞬态下CSR1000堆芯的安全性能。堆芯三维落棒瞬态分析表明,当落入堆芯棒束价值较高时,落棒初期堆芯功率下降较快,之后由于水密度的反应性反馈,堆芯功率缓慢回升至新的平衡,堆芯功率下降速率超过了停堆信号整定值,将触发保护停堆;当落入堆芯棒束价值较低时,由于水密度的反应性反馈,堆芯功率下降缓慢,堆芯功率下降速率未能达到停堆信号整定值,不能触发保护停堆。控制棒落入堆芯对堆芯轴向功率分布影响很小,高价值落棒导致的落棒区域燃料组件功率坍塌相对低价值落棒更明显。无论是高价值落棒还是低价值落棒,瞬态过程中最大包壳壁面温度均低于瞬态安全限值850℃。水密度的显著反应性反馈及必要的保护停堆措施能保证CSR1000堆芯在控制棒落入堆芯过程中的安全性能。     

Dynamic dielectric recovery performance of serial vacuum and SF6 gaps in HVDC interruption and its regulation method

Vacuum gaps have rapid dynamic dielectric recovery speed while SF₆ gaps have high insulation strength. The series-connected vacuum and SF₆ gaps are used as the main switch (MS), which combines their advantages. The work aims to verify the feasibility of serial vacuum and SF₆ gaps in mechanical HVDC interruption. The test circuit of the dynamic dielectric recovery performance (DDRP) is set up. The DDRP is tested under free recovery condition by the high voltage pulse source. The DDRP of the vacuum circuit breaker (VCB) and SF₆ gas circuit breaker (GCB) in DC interruption with active current injection is analyzed and compared. The test results indicate that the dielectric recovery duration of the VCB is below 30 μs while that of the GCB is above 100 μs. In order to achieve the cooperation between the VCB and GCB, a novel hybrid HVDC circuit breaker (CB) based on series-connected vacuum and SF₆ gaps is proposed. The ‘voltage-zero’ duration is created by introducing the follow current loop and there more recovery time for the dielectric recovery of the MS. The voltage distribution is controlled by the voltage dividing method so that the VCB undertakes the initial transient recovery voltage (TRV) and the later TRV is took by the GCB. The theoretical synergy characteristic of the novel HVDC CB is obtained. The paper supplies a new method to improve the custom mechanical HVDC CB, which is useful to achieve the HVDC CB with less serial breaks.     

RELEASE OF ~(14)C—BUTACHLOR AND ~(14)C—OXADIAZON FROM CR FORMULATIONS INTO WATER

~(14)C-butachlor and ~(14)C-oxadiazon could be released from four kinds of CR formulations into water respectively, and the release percentage of each herbicide increased with time, which could be expressed by regression equations (very obvious positive relationship). The release percentages of ~(14)C-herbicides from CR formulations were related to herbicide CR formulation and water type. Total recovery including ~(14)C-released and ~(14)C-left in formulations for each ~(14)C-herbicide was high at the 56th day after treatment. Some of the released ~(14)C-butachlor in water could be hydrolysed although under dark condition. The rate of hydrolysis was influenced by water type and formulations.     

Status and progress of Indian LLCB test blanket systems for ITER

The lead–lithium ceramic breeder (LLCB) TBM and its auxiliary systems are being developed by India for testing in ITER machine. The LLCB TBM consists of lithium titanate as ceramic breeder (CB) material in the form of packed pebble beds. The FW structural material is ferritic martensitic steel cooled by high-pressure helium gas and lead–lithium eutectic (Pb–Li) flowing separately around the ceramic breeder pebble bed to extract the nuclear heat from the CB zones. Low-pressure helium is purged inside the CB zone for in situ extraction of bred tritium. Currently the LLCB blanket design optimization is under progress. The performance of tritium breeding and high-grade heat extraction is being evaluated by neutronic analysis and thermal–hydraulic calculations for different LLCB cooling configurations and geometrical design variants. The LLCB TBM auxiliary systems such as, helium cooling system (HCS), lead–lithium cooling system (LLCS), tritium extraction system (TES) process design are under progress. Safety analysis of the LLCB test blanket system (TBS) is under progress for the contribution to preliminary safety report of ITER-TBMs. This paper will present the status of the LLCB TBM design, process integration design (PID) of the auxiliary systems and preliminary safety analysis results.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.     

辐射交联对LDPE/CB复合物PTC效应稳定性的影响

研究了低密度聚乙烯（LDPE）／炭黑（CB）复合物在升温、降温循环中的导电性能。利用示差扫描量热分析仪（DSC）研究了复合物的熔融行为，以及应用压力－体积－温度分析仪（PVT）研究了复合在聚合物熔点时的体积膨胀性能。结果表明，辐射交联可以有效地提高复合物正温度系数（PTC）效应的重复性，纯凝胶复合物的PTC强度显著降低，说明溶胶在聚乙烯熔点时的体积膨胀是交联复合物正温度系数（PTC）效应的产生的重要原因。     

Optical properties of carbon materials filled HDPE composites in THz region

The optical and electrical properties of several composites,formed by filling the high density polyethylene (HDPE) with similar amount of carbon black (CB),multi-walled carbon nanotubes (MWNT) and fullerene (C60),respectively,were characterized using a THz-TDS setup.It was found that the optical parameters and the details of their variation with frequency differ significantly for different kinds of carbon materials.The results are analyzed by using Cole-Cole formula of dipole relaxation under the assumption that carbon particles dispersed in the matrix behave like dipoles and contribute mainly to the dielectric loss in the THz frequency range.Fitting results indicate that MWNT and CB filled composites have a broader distribution of the relaxation time compared with C60 which possesses a nearly single relaxation time.Compared with CB and C60,MWNT filled composite possesses the larger relaxation strength due to its higher electron density and larger conductive clusters.The real part of conductivity for three kinds of composites all follows power law behavior with respect to frequency but the exponents are quite different.These phenomena may be related to the special properties of the fillers as well as their particulate structures,such as aspect ratio,particle size,and aggregate structure,etc.     

CB20结构模块组安装施工技术分析

CB20模块是AP1000核电站非能动安全壳冷却系统(PCS)的钢结构水箱模块,它是一个多部件组合体,外形尺寸大,结构复杂,且要在现场露天组成一个整体,其中涉及组装、焊接、运输及吊装等环节,施工难度大。本文介绍了CB20模块的组装、运输、吊装和安装等施工工艺流程,分析了CB20模块施工的重点及难点,结合现场实际情况,提出一些应对措施,尤其是对其变形的控制方面。这为后续CB20模块组安装施工及其他大型模块施工起到一定的参考和借鉴作用。     

Formation of spectral characteristics of channeling radiation from 800 to 2000 MeV electrons and positrons in a thin silicon crystal

The influence of the tails of particle trajectories on planar channeling radiation (CR) spectra from relativistic (800-2000 MeV) electrons and positrons in a thin silicon crystal is investigated. It is shown that the trajectory tails significantly change the CR spectra from electrons and positrons in specific parts of the spectra compared to calculations which do not take into account this effect.     

Assessment of the MDNBR enhancement methodologies for the SMART control rods banks withdrawal event

For an electricity generation and seawater desalination, a 330 MW System-integrated Modular Advanced ReacTor (SMART) was developed by KAERI. The safety level of the SMART is enhanced when compared to that of the typical commercial reactors, with the aid of an elimination of a large break loss of coolant accident by placing the major components of the primary system in a reactor vessel and the adoption of a new technology and a passive design concept into the safety system. However, the events related to reactivity and power distribution anomalies have been evaluated as vulnerable points when compared to the other initiating events in the SMART, since the reactivity worth of the control rods (CR) banks is quite large due to the boron free core concept. Especially, safety margins, i.e., minimum departure from nucleate boiling ratio (MDNBR), are significantly threatened during the CR banks withdrawal event. Therefore, MDNBR enhancement methodology for the CR banks withdrawal event should be considered to further enhance the safety level of the SMART design. Two methodologies have been suggested to enhance the MDNBR during the CR banks withdrawal event: the application of a DNBR trip function into a core protection system and a turbine trip delay methodology. Sensitivity studies are performed to evaluate the two MDNBR enhancement methodologies and show that the suggested methodologies could enhance the MDNBR during the CR banks withdrawal event of the SMART.     

Effective Homogenization Method for Control Rod Channels

A cell calculation method has been developed for accurately treating neutron transport and heterogeneity effects of control rods (CRs) within the bounds of homogeneous neutron diffusion theory. In this method, CR cell-averaged homogeneous neutron cross sections are calculated by a heterogeneous neutron transport calculation with an annular supercell model, in which a CR assembly is surrounded by a homogeneous fuel region. Then, a neutron diffusion calculation is carried out using the homogeneous neutron cross sections in the same supercell, and the CR cell-averaged radial neutron diffusion coefficients are modified in an iterative manner such that the CR cell-interface neutron current which is obtained by the heterogeneous transport calculation can be reproduced by the homogeneous diffusion calculation. In the case of a 1,000-MWeclass FBR, the center CR worth, which was calculated by an RZ diffusion calculation using the cross sections obtained by the above method, agreed within 1% with that obtained by a heterogeneous transport calculation, proving the validity of the method.     

Channeling radiation from relativistic electrons in a thin LiF crystal: When is a classical description valid?

Calculation of channeling radiation from relativistic electrons under (1 1 1) planar channeling conditions in a LiF crystal is performed using both classical and quantum methods. The complicated shape of the periodic (1 1 1) planar potential allows the existence of a different number of discrete energy levels (quantum states) in the potential well formed by planes consisting of only Li atoms and the potential well consisting of only F atoms is large enough to apply the classical method. With increasing electrons energy, the classical method becomes valid to describe CR from under-barrier electrons in a deeper potential well, while one should still apply the quantum method to calculate CR from electrons in neighboring planes. Thus, the quantum feature of a CR spectrum from relativistic electrons maintains its quantum characteristics up to relativistic factors 1000.     

The study on the hydraulic control rod driving system in cyclical swing

This paper discusses the behavior of the hydraulic control rod driving system (HCRDS) in cyclical swing. The first generation HCRDS with the hole–hole step cylinder, the important driving component, has been applied in 5 MW nuclear heating reactor for several years and run well all along. The second generation with the chamfer-hole step cylinder has also been developed and studied.The HCRDS working principle, as well as the particular design of the hole–hole step cylinder, has been introduced in the paper. The control rod (CR) behavior when HCDRS vacillating in certain swing and cycle has been analyzed subsequently. The calculating result indicates that the CR can keep its balance in such unstable state and the operation of driving CR upwards or downwards can function properly likewise. In cyclical swing, the CR can drop down quickly and meet the reactor shut-down needs. The theoretical analysis proves the HCRDS reliable and safe, establishing basement for its further research and wide use.     

SPECT reconstruction of combined cone beam and parallel holecollimation with experimental data

Three methods for combining parallel and cone beam (P&CB) SPECT data using modified maximum-likelihood expectation-maximization (ML-EM) algorithms are presented. The first method applies both parallel and cone beam data sets to reconstruct a single intermediate image after each iteration using the ML-EM algorithm. The other two are iterative methods that combine the intermediate parallel beam and cone beam source estimates to enhance the uniformity of images. These two methods are ad hoc methods. These combined collimation methods are qualitatively evaluated using experimental data. Attenuation compensation is performed by including the effects of attenuation in the transition matrix as a multiplicative factor. The results indicate that the combined P&CB approaches suppress artifacts caused by truncated projections and corrects for th distortions of the CB-only images