研究性重水堆中毒碘坑的分析

本文分析了中国科学院的研究性重水堆运行初期两次中毒碘坑实验值与理论值相差悬殊的原因。针对这些原因,在进一步的工作中考虑了重水堆的以下一些具体特点,因而得到理论与实验较为满意的符合:1.反应堆内控制棒栅的位置将影响自动调节律的效率;2.重水堆内光中子源的变化对测量反应性有影响;3.石墨层温度变化对自动调节棒电离室电流的影响;4.反应堆内中子通量分布不均匀,理论计算必须考虑这一影响。     

系统辨识方法在HWRR反应堆动态参数估计中的应用

利用动态系统辨识方法,以控制棒扰动做为堆内已知反应性输入,实现了控制微分效率、温度系数等反应堆动态参数的热态估计,并在重水型研究反应堆(HWRR)上进行了实验研究。结果是可信的,系统辨识方法能够实现反应堆某些动态参数的估计。值得指出的是,在有计算机检测或控制的反应堆上,该方法不需要增加任何设备即可应用。     

重水研究堆光激中子强度——停闭时间特性研究

本文利用ORIGEN-ARP程序计算得到重水堆停堆后堆内γ源强,通过D(γ,n) H反应率与γ源强关系计算出重水堆停堆后光激中子源强水平变化。研究结果表明,重水堆停闭1 900 d后光激中子源强水平约为7.2×106n/s,比首次临界外加的Am-Be源强度高,物理启动无需添加外加中子源。     

研究性重水反应堆工艺管水力特性实验

一、概述中国科学院原子能研究所研究性重水反应堆,于1958年开堆时发现,当反应堆处于满负荷的正常运行状态时,重水泵的磨损指示器中气体增长非常迅速,经十五分钟即将指示器充满(约0.3升);当重水泵在1500转/分运行时,气体增长的速度更加显著。试验证明,气体是来自反应堆内部。由于活性区液面气泡层的存在,会降低反应堆的反应性并影响重水泵的正常工作。     

反应性测量中本底与中子源修正计算方法研究

在核电厂反应堆的反应性测量中,γ本底电流、中子源引入的电流、电路噪声等干扰项在实测电流中占有显著份额,给反应性的测量计算带来很大影响,在动态刻棒等反应性测量工作中必须对其进行修正。本文分析了本底与中子源电流对反应性测量的影响,并自主开发了一种本底电流、中子源电流修正方法--双重拟合法。该方法基于点堆模型,通过对包含本底与中子源的逆动态方程的分析,计算得到准确的反应性以及本底电流、中子源电流。通过试验堆动态刻棒实验的数据对本方法进行了验证,得到了理想的结果。     

控制棒栅反应性曲线的实验研究

在研究性重水反应堆HWRR中,对控制棒栅存留段所相当的剩余反应性公式ρ_(ex)=-δρ=G_1τ_1ε_1进行了理论推导和实验研究。结果表明:只要轴向加入贯穿毒物棒,则-δρ与G_1τ_1成正比,比例常数为ε_1。这样,对任何轴向贯穿加毒的新状态,只要在稳态下测量该状态的G_1τ_1就可获得剩余反应性的值。     

MHWRR在极低光激中子水平下的临界启动技术

阿尔及利亚比林核研究中心重水反应堆(Multi-purposes Heavy Water Research Reactor,MHWRR)实施了仪表、控制和电气数字化升级改造,改造后的首次临界启动对改造工程具有重要意义。为保证反应堆启动安全,需要解决升级改造后在极低光激中子水平下临界启动中存在的核测量盲区问题,首先对长期停堆后堆内剩余光激中子源强、核测量盲区以及临界棒位进行了理论计算与分析研究,在此基础上提出了在无外加启动中子源条件下首次临界启动的实验技术方案。在无参考数据的情况下,实验进程完全按理论设计的预期进行,临界启动一次成功;启动过程中核功率参数得到有效监测,启动测量装置与堆外电离室测量范围衔接完备,临界棒位理论值与实验值的误差小于0.84%,实验结果与理论计算结果符合良好,表明了这项实验技术的合理可行。     

冷中子源堆内部件失效分析

反应堆的冷中子源装置以液氢作为慢化剂,冷中子源堆内部件的安装位置靠近反应堆堆芯。基于对冷中子源及反应堆安全性影响的考虑,本文对冷中子源堆内部件在各种运行工况(包括失效事件)的状态及事故后果进行了分析。结果表明,堆内部件的失效影响仅局限于冷中子源内部,不会对反应堆安全造成危害。     

研究性重水反应堆冷却回路~(16)N的测量和计算

一、前言重水反应堆运行时,由于重水本身受快中子的辐照,产生强放射性的~(16)N,它发射高能γ,是冷却回路γ放射性的主要来源。在设计冷却回路生物屏蔽层时,其厚度主要决定于~(16)N的γ源强。此外,国外很多动力堆还利用~(16)N的γ放射性强度来监测反应堆的热功率,它具有响应时间快、不引起通量畸变等优点。因此,确切地给出冷却回路重水中~(16)N的放射性强度,无论从为堆的安全运行提供辐射剂量数据,或是为冷却回路屏蔽设计提供经验均是很有意义的。本文叙述了在我国研究性重水堆上所采用的测量和计算冷却回路重水中~(16)N浓度的方法和结果。     

HWRR屏蔽层活化源项研究

反应堆屏蔽层通常由钢筋混凝土浇筑而成,体积及重量巨大,是反应堆退役源项的重要来源之一。通过建立反应堆3D计算模型,利用MCNP和ORIGEN活化计算程序计算了重水研究堆(HWRR)屏蔽层不同位置的中子注量率和活化源项。为验证计算模型和计算结果的准确性,在HWRR屏蔽层活性区中央位置沿水平方向进行钻孔取样,对获得的混凝土样品中的~(60)Co和~(152)Eu的活度进行了测量,分析结果与计算结果较吻合,证明了理论计算模型的准确性。最后对HWRR屏蔽层的活化深度进行了计算,得出反应堆屏蔽层活化深度最大值为600 mm。计算结果证明保留外层屏蔽层的退役方案从理论上是可行的。     

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.     

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.