Measurement of CO2 Laser Pulse Narrowing in CF2HCl

The oxidation of Np(V) by nitrous acid was investigated spectroscopically in 0.2 M CMPO—1.4 M TBP—n-dodecane and the oxidation rate constant of Np(V) was estimated assuming the first-order reaction. By using the obtained oxidation rate constant as well as taking account of the Np(V) oxidation in aqueous phase and the distribution ratios of Np(V) and Np(VI) cited from literature, extraction kinetics of Np from 4 M nitric acid solution was calculated, and was compared with the extraction kinetics measured experimentally.     

HEHEHP从硫酸介质中萃取Y^3＋的动力学研究

利用水相酸度可控的恒定界面池，研究了在２９８±０．５Ｋ下２－乙基己基膦酸单酯－加氢煤油－Ｎａ２ＳＯ４ 体系萃取钇的动力学，以及在动力学坪区，Ｙ＾３＋离子浓度、萃取剂浓度、酸度及水相ＳＯ＾２－４和Ｃｌ＾－离子浓度对萃取反应速度的影响，并探讨了可能的萃机理。     

静电场激励液-液体系相间铜反萃传质特性

在改进的传质池中通过在线检测草酸浓度,应用瞬时传质系数与平均传质系数,研究了各种方向及组合、不同电压、电极板形状与面积等条件下静电场对体系Cu²⁺-HDEHP-CCl₄/H₂O-H₂C₂O₄伴随生成CuC₂O₄的传质过程特性。外场电压变化、电极面积可改变相间的传质速率,与传质方向成45°夹角的静电场作用对相界面传质速率的影响更为显著,表明相间传质阻力结构或相间传质层具有各向异性。     

Removal of Ruthenium from PUREX Process

Ruthenium in nitric acid solution is oxidized by the addition of eerie nitrate to ruthenium tetroxide, which is extracted with n-paraffin oil.

Ruthenium tetroxide in paraffin is immediately reduced by the solvent to black ruthenium dioxide as suspension, which can be readily filtered off through the ordinary cellulose filter paper.

Through the combined process of extraction and filtration, the ruthenium in a nitric acid solution can be eliminated.     

TODGA/正十二烷萃取Am(Ⅲ)的动力学

以N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)为萃取剂,正十二烷为稀释剂,研究了该萃取体系在恒界面池中萃取Am(Ⅲ)的动力学,考察了搅拌转速、两相界面面积、萃取剂浓度、金属离子浓度、酸度和温度等因素对Am(Ⅲ)萃取行为的影响,并推导了相应的萃取机理。结果表明：(1) 搅拌转速在130 r/min以下时,0.1 mol/L TODGA/正十二烷萃取Am(Ⅲ)的过程为扩散控制类型,在搅拌转速为150 r/min以上时,则属于化学反应控制的动力学控制模式;(2) 求得了在(170±2) r/min、温度为(25±0.1) ℃时0.1 mol/L TODGA/正十二烷萃取Am(Ⅲ)的初始速率方程：
r₀=(dc_org(M)/dt)_t=0=k•(S/V)c^0.94_aq,0(Am)c^1.05_aq,0(HNO₃)c^1.19_org,0(TODGA)
在25℃下,求得表观速率常数k=(24.2±3.4)×10^-3mol^-2.18•L^2.18•min^-1•cm;(3) 0.1mol/L TODGA/正十二烷萃取Am(Ⅲ)的初始速率随着温度的升高而增大,求得表观活化能E_a=(25.94±0.98)kJ/mol。     

A study of the unsteady flow and heat transfer in the reflooding of water reactor cores

In the event of a loss-of-coolant accident in a water-cooled reactor, the primary consideration is terminating the clad temperature excursion caused by release of the stored and decay heat in the fuel. This requires that emergency coolant injection systems reflood the reactor core.For certain break positions, the pressure loss incurred by venting steam partially offsets the hydrostatic head available to drive flow through the core. Flow oscillations can also be set up due to the fluid inertia and vapour compressibility.The present paper reports the results of an extensive series of experiments performed on unstable reflooding, covering wall temperatures up to 1000°C and reflooding rates typical of reactor values. Measurements are reported of quenching rates, oscillation frequencies and pre-quench heat transfer.It is shown, except for a short initial period of violent oscillations, that the rewetting rate and pre-quench heat transfer, for a given mass flow rate, are relatively unaffected by the presence of oscillations. The average pre-quench heat transfer coefficient is shown to vary as (water mass flow rate)ⁿ where n = 0.5–0.7, consistent with available world data.Theory and experiments also show that there is a critical value of outlet loss coefficient, for a given power level, where no further advance of the quench front can occur, the back pressure completely offsetting the available driving head for core reflooding. This value is much greater than the outlet loss coefficient for typical reactor designs, thus ensuring core reflooding. The critical loss coefficient is suggested as the relevant parameter for scaling purposes.A new theoretical model for the oscillations is derived which is shown to predict the oscillation frequencies of all available data. It is also shown that the frequency and damping are only weakly dependent on: upper plenum flow area, size of vapour space, effective inertia of water oscillating and pressure, and are independent of the outlet loss coefficient.     

U(Ⅵ)电还原反萃动力学研究——Ⅱ.U(Ⅵ)反萃和U(Ⅳ)萃取动力学

本文在带有阴阳极的恒界面池中研究了HNO_3-N_2H_5NO_3(H_2O)/UO_2(NO_3)_2-HNO_3(30％TBP-煤油)体系在U(Ⅵ)电解还原过程中的U(Ⅵ)反萃和U(Ⅳ)萃取动力学。这是U(Ⅵ)电还原反萃动力学研究的第二步。根据实验结果和数据处理,得到U(Ⅵ)反萃和U(Ⅳ)萃取过程的表观活化能分别为36.02kJ/mol和21.13kJ/mol;U(Ⅵ)反萃和U(Ⅳ)萃取速率随两相搅拌速率的增大而增大;U(Ⅵ)反萃和U(Ⅳ)萃取过程均由扩散控制。随着阴极电位的降低,U(Ⅵ)反萃和U(Ⅳ)萃取速率均增大。     

Influence of fission products on ruthenium oxidation and transport in air ingress nuclear accidents

In separate effect tests at 1000–1200 °C Ru oxidation rate and content of Ru in escaping air flow have been studied with special emphasis on effects of other fission product elements on the Ru oxidation and transport. The results showed that in the decreasing temperature section (1100–600 °C) most of the RuO₃ and RuO₄ (≈95%) decomposed and formed RuO₂ crystals; while the partial pressure of RuO₄ in the escaping air was in the range of 10^?6 bar. The re-evaporation of deposited RuO₂ resulted in about 10^?6 bar partial pressure in the outlet gas as well. Measurements demonstrated the importance of surface quality in the decreasing temperature area on the heterogeneous phase decomposition of ruthenium oxides to RuO₂. On the other hand water or molybdenum oxide vapour in air appears to decrease the surface catalyzed decomposition of RuO_x to RuO₂ and increases RuO₄ concentration in the escaping air. High temperature reaction with caesium changed the form of the released ruthenium and caused a time delay in appearance of maximum concentration of ruthenium oxides in the ambient temperature escaping gas, while reaction with barium and rare earth oxides extended Ru escape from the high temperature area.     

The systematics of (n,2n) reaction excitation function

Based on the constant temperature evaporation model taking the competition of (n,3n) reaction and the contribution of preequilibrium emission into account, the systematics formulae of (n,2n) reaction excitation function have been established. The systematics behaviours of (n,2n) reaction excitation function have been studied. There are two systematics parameters T and σ_n,M, and can be adjusted in the formulae. For getting the two parameters, the new evaluated data of (n,2n) reactions were adopted and fitted by means of the nonlinear least squares method. The fitted results agree fairly well with the measured data at below 30 MeV. Based on a body of new measurements, the reliability to predict (n,2n) reaction excitation function is improved. Hence more accurate systematics prediction for unmeasured nucleus or energy range may be provided.     

Simulation of two-phase flows in vertical tubes with the CTFD code FLUBOX

The computational two-fluid dynamics (CTFD) code FLUBOX is developed at GRS for the multidimensional simulation of two-phase flows. The single-pressure two-fluid model is used as basis of the simulation. A basic mathematical property of the two-fluid model of FLUBOX is the hyperbolic character of the advection. The numerical solution methods of FLUBOX make explicit use of the hyperbolic structure of the coefficient matrices. The simulation of two-phase flow phenomena needs, apart from the conservation equations for each phase, an additional transport equation for the interfacial area concentration. The concentration of the interfacial area is one of the key parameters for the modeling of interfacial friction forces and interfacial transfer terms. A new transport equation for the interfacial area concentration is in development. It describes the dynamic change of the interfacial area concentration due to mass exchange and a force balance at the phase boundary. Results from FLUBOX calculations for different experiments of two-phase flows in vertical tubes are presented as part of the validation.     

三烷基氧膦对硝酸介质中钌的萃取行为

研究了三烷基氧膦(TRPO)对硝酸介质中钌的萃取行为。使用TRPO为萃取剂,煤油(OK)为稀释剂,重点考察了萃取平衡时间、水相硝酸浓度、温度、萃取剂浓度、亚硝酸盐浓度等因素对钌的萃取影响,并进行了钌的三级错流萃取实验。另外,还研究了硝酸浓度、温度等因素对钌的反萃过程影响。结果表明,由于钌在水相和有机相中存在着多个种态的平衡和转化过程,热力学和动力学作用相互影响,使得TRPO对钌的萃取行为以及有机相中钌的反萃行为均十分复杂。为进一步了解TRPO对高放废液中钌的萃取行为,进行了TRPO/煤油对不同酸度、浓缩倍数的模拟高放废液中钌的萃取和反萃实验,相关结果为进一步优化TRPO流程工艺提供了重要参考。     

Measurement of interfacial area concentration in subcooled liquid-vapour flow

In two-fluid modelling, accurate prediction of the interfacial transport of mass, momentum and energy is required. Experiments were carried out to obtain a database for the development of interfacial transport models, or correlations, for subcooled water-steam flow in vertical conduits. The experimental data of interest included the interfacial area concentration, interfacial condensation heat transfer and bubble relative velocity. This paper focuses on the interfacial area concentration. The interfacial area concentration was obtained by measuring the distributions of bubble volume and surface area as well as the area-averaged void fraction at various axial locations in subcooled water-steam condensing vertical upward flow under low flow rate and low pressure conditions. The bubble size and surface area were determined using high-speed photography and digital image processing techniques. The area-averaged void fraction was measured by a single-beam gamma densitometer. The results were compared with existing correlations, which were developed on the basis of data obtained for air-water adiabatic flows. Poor agreement between the present data and the existing correlations was obtained. Accordingly, new correlations suitable for subcooled liquid-vapour bubbly flow are proposed.     

Growth of the interaction layer around fuel particles in dispersion fuel

Corrosion of uranium particles in dispersion fuel by the aluminum matrix produces interaction layers (an intermetallic-compound corrosion product) around the shrinking fuel spheres. The rate of this process was modeled as series resistances due to Al diffusion through the interaction layer and reaction of aluminum with uranium in the fuel particle to produce UAl_x. The overall kinetics are governed by the relative rates of these two steps, the slowest of which is reaction at the interface between Al in the interaction layer and U in the fuel particle. The substantial volume change as uranium is transferred from the fuel to the interaction layer was accounted for. The model was compared to literature data on in-reactor growth of the interaction layer and the Al/U gradient in this layer, the latter measured in ex-reactor experiments. The rate constant of the Al-U interface reaction and the diffusivity of Al in the interaction layer were obtained from this fitting procedure. The second feature of the corrosion process is the transfer of fission products from the fuel particle to the interaction layer due to the reaction. It is commonly assumed that the observed swelling of irradiated fuel elements of this type is due to release of fission gas in the interaction layer to form large bubbles. This hypothesis was tested by using the model to compute the quantity of fission gas available from this source and comparing the pressure of the resulting gas with the observed swelling of fuel plates. It was determined that the gas pressure so generated is too small to account for the observed delamination of the fuel.     

Counter-Current Computation on Trinitrato Complex of Nitrosylruthenium in the Primary Separation Plant of Reactor Fuel Processing, (III)

A mathematical treatment to the optimum flow ratio for the counter-current extraction of penta and tetra complexes of nitrosylruthenium in the primary separation plant of reactor fuel processing has been developed from the previous publication^(1×2).

The optimum flow ratio is a rather simple function of ratio of reaction rate constants and molar ratio of trinitrato complex to penta and tetra complexes.

Another, and much higher, volume flow ratio for the maximum decontamination factor of penta and tetra complexes has also been numerically introduced for justification of the optimum flow ratio.

The significant effect of lower nitric acidities in aqueous phase on the ruthenium decontamination has been discussed.

Calculated results from the obtained equation for the optimum flow ratio have been compared with the values used in practice in the ruthenium decontamination process, and have shown remarkable agreement.     

The lamb shift in hydrogen-like atoms, 1 ⩽ Z ⩽ 110

Theoretical energy levels and energy-level separations for n = 1 and n = 2 states of hydrogen-like atoms with nuclear charge numbers in the range 1 ? Z ? 110 are tabulated. Quantum electrodynamical corrections of first and second order in the fine-structure constant α are included, together with finite nuclear size corrections, reduced mass corrections, and recoil corrections.     

The engineering sizing of the packed desorption column of hydrogen isotopes from Pb–17Li eutectic alloy. A rate based model using experimental mass transfer coefficients from a Melodie loop

The model of the desorption of hydrogen isotopes from lead lithium alloy in a packed column is derived from the first principles using the plug flow in the liquid phase either the plug flow or ideal mixing in the gas phases. Sievert's law of non-linear equilibrium is followed. The volumetric mass transfer coefficient k_La and its dependence on the liquid metal flow rate are evaluated on the basis of the Melodie loop experiments.The presented model is used for evaluation of the minimum flow rate of the purge gas for which the concentration of the isotope in the gas leaving the column is at its highest, while the driving force of the interfacial transport of the isotope is still not reduced and the tritium desorption efficiency is therefore retained. The potential effect of the axial dispersion in the gas and liquid phase is evaluated. Highlighted are the issues of the optimum packing geometric surface area, above which the efficiency starts to decrease, and of the role of the surface tension and the contact angle with regard to the wettability of the packing. On the basis of the findings related to these factors, the Mellapak 500 Y and Mellapak packings with flat surfaces are recommended for the tests aiming to intensify the tritium desorption efficiency in the packed columns. The models were used for the engineering sizing of the packed columns in two breeding blanket concepts for the DEMO plant – utilizing DCLL (dual coolant lead lithium) and HCLL (helium cooled lithium lead).     

Ion mass effects on bombardment-induced disordering of γ'-Ni3Si

The kinetics of disordering of the ordered compound γ'-Ni₃Si during ion bombardment were investigated at a temperature of 270°C. The disordering followed first order kinetics and the rate constant was measured as a function of incident ion flux, ion energy, and ion mass. The rate constant varied approximately in direct proportion with the ion flux during bombardment with 1 MeV ⁸⁴Kr⁺-ions: from ~ 0.28 min ^?1 at ~ 70 nA/cm² to ~ 50 min ^?1 at ~ 4.4 μA/cm ². During bombardment with a flux of $\text{~ 1 μA}\text{cm}{}^2$ of ¹³²Xe⁺-ions, the rate constant was directly proportional to the calculated near-surface damage ra te. It varied from ~ 50 min ^?1 for 200 KeV ions with calculated damage rates of ~ 2.3 × 10^?1 dpa to ~ 1.8 min ^?1 for 3 MeV ions with damage rates of 2 × 10^?3dpa/s. The disordering rate was also observed to be directly proportional to the near surface damage rate for heavier mass ions (⁴⁰Ar⁺, ⁸⁴Kr⁺ and ¹³²Xe⁺); the ratio of disordering rate to damage rate was ~ 17. This ratio dropped to ~ 3 for ²⁰Ne⁺-ion bombardment, and to ~ 0.4 for bombardment with ⁴He⁺-ions. The decrease in the ratio with decreasing mass is discussed in terms of cascade size, replacement-to-displacement ratio, and random recombination.     

Crack growth properties of nuclear graphite under cyclic loading conditions

Crack growth properties of four kinds of nuclear graphites under cyclic loading conditions were investigated at room temperature, 373, 673 and 975 K, using double cantilever beam (DCB) specimens. The crack growth rates can be expressed as a function of the stress intensity factor range at the constant mean stress intensity factor (K_mean) and the constant minimum stress intensity factor (K_min): that is, da/dN = CΔK₁ⁿ, where the constants C and n depend upon the kind of graphite and its coke grain size. The crack growth rate at the constant K_mean becomes smaller than that at the constant K_min. For the fine-grained graphite tested at higher temperatures, the crack growth rate increases with increasing temperature. Also cracks in the coarse grained coke graphites extend at a higher rate than that in the fine-grained high strength graphites. It seems that cracks in graphites run mostly along the coke grain boundaries.     

Turbulence modeling for mass transfer enhancement by separation and reattachment with two-equation eddy-viscosity models

The prediction of mass transfer rate is one of the key elements for estimation of the flow accelerated corrosion (FAC) rate. Three low Reynolds number (LRN) k-? models (Lam-Bremhorst (LB), Abe-Kondoh-Nagano (AKN) and Hwang-Lin (HL)), one LRN k-ω (Wilcox, WX) model and the k-ω SST model are tested for the computation of the high Schmidt number mass transfer, especially in the flow through an orifice. The models are tested in the computation of three types of flow: (1) the fully developed pipe flow, (2) the flow over a backward facing step, (3) the flow through an orifice. The HL model shows a good performance in predicting mass transfer in the fully developed pipe flow but fails to give reliable prediction in the flow through an orifice. The WX model and the k-ω SST model underpredict the mass transfer rate in the flow types 1 and 3. The LB model underestimates the mass transfer in the flow type 1, but shows abnormal behavior at the reattaching point in type 3. Synthetically evaluating all the models in all the computed case, the AKN model is the best one; however, the prediction is still not satisfactory. In the evaluation in the flow over a backward facing step shows k-ω SST model shows superior performance. This is interpreted as an implication that the combination of the k-? model and the stress limiter can improve the model behavior in the recirculation bubble. Both the stress limiter similar to that utilized in WX and SST model and Kato-Launder modification are implemented in the AKN model and help to lower the peak of mass transfer coefficient, while raising the values in the downstream. The value of turbulent Schmidt number is also investigated in this paper. If a uniform value is used, Sc_t ≈ 1.0 can be reasonable in the case of high Schmidt mass transfer. Sct=1.71(y⁺)^−0.38 can be used to predict the high Schmidt mass transfer in the simple flows.