HNO3氧化去除铀反萃液中的C2O^2—4

研究了用ＨＮＯ３氧化去除ＴＲＰＯ流程铀的（ＮＨ４）２ＣＯ３反萃液中Ｃ２Ｏ＾２－４的条件。将含铀的（ＮＨ４）２ＣＯ３反萃液调节成０．２￣０．８ｍｏｌ．Ｌ＾－１Ｈ２Ｃ２Ｏ４－７．５￣９．５ｍｏｌ．Ｌ＾－１ＨＮＯ３溶液，在１００℃下蒸馏回流７ｈ，其中的Ｃ２Ｏ＾２－４被完全分解去除，得到ＵＯ２（ＮＯ３）２－ＮＨ４ＮＯ３溶液。蒸馏回流过程中，ＮＨ４ＮＯ３部分分解，在该条件下操作是安全的。     

HNO3洗涤法去除TRPO相中的H2C2O4

研究了ＨＮＯ３洗涤法去除ＴＲＰＯ相中Ｈ２Ｃ２Ｏ４的条件。结果表明，用５．５ｍｏｌ／Ｌ ＨＮＯ３２级洗涤ＴＲＰＯ流程中Ｈ２Ｃ２Ｏ４反萃Ｎｐ、Ｐｕ段的ＴＲＰＯ相，可以完全去除Ｈ２Ｃ２Ｏ４，ＴＲＰＯ相不再出现混浊。再用（ＮＨ４）２ＣＯ３溶液从ＴＲＰＯ相中反萃Ｕ（Ⅵ），水相不再产生白色沉淀。确保ＴＲＰＯ提取锕系元素的萃取流程正常进行。     

萃取液闪法测定尿中^239,240Pu

从２４ｈ尿中取样７５０ｍｌ，加入ＨＮＯ３－Ｈ２Ｏ２，以湿式灰化去除有机物。在０．５－１．０ｍｏｌ／ｌ ＨＮＯ３介质中，用３０％ＴＲＰＯ－二甲苯萃取＾２３８，２４０Ｐｕ等α核素。在Ｈ２Ｏ２作用下，Ｎｐ为Ｎｐ（Ｖ），其萃取分配比极低；Ａｍ（Ⅲ）等核素被萃取，用５．５ｍｏｌ／ｌＨＮＯ３洗涤去除。以０．０１ｍｏｌ／ｌ ＨＮＯ３洗涤有机相，去除绝大部分被萃ＨＮＯ３后，加入Ｕｌｔｉｍａ Ｇｏｌｄ Ｆ闪烁液，于     

亚硝酸与正丁醛和Np（Ⅵ）反应的动力学研究

研究了（１）ＨＮＯ２与正丁醛的反应，得速率方程为：－ｄｃＨＮＯ２／ｄｔ－ｋ１ｃＨＮＯ２．ｃｎ－ｃ３Ｈ７ＣＨＯ．ｃＨＮＯ３，在２０℃、Ｉ＝２．０ｍｏｌ／ｋｇ时，速率常数Ｋ１＝０．７６ｌ＾２（ｍｏｌ＾２．ｍｉｎ）（２）在固定１．０ｍｏｌ／ｌＨＮＯ３条件下，ＨＮＯ２与Ｎｐ（Ⅵ）的反应，得速率方程为：－ｄｃＮｐ（Ⅵ）ＣＨＮＯ２在２０℃、Ｉ＝２．０ｍｏｌ／ｋｇ时，表观速率常数ｋ３＾１＝９３ｌ／ｍｏ     

TRPO流程中U的反萃Ⅰ.反萃剂的选择

研究了ＴＲＰＯ萃取流程中的Ｈ２Ｃ２Ｏ４反萃Ｎｐ、Ｐｕ段,在含Ｕ的ＴＲＰＯ相中出现沉淀的条件及消除办法。结果表明,提高洗涤段硝酸浓度,使ＴＲＰＯ相中Ｈ２Ｃ２Ｏ４与ＨＮＯ３的浓度比小于３,在该相中就不会出现沉淀。当用０．２ｍｏｌ／Ｌ或０．８ｍｏｌ／ＬＨＮＯ３洗涤ＴＲＰＯ相２次后,再用（ＮＨ４）２ＣＯ３或Ｎａ２ＣＯ３溶液反萃Ｕ时,水相也不会产生（ＮＨ４）２Ｃ２Ｏ４或Ｎａ２Ｃ２Ｏ４沉淀,保证萃取过程正常进行     

单甲基肼还原Np（Ⅵ）：Ⅱ.Purex流程中U—Np分离的研究

用单级萃取试验研究了水相ＨＮＯ３浓度和ＣＨ３Ｎ２Ｈ３浓度对３０％ＴＢＰ－煤油相从含Ｕ和不含Ｕ水相中萃取Ｎｐ行为的影响，以及反萃液中的ＨＮＯ３浓度和ＣＨ３Ｎ２Ｈ３浓度对从含Ｕ和不含Ｕ的３０％ＴＢＰ－煤油相中Ｎｐ的反萃取率的影响。试验结果表明：提高水相ＣＨ３Ｎ２Ｈ３浓度和降低ＨＮＯ３浓度有利于抑制Ｎｐ的萃取和改善Ｎｐ的反萃取。按照动力堆乏燃料后处理流程１Ａ槽工艺条件和类似于１Ｂ槽的工艺条件，以ＣＨ３Ｎ２Ｈ３为Ｎｐ的选择性还原剂，进行了串级试验。对１Ａ槽串级，Ｕ中除Ｎｐ的净化系数为１．４×１０４，对１Ｂ槽串级，Ｕ中除Ｎｐ的净化系数为１２．８。试验结果初步表明：单甲基肼作为Ｎｐ还原剂在Ｐｕｒｅｘ流程中有一定的应用前景     

甲基肼及β-羟基乙基肼γ辐解产物叠氮酸的生成量

对肼、甲基肼（ＭＭＨ）及β－羟基乙基肼（ＨＥＨ）进行γ射线辐照实验，分别用红外光谱和比色分析法对它们的辐解产物叠氮酸（ＨＮ３）进行定性和定量分析。０．２ｍｏｌ．Ｌ＾－１ＭＭＨ与０．２ｍｏｌ．Ｌ＾－１ＨＥＨ的水溶液体系辐照１０￣５００ｋＧｙ后，ＨＮ３的生成量为０．１￣０．４ｍｍｏｌ．Ｌ＾－１，含３ｍｏｌ．Ｌ＾－１ＨＮＯ３的各体系中ＨＮ３的生成量为０．１￣３．３ｍｍｏｌ．Ｌ＾－１；作为对比的０．２ｍｏ     

2—羟基乙基肼还原Np（Ⅵ）：Ⅰ.反应动力学的研究

用分光光度法研究了ＨＮＯ３介质中ｃ（ＨＯＣ２Ｈ４Ｎ２Ｈ３）、ｃ（Ｈ＋）、ｃ（ＵＯ２＋２）、ｃ（Ｆｅ３＋）、ｃ（ＨＮＯ２）、离子强度和温度等因素对还原Ｎｐ（Ⅵ）反应速率的影响。测定了不同条件下的表观速率常数，确定了Ｎｐ（Ⅵ）还原反应速率方程式。２５℃时，还原反应的表观速率常数ｋ２＝３９１ｍｉｎ－１；反应活化能为５６．６ｋＪ·ｍｏｌ－１。提高２－羟基乙基肼浓度、降低ＨＮＯ３浓度或升高温度，Ｎｐ（Ⅵ）的还原加快；增加ＵＯ２＋２浓度和离子强度，还原速率稍有降低；当ｃ（Ｆｅ３＋）≥１．０ｍｍｏｌ·Ｌ－１时，Ｆｅ３＋对Ｎｐ（Ⅵ）的还原有一定的加速作用。     

动力堆燃耗测定的样品溶解

文章介绍动力堆燃料燃耗测定中样品的溶解方法，试验不同浓度ＨＮＯ３－ＨＣｌ混合液在沸腾温度下溶解ＵＯ２冷样品的效果，以萤光光度计测定溶解液的透明度予以判别。用７．５ｍｏｌ．ｌ＾－１ＨＮＯＥ－ＨＣｌ混合液（ｃ（ＨＮＯ３）：ｃ（ＨＣｌ）＝４：１），溶解热样品，溶解液涂片在超显微镜下检查未见不溶颗粒存在。     

2-羟基乙基肼还原Np(Ⅵ)Ⅱ.在Purex流程中用于U-Np分离的初步研究

用单级萃取试验研究了水相料液中ＨＮＯ３浓度和２－羟基乙基肼浓度对３０％ＴＢＰ－煤油相从水相中萃取Ｎｐ行为的影响,以及反萃液中ＨＮＯ３浓度和２－羟基乙基肼浓度对从含Ｎｐ的３０％ＴＢＰ－煤油相中还原反萃Ｎｐ的效率的影响。试验结果表明：提高水相料液中２－羟基乙基肼浓度和降低ＨＮＯ３浓度有利于抑制Ｎｐ的萃取,提高反萃液中２－羟基乙基肼浓度和降低ＨＮＯ３浓度有利于改善Ｎｐ的反萃取。在２－羟基乙基肼还原Ｎｐ（Ⅵ）过程中,３ｈ内几乎无Ｎｐ（Ⅳ）生成。当水相料液中有一定量Ｆｅ３＋存在时,有少量的Ｎｐ（Ⅳ）生成。在Ｐｕｒｅｘ流程中可望采用２－羟基乙基肼作为Ｎｐ（Ⅵ）的选择性还原剂进行Ｕ－Ｎｐ的分离。     

Thermophysical properties of NpO2, AmO2 and CmO2

The information on thermal and mechanical properties of the minor actinide dioxides: NpO₂, AmO₂ and CmO₂, is still very scarce, and a large uncertainty exists because of difficulties related to their fabrication and manipulation. Prognosis based on a set of the sound physical models and the similarity principle can be useful in this situation. Using the combination of the macroscopic and microscopic approaches developed earlier for thermodynamic properties of actinide dioxides, and the Klemmens model for their thermal conductivity, a few relationships bounding the main thermophysical properties of the actinide dioxides were deduced. These relationships were applied for the calculation of the isochoric and isobaric heat capacity, the isobaric thermal expansion coefficient, the isothermal bulk elastic modulus and the thermal conductivity of NpO₂, AmO₂ and CmO₂ in a large temperature range. A rather satisfactory agreement with the available experimental data and recommendations was demonstrated.     

Reduction of UO2 by H2

The reactivity of H₂ towards UO₂²⁺ has been studied experimentally using a PEEK coated autoclave where the UO₂²⁺ concentration in aqueous solution containing 2 mM carbonate was measured as a function of time at p_H2∼40 bar. The experiments were performed in the temperature interval 74-100 °C. In addition, the suggested catalytic activity of UO₂ on the reduction of UO₂²⁺ by H₂ was investigated. The results clearly show that H₂ is capable of reducing UO₂²⁺ to UO₂ without the presence of a catalyst. The reaction is of first order with respect to UO₂²⁺. The activation energy for the process is 130 ± 24 kJ mol⁻¹ and the rate constant is k_298K=3.6×10⁻⁹ l mol⁻¹ s⁻¹. The activation enthalpy and entropy for the process was determined to 126 kJ mol⁻¹ and 16.5 J mol⁻¹ K⁻¹, respectively. Traces of oxygen were shown to inhibit the reduction process. Hence, the suggested catalytic activity of freshly precipitated UO₂ on the reduction of UO₂²⁺ by H₂ could not be confirmed.     

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     

Formation of U2C3 in the reaction of UC2 with UO2

The formation of U₂C₃ by the reaction of UC₂ with UO₂ has been studied by chemical and X-ray analyses at temperatures between 1400 and 1700 °C in vacuo. The reaction is represented by 7 UC₂ + UO₂ → 4 U₂C₃ + 2 CO.     

Radiotoxicity hazard of U-free PuO2+ZrO2 and PuO2+ThO2 spent fuels in LWR

The radiotoxicity hazard of U-free Rock-like oxide: ROX (PuO₂+ZrO₂) and Thorium oxide: TOX (PuO₂+ThO₂) LWR spent fuels is investigated and radiotoxicity hazard of MOX spent fuel is considered as a reference case. The long-term ingestion radiotoxicity hazard of ROX spent fuel is one third and nearly one fourth of that of TOX and MOX spent fuels, respectively. This is because the discharged Pu and long lived Np in ROX fuel is less than that of TOX and MOX fuels. In TOX fuel, discharged Pu and MA are lower than that of MOX fuel but the long-term radiotoxicity hazard of spent fuel is nearly the same as MOX spent fuel. At the cooling 10⁵ years, the radiotoxicity hazard of TOX spent fuel is approximately ten and three times higher than that of ROX and MOX spent fuels, respectively due to higher toxic contribution of ²²⁹Th in TOX spent fuel.     

Optical properties of UO2 and PuO2

We perform first-principles calculations of electronic structure and optical properties for UO₂ and PuO₂ based on the density functional theory using the generalized gradient approximation (GGA) + U scheme. The main features in orbital-resolved partial density of states for occupied f and p orbitals, unoccupied d orbitals, and related gaps are well reproduced compared to experimental observations. Based on the satisfactory ground-state electronic structure calculations, the dynamical dielectric function and related optical spectra, i.e., the reflectivity, adsorption coefficient, energy-loss, and refractive index spectrum, are obtained. These results are consistent with the available experiments.     

High-temperature specific heat of UO2 ThO2, and A12O3

The high-temperature specific heat of solid UO₂, ThO₂, and Al₂O₃ can be represented by an equation of the form $\text{C}{}_{\mathrm{p(s)}}\text{= 3}{}_{\mathrm{n}}\text{RF(?}{}_{\mathrm{D}}\text{/T) + dT}{}^3$, (1) where ?_D is the Debye temperature, F(?_D/T) is the Debye function, $\text{d}$ represents contributions of the anharmonic vibrations within the lattice, and $\text{n}$ denotes the number of atoms per molecule. In the liquid the corresponding equation is $\text{C}{}_{\mathrm{p(1)}}\text{= 3}{}_{\mathrm{n}}\text{RF(?}{}_{\mathrm{D}}\text{/T) +}\text{h}\text{T}{}^2$, (2) where h is the anharmonic term. It is shown that for Al₂O₃ and UO₂, where experimental data for the liquid phase are also available, $\text{d}\text{h}$ has the same value, Indicating that both materials behave identically. If we compare the thermodynamic relationship $\text{C}{}_{\mathrm{p}}\text{? C}{}_{\mathrm{v}}\text{= Vα}{}^2\text{KT}$, (3) where V is the volume, $\text{α}$ the volume expansion coefficient, and $\text{K}$ the bulk modulus, with equation (1), It follows that d must be equal to $\text{Vα}{}^2\text{K}\text{T}{}^2$; the value of $\text{Vα}{}^2\text{K}\text{T}{}^2$ is calculated in the temperature region where d was obtained; within experimental error they are equal.     

Molecular dynamics simulations of C2, C2H, C2H2, C2H3, C2H4, C2H5, and C2H6 bombardment of diamond (1 1 1) surfaces

The sticking and erosion of C₂H_x molecules (where x=0-6), at 300 and 2100 K onto hydrogenated diamond (1 1 1) surfaces was investigated by means of molecular dynamics simulations. We employed both quantum-mechanical and empirical force models. Generally, the sticking probability is observed to somewhat increase when the radical temperature increases and strongly decrease with increasing number of H atoms in the molecule.     

One-Dimensional Fluid Model of Pulse Modulated Radio-Frequency SiH4 /N2 /O2 Discharge

Driven by pulse modulated radio-frequency source,the behavior of SiH 4 /N 2 /O 2 plasma in capacitively coupled discharge are studied by using a one-dimensional fluid model.Totally,48 different species(electrons,ions,neutrals,radicals and excited species) are involved in this simulation.Time evolution of the particle densities and electron temperature with different duty cycles are obtained,as well as the electronegativity n SiH3 /n e of the main negative ion(SiH3).The results show that,by reducing the duty cycle,higher electron temperature and particle density can be achieved for the same average dissipated power,and the ion energy can also be effectively reduced,which will offer evident improvement in plasma deposition processes compared with the case of continuous wave discharge.