环境和生物样品中3H和14C的测量

研究了环境和生物样品中^3H和^14C的测量方法。^3H测量步骤包括：样品氧化燃烧,使有机结合氚(OBT)转化为氚化水,用液闪法测量^3H活度。该方法的探测下限为1．2Bq／L。^14C测量步骤包括：将8g左右的样品经过燃烧爆炸后转变为CO2,并最终合成苯,用液闪法测量^14C的活度。该方法的探测下限(以C质量计)为1．0Bq／kg。文章同时给出了树叶、牛奶、动物、土壤等多种生物样品中^3H和^14C的测量结果。     

氧化燃烧法测量生物介质中有机~3H和~(14)C的活度

随着核能的快速发展,氚(~3H)和~(14)C已成为向环境排放的主要放射性核素,并愈来愈受到人们的关注。对环境生物介质中有机~3H和~(14)C的监测技术也已成为环境监测工作的重点,而如何提取生物样品中的有机~3H和~(14)C是监测分析工作中的关键。本工作采用氧化燃烧法同时提取松针生物中的~3H和~(14)C并进行测量,测量结果表明,其装置空白回收率分别可达到87.1%和96.4%,加标回收率分别为84.8%和95.7%。测得松针生物样品中有机~3H、~(14)C的比活度分别为(8.89±0.54)Bq/kg(鲜重,3.19Bq/L,n=3)、(22.2±1.90)Bq/kg(鲜重,0.150Bq/g(以碳计),n=3);探测下限分别为4.04Bq/kg(鲜重,1.29Bq/L)、14.3Bq/kg(鲜重,0.096Bq/g(以碳计));该分析方法的扩展不确定度分别为25.6%、39.4%(k=2)。分析结果与同类生物样品为同一水平,分析结果可靠。     

~(14)C-碳酸钠测量方法的改进

本文介绍用液体闪烁技术测量Na_2~(14)CO_3或NaH~(14)CO_3的一种改进方法。在一定量的蒸馏水中加入适量的Na_2CO_3载体和NaOH,再加一定量的待测Na_2~(14)CO_3溶液,制成供测量用的放射性浓度适中的Na_2~(14)CO_3贮备液。在甲苯/Triton X-100闪烁系统(PPO4g,POPOP 0.25g,Triton X-100 165ml,加甲苯至500ml)中加入DL-α-苯乙胺,最后加入Na_2~(14)CO_3贮备液,制备样品。用样品道比法测定效率。每日测量一次,在连续测量的9天中,未发现~(14)C损失,也未发现存在化学发光,探测效率约为83％。     

用湿法氧化预处理进行水中~(14)C分析研究

介绍了一种基于湿法氧化预处理环境水中14C的分析方法。设计了一套湿法氧化装置,样品处理量为20 L,可对水中无机碳和有机碳分别进行转化和吸收。经转化和吸收后的样品在二氧化碳释放吸收装置上与闪烁液混合,最后在低本底液闪谱仪上进行测量。分析了有机碳和无机碳回收率的稳定性和准确性,给出了典型样品最小可探测活度浓度和测量值。采用本方法可高效、稳定提取环境水体中的有机碳和无机碳,回收率分别为96.8%和97.8%,典型环境条件下对14C的最小可探测活度浓度可达到0.015Bq·(g C)-1。     

核设施液态流出物中~(129)I的测定

研究了核设施液态流出物中^129I的分析方法。该方法先用阴离子交换树脂浓集水样中的碘，经NaClO溶液解吸，CCl4萃取，NaHSO3溶液反萃分离后制成AgI沉淀源，再用HPGeγ谱仪进行γ谱测量，也可对反萃液直接进行液闪测量。结果表明：HPGeγ谱仪对^129I的39.6keVγ射线全能峰的探测随质量厚度呈指数下降；碘载体含量对液闪测量的探测效率影响不大，在本实验条件下，探测效率为85％；γ谱测量时间为1000min，方法的探测限为0.016Bq/L；液闪测量时间为100min，方法的探测限为0.037Bq/L。该方法的全程回收率为60％－85％。     

宁德核电厂液态流出物中14C测量

建立了一种测量核电厂液态流出物中¹⁴C的分析方法——使用1030 W总碳分析仪将样品中的碳酸化、氧化成CO₂,然后用NaOH溶液吸收,最后用3180液闪计数器对NaOH吸收液进行测量。该方法能够有效消除其他放射性核素的干扰,且能准确测定样品中¹⁴C的活度。实验结果表明,方法的加标回收率平均为96.91%,探测限为2.07 Bq/L,测定结果的精密度(相对标准偏差)小于±5%,准确度(相对误差)小于±5%。     

铀钍矿石、土壤中,天然钍同位素的分光光度法-α计数(内闪)法联合测定

样品用过氧化钠熔融分解,草酸钙预沉淀分离杂质浓集后,溶于3mol/L HNO_3中,以4％P204-甲苯萃取,5％草酸反萃取,再次沉淀为草酸钙并溶于4mol/L HCl中,用偶氮胂Ⅲ分光光度法测淀钍(≈~(232)Th)含量。测量完毕,收集全部显色液重新沉淀出草酸钙,加入ZnS(Ag)混合均匀,用α计数(内闪)法测量总钍α计数(Th(α)_1),放置5天以上再测一次总钍α计数(Th(α)_2),根据两次α计数率的变化,计算得到样品中~(228)Th的含量。假定~(227)Th与~(230)Th在样品中近似保持放射系平衡的比例关系,则样品中~(230)Th含量等于总钍(Th(α)_1)减去~(232)Th(换算为活度)、~(227)Th(按与~(230)Th的比例关系)、~(228)Th及其子体总α活度之和。此法利用一般仪器设备,能较快得到总钍α-比活度、~(232)Th、~(230)Th和~(228)Th等四个天然钍同位素的重要数据,精密度、准确度满足常规分析要求,分光光度法对钍的测定限为0.06μg,α计数(内闪)法的4π探测效率为(95±1)％,本底计数率为(1.5±0.3)×10~(-3)Bq。     

单细胞藻类光合作用研究中~(14)C的测量

用~(14)C作示踪剂,可以测定海水中单细胞藻类光合作用的强弱。其实验方法是将海洋某区域取回来的海水中,加入Na_2~(14)CO_3溶液,在一定强度光照下,经若干小时光合作用。光合作用结束后,将海水中单细胞藻类滤到醋酸纤维薄膜上。本文介绍用液闪对~(14)C进行正确计数。     

β射线对水稻的诱变效应研究

以水稻为试材,以M_2代熟期和株高突变率作为主要考察指标,比较了~(14)C与其他若干诱变因素的诱变效果,研究了~(14)C诱变效应与处理时期、剂量和方法等关系。结果表明,~(14)C比其它几种诱变因素具有更好的诱变效果,诱发早熟突变以花粉母细胞形成期引入,剂量为333×10~4Bq/株左右最适宜,诱发矮秆突变以雌雄蕊形成至花粉母细胞形成期引入,剂量为74×10~4Bq/株最适宜,处理方法以植株基部注射引入Na_2~(14)CO_3最佳。     

~(85)Kr气体液闪测量方法研究

采用反康普顿γ谱仪对~(85)Kr样品进行活度标定作为工作参考,通过自行设计的Kr气体收集装置和液闪制样装置,建立了一种~(85)Kr气体样品的液闪测量方法。结果表明:以甲苯为溶剂、1,4-双-2-(4-甲基-5-苯基噁唑基)(POPOP)和2,5-2苯基噁唑(PPO)为溶质的闪烁液,当体积为20mL,硅胶加入质量为1.0g时,能够完全溶解0.5m~3空气中的Kr气,且样品液闪测量无需进行淬灭校正;对于~(85)Kr活度小于1Bq的样品,液闪测量相对偏差绝对值小于7%;制备的样品放置20h以内计数率稳定。该方法适用于环境大气中~(85)Kr放射性水平的测量。     

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.     

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.     

微型X射线管空气比释动能和能谱的测量

为研究微型X射线管的特性,通过电离室测量光管出射口30 cm远处的空气比释动能,使用高纯锗探测器分别测量了Ag过滤和Cu过滤下的X射线能谱。结果表明,空气比释动能随电流的增加有线性增加的趋势,能谱图明显的观察到银的两个特征X射线。完成了微型X射线管空气比释动能和能谱的测量方法以及实验测量的工作,为微型x射线管下辐射质的建立提够了条件基础。     

Gamma-ray attenuation technique for measuring void fraction in horizontal gas-liquid two-phase flow

The measurement of void fraction is of importance to the oil industry and chemical industry. In this article, the principle and mathematical method of determining the void fraction of horizontal gas-liquid flow by using a single-energy γ-ray system is described. The γ-ray source is the radioactive isotope of 241Am with γ-ray energy of 59.5 keV. The time-averaged value of the void fraction in a 50.0-mm i.d. transparent horizontal pipeline is measured under various combinations of the liquid flow and gas flow. It is found that increasing the gas flow rate at a fixed liquid flow rate would increase the void fraction. Test data are compared with the predictions of the correlations and a good agreement is found. The result shows that the designed γ-ray system can be used for measuring the void fraction in a horizontal gas-liquid two-phase flow with high accuracy.