福岛核电厂3号机组严重事故模拟分析

本文应用MELCOR程序,通过建立全厂详细的模型,对福岛第一核电厂3号机组在地震发生后3 d内的严重事故进程进行了模拟分析并与电厂实测数据进行了比较,再现了从事故开始到堆芯失效坍塌直至氢气爆炸在内的主要严重事故现象。基于文中假设的模拟计算得到的趋势与电厂现有实测数据较为一致,结果表明：地震发生后约36 h反应堆水位降至堆芯活性区顶部。操纵员未能及时成功对安全壳和反应堆进行快速卸压,以在堆芯底部出现裸露前向反应堆补充冷却水,使得堆芯出现严重的锆水反应,大部分燃料包壳已破损而导致易挥发的放射性裂变产物的释放;但此时堆芯整体依然维持可冷却几何形状;在消防水泵向反应堆注入冷却水期间,由于冷却注入流量出现中断,导致堆芯进一步熔毁坍塌;碎片迁移至下腔室后,进一步的锆水反应(金属 水反应)新增的氢气泄漏并积聚在反应堆厂房上部,引发了安全壳厂房的爆炸;72 h内,堆芯内约50%的锆合金发生了氧化,压力容器下封头未发生失效。     

全厂断电事故下模块化小堆非能动余热排出系统实验研究

针对模块化小堆非能动安全系统(PRHRS)的设计特点,建立了非能动安全系统综合实验装置CREST。在CREST实验装置上,进行了全厂断电事故短期性能实验,研究了PRHRS的冷却能力及运行特性。研究结果表明:全厂断电事故发生后,PRHRS能正常启动,非能动余热排出冷却器和蒸汽发生器之间能形成0.4 t/h稳定的两相自然循环流量,并有效地将堆芯衰变热量和显热带入安全壳水池(CWT)。堆芯补水箱(CMT)中的冷水可以有效注入反应堆压力容器冷却堆芯。在事故过程中,一回路系统最高压力为16.3 MPa,低于安全阀开启压力16.9 MPa,堆芯冷却剂平均温度可以冷却至210℃以下,反应堆处于安全运行状态。     

AP1000小破口叠加重力注射失效严重事故分析

应用新版MELCOR程序,建立了AP1000一二回路、非能动安全系统及安全壳隔室的热工水力模型,并以热段小破口叠加重力注射系统失效事故为例,对该严重事故进程在压力容器内阶段进行模拟计算,对缓解措施的功能进行了分析和评价。结果表明：自动卸压系统（ADS1～4）的成功实施,可使来自堆芯补水箱和安注箱的冷却水快速有效地注入堆芯,在冷却水完全耗尽前,堆芯始终处于淹没的状态。ADS4爆破阀开启后,使回路压力快速与安全壳压力平衡;非能动安全壳冷却系统对抵御严重事故下由于衰变热和非冷凝气体带来的缓慢升温升压是行之有效的措施;点火器在氢气浓度较低时点火,缓解了安全壳大空间发生全局燃爆而引发安全壳超压失效的风险,但连续点火燃烧会引起局部隔室温升远超出设计温度而危及后备缓解设施的存活。     

波动管小破口失水事故实验研究

在模块化小型反应堆非能动安全系统综合模拟实验装置上进行波动管小破口尺寸失水事故实验,研究波动管小破口失水事故过程中的热工水力现象和非能动安全系统运行特性。模块化小型反应堆发生失水事故后,压力平衡管和安注管线内流体的密度差可以驱动堆芯补水箱(CMT)内的冷流体注入反应堆压力容器,压力平衡管裸露后CMT安注流量出现波动;安注箱(ACC)的安注对事故初期的堆芯冷却效果显著;经自动卸压系统卸压后,内置换料水箱(IRWST)可以对堆芯进行持续稳定的安注和冷却。研究结果表明:波动管小破口失水事故中,非能动安注系统可以对堆芯进行有效注水,并带走堆芯衰变热量。     

美国核管会开始调查塞勒姆核电站的冷却剂丧失事故

【欧洲核学会《核新闻网》 1998年 12月10日报道】　美国正在调查塞勒姆核电站 2号机组 1998年 12月 8日发生的冷却剂丧失事故。该电站是由于公用事业电力与煤气公司运营的。核管理委员会 (NRC)在有关该事故的一篇报告中说 ,反应堆冷却剂过多泄漏是由通向余热排出泵的管道上的一个泄压阀的开启引起的。发现稳压器水面下降时仍有电站工作人员在安全壳内 ,当他们注意到有蒸汽逸出时 ,工人们顺利地离开了安全壳。 3个小时之后该事故被排除。还不清楚该泄压阀为什么在反应堆冷却剂压力略低于其设定值时打开。 NRC说 ,对泄漏数据进行的一次调…     

采用能动和非能动安全系统的HPLWR安全壳设计建议

基于最新的沸水堆安全壳设计概念，提出了类似带有余热排出系统的高性能轻水堆安全壳的概念。它包括1个抑压水池、4个堆芯淹没水池、4个能动余热排出系统和4个非能动余热排出系统。安全壳的内径为20m，高度约为22m。4个冗余的能动系统在低压下从抑压水池向反应堆提供补水。8个压力释放阀和上都堆芯淹没水池中的8个喷头提供快速卸压。作为一种替代方法，堆芯产生的蒸汽可通过8个非能动热移出系统排放，每个系统都有一个蒸汽喷射器和一个浸入堆芯淹没水池的冷凝器。这个方案虽然还没有进行过任何瞬态分析研究，但可以作为一个可行的安全壳设计概念的基础来讨论。     

SuperLWR的LOCA分析

为了验证带有向下流水棒的超临界压力轻水冷却热中子反应堆（简称SuperLWR）的特性，进行了该堆的冷却剂丧失事故（LOCA）分析。分析范围为热／冷段的1％-100％破裂。在冷段大破口情况下，喷放期间过分的堆芯加热将通过自动卸压系统（ADS）得到缓解，这是因为反应堆卸压会导致堆芯冷却剂流动。在顶部水室和水棒内的冷却剂装量被有效地用于堆芯冷却。在喷放之后，像压水堆（PWR）一样，堆芯慢慢地被低压应急堆芯冷却系统（ECCS）再淹没。大破EILOCA的最高包壳温度低于准则值（1260℃）大约为430℃，出现在再淹没阶段。冷段的小破口给出了比大破口更高的包壳温度，这是因为在本分析中没有启动ADS。最高包壳温度低于准则值大约260℃。如果假定ADS被“干井压力高”信号启动，包壳温度将更低。热段破口不会比冷段破口严重，因为热段破口将增加堆芯冷却剂流量，预计在喷放之后将强迫淹没堆芯。     

海阳核电一期工程严重事故下非能动安全壳冷却能力分析

采用一体化事故分析程序建立了包括主冷却剂系统、专设安全设施、安全壳系统和非能动安全壳冷却系统(PCS)的海阳核电一期工程核电厂模型,对核电厂压力容器直接注射(DVI)管线破裂、冷段双端断裂、自动卸压系统(ADS)误启动、热段2英寸破口等严重事故序列进行了模拟计算,分析反应堆系统的热工水力行为。并通过安全壳系统的压力和温度响应,分析了非能动安全壳冷却系统在严重事故工况下的冷却能力。计算表明,对于分析的严重事故工况,在72h内,PCS的冷却能力能够保持安全壳内压力和温度处于较低水平,可以保障安全壳完整性。分别针对PCS水膜覆盖率以及环境温度对PCS冷却效果进行了敏感性分析,表明水膜覆盖率降低和环境温度升高均会使PCS冷却能力降低,安全壳内压力升高,但均未超出其设计压力。     

百万千瓦级核电厂超设计基准事故对策分析

以小破口失水事故(SBLOCA)为例,使用RELAP5和MAAP程序,计算超设计基准事故不同情况下操纵员操作时间窗口。计算结果表明:堆芯未熔化情况下,SBLOCA时执行充-排操作的时间窗口为1800 s,安全壳喷淋手动开启时间窗口为5400 s。严重事故情况下,操纵员需要对一回路卸压,针对二代改进型压水堆核电厂,避免堆芯熔化的时间窗口为300 s,避免压力容器损坏的时间窗口为3000 s。通过计算分析,给出设计扩展工况不同情况下安全设施需求及操纵员操作时间窗口。     

压水堆核电厂严重事故卸压阀能力评估

在百万千瓦级压水堆核电厂中为防止高压熔堆严重事故发生时发生高压熔喷(HPME)和安全壳直接加热(DCH),参考EPR堆型在稳压器上额外设置严重事故卸压阀(SADV),对主系统进行快速卸压。建立百万千瓦级压水堆核电厂事故分析模型,选取丧失厂外电叠加汽动辅助给水泵失效,一回路管道小破口以及丧失主给水三条典型严重事故序列,进行系统热工水力及卸压能力分析。计算结果表明:如果不开启严重事故卸压阀,三条事故序列在压力容器下封头失效时一回路压力均较高,有发生高压熔喷和安全壳直接加热的风险。根据严重事故管理导则开启严重事故卸压阀,可以有效降低一回路压力,三条事故序列均可以防止高压熔喷和安全壳直接加热发生。针对卸压阀阀门面积的影响进行分析,表明阀门面积减小到4.8×10-3 m2后下封头失效时RCS压力会有所增加,仍然能够满足RCS的卸压要求,且可延迟下封头失效时间。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ~(232)Th,~(238)U and ~(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ~(232)Th in the present study is 1.19 times higher than world median value while the activity of ~(238)U and ~(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ~(232)Th,~(238)U and ~(40)K in soil samples is 36.99 nGy·h~(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.     

Non-FDG PET imaging of brain tumors

Due to relatively high uptake of glucose in the brain cortex, the use of FDG PET imaging is greatly limited in brain tumor imaging, especially for low-grade gliomas and some metastatic tumours. More and more tracers with higher specificity were developed lately for brain tumor imaging. There are 3 main types of non-FDG PET tracers： amino acid tracers, choline tracers and nucleic acid tracers. These tracers are now widely applied in many aspects of brain tumor imaging. This article summarized the general use of non-FDG PET in different aspects of brain tumor imaging.     

基于NPL-NMC系统的γ测量子系统的建模与优化

在军控核查中,核部件的质量、丰度、年龄属性需采用无损方法进行核查,NPL-NMC系统是一套利用中子多重性测量核部件质量属性的装置,为建立完善的属性测量系统,还需在NPL-NMC系统的基础上建立γ测量子系统。本文通过设计γ测量子系统在NPL-NMC系统上的布局及对中子屏蔽的优化,使系统能对铀部件的丰度、年龄属性进行测量。模拟计算结果表明,该γ测量子系统能很好地满足军控核查对铀部件丰度、年龄属性测量的要求。     

Improvement of carbon fiber surface properties using electron beam irradiation

Carbon fiber-reinforced advance composites have been used for structural applications,mainly on account of their mechanical properties.The main factor for a good mechanical performance of carbon fiber-reinforced com- posite is the interfacial interaction between its components,which are carbon fiber and polymeric matrix.The aim of this study is to improve the surface properties of the carbon fiber using ionizing radiation from an electron beam to obtain better adhesion properties in the resultant composite.EB radiation was applied on the carbon fiber itself before preparing test specimens for the mechanical tests.Experimental results showed that EB irradiation improved the ten- sile strength of carbon fiber samples.The maximum value in tensile strength was reached using doses of about 250 kGy.After breakage,the morphology aspect of the tensile specimens prepared with irradiated and non-irradiated car- bon fibers were evaluated.SEM micrographs showed modifications on the carbon fiber surface.     

Measurement system for SSRF pulsed magnets

This paper describes the magnetic field measurement system for pulsed magnets in SSRF.The system consists of magnetic probes,analog active integrator,oscilloscope,stepper motor and a controller.An application pro- gram based on LabVIEW has been developed as main control unit.After the magnetic field mapping of a septum magnet prototype,it is verified that the test results accord with the results of theoretical calculation and computer simulation.     

旁路阀调节对高温气冷堆闭式布雷顿循环瞬态特性影响研究

闭式布雷顿循环是第4代高温堆核能系统的关键技术之一,其典型的动态过程是旁路阀调节。为分析这一过程,建立了循环中关键部件的动态模型,其中压气机在径向平衡模型基础上耦合了对附面层发展的预测,兼顾了计算效率与准确性;换热部件模型基于双曲型守恒律方程,对工质的热物性和参数的快速变化有较好的适应性。在此基础上根据回路的质量守恒和压力平衡原则将各部件的模型耦合,建立了系统的动态模型。由于旁路阀调节是氦气透平发电系统主要的功率快速调节手段,瞬态效应较为显著,以模块式高温气冷堆（HTR-10GT）旁路阀开启后的过渡过程作为算例,分析了主要循环参数的响应特性,并通过分析,给出了降低输出功率的机制。计算结果表明：系统的容积惯性对旁路阀调节的响应速度影响较大,而阀门的开度则决定了系统在末态的输出功率;回热器的温度冲击现象可能发生在调节过程中,但可通过两旁路阀联动的方式缓解;反应堆出口温度变化幅度很小,因此反应堆模型的准确程度对结果基本无影响。     

CEFR 100%额定功率运行汽轮机发电能力分析

中国实验快堆(CEFR)首次100%额定功率发电运行中,实际电功率较设计值相差较多。为判断影响机组实际发电能力的主要原因,以现场采集的运行数据和汽轮机厂商提供的设计资料为基础,进行了相应的计算分析。对汽轮机内效率进行修正,绘制汽轮机近似热力过程曲线,并通过实测的各段抽汽压力,在热力过程曲线上获得抽汽焓值;利用换热器的能量守恒和流量守恒的基本方程进行除氧器和各加热器的热平衡计算,获得各段抽汽的流量;利用汽轮机的功率计算方程,得到汽轮机发电功率的计算值。通过计算值与实际值的比较分析,得出主蒸汽参数不达标是影响CEFR汽轮机发电能力的主要因素。