核电厂运行现场高能γ射线的剂量调查

在核电厂正常运行期间,反应堆冷却剂系统内存在能够发射高能γ射线的¹⁶N等放射性核素。为了初步掌握核电厂运行期间不同区域内高能γ射线的辐射水平,利用NaI(Tl)谱仪在国内某核电站测量了反应堆厂房内的γ能谱,并根据γ测量谱和测量系统的响应函数计算了能量大于3 MeV的γ射线的场所剂量率。结果显示:在15个测量位置中,6个位置的γ测量谱中存在明显的高能成分,其对应的剂量率在1.02～30.14 μSv/h范围内。     

Measurements of keV-neutron capture cross sections and capture gamma-ray spectra of 105Pd

The neutron capture cross sections and capture gamma-ray spectra of ¹⁰⁵Pd were measured in the region from 15 to 100 keV and at 585 keV. A neutron time-of-flight method was utilised with an anti-Compton NaI(Tl) spectrometer and a 1.5-ns pulsed neutron source by the ⁷Li(p,n)⁷Be reaction. The capture yields were obtained by applying a pulse-height weighting technique to the observed net capture gamma-ray pulse-height spectra. The capture cross sections of ¹⁰⁵Pd were derived with errors less than 5%, using the standard capture cross sections of ¹⁹⁷Au. The evaluated capture cross sections of JENDL-4.0 and ENDF/B-VII.1 were compared with the present results. The evaluations of JENDL-4.0 and ENDF/B-VII.1 were larger than the present results by 3%–15% in the region from 15 to 100 keV and at 585 keV. The capture gamma-ray spectra of ¹⁰⁵Pd were also derived by unfolding the observed net capture gamma-ray pulse-height spectra. The multiplicities of capture gamma rays of ¹⁰⁵Pd were obtained from the capture gamma-ray spectra.     

New Technical Approach to Monitoring of Low-Level Environmental Gamma Radiation Using NaX(Tl) Scintillation Instrument

The environmental dose evaluation around a nuclear facility is usually performed by means of calculational methods on the basis of effluent monitoring at a release point. It has been desired to develop practical techniques of direct monitoring in the environment, because the Japan Atomic Energy Commission set up 5 mrem/yr as an objective dose value for the whole-body exposure due to normal operation of LWRs on a single site.

In evaluating gaseous plume doses less than 5 mrem/yr in routine monitoring, there are many difficult problems to be solved. We have developed two techniques for separation of the plume exposures less than 1 mrem/yr from the background radiation, using a NaI(Tl) scintillation counter having flat energy response.

One technique is based on the difference in energy spectrum distribution between plume gamma and natural gamma radiation. And, separation of the respective exposures is made by analysis of the two informations obtained by a two-channel monitoring system. Another technique is to reduce the natural gamma radiation components by using a special concave lead shield for the NaI(Tl) scintillation probe. A combination of the techniques can much improve the efficiency of separation of ⁴¹Ar plume radiation from fluctuating background radiation.     

CsI(Tl)探测器对带电粒子能量响应的入射位置依赖关系

在放射性核束物理的实验研究中,通常采用CsI(Tl)探测器对反应产物中的带电粒子进行总能量测量.使用GEANT4软件对CsI(Tl)闪烁体探测器能量响应通进行了蒙特卡罗模拟,在考虑了晶体外表面包覆材料反射率、耦合光敏二极管面积、射程等影响因素后,重点研究了CsI(Tl)闪烁体探测器对带电粒子能量响应的入射位置依赖关系....     

Resin Ion Exchange and Liquid-Liquid Extraction of Indium and Thallium from Chloride Media

Separation procedures of indium and thallium for both future investigation of superheavy element 113 and fundamental research of its light homologues have been developed. Two chemical methods, namely ion exchange and solvent extraction, have been applied. Cation exchange behavior in hydrochloric acid media and the reversibility of the In and Tl elution order due to oxidation state of the latter are described. Extraction of Tl(I), Tl(III), and In(III) from aqueous HCl solutions with and without tri-n-butyl phosphate into the ionic liquid 1-butyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide has been investigated. The extraction efficiencies of Tl(I) and In(III) have been found to be much lower than those of Tl(III) both with and without an organic ligand. The extraction mechanism is suggested. Suggestions for both liquid and gas phase experiments aimed at element 113 studies have been considered based on the results observed.     

Determination of Tehran Research Reactor power by N gamma detection

The radioisotope ¹⁶N is produced by the interaction of fast neutrons with ¹⁶O in water reactor coolant. This radioisotope emits at the two major gamma ray energies of 6.13 MeV and 7.1 MeV. Exploiting the linear relation between the number of gamma particles versus the reactor power change, the reactor power is determined by detecting and counting the emitted gammas. In this work, for the detection of gammas to measure the reactor power, two different methods are employed. First, by NaI(Tl) scintillator detector and second, by assembly of ten GM detectors. The obtained results confirm that the number of emitted gammas is proportional to the change in reactor power as shown by different monitoring systems such as UIC, CIC, FC, Cherenkov and thermal power. Both of the applied methods are shown to give reliable results for reactor power above 20 kW. Both systems, having been calibrated, are being used as monitoring systems of power in Tehran Research Reactor. These systems are usable in other research reactors and possibly in power reactors as well.     

降低NaI（Tl）γ谱仪探测限的技术探讨

核爆后其放射性元素种类复杂、量少,用NaI（Tl）γ谱仪监测时,多种核素峰重叠在能谱的散射区内难以识别,因此对谱仪的稳定性,能量分辨率,解谱技术以及最小可探测活度有很高的要求.本文通过实验和MCNP模拟,分析了对某NaI（Tl）γ谱仪探测限的影响因素以及降低探测限的措施,提出了通过屏蔽来降低本底,提高其最小可探测活度的方法,实验表明,通过选择合理的屏蔽尺寸,有效的降低了本底,提高了谱仪的低水平放射性监测能力.     

Pressure dependence of Tc in Tl0.2Hg0.8Ba2Ca2Cu3Ox

We report results of our study of the pressure dependence of T_c in Tl_0.2Hg_0.8Ba₂Ca₂Cu₃O_x to 6 GPa in a diamond anvil cell. The sample studied has an ambient T_c of 136.4 K and application of quasihydrostatic pressure raised T_c to 144.4 K at 6 GPa. We will also describe recent modifications of our ac susceptibility apparatus that have improved our sensitivity while simplifying the coil design and the balancing.     

^201TlCl注射液中铊载体的分光光度测定

研究了分光光度法测定２０１ＴｌＣｌ注射液中载体铊的含量。用溴水作氧化剂，将Ｔｌ（Ⅰ）氧化为Ｔｌ（Ⅲ），并加入磺基水杨酸除去过量溴，以对硝基苯重氮氨基偶氮苯（简称镉试剂）为显色剂，聚乙二醇辛基苯基醚（乳化剂ＯＰ）为胶束增溶剂在水相中直接测定Ｔｌ（Ⅲ），显色体系为ｐＨ＝１１．７的ＮＨ４Ｃｌ－ＮＨ４ＯＨ缓冲溶液，配合物的最大吸收波长为４６９ｎｍ，摩尔吸光系数为１．３７×１０４ｍ２／ｍｏｌ。