~(40)K-~(40)Ca法的初步研究

报道了样品中钾、钙化学分离和纯化,以及质谱测定流程的建立。测试了国家球团矿标样W7220和W7107、国家40K-40Ar法标准矿物黑云母(ZBH-25)和角闪石(ZBJ)的钾钙含量,以及国际二级钙标样Tachiti和国家钾含量标样的钙和钾同位素比值。实测结果与相应的标称值在误差范围内一致。在此基础上,用实验所得的两组黑云母和角闪石的(40Ca/42Ca) 和 (40K/42Ca)数据,构筑了40K-40Ca法等时线年龄为(133.532.1)Ma, 此与标称值年龄132.7Ma在误差范围内一致。而所得的初始值(40Ca/42Ca)i为151.4160.003, 相应的xCa 值为+26.5,示踪了该矿物组合的原岩具有陆源性质,为固体地球化学的研究提出了新的判据。     

单斜晶系角闪石族矿物的穆斯堡尔效应的研究

单斜晶系角闪石族矿物是一类成分复杂、具有双链状结构矿物的总称。测试了宁镇地区的花岗闪长岩、矽卡岩和豫西地区的角闪片麻岩中的12个角闪石的穆斯堡尔谱,包括普通角闪石、阳起石和绿钙闪石,它们属Ca-角闪石类型。它们的晶体化学式为X_(2-3)Y_3Z_8O_(22)(OH)_2,阳离子在晶格中占有六种位置,但主要占据四个八面体M_1、M_2、M_3和M_4位:其中X阳离子Ca、Na、K、Mn为M_4或A占位;Y阳离子Mg、Fe~(2 )、Fe~(3 )、     

西德巴伐利亚东北部基岩中次生铀矿化的年龄

巴伐利亚东北部基岩中所有铀矿化点的上部几乎大部分都呈现有表生再沉积现象。对在再沉积作用中形成的次生铀矿物(硅钙铀矿、铜铀云母、钙铀云母、钡铀云母及镁磷铀云母)用铀-铅法和锾-铀法进行了年龄测定。所有样品都得出不一致的铀-铅年龄。在~(207)Pb/~(206)Pb对~(238)U/~(200)Pb图式中不一致线与一致曲线的上交点仅在某些情况下可看作是原生沥青铀矿的形成年龄,而在所有情况下其下交点都给出了次生铀矿化的年龄。曾获得了0.110±0.006 Ma(用锾-铀法测定)到8.6 Ma的一系列年龄值;这些年龄值可以划分为3组:Ⅰ组包括所有~(330)Th/~(234)U放射性比值低于1的矿物。假定在矿物形成时不存在~(230)Th,则对3个铜铀云母矿化点计算的年龄为1.110—0.164 Ma。Ⅱ组包括那些处于放射平衡状态下(即老于0.4 Ma)的铀矿物,其铀-铅年龄为0—3 Ma。由于下交点精度限制,故得不到更准确的年龄。Ⅲ组包括最老的次生铀矿物,它们的年龄能很好地确定为5.6—8.4 Ma。     

乌克兰地盾钠交代岩中铀矿床矿石的矿物类型

乌克兰地盾钠交代岩中的铀矿床产生于约1800Ma之前的古地台初始活化过程中,形成于不同成分的围岩中:在东部克里沃罗日铁矿盆地的铁镁岩石中是角闪片岩、含铁石英岩、铁矿石。在中部基洛夫格勒地区为铝硅酸盐岩石——角闪石黑云母片麻岩、混合岩和花岗岩。岩石成分的差异导致在统一的热液交代作用过程中形成了不同组分的交代岩(在铁镁岩石中形成霓石岩、磁铁矿-碱性角闪石交代岩和含铁碳酸盐交代岩,在铝硅酸盐岩石中形成碱性角闪岩-霓石钠长岩)和铀矿石。详细的研究和区域矿物学编图可将钠交代岩中的矿床矿石分为6种矿物类型,以及它们在时间和空间上的联系。每一类型均具有其独特的成分和定位条件。     

钕在钙钛锆石和榍石组合矿物中的固溶机制

以ZrSi O4、CaCO3、Ti O2、Al2O3、Nd2O3为原料,引入Al3+作价态补偿,通过固相反应制备包容模拟三价锕系核素Nd的钙钛锆石(CaZrTi2O7)和榍石(CaTiSi O5)组合矿物固化体。利用X射线衍射(XRD)、扫描电镜/能谱仪(SEM/EDS)研究其矿相组成、微观结构和元素分布,探讨Nd在钙钛锆石和榍石组合矿物固化体中的固溶机制。研究表明:钙钛锆石和榍石组合矿物固化体较佳的合成条件是在1 230℃条件下保温30 min,较佳配方的摩尔比为n(Ca1-x/2-y/4Nd(x+y)/2Zr1-y/4Alx/2Ti2-x/2O7)∶n(Ca1-xNdxAlxTi1-xSi O5)=[4/(4-y)]∶1;Nd3+能够进入钙钛锆石和榍石晶格,榍石能够固溶Zr4+、Al3+、Nd3+,Zr4+和Nd3+取代Ca2+位,Al3+占据Ti4+位,钙钛锆石能够固溶Al3+、Nd3+,Nd3+进入Ca2+位和Zr4+位,Al3+占据Ti4+位。     

泥土中钾的原子吸收法测定和~(40)K的β放射性计算

在放射性的环境总β监测中,为了确定泥土β核素的污染程度和对泥土环境质量作出评价,就要首先准确地测知其含钾量或预先从试样中将钾除去,但后者较麻烦。 测定环境介质或生物样品中的钾含量(按丰度可算出~(40)K含量)一般可采用四苯硼钠法、火焰光度法和原子吸收法。其中,用空气-乙炔火焰的原子吸收法操作快速简便,既能测定微克量钾(选用灵敏谱线),又可测毫克量钾(稍作稀释后用非灵敏线),灵敏度和精密度均较满     

ICP-OES测定环境水样中的钾-40

建立了利用电感耦合等离子体发射光谱仪(ICP-OES)测定环境水样中钾-40的方法。此方法标准工作曲线线性关系良好,检出限为0.001 Bq/L,相对标准偏差小于1.5%,相对误差小于4.0%,加标回收率在94.1%~105.5%之间,具有前处理简单、检出限低、精密度和准确度高、干扰小等优点,值得推广应用。     

广东珠海地表介质中238U、232Th和40K的活度水平

采用就地伽马能谱测量方法对珠海市进行了以评价环境电离辐射水平为目的测量,实测面积100 km2,970个测点.采用NaI(Tl)闪烁伽马谱仪实测珠海风化花岗岩中40K、238U和232Th的比活度分别为654.2±338.0,85.7±31.6和159.8±49.0 Bq*kg-1;第四纪沉积物中则分别为632.3±75.1,35.2±14.6和70.2±18.6 Bq*kg-1.研究结果表明,地表介质中40K、238U和232Th主要来源于晚侏罗纪黑云母二长花岗岩,其比活度与地质背景密切相关.     

乌鲁木齐市沉降物中^(7)Be、^(40)K放射性水平

为了解乌鲁木齐市辐射环境水平,监测了乌鲁木齐市周围环境空气中沉降物2017—2021年^(7)Be、^(40)K放射性水平。结果表明:乌鲁木齐市沉降物中^(7)Be的最大值为2.8 Bq/(m^(2)·d),最小值为1.1 Bq/(m^(2)·d),5年均值为1.94 Bq/(m^(2)·d);^(40)K的最大值为1050 mBq/(m^(2)·d),最小值为104 mBq/(m^(2)·d),5年均值为354.3 mBq/(m^(2)·d);乌鲁木齐市沉降物中的^(7)Be、^(40)K放射性水平处于正常天然放射性水平,且5年测值基本处于稳定状态。     

原子吸收分光光度法测定并计算天然水和废水中的~(40)K

用乙炔—空气火焰的原子吸收光度法测定钾,方法准确度和精密度良好,适用于测定天然水和废水中的~(40)K含量。     

A YAP camera 40×40 mm2 with fast readoutelectronics

Previous papers have already demonstrated the suitability for single-photon emission computed tomography (SPECT) tracers biodistribution studies on small animals, of a miniature gamma camera composed by a YAP:Ce scintillating array 4×4×1 cm³ coupled to a 3-in Hamamatsu crossed-wire anode position sensitive photomultiplier (PSPMT). Some modifications have been applied to the imaging system readout in order to adapt its utilization for specific purposes (i.e. SPECT radiopharmaceutical testing) and to reduce construction costs so that a larger scale production may be feasible. In particular, the system introduced here is based on a resistive chain readout and an integrated acquisition electronics. The intrinsic performance of this new version has been analyzed and compared to the previous system, which had a single-wire readout. Results showed that the basic characteristics of the imaging system remain substantially unchanged in this simplified version, while a faster count rate is achieved. A test on a biological sample performed with the YAP camera both in single-wire and in resistive chain readout modality is also presented, which shows the system high performance in comparison to the Auger camera     

Study on Fragments Emission in the 64Ni+64Ni Reaction at 40 AMeV

The multiplicity of fragments in Fermi energy heavy-ion collisions was experimen-tally extracted. Compared with the results of calculation using the antisymmetrized molecular dynamics (AMD) model which accounts for the primary fragments only, the results calculated using the AMD together with a statistical decay code GEMINI to account for the deexcitation of excited primary fragments are in better agreement with those extracted from the experiment. This observation indicates that the experimental multiplicity distribution may be significantly different from those of primary fragments.     

Gd2O3-Nd2O3-ZrO2-CeO2体系的高温固相反应研究

为研究Gd₂O₃-Nd₂O₃-ZrO₂-CeO₂四元氧化物体系的高温固相反应,以Gd₂O₃、Nd₂O₃、ZrO₂、CeO₂混合粉体为原材料,在1 673 K和1 773 K温度下煅烧24、48、72 h,分别制备了系列样品,并对合成样品进行了XRD和SEM分析。结果表明,合成产物为具有缺陷萤石相且伴有少量烧绿石相的Gd_2-xNd_xZr_2-xCe_xO₇（0≤x≤2）晶体化合物。随着煅烧温度的升高和煅烧时间的延长,产物中立方烧绿石相的化合物增多,晶粒尺寸变大,且有少量未知相生成。进而探讨了锆基陶瓷固化多核素的潜在应用,并提出了未来研究的相关热点问题。     

Enthalpy measurements of La2Te3O9 and La2Te4O11

Enthalpy increment measurements on La₂Te₃O₉(s) and La₂Te₄O₁₁(s) were carried out using a Calvet micro-calorimeter. The enthalpy values were analyzed using the non-linear curve fitting method. The dependence of enthalpy increments with temperature was given as: H°(T) − H°(298.15 K) (J mol⁻¹) = 360.70T + 0.00409T² + 133.568 × 10⁵/T − 149 923 (373 ? T (K) ? 936) for La₂Te₃O₉ and H°(T) − H°(298.15 K) (J mol⁻¹) = 331.927T + 0.0549T² + 29.3623 × 10⁵/T − 114 587 (373 ? T (K) ? 936) for La₂Te₄O₁₁.     

Total cross sections for the 40Ca(n,p) and (n, α) reactions between 2.7 and 5.5 MeV

Measurements have been made of the ⁴⁰Ca(n,p), ⁴⁰Ca(n,α), ⁴⁰Ca(n,n′) ⁴⁰Ca(3.35) cross sections in the energy range 2.7–5.5 MeV. Neutron flux measurements are made using the associated particle technique. The data are compared to previous data and the recent Hauser-Feshbach calculations made by Fu (1979).     

Reactivity of hydrogen peroxide towards Fe3O4, Fe2CoO4 and Fe2NiO4

The kinetics of CRUD oxidation by H₂O₂ has been studied using aqueous suspensions of metal oxide powder. Fe₃O₄, Fe₂CoO₄ and Fe₂NiO₄ were used as model compounds for CRUD. In addition, the activation energies for the reaction between H₂O₂ and the three CRUD models were determined. The rate constants at room temperature were determined to 6.6 (±0.4) × 10⁻⁹, 3.4 (±0.4) × 10⁻⁸ and 1.6 × 10⁻¹⁰ m min⁻¹ for Fe₃O₄, Fe₂CoO₄ and Fe₂NiO₄, respectively. The corresponding activation energies are 52 ± 4, 44 ± 5 and 57 ± 7 kJ mol⁻¹, respectively. The mechanism of the reaction is briefly discussed indicating that the final solid product in all three cases is Fe₂O₃. In addition to the experimental studies, the theoretical grounds for kinetics of reactions in particle suspensions are discussed. The theoretical discussion is also used to explain the somewhat unexpected trends in reactivity observed experimentally.     

能量色散X射线荧光谱仪在土壤中40K活度分析中的应用

对粉末样品进行压片制样,建立了能量色散X射线荧光（EDXRF）谱仪测定环境土壤样品中⁴⁰K放射性活度的方法。方法标准曲线的相关系数为0.991 0,测量的精密度为2.98%,测量标准样品的最大相对偏差为6.40%。采用本方法和γ谱仪同时测量7个土壤样品,并对这两种分析方法的测量结果采用配对t检验SPSS程序计算。结果表明,两种方法所得数据无显著性差异（P＞0.05）,可使用X射线荧光谱仪法分析土壤中40K的放射性活度。这种方法操作简便,精密度和准确度较好,具有广泛的实用性。     

Radiation effects on PbO-Al2O3-B2O3-SiO2 glasses by FTIR spectroscopy

The infrared absorption spectra of PbO-Al₂O₃-B₂O₃-SiO₂ glasses have been measured in the spectral range 600-4000 cm⁻¹ before and after absorbed dose of 50 Gy, 4 kGy and 50 kGy to investigate the structural change due to irradiation. The structural change due to composition has also been discussed. The experimental results clearly indicate that after irradiation, a significant change in structure of lead alumino borosilicate glass network is observed. It was shown that BO₄ groups decreases and BO₃ groups increases with the increase of Al₂O_3.     

XRD investigation of ion irradiated Ti3Si0.90Al0.10C2

Ti₃SiC₂ is one of the most promising materials belonging to M_n+1AX_n phases, which exhibit good damage tolerance, thermal stability and mechanical properties.Recently, in the frame of research on future gas cooled fast nuclear reactors, Ti₃SiC₂ has been considered as an innovative candidate material, which could be incorporated in some core components such as fuel cladding. At the present time, however, very few data are available concerning the behaviour of this material after irradiation. In this work, Ti₃Si_0.90Al_0.10C₂ samples were irradiated with high energy Kr and Xe ions and characterized by X-ray diffraction. Patterns were analysed in terms of change in peak intensity, peak position and width. Rietveld refinements were also performed. Increase in micro-strains and lattice parameter with irradiation dose was highlighted. The formation of β-Ti₃SiC₂, which has never been observed by experimental XRD on non irradiated material, was proposed for the highly irradiated samples. A partial recovery of the microstructure with temperature was found.