长程α粒子探测器研究进展北大核心CSCD

α粒子射程短,常规α放射性活度直接测量方法难以测量不规则表面及管道内等区域的α放射性活度。长程α粒子探测器(long-rangeαdetector,LRAD)是目前用于此类区域α放射性污染的有效测量手段之一,被广泛应用于坑洞、核设施管道内等难以近距离测量环境的α放射性活度监测。本文介绍了LRAD的基本原理、发展及现状,并展望了LRAD的应用前景及发展方向。     

核燃料棒α表面污染在线检测系统设计

设计了一套用于核燃料棒α表面污染的在线检测系统.该系统使用ZnS闪烁体探测器,通过检测燃料棒表面污染物自发衰变产生的α射线,能自动得到燃料棒表面的分段污染水平和全棒平均污染水平,并根据设定的阈值自动判断是否报警.该系统目前已成功用于核燃料棒实验生产线.     

α表面污染检测模拟训练系统设计

根据α表面污染检测模拟训练需求,设计了α表面污染检测模拟训练系统。该系统由模拟源、模拟检测设备和仿真软件组成。模拟源采用钕铁硼磁粉和琼脂糖胶体制备,应用磁场模拟辐射场;模拟检测设备通过磁阻传感器阵列采集模拟源信号,信号经过放大滤波后使用C8051F120单片机进行处理;仿真软件模拟了Como170型α表面污染检测的界面和操作流程。测试结果表明:系统能够有效模拟α表面污染检测和洗消过程,可用于α表面污染检测相关的模拟训练。     

地表土壤中铀污染特征评价技术的野外示范

本文介绍了一种与CERCLA和RCRA有关的,用于提高铀污染地研究效果的全新的野外筛析方法。该方法能圈定地表土壤中污染分布。为此,在Fernald环境管理项目(FEMP)中评估了4种适用于土壤中铀浓度野外测量方法的性能。这4种试验的技术是:高分辨率γ能谱测量、宽域β闪烁计数、激光烧蚀-等离子体-原子发射光谱法(LA-ICP-AES)和远距离α探测(LRAD)。对每一种所实施的技术都要与野外获得的结果进行比较,并与土壤样品实验室分析得到的数据进行比较从而作出评价。数据表明,用这4种技术得到的结果通常是一致的,但仍相当离散。同时系统差异也表现出来,特别是当γ能谱结果与β闪烁和LRAD的结果比较时。这些情况归因于测量地点铀分布的不均匀和这种不均匀性对每一种技术发生较大的影响。初步的结论是(虽然一种新野外筛析技术的示范试验是非常重要的,但是这些工作必须与根据从其他特殊方法中得到信息来解释新数据的手段相结合,并与基于适用于净水平条件的测量灵敏度需要的阐述相结合。     

核燃料元件表面污染检测系统研究

开展针对燃料元件表面污染检测系统的研究,分析表面污染检测的主要原理,并建立检测系统。通过对表面α标准源测试实验数据分析,获得检测系统的测量不确定度;实际的检测结果表明:采用α—计数法的检测系统稳定可靠,探测效率高,能够实现1.5 m长燃料元件的表面污染检测。     

LRAD测量管道内α污染活度的BP网络模拟

针对风速、流量、探源距、测试管管长和管径等因素对核设施退役中管道内α污染测量造成的非线性影响,采用控制变量法开展长距离α测量(Long range alpha detector,LRAD)模拟装置下的多参数影响实验,初步分析了各种因素对系统测量值的影响特征,建立了以影响因素和测量值为输入、放射源活度为输出的BP神经网络模型,分别对948和100组数据进行了模型建立和实例检验,结果说明,预测平均相对误差为3.4218×10–4,实例平均相对误差为2.217×10–2。应用BP网络模型模拟LRAD装置下的α活度是可行且有效的。     

基于嵌入式模块的α表面污染测量仪的研制

介绍了一种高性能的嵌入式386SX CPU模块和基于此模块研制的便携式α表面污染测量仪的系统结构,详细说明了仪器软、硬件各部分的设计思路和实现的技术.通过标准源239Pu的对比测量试验,对仪器的探测效率进行了具体评价,并给出其它主要性能指标.该测量仪操作简单,测量结果准确,经现场试用,满足了用户的基本生产需求.     

GEM探测器α表面污染监测系统研制

研制了大面积GEM探测器,构建了位置灵敏α表面污染监测系统。该系统主要由GEM膜、多路读出电子学系统、数据获取与展示软件等组成。该系统对α粒子的本征探测效率可达95%以上,并实现了系统对α粒子的位置灵敏成像,可为表面污染类α粒子的精确位置测量提供一种有效手段。     

大批量人群核辐射体内污染快速检测仪的研制

发生核应急事件时需进行核辐射体内污染检测。针对大批量人群核辐射体内污染快速检测要求,研制了一款可同时完成α和γ放射性检测的一体机。该系统基于数字化能谱处理技术,利用离子注入表面钝化硅半导体(Planar Implanted Passivated Silicon,PIPS)探测器和NaI(Tl)探测器分别实现人体内α、γ射线测量。测试结果表明,仪器对~(239)Pu的能量分辨率为6.1%,对~(137)Cs的能量分辨率为6.9%。该系统能够以每小时大于等于10人次的速率实现检测,满足内污染快速检测要求,能够为后续诊断提供可靠依据。     

用离子收集法测量α粒子技术研究

介绍了离子收集的原理及长距α粒子探测器.经实验测定,电流探测限为12.15 fA,α源在11.13～4 265.0 Bq范围内有良好的线性关系.估算了各种因素对本底电流的贡献.研究了这种技术在α、β表面污染方面的应用并对静电式α粒子探测器作了初步探索.     

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.     

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.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 15 (2013)

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