应用CDAG方法进行EPR机组的严重事故堆芯损伤研究

介绍了堆芯损伤评价的指导方法,并将西屋公司的CDAG方法论应用于EPR机组进行严重事故堆芯损伤研究。CDAG堆芯损伤程度的评价主要由2个参数判断:安全壳辐射监测值(CRM)和堆芯出口热电偶读数(CET)。本文讨论了CRM与CET的堆芯损伤估算结果存在差异的原因,分析结果表明:①CDAG是一种适用于EPR机组严重事故下堆芯损伤评价的方法;②CDAG方法能反映实时的堆内裂变产物释放的份额,能够快速地为应急组织决策提供支持;③基于EPR设计的CRM和CET整定值的保守计算结果显示出一个较为合理的趋势和范围;④释放方式、燃耗、RCS裂变产物滞留等因素对堆芯损伤估算结果有较大的影响。     

基于层次分析法选取影响硝酸盐自然循环回路性能的关键参数

硝酸盐自然循环回路(Nitrate natural circulation loop,NNCL)中驱动力和阻力在量级上非常接近,由于环境、材料参数、结构参数和运行参数的波动都可能对NNCL系统性能造成不可忽略的影响,因此需要寻找出影响NNCL系统性能的关键参数。层次分析法是一种采用专家经验构造判断矩阵,通过计算参数不同权重供人们决策的系统分析方法。利用层次分析法对影响NNCL系统性能的40个参数进行建立层次结构模型和判断矩阵,通过权重计算从而选出12个关键参数,这些参数既包括物性参数、结构参数,也包括运行参数。通过分析得出NNCL系统运行阶段应关注的关键参数依次为空气入口温度、加热功率和空气流量。     

熔融物堆内滞留条件下压力容器外部自然循环特征分析

基于一维稳态两相分离流模型,并引入低流速过冷沸腾净蒸汽产生点方法,建立熔融物堆内滞留(IVR)条件下的两相流动数值计算模型,以获取两相流真实含气率。通过对比ULPU-V试验中自然循环流量,验证数值计算模型预测结果的准确性。针对AP1000堆型,分析几何结构参数和热工参数对其IVR策略中自然循环流量的影响。分析结果显示,冷却水过冷度、流道间隙、堆腔淹没水位、流道入口面积和出口阻力系数对自然循环过程有着不同程度的影响,自然循环稳态流量呈现出不同的变化趋势。     

海洋条件下核动力装置自然循环流动特性的无量纲分析

利用无量纲分析法推导出海洋条件下核动力装置的自然循环流量表达式,导出了稳态自然循环流量方程,结果与实验值吻合.以自然循环流量的波动不引起功率调节系统动作为限制条件,采用无量纲分析法推导出此条件下摇摆振幅与摇摆周期的关系式;两者呈二次函数关系,理论计算结果与大型分析程序的计算结果吻合.功率调节系统动作与否取决于最大摇摆角加速度的大小,而与最大摇摆角速度无关.     

混合能谱超临界水冷堆反应性引入事故安全分析

本文研究了混合能谱超临界水冷堆(SCWR-M)在发生控制棒失控提升事故和弹棒事故这两类反应性引入事故后的反应堆系统响应。首先利用修改的可用于超临界条件下的系统程序RELAP5对混合能谱超临界水冷堆进行系统建模,并计算分析在功率运行工况下事故过程中功率、流量及包壳温度等重要参数的变化趋势,最后对反应性参数如控制棒价值、控制棒抽出速率和负反馈系数进行了参数效应分析。结果表明,在设计工况下混合能谱超临界水冷堆系统可有效地将衰变热导出堆芯,保证了燃料棒的完整性。另外,反应性参数对控制棒失控提升事故的安全性影响不大,但对弹棒事故的包壳峰值温度影响很大,过于保守的反应性参数估计会使安全裕量大为减小。     

放射性废液蒸发系统的操作条件选择

在对放射性废液蒸发处理系统进行调试过程中,通过调节废液上料量、蒸汽发生器液位、一次蒸汽流量等系统参数来改变系统运行工况,得出各工况下的净化系数,分析系统净化效果的影响因素。调试结果表明:对于该系统,蒸汽发生器液位在500mm时净化系数最高;蒸发量为1m3/h时,净化系数最高;系统在变工况运行时产生波动,净化系数降低。系统原有两条控制联锁,为一次蒸汽流量与预热器出口温度、一次蒸汽流量与蒸汽发生器液位的联锁,仅此两条联锁对于系统的稳定性不够,且一次蒸汽控制液位的控制方式灵敏性差,滞后严重。文章通过分析系统运行各参数的关系,从系统运行稳定性和净化效果的角度,提出对该系统控制方式的合理改进——调整蒸汽发生器液位与上料量联锁控制。     

基于GO-FLOW方法的可维修系统可靠性分析

将GO-FLOW方法用于限定维修工和维修优先权的可维修系统的可靠性分析,推导适于GO-FLOW模型计算的可维修系统可靠性参数近似等效模型,并进行模型的验证和误差分析。以冗余泵单元为实际算例,将分析结果与采用GO法的情况进行对比。研究结果表明,在对该类可维修系统进行可靠性定量分析时,与GO法相比,改进后的GO-FLOW算法模型是有效的,并且计算更为简捷。     

某同位素生产线放射性废气处理系统设计

为确保某同位素生产线项目产生的气态放射性流出物能满足排放标准,根据释放源项及气体流量,对比了加压衰变法与滞留床吸附法的优缺点。借鉴国内核电站放射性废气处理系统的工艺设计,提出了“碱洗+冷冻除湿+吸附干燥+活性炭滞留”联合工艺。文章中详细介绍了处理工艺流程、主要设备的参数设计及滞留床活性炭用量的优化计算,对废气处理装置的功能、系统流程、系统配置、布置方案等进行阐述,给出装置总体设计方案。装置设计完毕后进行了相应的试验,单床滞留时间4.6 h(以Kr-85计),优于设计值。干燥装置压降在216~274 Pa之间、滞留装置单床压降在183~310 Pa之间,均满足设计指标要求,在安全性、经济性和可实施性方面作到了较好的综合平衡。     

HTR-10堆芯球流运动的唯象学DEM模拟

清华大学研发的10 MW高温气冷堆（HTR-10）是国际上重要的先进实验反应堆,球流运动的研究具有基础性地位。通过唯象的方法对HTR-10堆芯的球流运动进行了离散元数值模拟,通过已由实验验证的计算程序,采用与HTR-10堆芯1∶1的计算模型,计算了27 000个元件单元的运动,包括不同摩擦系数f和不同底部锥角A下的球流运动。结果表明：在HTR-10堆芯设计条件下,球流运动较均匀,堆芯底部不存在滞留区;f越大或A越大,堆芯球流越均匀,表现出更好的整体性向下运动;当f达到0.8上限时,HTR-10堆芯球流依然保持了整体性运动,底部无任何被滞留的球。本工作对进一步优化球床式高温气冷堆堆芯设计具有重要意义。     

放射性废气处理系统活性炭滞留单元工程规模装置性能研究

设计了放射性惰性气体滞留单元工艺流程,建立可模拟核电站不同气流参数条件下的活性炭滞留单元工程样机系统。对主要单元模块进行了性能实验,包括气体冷却器冷凝除湿性能、吸附剂装填实验、干燥单元除湿与再生性能以及活性炭滞留时间测试实验。结果表明:气体冷却器满足除湿性能要求,硅胶干燥单元除湿与再生性能优异,活性炭滞留单元具有良好的惰性气体滞留性能。研制的工程样机满足工程应用要求,具备实际工程应用条件。     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

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.     

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.