山西、河南三地土壤样品中239+240Pu、137Cs分析

采用电感耦合等离子体质谱(ICP-MS)分析了中国中部地区三地(山西长治、河南濮阳和商丘)钻芯(0～30 cm)土壤样品中的239 240 Pu活度浓度和240Pu/239pu同位素比值,并对239 240 Pu和137Cs在土壤中的深度分布进行了研究.结果表明,三地表层土壤(0～2 cm)中239+ 240pu活度浓度为0.078 ～0.122mBq/g,137Cs为1.56 ～2.91 mBq/g,且浓度整体随深度增加而降低;240Pu/239 Pu原子比的平均值为0.188±0.016(全球沉降平均值为0.180±0.014),137Cs/239240Pu活度比值为34.61 ±5.91(1998年7月,全球沉降平均值为34±4).三地土壤中放射性核素137 Cs、239+240Pu浓度及钚同位素比值均与全球沉降值相当,说明其来源可能属于全球沉降.     

环境空气中239+240Pu的分析测定

建立了环境空气中^239+240Pu的测量方法。该方法采用NF-2型滤膜采集空气样品5 000～10 000 m³,干法灰化,硝酸加热浸取钚,氨基磺酸亚铁和亚硝酸钠将钚转化为四价态,用三正辛胺—聚三氟氯乙烯粉萃取色层柱分离纯化钚,0.025 mol/L草酸—0.15 mol/L硝酸解吸,最后电沉积制源,在α谱仪上测量^239+240Pu计数。通过实验确认了测量方法的主要条件和参数:电沉积制源极间距为4.0 mm,pH值为2.0;溶液萃取分离色层柱高度为6.0 cm,溶液流速2 mL/min;氧化还原时间为10 min。方法全程回收率为52.5%~82.5%,平均值68.3%;气溶胶样品量为10 000 m³时,方法探测下限为1.31×10^-7Bq/m³。该方法可用于环境气溶胶中^239+240Pu测量,采用本方法测定了我国西北某地区气溶胶中^239+240Pu活度浓度, 结果平均值为3.25×10^-6 Bq/m³。     

环境样品中~(90)Sr和~(239+240)Pu的联合分析

针对气溶胶、沉降灰、土壤、生物及淡水等环境样品中90Sr、239+240Pu的联合分析进行了流程设计,并通过实际样品的测量对流程进行了验证。结果表明:90 Sr分析流程的化学回收率为44.3%~90.2%,平均值为73.8%;239+240Pu分析流程的放化回收率为40.2%~104.3%,平均值为79.3%。在可给出单个样品化学(放化)回收率的前提下,该联合分析流程可以满足日常环境监测的要求。     

我国部分省份环境气溶胶中239+240 Pu的测定

采用阴离子交换树脂分离结合α谱仪测量的方法对我国7个省份环境气溶胶中^239+240Pu含量进行测定,实验全程回收率为60.8%～94.6%,对气溶胶中^239+240Pu的最小可探测限为0.008 μBq/m³。普通环境气溶胶采样量需要达到30 000 m³以上,在应急情况等特殊环境气溶胶采样量为10 000 m³可满足要求。一般情况下气溶胶中²¹⁰Po含量比^239+240Pu高4～6个数量级,在分析和测量中要关注²¹⁰Po对^239+240Pu测量的影响。测量结果显示,我国普通省份环境气溶胶中^239+240Pu含量为0.009～0.099 μBq/m³,与美国、韩国和西班牙等国家空气气溶胶中的Pu含量处于同一水平。     

爱尔兰海东北部沉积物中~(239)Pu、~(240)Pu和~(241)Am的孔隙水化学

为了查定Pu和Am2个核素在沉积物沉积后的性状和评估其活化的可能性,对爱尔兰海东北部沉积物和孔隙水中的来自Sellafield的~(230)Pu、~(240)Pu和~(241)Am的分布作了研究。~(239)Pu、~(240)Pu、和~(241)Am的固相剖面中具有明显的地下峰,它与有机炭、Fe或Mn的分布无关,但可能反映Sellafield排放的历史。还原型Pu和Am的孔隙水剖面同样表明有明显的地下峰,它与有机质被氧或硝酸盐氧化的成岩作用无关,也与Fe和Mn的活化无关。孔隙水中的放射性核素剖面表明与固相中的放射性核素剖面之间在性质上有联系,这就提出一个由视Ka′s来描述的吸附/解吸作用,对还原型Pu,其范围为1.7×10~5—11.8×10~5,对还原型Am其,范围为3.5×10~5—3.9×10~5。然而对Pu(可能还有Am)来说,这种实测视K_d随深度而发生的系统变化,说明沉积物/孔隙水体系之间是不平衡的。已有的资料没有证实这种说法,即在孔隙水中,Pu的络合作用是由可溶性有机炭引起的。提出了通过近沉积物表面氧化物相的沉淀来清除Pu和Am.     

ICP-MS测量超痕量钚时质谱干扰的消除及水中钚的测定

研究了感应耦合等离子体质谱(ICP-MS)测定超痕量钚时的质谱干扰及干扰元素的去除;建立了环境水样中超痕量钚的测定方法。方法所用的解吸液适于ICP-MS直接进样,并有效地消除铅等元素形成的多原子离子干扰。测量了溶液中的m／z238和2％HNO3空白液中的^239Pu和^242Pu计数率,对测量结果进行校正。方法的本底为20fg,方法对^239Pu的检出限为43fg,测定限为88fg。所分析的水样中,井水中的^239Pu含量低于检出限,地表水中^239Pu的含量高于检出限,湖水和河水中的^239Pu高于测定限,但属于全球沉降引起的本底,不会对公众造成辐射危害。     

Presence of plutonium isotopes, Pu and Pu, in soils from Chile

Plutonium is present in every environmental compartment, due to a variety of nuclear activities. The Southern Hemisphere has received about 20% of the global ²³⁹Pu and ²⁴⁰Pu environmental inventory, with an important contribution of the so-called tropospheric fallout from both the atmospheric nuclear tests performed in the French Polynesia and in Australia by France and United Kingdom, respectively. In this work we provide new data on the impact of these tests to South America through the study of ²³⁹Pu and ²⁴⁰Pu in soils from different areas of Northern, Central and Southern Chile. The obtained results point out to the presence of debris from the French tests in the 20-40° Southern latitude range, with ²⁴⁰Pu/²³⁹Pu atomic ratios quite heterogeneous and ranging from 0.02 to 0.23. They are significantly different from the expected one for the global fallout in the Southern Hemisphere for the 30-53°S latitude range (0.185 ± 0.047), but they follow the same trend as the reported values by the Department of Energy of United States for other points with similar latitudes. The ^239 + 240Pu activity inventories show as well a wider variability range in that latitude range, in agreement with the expected heterogeneity of the contamination.     

基于MnO2共沉淀的海水中234Th的分析方法

利用室内模拟MnO₂共沉淀和直接β计数分析海水中²³⁴Th。实验中对模拟条件进行了优化,结果表明：共沉淀滤膜选择混合膜时,实验流程空白计数率稳定在(0.50±0.04)min^-1;共沉淀前若酸化,会破坏海水中U和CO₃^2-络合作用,导致U-Th分离效果减弱;共沉淀时最佳pH=10.0;海水中添加碳酸盐能明显降低海水中U的共沉淀效率;增大沉淀剂的用量,会一定程度改善U-Th的分离效果,每升海水中加入1.2mg KMnO₄和3.0mg MnCl₂·4H₂O时最佳。本实验方法已经将模拟条件的结论结合实际情况应用到东海天然海水中²³⁴Th的分析,该方法的全程回收率为（36.0±5.2)%(n=3)。     

Effect of curing agent polarity on water absorption and free volume in epoxy resin studied by PALS

Microstructure and water absorption were systematically studied by positron annihilation lifetime spectroscopy (PALS), gravimetric measurements and Differential Scanning Calorimetry (DSC) for epoxy resins DER331 (E51) cured with three different kinds of amine curing agents DDS, DDM and MOCA. Experimental results indicated that the water absorption as a function of immersed time could be well fitted to Fick’s second law. Based on the gravimetric measurement, we found that the equilibrium water sorption M_∞ and the diffusion coefficients D of the epoxy resins have an order: E51-DDS > E51-DDM > E51-MOCA, which indicated that the curing agent plays an important role in determining the content of the water absorbed. Positron experimental results showed that the o-Ps lifetime dramatically decreased with the immersed time from 0 to 6 h, which suggested that water molecules were filled into free-volume holes and the interaction between the water-polymer decreased the mobility of molecular chains. In order to deeply discern the influence of water absorption upon the free volume, the continuous lifetime analysis, i.e. the maximum entropy lifetime method (MELT) was employed to obtain the distributions of the ortho-positronium (o-Ps) lifetime and the of the free-volume holes. From MELT analyses, we found the existences of two the long-lived components (τ₃ and τ₄), which indicated that two kinds of different o-Ps states exist. The shorter long-lived component (τ₃) is related to the segmental packing density in local ordered region. Compared to dry sample, two peaks of the o-Ps lifetime and the free-volume hole in the wet samples all drift to low values, especially, this drifts is more marked for the water sorption occurring at higher temperature 75 °C. This fact suggested that when the epoxy resin is in the glassy state, the interaction between the water and matrix restricts the motion of segmental chains and prevents from the free-volume hole swelling.     

事故条件下模块化小堆与同厂址大堆的辐射影响对比分析

本文针对海南小堆的实际厂址环境特征,根据机组初步的二级PSA源项,利用更实际的CALPUFF烟团模式开展事故条件下小堆和大堆对场外公众的辐射影响分析,比较不同事故下对周边居民和工作人员的受照特征。按照针对小堆的剂量准则,确定各种天气条件下满足该准则的距离,有助于更深入地认识小堆的事故特征及应急计划区划分等问题,为相关工程实践和应急监管工作提供参考。     

鼓泡法结合CO_2直接吸收法进行环境水中无机~(14)C的分析方法研究

对目前测量水中~(14)C的4种方法(沉淀法、直接吸收法、苯合成法和加速器质谱法)进行分析和比较后,采用鼓泡法和Carb-sorb E直接吸收CO_2法对环境水中的无机~(14)C进行了测量。取50 L水样,加入H_3PO_4,将其中的CO_2释放出来,碱液吸收,然后转变为碳酸钙沉淀,将碳酸钙沉淀酸解,生成的CO_2由Carb-sorb E吸收后,加入闪烁液后用液闪测量。建立的水中无机~(14)C分析方法全程回收率为90.3%,液闪测量探测下限可达0.20 m Bq/L。用该方法测定了地表水、地下水等不同的水样品,结果在1.31~10.26m Bq/L之间。     

用PIXE技术分析山东省胃癌高,低发区饮水中的微量元素

介绍了用ＰＩＸＥ技术分析饮水中微量元素的方法，给出了山东省胃癌高发区栖霞县与低发区苍山县饮水中的微量元素谱。两地饮水中微量元素含量的检验显示，Ｔｉ，Ｖ，Ｃｕ，Ｆｅ和Ｆｒ等５种元素栖霞均显著高于苍山县。