基于广义最小二乘法原理的中子能谱解谱程序开发及验证

中子能谱是反应堆的一项重要参数,为验证理论计算,常使用阈探测器活化法对中子能谱进行实际测量。为解决由于活化片数量小于能群数量而引起的解谱问题并获得较高的解谱精度,基于广义最小二乘法原理开发了解谱程序NSAGLS。使用IAEA给出的例题进行了验证,结果表明该程序能够得到正确的解谱结果。该程序可用于反应堆中子能谱的解谱,并能够考虑输入谱、核反应截面及测量活度不确定度信息对解谱结果的影响。     

微机上求解中子谱的实现

利用最小二乘法和ＳＡＮＤ－Ⅱ迭代法在微机上设计２个中子谱解谱程序，分别计算＾２５２Ｃｆ中子源通过空气及石墨、铝、铁、铅、混凝土、聚乙烯后的中子场和反应堆热柱超热中子谱，并由此计算出几个防护量。２种方法的计算结果及实验结果，相互符合较好。     

用SAND—Ⅱ迭代法和最小二乘法微机上求解中子谱

利用最小二乘法和ＳＡＮＤ－Ⅱ迭代法在微机上设计２个中子谱解谱程序，分别计算＾２＾５＾２Ｃｆ中子源通过空气及其它材料后的中子场和反应堆热柱超热中子谱，并由此计算出几个防护量。２种方法的计算结果及实验结果，相互符合较好。     

三种解谱算法求解中子能谱的解谱效果比较

使用多球谱仪测量中子能谱时,需要使用"少道"解谱算法。为此,本文分别将迭代算法、蒙卡算法和遗传算法应用到中子能谱解谱中,通过MCNP模拟几种辐射防护常见的中子能谱,模拟得到探测器在各个球中的计数,然后使用迭代算法、蒙卡算法和遗传算法进行解谱,并对三种解谱算法的解谱效果进行比较。结果显示,三种算法均能够很好的完成解谱,且给出的中子注量、周围剂量当量和平均能量与参考值符合的也较好。另外,在典型的中子辐射场,三种算法的使用条件不同,可相互配合,较好的给出解谱结果。     

单球多计数器中子解谱方法和剂量评价简析

介绍了当前常用的“少道”解谱软件和解谱方法,并利用UMG解谱软件包中的MXD-FC31和GRV-FC31两种解谱软件,针对单球多计数器的测量方法,分析了^252Cf裂变中子源的中子能谱模拟解,讨论了解谱方法对注量率和剂量率的影响。     

活化法测量中子能谱实验中反应率及初始谱的检验

利用活化法对西安脉冲反应堆辐照腔进行了中子能谱测量。对活化片的测量数据进行了分析,发现其中一个反应道的反应率测量值不准确,并以此为切入点展开深入研究,总结出评定实验数据的定性分析方法:在有限次迭代后,通过对各反应道反应率计算值与实验值之比与1的偏离程度判断实验数据的置信度,进行实验数据取舍后再进行解谱。此外,分析了不同初始能谱对解谱结果的影响。结果表明:初始能谱与实际能谱偏差越大,共振区的截面数据对结果的影响越明显。为此,提出了一种判断初始能谱是否合适的方法。     

核电厂辐照监督管中子解谱程序2NP

中子解谱方法是准确确定压力容器的中子注量的有效方法。本文研制了以广义最小二乘法为核心的中子解谱程序2NP,用于核电厂反应堆压力容器(RPV)中子注量的估计。通过对国际原子能机构(IAEA)发布的中子解谱例题ANO的验算,证明2NP具有较高的计算精度。     

热中子堆内中子通量谱的多箔法测定

用多箔法测定热中子堆内活性区和反射层内的全能区中子通量谱。选择26种探测器,把10~(-4)eV至20MeV的整个能区分为640群,考虑箔自身吸收和散射,按群内中子是单能的计算14种热与中能探测器的自屏因子。按各箔截面互相一致适用原则选择活化反应截面。文中给出计算得的通量谱和谱误差。还给出两测点的“宏观谱量”,包括热中子通量,中子温度,费米谱量,偏离费米谱指数和快中子积分通量。检验了反应率、截面和初始通量谱对解谱的灵敏度。在初始谱变化较大的情况下都获得大体一致的结果。在能量<0.01eV与约10～500keV的两个能区,探测器响应均不灵敏,亦获得合理的通量谱分布。     

反应堆堆外中子剂量测量技术试验验证

堆外中子剂量测量技术在反应堆压力容器辐照监督中有广泛的应用。本文介绍了在国内某试验堆上进行的堆外中子剂量测量技术验证试验及其结果。比较了堆外中子剂量测量所用探测片活度的理论计算值、实测值及解谱计算结果,同时分析对比了试验中各辐照位置处中子能谱的理论计算值及解谱结果。结果表明,基于测量值的解谱结果与理论计算结果符合良好。堆外中子剂量测量技术可以有效完成中子能谱测量。     

微型中子源反应堆中子谱参数测量

以Au、Zr和Fe为活化探测器,采用裸探测器法测量中国原子能科学研究院微型中子源反应堆的中子谱参数f、α、f_F和φ_th。内辐照座的α、f和f_F分别为－0.007±0.003、20.8±0.4、5.5±0.2。该方法对φ_th的测量结果与4πβ-γ符合法的一致,相对偏差小于2%。与SLOWPOKE相比,微堆有较高的α、f_F值。与已有测量数据的比较表明,微堆中子谱在很长一个时期内是稳定的,利用微堆作为中子源的k₀法中子活化分析不需中子注量率监测器,且比较器一经照射和测量后,可用于其后较长时间内所有分析的计算标准。     

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.