The rates of thermal decomposition of LiOH(s), LiOD(s) and LiOT(s)

Kinetic studies on the thermal decomposition reactions, 2LiOH(s) → Li₂O(s) + H₂O(g), 2LiOD(s) → Li₂O(s) + D₂O(g), and LiOH(s) + LiOT(s) → Li₂O(s) + HTO(g), have been carried out with mass spectrometric and radiometric methods over the temperature range 530–690 K. Those reaction rates were found to be of first order in the quantity of released water. The rate-constants, k, in s^?1, were: k_H2O = 1.8 × 10⁸ exp(29 500/RT), k_D2O = 1.7 × 10⁸ exp(29 000/RT), and k_HTO = 1.6 × 10⁷ exp(30 700/RT), respectively. The apparent activation energy obtained for the thermal decomposition of LiOH(s), E_a = 29.5 ± 1.1 kcal/mol, coincided with a literature value of the enthalpy of reaction, ΔH°₆₀₀^° = 29.8 ± 1.0 kcal/mol.     

Thermal conductivity and thermal expansion of hot-pressed trisodium uranate (Na3UO4)

Thermal conductivity and thermal expansion of Na₃UO₄ prepared by two different reaction processes were determined over a temperature range of 20–1000°C. Compositional differences in the samples resulting from the different reaction processes have a pronounced effect on thermal expansion and on thermal conductivity below 500°C. Above 500°C, these compositional differences in the thermal conductivities decrease.     

Immobilization of Cs and Sr to HZr2(PO4)3 using an autoclave

The proton-type crystalline zirconium phosphate, HZr₂(PO₄)₃, was prepared by a thermal decomposition of NH₄Zr₂(PO₄)₃ at about 450 °C, where NH₄Zr₂(PO₄)₃ was obtained in advance by a hydrothermal synthesis using a mixed solution of ZrOCl₂, H₃PO₄ and H₂C₂O₄. Cs or Sr ion was immobilized to HZr₂(PO₄)₃ by mixing HZr₂(PO₄)₃ with an aqueous solution of CsNO₃ or Sr(NO₃)₂ under the molar ratio CsNO₃/HZr₂(PO₄)₃ = 1.0 or Sr(NO₃)₂/HZr₂(PO₄)₃ = 0.5. The mixtures were treated thermally in an autoclave at different temperatures from 200 to 275 °C and Arrhenius equation was applied to the Cs and Sr immobilization process to HZr₂(PO₄)₃. The activation energy for the immobilization process of Cs or Sr was estimated as 179 kJ mol^?1 and 186 kJ mol^?1, respectively.     

Effect of yttria substitution on the light output of (Gd,Y)2O3:Eu ceramic scintillator

For the application of the computed tomography (CT) scanner, Gd_1.94−xY_xEu_0.06O₃ ceramic scintillator was prepared. We investigated the effect of the relative contents of Y₂O₃ for Gd₂O₃ matrix on the light output properties by the measurements of the emitted light spectra, relative light output, and X-ray diffraction (XRD) patterns. From the measurement results, it was found that maintaining the crystalline structure as cubic phase after sintering process is important to achieve high light output properties on (Gd,Y)₂O₃ ceramic scintillators, and the scintillation conversion process is more dominant for high light output of cubic phase than the optical transparency.     

Modification of thermal hydraulic code,THEATRe, with fuel rod behavior models and its application to reactivity-initiated accident (RIA)

During reactor operation, many complex changes occur in fuel rod which affects its thermal, mechanical and material properties. These changes also affect the reactor response to the transient and accident situations. Realistic simulation of fuel rod behavior under transients such as reactivity-initiated accident (RIA) is of great significance. In this study, thermal hydraulic analysis code THEATRe (Thermal Hydraulic Engineering Analysis Tool in Real-time) has been modified by addition of fuel rod behavior models for dynamic simulation of nuclear reactor. Transient changes in gas-gap parameters were taken into account by modeling the gas-gap behavior. Thermo-mechanical behavior of fuel rod is modeled to take into account the thermal, elastic and plastic deformation. To simulate RIA, point reactor kinetics model is also incorporated in the THEATRe code. To demonstrate the transient fuel rod behavior, AP1000 reactor is modeled and three hypothetical RIA cases are simulated. The RIA is considered at three different reactor power levels, i.e. 100, 50 and 1% of nominal power. The investigated parameters are fuel temperature, cladding stress and strain, fuel and cladding thermal conductivity and heat transfer coefficient in gas-gap. Modified code calculates the fuel rod temperatures according to updated fuel, clad and gas-gap parameters at the onset of steady-state operation and during the transient. The modified code provides lower steady-state fuel temperature as compared to the original code. Stress and strain analyses indicate that the hoop and radial strain is higher at high power locations of the fuel rod; therefore, gap closure process will initially occur in the central portion of the fuel rod and it should be given more emphasis in the safety analysis of the fuel rod and nuclear reactor during accidents and transients.     

Measurement of 186W(4He,p3n)186Re, 186W(4He,pn)188Re, 186W(4He,p)189Re Reaction Cross Sections By 4He Irradiation of 186W TARGET

Atomic Energy - The cross sections of the reactions 186W(4He, p3n)186Re, 186W(4He, pn)188Re, and 186W(4He, p)189Re were measured by the activation method in the energy range of 4He nuclei...     

Measurement of the cross sections for the reactions Cr(n,2n)Cr, Zn(n,2n)Zn, Y(n,2n)Y and Zr(n,2n)Zr from 13.5 to 14.8 MeV

Cross section measurements for the reactions ⁵²Cr(n,2n)⁵¹Cr, ⁶⁶Zn(n,2n)⁶⁵Zn, ⁸⁹Y(n,2n)⁸⁸Y and ⁹⁶Zr(n,2n)⁹⁵Zr were carried out in the neutron energy range 13.47–14.79 MeV applying the activation technique. Neutrons were produced via the T(d,n)⁴He reaction, making use of the variation of neutron energy with the emission angle. The neutron fluences incident on the samples were determined relative to the well-evaluated cross section for the reaction ⁹³Nb(n,2n)^92mNb.

The induced γ-ray activities of the irradiated Zn, Zr and Y₂O₃ samples and their monitor foils were measured by means of a calibrated Ge(Li) γ-ray detector at the KFI, Debrecen. At the IRK, Vienna, relative γ-ray measurements using a high-purity Ge detector were combined with integral γ-ray counting by means of a NaI(TI) well-type detector on the Cr, Zn and Zr foils of highest activity and on some Nb monitor foils; integral γ-ray counting only was applied in the case of the Y₂O₃ samples. All necessary corrections were taken into account.

The results are compared to the corresponding results of cross section measurements published in the literature. The uncertainties obtained in this work are considerably smaller in most cases than the uncertainties given by other authors.     

FT3 FT4 放射免疫分析（直接法）方法学研究

自行研制了~(125)I标记的T_3X、T_4X(酰胺类衍生物)。免疫所得抗T_3抗体滴度1:160000,K=1.13×10~(11)l/mol;抗T_4抗体滴度1:6000,K=7.6×10~(10)l/mol。以PR试剂为分离剂,建立一步直接放免测定法。灵敏度FT_3为0.24 pmol/l;FT_4为0.16pmol/l。方法精确、特异、稳定。临床应用结果与英国Amersham Amerlex—M法相关极好。     

Fuel-to-cladding gap evolution and its impact on thermal performance of high burnup fast reactor type uranium-plutonium oxide fuel pins

Drastic evolution of fuel-to-cladding gap is observed in high burnup JOYO Mk-II driver and MONJU type uranium-plutonium oxide fuel pins. The effect of the evolution is examined from viewpoints of fuel restructuring, gaseous FP release and retention and cesium migration behaviors. Its thermal impact on fuel pin performance is also studied by one-dimensional steady state thermal analysis. Threshold condition of the evolution depends on fuel pellet characteristics, burnup and probably temperature. The evolution directly relates to as-fabricated microstructures and to gaseous FP release and retention behavior. A comparison of fuel restructuring with predicted temperature profiles indicates that, even where large residual gaps are observed, non-gaseous filler always improves the heat transfer across the gaps.     

Selected engineering and fabrication aspects of nuclear metal hydrides (Li, Ti, Zr, and Y)

Metal hydrides are useful hydrogen reservoirs. Lithium, titanium, zirconium and yttrium hydride systems are discussed, with attention to factors which affect both methods of fabrication and selection for nuclear and non-nuclear applications. The use of recently declassified boride and carbide additives and selective thermal arrest hydriding cycles are referenced. Collectively, these processes have simplified the manufacture of crack-free massive hydrides of a variety of hydridable metals and have improved the mechanical properties of the as-fabricated and the thermally aged hydrides.     

Preparation and characterisation of Tl2Pu(MoO4)3 and Tl4Pu(MoO4)4 in Tl-Pu-Mo-O system by X-ray and thermal methods

The quaternary Tl-Pu-Mo-O system was investigated for the first time and two new quaternary compounds Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ were synthesized by solid state reactions of Tl₂MoO₄ with Pu(MoO₄)₂ in 1:1 and 2:1 molar proportions at 773 K and 823 K, respectively. X-ray powder diffraction data of these compounds were indexed on orthorhombic system. Thermogravimetric (TG) curves of Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ were recorded in air and no significant weight changes were observed up to 973 K and 1033 K, respectively. Differential thermal analysis (DTA) curves of Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ showed endothermic peaks due to the melting of the compounds at 838 K and 1013 K, respectively. Non-isothermal kinetics of decomposition of Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ in air was studied using thermogravimetric technique. Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ when heated up to 1673 K decomposed to Tl₂O and MoO₃ in the gaseous form, giving solid PuO₂ as an end product. The reactions followed unimolecular nucleation and growth mechanism with activation energies of 106 kJ/mol and 157 kJ/mol, respectively.     

Differential cross section calculations of positron and electron impact ionization of Ar (3p)

We report the distorted wave Born approximation results of triple differential cross section of Ar (3p) by positron and electron impact. We compare the results of our calculations with the recent available experimental and theoretical results. We also provide a comparison of our positron impact ionization results with the electron impact ionization results to understand the effect of projectile charge on the projectile-target interaction.     

氘团簇离子(d3+)固体与相互作用过程中的团簇行为研究

讨论了由三个氘原子组成的氘团簇离子(d     

LiF(Mg,Ti)、CaSO_4(Tm)低能X、γ响应的研究

本文给出了国产商品LiF(Mg,Ti)、玻璃管CaSO_4(Tm)热释光剂量计在5.8—58.5keV范围内的X射线能量响应曲线,并探讨了玻璃管CaSO_4(Tm)的低能补偿,较好的补偿是0.1mm厚铜和0.3mm厚锡复合打10％面积的孔,孔径为0.7mm。补偿后在12.2—58.5keV范围内相对~(137)Cs γ射线的能响是1.00±0.48。     

氢对12Cr-ODS钢中强化相(Y_2O_3)辐照稳定性影响研究

通过离子束-电子束(H++e-)双束同时辐照,原位观察氧化物在辐照过程中的组织损伤变化,研究了(H++e-)双束辐照对乙二胺四乙酸(EDTA)络合溶胶-凝胶法制备的12Cr-ODS铁素体钢中氧化物(Y2O3)稳定性的影响。实验结果表明:电子辐照剂量达15 dpa后,再进行(H++e-)双束辐照15 dpa,在此条件下,Y2O3氧化物会发生尺寸减小或溶解,辐照诱发点缺陷和合金元素界面化学反应是导致氧化物不稳定性的重要原因。     

(n,2n)和(n,3n)激发函数的计算

本文从入射中子能量为E=14MeV的σ_(n,2n)实验值出发,应用复合核模型,计算了十三种无分支比复合核衰变的非裂变重核(A>169)的(n,2n)、(n,3n)激发函数。与实验激发曲线比较,讨论了计算的合理性和可靠性。     

FOXM1在食管鳞癌中的表达及对其放射敏感性的影响

采用Real-time PCR检测40例食管鳞状细胞癌及相对应癌旁组织中FOXM1(Forkhead box M1)m RNA表达情况;免疫组织化学方法检测94例食管鳞状细胞癌组织中FOXM1蛋白的表达情况,分析其与鳞状细胞癌临床病理之间的关系;采用针对FOXM1的si RNA沉默ECA-109、TE-1细胞中FOXM1基因表达水平,通过免疫荧光染色、克隆形成实验检测FOXM1对食管鳞状细胞癌放射敏感性的影响。结果表明,FOXM1m RNA表达水平在食管癌组织中显著高于癌旁组织(p0.01),其蛋白表达水平与病人生存期负相关。si RNA能有效干扰ECA-109细胞中的FOXM1表达水平,FOXM1沉默细胞中X-射线诱发的γH2AX焦点显著多于对照细胞,FOXM1沉默细胞电离辐射后克隆形成能力显著低于对照细胞。结果提示,FOXM1在食管鳞癌中的表达增加,其表达水平与病人预后负相关;FOXM1基因沉默可显著增强细胞放射敏感性,因此,FOXM1有可能成为食管鳞癌的治疗靶点。     

用Klein-Elsler法测量~3H、~(125)I双标记样品的条件选择

~3H和~(125)I是目前在生物学和医学中使用相当广泛的核素。用液体闪烁测量法测~(125)I近来也有很大发展。由于~(125)I标记化合物在一般实验室中都可制备,并且碘标记化合物可以达到较高的比放射性。故使用~3H、~(125)I双标记样品具有操作简便、费用低廉的优点。 我们采用Klein-Elsler法,利用计算Klein-Elsler值,以该值最大的一组测量道为分离效率最佳的双标记测量道。然后根据双标记样品在每一道的计数和每一种核素在两道的计数比值来求出两种核素各自的放射性大小。