ICP-MS measurement of uranium and thorium contents in minerals in China

The activity levels of long-lived radionuclides in minerals have received more and more concern for the public health. The inductively coupled plasma mass spectrometry was used to measure the content of uranium and thorium in 60 mineral samples collected from 16 mines of seven provinces in China. The contents of uranium and thorium ranged0.17 ± 0.04 lg g~(-1)to 15.3 ± 2.39 lg g~(-1), and 0.19 ± 0.04 lg g~(-1)to 19.6 ± 7.56 lg g~(-1), respectively. The highest levels of U and Th contents were found in aluminum ore,whereas the lowest was found in antimony and copper ores.     

Actinide breeding and reactivity variation in a thermal spectrum ADSR – Part 1: Development of a lumped thermal reactor model

The beneficial properties of fast reactor systems in being able to both burn and breed actinides have led to renewed interest in this technology as a means of providing a more sustainable form of nuclear power production. However, despite significant investment over many years in the development of the technology, fast reactors have never been deployed in significant numbers. In view of the difficulties encountered in fast reactor development, enhancements to the existing, well proven light water reactor (LWR) technology may provide a more accessible path to improved sustainability.     

Risk of malignancies in relation to terrestrial gamma radiation in a Swedish population cohort

Results of epidemiological studies on terrestrial gamma radiation (TGR) and related malignancies have not been consistent. This study is a thorough examination of this relationship. Records on all individuals living in two Swedish counties in 1973, along with their annual dwelling coordinates during the 28-year follow-up period, were retrieved from the National Archives and Statistics Sweden. We used Geographical Information System (GIS) to match the individuals' dwelling coordinates annually to the TGR given in 200 × 200 m grids produced by the Geological Survey of Sweden. Cases of malignancies and deaths were retrieved from the Swedish Cancer Register. During the follow-up period 61,503 incident cases were included in the analyses and in total 11 million person-years were recorded. Cox regression was used both in a linear continuous model and analyses of six exposure categories. Adjustments were made for sex, age, and population density. The hazard ratio (HR) per 100 nanoGray/hour (nGy/h) was significantly increased for total malignancies and for several sites; however, contrary to expectations, an obvious and anticipated linear exposure-response relationship could not be identified. With the lowest exposure category (0-60 nGy/h) as reference, a statistically significantly increased HR for total malignancies was seen in all exposure categories, except in the highest category 96-366 nGy/h. For breast cancer, thyroid cancer and leukaemia an obvious exposure-response could not be seen.     

Retention,Thermodynamics and Adsorption Profile of Th(IV) Ions onto 1‐(2‐Pyridylazo)‐2‐Naphthol (PAN) Loaded Polyurethane Foam from Acetate Media and its Separation from Rare Earths

Abstract

The sorption behavior of 2.7×10^?5 M solution of Th(IV) ions on 1‐(2‐pyridylazo)‐2‐naphthol (PAN) loaded polyurethane foam (PUF) has been investigated. The quantitative sorption was occurred from pH 6 to 9 from acetate buffer solutions. The sorption conditions were optimized with respect to pH, shaking time, and weight of sorbent. The sorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms very successfully at low metal ions concentration. The Freundlich isotherm constant (1/n) is estimated to be 0.22±0.01, and reflects the surface heterogeneity of the sorbent. The Langmuir isotherm gives the maximum monolayer coverage is to be 8.61×10^?6 mol g^?1. The sorption free energy of the D‐R isotherm was 17.85±0.33 kJ mol^?1, suggesting chemisorption involving chemical bonding was responsible for the adsorption process. The numerical values of thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) indicate that sorption is endothermic, entropy driven, and spontaneous in nature. The adsorption free energy (ΔG_ads) and effective free energy (ΔG_eff) are also evaluated and discussed. The effect of different anions on the sorption of Th(IV) ions onto PAN loaded PUF was studied. The possible sorption mechanism on the basis of experimental finding was discussed. A new separation procedure of Th(IV) from synthetic rare earth mixture using batch, column chromatography, and squeezing techniques were reported.     

Transport of thorium from nitric acid solution by non-dispersive solvent extraction using a hollow fibre contactor

Membrane based non-dispersive solvent extraction (NDSX) of Th(IV) from aqueous nitric acid medium was carried out using di-n-hexyl octanamide (DHOA) in normal paraffin hydrocarbon (NPH) using a commercial hollow fiber module containing microporous hydrophobic polypropylene capillaries. The NDSX operation was carried out with pumping various concentrations of nitric acid (1–6 M) containing Th(IV) through the tube side and organic extractant (usually 1.1 M DHOA in NPH) through the shell side of the hollow fibre capillaries at aqueous and organic phase flow rates of 3.5 mL/s and 4.5 mL/s, respectively. Extraction studies were performed under different hydrodynamics conditions and the overall mass transfer was evaluated under cuonter-current flow condition. The percentage NDSX of Th(IV) increased with the increase in the extractant concentration (from 0.1 M DHOA to 1.1 M DHOA) as well as with nitric acid concentration (from 1 M to 6 M). Stripping studies were carried out using both distilled water as well as oxalic acid as the strippant. The possibility of the separation of U from Th was also evaluated.     

N,N,N’,N’-四丁基己二酰胺在硝酸介质中萃取铀、钍及硝酸的研究

研究了N,N,N＇,N＇－四丁基己二酰胺（TBAA）从硝酸介质中萃取铀、钍及硝酸的机理,考察了HNO3浓度、TBAA浓度、温度及盐析剂（LiNO3）对铀和钍分配系数的影响,还对铀、钍的反萃进行了研究,得出了萃合物的组成为UO2（NO3）2·TBAA和Th（NO3）4·TBAA。在低酸度下,TBAA与硝酸主要以TBAA·HNO3的形式存在;在高酸度下,TBAA与硝酸的加合物不但有（TBAA）2·HNO3,而且还有TBAA·HNO3、TBAA·（HNO3）2的存在。对萃取反应的表现平衡常数及热力学函数也进行了计算。     

改性稻草对钍的吸附行为

采用丁二酸对稻草进行改性处理,系统研究了不同稻草添加量、pH值、吸附时间和吸附温度条件下,丁二酸改性稻草对水溶液中Th4+的吸附效果。结果表明当吸附剂投加量为0.50 g、pH=3.5、反应时间为30 min、钍溶液初始浓度为10 mg?L?1、温度为65 oC时,改性稻草对Th4+的吸附效果最好,去除率可达96%。傅里叶变换红外光谱分析揭示改性后的稻草样品添加了羧基、羟基、酯基的吸收峰。改性稻草的吸附行为符合Freundlich等温吸附模型以及准二级动力学方程,其吸附性能的提高,认为是改性处理暴露了更多的木质素、纤维素内部多孔结构,及增加了木质素、纤维素上的特殊基团。     

不同燃料球排布方式下熔盐堆堆芯流动和换热特性研究

固态燃料熔盐堆（Thorium Molten Salt Reactor-Solid Fuel,TMSR-SF）的堆芯是由燃料石墨球随机堆积而成的,在分析中建立随机堆积的小球模型存在较大困难和不确定性,通常假设为规则的排布方式。利用计算流体力学分析程序,选取了面心立方和体心立方两种规则的小球排布方式进行建模,分析不同排布方式下堆芯流动和换热的特性。结果表明,面心立方排布下的流线呈现出周期性弯曲,小球中心最高温度为1153 K,总压降为1323 Pa,体心立方排布下的流线大体呈直线,小球中心最高温度为1155 K,总压降为574 Pa,面心立方排布的流动压降明显大于体心立方排布。对于单个中间小球,面心立方排布的小球表面温度分布更均匀,热点温度更低,但熔盐从燃料球底部流动到顶部的压降更大。     

N-（2-乙基）己基己内酰胺对铀（Ⅵ）、钍（Ⅵ）萃取行为的研究

研究了N-（2-乙基）己基己内酰胺（EHCLA）-三甲苯从硝酸介质中萃取铀、钍。EHCLA对这两种元素的萃取规律类似于TBP。用斜率法求得铀、钍的溶剂化数均为2,硝酸为1。还就温度对于萃取的影响和铀、钍的反萃以及三相的形成进行了研究,计算了萃取平衡常数和铀、钍的△H值。初步探讨了萃取的机理。     

Simultaneous determination of thorium and uranyl ions by optode spectra and chemometric techniques

A sensitive optode was fabricated from a recently synthesized ligand (triazene-1,3-di(2-methoxyphenyl)). Simultaneous determination of thorium and uranium in aqueous samples were performed by this optode in conjunction with partial least squares (PLS) and artificial neural network (ANN) techniques. The measured absorbances at 27 selected wavelengths were used for training. A PLS1 model with 4 and 3 latent variables for thorium and uranium respectively, a PLS2 model with 4 latent variables and a principal component ANN model (4-2-2) with linear transfer function after hidden and output layers were created. Relative error of prediction for PLS1, PLS2 and ANN models in synthetic mixtures were 7.40%, 7.12% and 5.04% respectively.