关于压水堆产武器级钚的模拟计算

防止核扩散是国际社会共同努力的目标,其中武器级核材料的防扩散是重中之重.钚是反应堆的副产品,如果不计较经济效益,利用铀为核燃料的反应堆都可以生产武器级钚.本文基于日本Takahama-3压水堆建立了五个模型,并进行中子和燃耗计算,得到两种燃料棒产武器级钚的条件、燃料棒轴向的燃耗分布、组件内燃料棒燃耗的变化区间和全堆芯燃料棒径向燃耗分布.基于上述模型和计算数据给出压水堆堆芯内含有武器级钚的准确位置和UO_2燃料棒中武器级钚的产量.这种低燃耗的乏燃料给国际核不扩散带来了巨大风险,国际社会应该加强对此类乏燃料的监管.     

Natural Transmutation of Actinides via the Fission Reaction in the Closed Thorium–Uranium–Plutonium Fuel Cycle

It is shown for a closed thorium–uranium–plutonium fuel cycle that, upon processing of one metric ton of irradiated fuel after each four-year campaign, the radioactive wastes contain ~54 kg of fission products, ~0.8 kg of thorium, ~0.10 kg of uranium isotopes, ~0.005 kg of plutonium isotopes, ~0.002 kg of neptunium, and “trace” amounts of americium and curium isotopes. This qualitatively simplifies the handling of high-level wastes in nuclear power engineering.     

5×5棒束CFD模拟计算域和网格标准

采用不可压N-S方程、标准k-ε湍流模型、SIMPLE算法,对某压水堆的两跨距5×5燃料组件的水循环区域流动进行数值分析.对比流道横截面上的压降、速度及其横向分量的相对误差,得到计算域的进出口段长度、网格形式、网格尺寸的选取标准.结果显示：计算域的进口段、出口段长度不宜过短或过长,分别为2.0倍、2.3~2.8倍格架中心距长度;格架区宜采用非结构蜂窝网格,光棒区宜采用结构网格;格架区网格尺寸可取0.3 mm,最大不宜超过0.35 mm,而结构网格横向尺寸可取0.3 mm~0.5 mm,纵向稀疏比应小于1.5为宜.满足上述标准,数值分析能保证较高的可信度,同时保持可接受的计算量.     

Sonocatalytic recovery of ceria from graphite and inhibition of graphite erosion by ionic liquid based platinum nanocatalyst

Use of ultrasound as an intensified non-destructive decontamination technique for processing graphite limits its reusability beyond a few number of decontamination cycles due to the exfoliation of graphite due to cavitation effects. The current work establishes that the use of platinum nanoparticles in the leachant reduces the erosion of graphite substrate due to cavitation. It presents an improved way of sonochemical recovery of ceria using a mixture of nitric acid, formic acid and hydrazinium nitrate in the presence of platinum nanoparticles and ionic liquid. The platinum nanoparticles catalyst in ionic liquid prevented the generation of the carbon residue due to the combined effect of denitration and reduced sonication. The presence of the catalyst showed a fivefold increase in dissolution kinetics of ceria as well as absence of graphite erosion, facilitating better chances of graphite recycling than the decontamination without the catalyst. The catalytic approach offers a better recycle strategy for graphite with reduced exfoliation and NOx generation due to denitration, making it a more sustainable decontamination process. Since ceria is used as a surrogate for plutonium oxide, the results can be extended to decontaminate such deposits clearly establishing the utility of the presented results in the nuclear industry.     

基于广义等价理论的高保真共振计算方法

采用伪核素方法,建立了能够精确快速处理干涉效应的计算方法,在分析广义等价理论特点的基础上,提出了高保真的共振计算方法。该方法首先根据实际问题的几何,建立238U的非均匀共振积分表,基于此核素采用广义等价理论处理栅元间的互屏效应,获得不同位置燃料棒的背景截面,然后根据背景截面在非均匀截面表中插值建立不同燃料棒的等效栅元,在此栅元的基础上根据实际问题中燃料棒内的温度分布和核素分布进行超细群计算,从而获得燃料棒内不同位置共振核素高保真的有效共振截面。     

Preliminary results of calculations for heavy-water nuclear-power-plant reactors employing <Superscript>235</Superscript>U, <Superscript>233</Superscript>U,and <Superscript>232</Superscript>Th as a fuel and meeting requirements of a nonproliferation of nuclear weapons

A physical design is developed for a gas-cooled heavy-water nuclear reactor intended for a project of a nuclear power plant. As a fuel, the reactor would employ thorium with a small admixture of enriched uranium that contains not more than 20% of ²³⁵U. It operates in the open-cycle mode involving ²³³U production from thorium and its subsequent burnup. The reactor meets the conditions of a nonproliferation of nuclear weapons: the content of fissionable isotopes in uranium at all stages of the process, including the final one, is below the threshold for constructing an atomic bomb, the amount of product plutonium being extremely small.     

Variants of Regenerated Fissile Materials Usage in Thermal Reactors as the First Stage of Fuel Cycle Closing

At present, 240 000 t of spent nuclear fuel (SF) has been accumulated in the world. Its long-term storage should meet safety conditions and requires noticeable finances, which grow every year. Obviously, this situation cannot exist for a long time; in the end, it will require a final decision. At present, several variants of solution of the problem of SF management are considered. Since most of the operating reactors and those under construction are thermal reactors, it is reasonable to assume that the structure of the nuclear power industry in the near and medium-term future will be unchanged, and it will be necessary to utilize plutonium in thermal reactors. In this study, different strategies of SF management are compared: open fuel cycle with long-term SF storage, closed fuel cycle with MOX fuel usage in thermal reactors and subsequent long-term storage of SF from MOX fuel, and closed fuel cycle in thermal reactors with heterogeneous fuel arrangement. The concept of heterogeneous fuel arrangement is considered in detail. While in the case of traditional fuel it is necessary to reprocess the whole amount of spent fuel, in the case of heterogeneous arrangement, it is possible to separate plutonium and ²³⁸U in different fuel rods. In this case, it is possible to achieve nearly complete burning of fissile isotopes of plutonium in fuel rods loaded with plutonium. These fuel rods with burned plutonium can be buried after cooling without reprocessing. They would contain just several percent of initially loaded plutonium, mainly even isotopes. Fuel rods with ²³⁸U alone should be reprocessed in the usual way.     

Laser-assisted decontamination—A wavelength dependent study

We present here the experimental results on cleaning of radioactive dielectric particulates, loosely deposited on stainless steel, by coherent light of 1064 nm wavelength and its three harmonics occurring at 532 nm, 355 nm and 266 nm, derived from an Nd-YAG laser. For the initial few exposures, the decontamination factor has been found to be highest when exposed to 1064 nm radiation. With increasing number of exposures, however, the radiation with reducing wavelength assumes a more important role as a cleaning agent. The observation of almost no cleaning with 1064 nm and much reduced cleaning with its harmonics when the contamination is deposited on a transparent substrate confirms the dominant role played by metal substrate towards expelling the loose particulates from its surface.     

On the equilibrium isotopic composition of the thorium–uranium–plutonium fuel cycle

The equilibrium isotopic compositions and the times to equilibrium in the process of thorium–uranium–plutonium oxide fuel recycling in VVER-type reactors using heavy water mixed with light water are estimated. It is demonstrated thEhfat such reactors have a capacity to operate with self-reproduction of active isotopes in the equilibrium mode.     

“Trapped fraction” effect in microfuel with plutonium fuel

Results of the investigation into the thermodynamics of two types of microfuel (with oxygen getter and without it) with plutonium fuel for various degrees of burnup are presented. The behavior of the trapped fraction of Ag, Ce, Cd, Cs, La, Mo, Pu, Pd, Ru, Sr, Te, and Y is investigated. The fraction of any fission product bound into stable chemical compounds with other components of the system and excluded from the diffusion process is called the trapped fraction. An abrupt increase in the trapped fraction of cesium and, correspondingly, a decrease in free cesium during the burnup of ～26% FIMA (fissions per initial metal atom) or more are found for the microfuel containing no oxygen getter. This leads to a substantial nonlinear burnup dependence of the trapped fraction and should be the cause of an abrupt decrease in the Cs output from the microfuel. It seems likely that the found effect is associated with the formation of carbonate Cs₂CO₃ in the plutonium fuel. In the case of microfuel containing the oxygen getter, no formation of cesium carbonate occurs and the trapped fraction of cesium is almost independent of the burnup.     

两种光纤探针在冲击波作用下的时间响应特性

 对冲击波参数的测量开发了两种光纤探针，以满足强电磁环境和冲击压力较低的情况。一种是冲击自发光光纤探针，另一种是闪光隙光纤探针。这两种光纤探针分别利用融凝石英在受到冲击压缩时发光和氩气（或空气）隙在受到压缩时会产生很强的光辐射的机理研制而成的。自发光光纤探针在大于70 GPa冲击压力下，其信号上升时间在1~3 ns之间；闪光隙光纤探针在10～30 GPa的冲击压力下，其信号上升时间稳定在2~7 ns之间。     

核燃料后处理中锕系元素的声化学调价研究进展

硝酸水溶液在超声波辐照下产生自由基及活性分子,通过加入辅助试剂或控制硝酸浓度可以选择性地利用这些活性组分氧化或还原铀、镎、钚等锕系元素。在核燃料后处理流程中可利用上述反应对锕系元素进行声化学调价,实现锕系元素调价的无盐化,在某些调价过程中甚至无需额外加入任何试剂。由于上述优点,声化学方法有望在后处理流程的钚、镎调价方面得到应用。     

Ultrasonically improved galvanochemical technology for the remediation of industrial wastewater

Two general methodologies adopted for the decontamination of industrial wastewater containing oil and metal ions are flocculation and coagulation. Both methods require the addition of chemicals and in the case of electrocoagulation the additional use of electrical power. Another methodology that was developed in Russia some years ago involves the production of Fe₂O₃ particles as coagulants by a galvanochemical reaction between iron and coke. Both of these materials are inexpensive and generally available in bulk. Ultrasonic processing of the particles generated in this reaction reduces the particle size of the Fe₂O₃ particles and provides surface cleaning making them more effective. Trials have proved their efficiency for the decontamination of wastewater made up in a laboratory and real wastewater from a carriage cleaning station on the St. Petersburg Metro. A mathematical model for the process has been developed.     

冲击波加热的氦气与氩气对电探针导通的影响

 用炸药透镜加载装置观察到置于氦气与氩气中的电探针回路有不同的导通现象。基于一维冲击波和局域热平衡假设,分别计算了两种气体的冲击状态参数。当飞片速度在3～5 km/s范围时,理论估算的氩气电离度超过1%,这说明氩气的电离已引起了探针回路的提前接通,而氦气几乎没有电离,对探针能起到很好的保护作用。     

The influence of changes in the VVER-1000 fuel assembly shape during operation on the power density distribution

A new approach to calculation of the coefficients of sensitivity of the fuel pin power to deviations in gap sizes between fuel assemblies of the VVER-1000 reactor during its operation is proposed. It is shown that the calculations by the MCU code should be performed for a full-size model of the core to take the interference of the gap influence into account. In order to reduce the conservatism of calculations, the coolant density and coolant temperature feedbacks should be taken into account, as well as the fuel burnup.     

Comparisons of Heat Transfer Enhancement of an Internal Blade Tip with Metal or Insulating Pins

Cooling methods are needed for turbine blade tips to ensure a long durability and safe operation. A common way to cool a tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of the three-dimensional turning effect and impingement like flow. Improved internal convective cooling is therefore required to increase the blade tip lifetime. In the present study, augmented heat transfer of an internal blade tip with pin-fin arrays has been investigated numerically using a conjugate heat transfer method. The computational domain includes the fluid region and the solid pins as well as the tip regions. Turbulent convective heat transfer between the fluid and pins, and heat conduction within pins and tip are simultaneously computed. The main objective of the present study is to observe the effect of the pin material on heat transfer enhancement of the pin-finned tips. It is found that due to the combination of turning, impingement and pin-fin crossflow, the heat transfer coefficient of a pin-finned tip is a factor of 2.9 higher than that of a smooth tip at the cost of an increased pressure drop by less than 10%. The usage of metal pins can reduce the tip temperature effectively and thereby remove the heat load from the tip. Also, it is found that the tip heat transfer is enhanced even by using insulating pins having low thermal conductivity at low Reynolds numbers. The comparisons of overall performances are also included.     

Magnetic viscosity and domain wall pinning in an MnAlC permanent magnet

Magnetic viscosity in a hot extruded MnAlC permanent magnet has been measured over a temperature range from 80 to 295 K. The results are fitted to a recent theory of “strong” and “weak” domain wall pinning which allows values of the thermal activation free (“absolute zero”) coercive field to be determined from the data. If the pinning is due to strong pins, randomly distributed throughout the material, a pin density of ≈3×10¹⁵ cm^-3 is predicted. There is no obvious evidence of pin sites of this density within the grains visible in electron micrographs.If the pinning is localized (possibly at grain boundaries) then weak pinning by a similar, but localized, density of pins is predicted. Lorentz electron microscopy domain contrast in such regions might however be overwhelmed by strain contrast effects.     

The effect on bending waves by defects in pinned elastic plates

This paper presents solutions to a number of problems posed for the out-of-plane displacement of infinite thin elastic plates that are rigidly pinned in periodic configurations, but that possess a finite number of ‘defects’. We begin by considering a single one-dimensional periodic array of pins. We derive an analytic solution for the displacement produced by the forced oscillation of the central pin in the array, and this solution is shown to be closely connected to the problem of scattering of plane waves by an array when a finite number of pins are removed. Attention then focuses on doubly periodic rectangular arrays of pinned points possessing defects. Central to approaching such problems is an understanding of Bloch–Floquet waves in periodic arrays in the absence of defects and a simple method is described for computing the associated dispersion surfaces. The solutions to three problems are then sought: the trapping of localised waves by a finite number of missing pins; trapping of waves by entire rows of missing pins; and the wave radiation pattern due to the forcing of a single pin. All problems are treated analytically using bounded Green's functions for thin elastic plates, a discrete Fourier transform solution method and simple, explicit and rapidly convergent evaluations of the one- and two-dimensional lattice sums that arise.     

Fuel breeding in a hybrid muon catalyzed fusion reactor

We discuss the processes of nuclear fuel burnup and plutonium breeding in the uranium blanket of a hybrid mesocatalytic reactor. The time dependence of the nuclear fuel isotopic concentrations was calculated by the BURNFL code. Using a three-dimensional Monte Carlo MORSE-H code the plutonium and tritium breeding coefficients, the fission rates of uranium and plutonium and a specific power distribution in the blanket were computed. The total fusion energy multiplication factor was obtained as a function of the fuel residence time using results of a detailed calculation of the mesocatalytic channel and estimations of the electronuclear channel.     

Local Heat Transfer Distribution in a Rectangular Pin Channel With and Without Vortex Generators

Short pin fins are used to enhance heat transfer rates by increasing the level of turbulence in the trailing edge of gas turbine blades. Experiments are conducted to investigate the local Nusselt number distributions in a staggered pin-fin array using the infrared thermal imaging technique. The pin fins are arranged in a rectangular channel with an aspect ratio of 9. The pins have streamwise pitch-to-diameter (X_S/D) and spanwise pitch-to-diameter (X_T/D) ratios of 2 with a pin height-to-diameter (H/D) ratio of 2. Ejection holes of 5-mm diameter with a pitch of 12.7 mm are used to study the effects of lateral ejection. Both one-wall and two-wall heating situations are studied for straight-flow and lateral-ejection cases. It is found that the local Nusselt numbers are highest below the horseshoe vortices just upstream of the individual pin fins. For the straight-flow case, the Nusselt numbers for the two-wall heating case are observed to be 15–20% higher than those of the one-wall heating case. Lateral ejection causes a decrease of about 1–10% for the one-wall heating case, while there is an increase of about 10% for the two-wall heating case. Experiments are also carried out with vortex generators between individual pin fins. Vortex generators cause an increase in heat transfer by about 50% compared to the straight-flow cases.