U_3Si_2Al弥散型燃料的辐照肿胀研究

介绍了U3Si2 Al弥散型燃料的辐照肿胀机理。将弥散型燃料的芯体视为连续基体中的微型燃料元件 ,应用裂变气体的行为机理描述燃料相中的气泡形成过程。研究结果表明 :燃料相的肿胀引起燃料颗粒和金属基体之间的力学相互作用 ,金属基体能抑制燃料颗粒的辐照肿胀。在一定辐照条件下 ,本模型对燃料元件辐照肿胀的预测值与测量值相符     

气冷堆用棱柱型弥散微封装燃料性能分析及优化研究

棱柱型弥散微封装燃料是将三重各向同性包覆（TRISO）燃料颗粒弥散于金属或陶瓷基体形成的颗粒增强复合燃料,具有良好的结构稳定性、裂变产物包容能力和辐照稳定性,是高温气冷堆中较具发展前景的燃料形式之一。本文提出将TRISO燃料颗粒弥散于SiC基体的棱柱型弥散微封装燃料设计方案,并基于有限元分析软件COMSOL建立了该燃料元件三维热流固耦合分析模型,初步实现了该燃料元件性能分析和优化设计。结果表明,棱柱型弥散微封装燃料元件的温度最大值位于燃料元件外侧,应力峰值位于冷却剂通道壁面,边距比为0.76~0.84、孔距比为0.68~0.75时燃料元件热应力最小。本文建立的棱柱型弥散微封装燃料性能分析方法和研究结论,可为后续该型气冷堆燃料元件设计提供指导和参考。      

弥散核燃料等效辐照肿胀计算模拟

本文将弥散核燃料芯体看作一种特殊的颗粒复合材料,利用细观计算力学的方法,假设燃料颗粒在芯体中周期性分布,建立了对芯体等效辐照肿胀进行计算模拟的有限元模型。考虑颗粒的辐照肿胀和基体材料的辐照硬化效应,分别建立了燃料颗粒和基体材料的应力更新算法,编制了用户材料子程序,在Abaqus软件中实现了芯体等效辐照肿胀的有限元模拟。计算分析了颗粒大小和体积含量对芯体等效辐照肿胀的影响,并得到了等效辐照肿胀的拟合公式。研究结果表明,影响芯体等效辐照肿胀的主要因素是颗粒的辐照肿胀和体积含量。     

研究堆降低铀浓缩度计划（RERTR）燃料研究开发进展

20世纪90年代中期开始的UMo弥散型燃料辐照试验结果表明，UMo燃料的辐照性能良好；但2003年发现，在高功率和高温时出现枕状肿胀。随后的深入研究表明，肿胀不是由于UMo燃料颗粒本身引起的，而是由于辐照使铝与燃料反应所形成的反应层产生的大气泡引起的。要继续成功开发很高铀密度的低浓铀燃料元件需要有详细的研究计划，这包括：燃料制造工艺开发、堆外性能研究、辐照、辐照后检查、燃料性能评价和模型以及程序的开发。可以通过几个途径克服肿胀问题：稍为改变燃料和基体材料的化学成分；用另一种材料取代铝基体，甚至取消铝基体，开发单片式燃料板。目前6个国家（阿根廷、加拿大、法国、韩国、俄罗斯、美国）正在合作进行上述工作。本文总结了RERTR．6辐照试验及相关实验的最新试验结果，讨论了到2010年开发和鉴定出很高铀密度的低浓铀燃料元件的途径。     

基于弥散燃料颗粒开裂的金属基体裂纹特征模型

金属基弥散燃料元件在特殊工况下会发生表面起泡失效。燃料颗粒开裂是金属基体开裂的前提条件,只有当金属基体开裂后元件才会发生表面起泡。燃料颗粒开裂后,裂纹宽度和塑性区长度等裂纹特征决定了金属基体开裂行为。基于弹塑性断裂力学和应力平衡条件,建立了基于弥散燃料颗粒开裂的金属基体裂纹特征模型。计算结果表明:裂纹张开位移随退火温度和燃耗深度的升高而增加;裂纹尖端塑性区长度主要与退火温度相关。裂纹张开位移和塑性区长度的计算结果与实验数据均符合较好,验证了金属基体裂纹特征模型的有效性。     

低富集U-Mo弥散型燃料小板RERTR-6辐照试验结果——Si对U-Mo／Al弥散燃料辐照行为影响的初步分析

辐照时Al基体中弥散的U-Mo燃料颗粒表面形成包覆的反应物。在一些辐照试验中,反应物和舢基体交界面处有气孔产生。受辐照条件的影响,气孔可能会长大并彼此连接形成连通的大气孔,严重时形成连续网络结构使燃料板出现不可接受的枕形肿胀。在美国和其他国家的辐照实验中都观察到了这种现象。冶金学和热动力学分析表明,Al基体中加入Si以及U-Mo燃料中添加Zr或Ti都可以提高U-Mo／Al弥散型燃料反应产物的稳定性。本文介绍了添加Si辐照试验的初步结果,即将适量的Si添加到Al基体中能有效降低U-Mo／Al燃料扩散反应和消除气孔形成。     

基于弥散燃料颗粒开裂的金属基体裂纹特征模型

金属基弥散燃料元件在特殊工况下会发生表面起泡失效。燃料颗粒开裂是金属基体开裂的前提条件，只有当金属基体开裂后元件才会发生表面起泡。燃料颗粒开裂后，裂纹宽度和塑性区长度等裂纹特征决定了金属基体开裂行为。基于弹塑性断裂力学和应力平衡条件，建立了基于弥散燃料颗粒开裂的金属基体裂纹特征模型。计算结果表明：裂纹张开位移随退火温度和燃耗深度的升高而增加；裂纹尖端塑性区长度主要与退火温度相关。裂纹张开位移和塑性区长度的计算结果与实验数据均符合较好，验证了金属基体裂纹特征模型的有效性。     

U_3Si_2-AI 弥散型燃料元件

U_3Si_2-Al 弥散型板状燃料元件是新发展的高铀密度的研究堆燃料.辐照和全堆芯试用表明:元件外形尺寸稳定;无裂变产物泄漏;直到燃耗达98%时,U_3Si_2颗粒肿胀都是裂变密度的线性函数;U_3Si_2与铝基体和铝包壳在制造和辐照中都是相容的。芯体铀密度最高达4.8g(U)/cm~3的 U_3Si_2-Al 燃料都是适合研究堆使用的低浓铀燃料.     

阿贡国家实验室单片式燃料研制

最初的U-Mo弥散型燃料元件已经最示出铀装载量方面的优越性，可以用它来成功地把部分研究堆燃料转换成低浓铀。另外，辐照实验显示出在高温下U-Mo弥散型燃料元件的芯体与铝基发生了相互反应。解决这些现象的潜在方法是使用燃料合金片代替铝基弥散型燃料。这种单片式燃料提供了比弥散型燃料更低的燃料一基体反应层和更高的铀密度。由于弥散型燃料基体的不足，单片式燃料元件生产需要研究新的制造方法。经过阿贡国家实验室研究人员的努力，已经得到一种可行的单片式燃料板生产方法，本文将介绍这种方法。     

包覆燃料颗粒应力的有限元分析

高温气冷堆的燃料元件由包覆燃料颗粒弥散在石墨基体中组成。在反应堆运行过程中,辐照及各复杂的物理化学反应产生的应力会使包覆燃料颗粒发生破损,对包覆燃料颗粒进行应力分析是评价燃料元件和反应堆运行安全性能的主要内容之一。本文基于压力壳模式,主要考虑内压作用下的球形壳层应力及包覆燃料颗粒的非球形因素,用有限元法对应力进行了分析。     

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.     

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。     

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.     

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.     

HfO2 and Ta2O5 as grain growth inhibitors in Eu2O3

Because of the high neutron capture cross section for five consecutive europium isotopes, Eu₂O₃ is of interest as a control material for nuclear reactors. A tendency toward excessive grain growth degrades its mechanical properties. Small amounts of HfO₂ and Ta₂O₅ were added to the Eu₂O₃ in attempts to suppress this grain growth. Three at % substitution of Hf for     

热-水-力-化学耦合作用下Ca0.86Nd0.14Ti0.86Al0.14SiO5固溶体的化学稳定性

以CaCO₃、Nd₂O₃、TiO₂、SiO₂、Al₂O₃为原料,用固相法制备掺钕榍石固溶体（Ca_0.86Nd_0.14Ti_0.86Al_0.14SiO₅）。采用PCT法进行浸泡实验,借助X射线衍射（XRD）、扫描电镜（SEM）、电感耦合等离子体发射光谱（ICP-OES）等分析手段,研究掺钕榍石固溶体在热 水 力 化学（THMC）耦合作用下的化学稳定性。结果表明,在pH值为5～9、温度150～200 ℃、压强0.476～1.554 MPa的耦合作用下,Ca_0.86Nd_0.14Ti_0.86Al_0.14SiO₅固溶体具有良好的化学稳定性;pH值、温度（压力）对Ca_0.86Nd_0.14Ti_0.86Al_0.14SiO₅固溶体中Si⁴⁺、Al³⁺、Nd³⁺的归一化浸出率无明显影响;Ca²⁺在200 ℃（1 554 MPa）时的抗浸出性能较150 ℃时的好;在浸泡初期（1～21 d）Ca²⁺在pH值为9时的抗浸出性能优于pH值为5和7时的,浸泡后期（28、42 d）3种溶液中固溶体的Ca²⁺抗浸出性能趋于一致;Ti⁴⁺在pH值为9时的抗浸出性能较pH值为5和7时的好。     

NHO3氧化去除Np—Pu反萃液中的H2C2O4

研究了用ＮＨＯ３氧化去除ＴＲＰＯ流程反萃Ｎｐ－Ｐｕ的Ｈ２Ｃ２Ｏ４反萃液中Ｈ２Ｃ２Ｏ４的条件。７．５ｍｏｌ．Ｌ＾－１ＨＮＯ３－０．３ｍｏｌ．Ｌ＾－１Ｈ２Ｃ２Ｏ４混合液于９０℃下蒸发１３０ｈ和１００℃下蒸馏回流６ｈ，Ｈ２Ｃ２Ｏ４可完全分解去除；混合液中添加适量催化剂ＭｎＣＯ３，于１００℃下蒸发或蒸馏回流，Ｈ２Ｃ２Ｏ４分解加速，１－１．５ｈ内Ｈ２Ｃ２Ｏ４完全分解。蒸发或蒸馏回流过程中产生的ＨＮＯ２把Ｎｐ     

Thermal expansion studies on UMoO5, UMoO6, Na2U(MoO4)3 and Na4U(MoO4)4

In the present work, thermal expansion behavior of lower valent sodium uranium molybdates, i.e., Na₂U(MoO₄)₃ and Na₄U(MoO₄)₄ were studied under vacuum in the temperature range of 298-873 K using high temperature X-ray diffractometry (HTXRD). Expansion behaviors of UMoO₅ and UMoO₆ were also studied in vacuum from 298 to 873 K and 773 K, respectively. UMoO₅ was synthesized by reacting UO₂ with MoO₃ in equi-molar proportion in evacuated sealed quartz ampoule at 1173 K for 14 h. Na₂U(MoO₄)₃ and Na₄U(MoO₄)₄ were prepared by reacting UMoO₅ and MoO₃ with 1 and 2 moles of Na₂MoO₄, respectively, at 873 K in evacuated sealed quartz ampoule. XRD data of UMoO₅ and UMoO₆ were indexed on orthorhombic and monoclinic systems, respectively, whereas, the data of Na₂U(MoO₄)₃ and Na₄U(MoO₄)₄ were indexed on tetragonal system. The lattice parameters and cell volume of all the four compounds, fit into polynomial expression with respect to temperature, showed positive thermal expansion (PTE) up to 873 K.