Development of an Improved Ceramic Tritium Breeder

The paper presents the advanced concept of a long-life small light water reactor in which the fuel irradiation time is comparable with reactor life-time. The equilibrium analysis reveals that the U-Np-Pu fuel with unique neutronic properties allows to keep sufficient criticality up to burnup value about 140GWd/tHM. The fuel recycle does not lead to additional Pu accumulation. Both Pu and Np are well protected against un-controlled proliferation by a large fraction of ²³⁸Pu in their mixture. To improve the reactor safety, the wider fuel pin lattice was applied. The radiation damage of structural materials is within the stainless steel limitation.     

Impact of Solid Breeder Materials on Tritium Breeding in a Hybrid Reactor

Tritium breeding ratio (TBR) is one of the important parameters in design of a Deuterium–Tritium (DT) driven hybrid reactor. Therefore, selection of tritium breeder materials to be used in the blanket is very crucial. In this study, tritium breeding potential of the solid breeders, namely, or in a (DT) fusion driven hybrid reactor fuelled with or was investigated. For this purpose in addition to these solid breeders, different types of liquid breeders, namely natural lithium, Flibe, Flinabe and were used to examine the tritium breeding behavior of liquid–solid breeder couple combinations. Numerical calculations were carried out by using Scale 4.3. According to numerical results, the blanket with fuel using natural lithium as coolant and as solid breeder had the highest TBR value.     

Numerical Estimation Method of the Hydrogen Isotope Inventory in the Hydrogen Isotope Separation System for Fusion Reactor

In the fuel cycle system of the ITER, a large fraction of tritium inventory is expected to be in the cryogenic distillation columns of the hydrogen isotope separation system (ISS). Therefore, the numerical estimation method of hydrogen isotopes inventory in the ISS with high precision is strongly required from safety point of view. Two series of experiments were performed to establish the numerical estimation method of the overall hydrogen isotope inventory in the ISS at steady state using ITER-scale large cryogenic distillation columns at the Tritium Systems Test Assembly in the Los Alamos National Laboratory under the US-Japan collaboration on tritium safety engineering. As a result of experiments, it was confirmed that the hydrogen isotope inventory in a cryogenic distillation column was estimated by the numerical estimation method proposed in this work with enough high precision from the engineering point of view, and it was proved that this method was applied for the ITER-scale cryogenic distillation columns. The precision of this estimation method was found to be almost independent on the composition profile in columns, and especially the liquid holdup ratio of deuterium to the volume of the column was less influential in the inner diameter of the packed section. In addition, the gaseous inventory in an ITER-scale cryogenic distillation column was found to have considerable impact on the total amount of holdup of the column.     

钛吸氕、氘和氚的热力学同位素效应

在金属氢化物热力学及动力学测试系统上测定了钛吸收氕、氘和氚单质气体的压力-组成等温线(p-c-T曲线),并根据范德荷夫方程得到了钛吸收氕、氘和氚形成不同物相时的热力学参数△H^0和△S^0。实验证明,钛吸收氕、氘和氚单质气体时有显著的热力学同位素效应,在相同温度、相同原子比下,吸气平衡压力从低到高依次是氕、氘和氚,但其反应焓变和熵变从小到大依次是氚、氘和氕。     

TBM TES手套箱泄漏事故下氚浓度与通风关系研究

为了分析TBM TES室内通风是否能在手套箱发生氚泄漏时控制室内氚浓度在安全剂量值,采用Fluent对手套箱的氚泄漏和扩散进行模拟,得到不同通风下手套箱泄漏时的氚泄漏速率以及室内氚浓度分布,并对比分析了模拟数据与理论数据。结果表明TES手套箱泄漏速率为1.41×10~(-5)g/s和1.02×10~(-5)g/s时,分别为5次/h和8次/h的换气通风能控制室内氚浓度在安全剂量值2.0×10~(10)Bq/m~3内;而氚泄漏速率为1.56×10~(-5)g/s时,3次/h的换气通风不能控制室内氚浓度在安全剂量值内;模拟结果与理论结果相一致。结果为TES通风除氚设计提供了理论依据。     

Intensity and Pressure Effects in CO2 Laser Isotope Separation of Tritium Photolysis of CF3CTCIF with 2-ns Pulses

Albedo-Sn method was developed to predict the angular flux near the coupling boundary in the bootstrap method, using the energy-and-angle dependent double differential albedo boundary condition. In order to verify the applicability of the method to the reactor shielding design, two types of shielding problem have been analyzed. First, the neutron skyshine dose rates measured at the YAYOI reactor in University of Tokyo are predicted within an accuracy of 20%. It is also found that the neutron spectrum in the air-over-ground is much affected by albedo reflection from the ground and is reproduced well by the albedo-Sn method. Second, as for the neutron streaming through a sodium pipe chase-way, the albedo-Sn calculation saves a computer time and gives the results which agree with those by the reference Sn calculation.     

Influences of Gas Stream Conditions on Efficiency of Tritiated Moisture Collection with P2O5-Desiccant and Isotope Effect

A method was proposed previously for collection and measurement of tritiated moisture in gas stream using P₂O₅-desiccant. Influences of the gas humidity, the gas flow rate and the distance between gas nozzle and P₂O₅-desiccant layer surface on the moisture collection efficiency have been examined through experiments, and the isotope effect on the collection has been investigated. The collection efficiency is the ratio of collected to supplied moisture, and the moisture supplying rate is in proportion to the humidity and flow rate of feed gas. The experiments show that; the collection efficiency does not depend on the gas humidity, but is affected by the gas flow rate and by the nozzle-layer distance. The effects of the flow rate and the nozzle position are related to the mass transfer distance from the bulk of gas stream to the desiccant layer surface in the collection cell. The moisture collecting rate is promoted by the approach of the gas stream to the layer surface. An expression of effective separation factor has been derived to explain the isotope effect on the moisture collection. Experimental data distribution of the separation factor have been reasonably simulated by the analysis.     

Gaseous Exchange Reaction of Deuterium between Hydrogen and Water on Hydrophobic Catalyst Supporting Platinum

The deuterium exchange reaction between hydrogen and water in the gas phase where the fed hydrogen gas is saturated with water vapor is studied experimentally by use of the proper hydrophobic catalysts supporting platinum. It is found that the activities of those catalysts for this reaction system are very high compared with the other known ones for the systems in which gas and liquid should coexist on catalyst surfaces, and that the apparent catalytic activity becomes larger as the amount of platimun supported on a catalyst particle increases. By analyses of the data the following informations are obtained. The exchange reaction can be expressed by a first order reversible reaction kinetics. The pore diffusion in the catalyst particles has significant effect on the overall reaction mechanisms.     

Effect of Changes in Feed Rate and Cut on Circulating Flow within Thermal Diffusion Column for Isotope Separation

A two-dimensional axisymmetric convectional flow field of an isotope separating thermal diffusion column with continuous feed and draw-offs is analyzed through the Newton iterative numerical solution of the equations of change without the Boussinesq approximation. Computations are performed for Ar gas within an inner hot radius of 0.2 mm and an outer cold radius of 5 mm, between which the temperature differs by 300 K. The rate of feed F, supplied into the middle point of the column, is varied from 1 to 5 cm³/s, while the cut θ, or the ratio of the upper drawing-off to feeding rates, from 0.1 to 0.9. Comparison of flow vectors, temperature and density profiles among various sets of (F, θ) makes it clear that the flow fields agree with one another for the same value of the total transport; that is, θF_pc (pc: feed gas density) in the upper section and -(1-θ)pc in the lower section of the column. Observations on the mass flow vectors near the feed slit lead to the finding that the multiplicative effect of separation cannot be expected in the column with the inner radius r_c of 5 mm at the feed rate F exceeding 2 cm³/s(i.e F/ΔTr_c ⁴ )>0.1 [1/(s·K·cm)]), because the feed flow interrupts the whole-length circulation of the natural convection.