Study on control characteristics for HTTR hydrogen production system with mock-up test facility: System controllability test for fluctuation of chemical reaction

The Japan Atomic Energy Research Institute has a demonstration test plan of a hydrogen production system by steam reforming of methane coupling with the High-Temperature Engineering Test Reactor (HTTR). Prior to the coupling of a hydrogen production plant with the HTTR, simulation tests with a mock-up test facility of the HTTR hydrogen production system (HTTR-H2) is underway. The test facility is a 1/30-scale of the HTTR-H2 and simulates key components downstream from an intermediate heat exchanger of the HTTR. The main objective of the simulation tests is the establishment and demonstration of control technology, focusing on the mitigation of a thermal disturbance to the reactor by a steam generator (SG) and on the controllability of the pressure difference between the helium and process gases at the reaction tube in a steam reformer (SR). It was confirmed that the fluctuation of the outlet helium gas temperature at the SG and the pressure difference in the SR can be controlled within the allowable range for the HTTR-H2 in the case of the system controllability test for the fluctuation of chemical reaction. In addition, a dynamic simulation code for the HTTR-H2 was verified with the obtained test data.     

First-principles simulations of removal process in EEM (Elastic Emission Machining)

Interactions between ultra-fine powder [SiO₂] and work [Si (1 0 0) surface] in EEM (Elastic Emission Machining) has been investigated by employing first-principles molecular dynamics (MD) simulations. Calculated results show the possibilities of the atomic removal through the solid phase chemical interaction between surfaces of ultra-fine powders and works.     

重离子射线照射后家蚕胚胎造血器官的修复再生

为了研究重离子射线照射后家蚕造血器官的修复再生作用，用碳离子射线局部照射家蚕接近孵化时紧贴翅原基内侧的胚胎造血器官，局部细微手术损伤造血器官，观察了对幼虫造血功能的影响，了解了造血器官的修复程度。100Gy以上剂量照射，家蚕出现变态困难，幼虫和蛹的生存率下降，眠中、化蛹或羽化时期出现死亡个体等缺血生理障碍，其影响程度随射线剂量增加而加重。200Gy照射组5龄存活幼虫血细胞含量下降，但其中部分个体的血细胞含量接近对照未照射处理，其体内出现了再生的造血器官。家蚕幼虫有很强的修复再生造血器官功能。     

Visualization of hydrogen diffusion in steels by high sensitivity hydrogen microprint technique

Hydrogen diffusion in steels was examined by both a high sensitivity hydrogen microprint technique (HMT) and an electrochemical hydrogen permeation method. The main diffusion path in an extremely low carbon steel was lattice within grains; grain boundaries were not accelerated diffusion paths. In the case of a hypo-eutectoid steel, hydrogen diffused through proeutectoid ferrite and ferrite in pearlite under steady-state of hydrogen diffusion. The diffusion paths, however, were carbide/ferrite interfaces when hydrogen charging was interrupted before achievement of the steady state. This is probably ascribable to the reversible trapping effect of the interface. The detection efficiency of the high sensitivity HMT was 75% for the low carbon steel and 40% for the hypo-eutectoid steel.     

The effect of the preparation conditions on the optical properties of transparent silica aerogels

Hemispherical and specular transmittance in visible wavelength region and small-angle neutron-scattering of silica aerogels were measured to investigate the effects of supercritical drying media and heat treatment on the optical properties and structure of them. Silica aerogels were prepared by using methanol, ethanol, 2-propanol and carbon dioxide as supercritical drying medium. The analysis of transmission spectra suggested that a reduction of transmittance in visible light can be attributed to Rayleigh scattering, and the scattering intensity depended on the supercritical drying medium. The difference of the scattering intensity among the samples was related to the difference of the cluster size of aerogels from the results of small angle neutron scattering. Heat treatment affected the scattering intensity, but the change of the cluster size was not observed.     

Unsteady stirring method staged used in suspension polymerization of styrene

The results of an unsteady stirring method staged, used in the suspension polymerization of styrene in a lab‐scale batch reactor, are presented. Variation of droplet size during the whole polymerization process under the unsteady stirring condition, compared with that under a steady stirring condition, was found to be small. According to the variable droplet size character, two methods were used to divide the polymerization process into four stages and the unsteady stirring method was used in only one stage of each experimental run. By these operations, the optimum operation of obtaining large particle product with uniform particle size distribution was achieved. The results suggest that controlling the droplet coalescence process is more important than controlling the initial droplet size distribution to obtain uniform final particle products. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1873–1881, 2001     

True Optimization of Pavement Maintenance Options with What-If Models

Abstract:  A prototypical problem road agencies are faced with is to find the optimal application schedule of maintenance works for a given road section. To solve such problems what-if models such as the road transport investment model (RTIM), the highway economic requirements system (HERS), and the highway development and management tool (HDM-4) are widely used to predict the consequences of different maintenance options. With these models maintenance options to be compared must be exogenously specified by an analyst, and the "optimization" with these routines simply chooses the best among those compared. As there are usually infinite numbers of options, it is impossible to exhaust all of them and only suboptimal optimizers may be found with this approach. The present article proposes the use of gradient search methods with what-if models to find the true optima without requiring exogenously specified alternatives. It demonstrates through a case study the feasibility of the use of the steepest descent method and the conjugate gradient method along with HDM-4 to find the true optimum maintenance options.     

Evaluation of lifecycle CO2 emissions from the Japanese electric power sector in the 21st century under various nuclear scenarios

The status and prospects of the development of Japanese nuclear power are controversial and uncertain. Many deem that nuclear power can play key roles in both supplying energy and abating CO₂ emissions; however, due to severe nuclear accidents, public acceptance of nuclear power in Japan has not been fully obtained. Moreover, deregulation and liberalization of the electricity market impose pressure on large Japanese electric power companies with regard to both the operation of nuclear power plants and the development of the nuclear fuel cycle. Long-term Japanese CO₂ reduction strategies up to 2100 are of environmental concern and are socially demanded under the circumstances described above. Taking these factors into account, we set the following two objectives for this study. One is to estimate lifecycle CO₂ (LCCO₂) emissions from Japanese nuclear power, and the other is to evaluate CO₂ emissions from the Japanese electric power sector in the 21st century by quantifying the relationship between LCCO₂ emissions and scenarios for the adoption of nuclear power. In the pursuit of the above objectives, we first create four scenarios of Japanese adoption of nuclear power, that range from nuclear power promotion to phase-out. Next, we formulate four scenarios describing the mix of the total electricity supply in Japan till the year 2100 corresponding to each of these nuclear power scenarios. CO₂ emissions from the electric power sector in Japan till the year 2100 are estimated by summing those generated by each respective electric power technology and LCCO₂ emission intensity. The LCCO₂ emission intensity of nuclear power for both light water reactors (LWR) and fast breeder reactors (FBR) includes the uranium fuel production chain, facility construction/operation/decommission, and spent fuel processing/disposal. From our investigations, we conclude that the promotion of nuclear power is clearly a strong option for reducing CO₂ emissions by the electric power sector. The introduction of FBR has the effect of further reducing CO₂ emissions in the nuclear power sector. Meeting energy demand and reducing CO₂ emissions while phasing out nuclear power appears challenging given its importance in the Japanese energy supply.     

Hydrogen bonding interactions of styrene‐maleimide copolymers with diaminotriazine derivatives

Poly(styrene‐co‐N‐maleimide) precursor and poly(styrene‐co‐N‐maleimide)‐block‐polystyrene have been synthesized by quasiliving radical polymerization. Low molecular weight compounds with the sites specific for the complementary binding to the maleimide moieties via triple hydrogen bonds, 2,4‐diamino‐6‐n‐alkoxy(C‐4, C‐8, and C‐12)‐s‐triazines, have been prepared. Hydrogen bonding between diaminotriazine and maleimide units in the copolymer–diaminotriazine mixtures has been investigated by FTIR. Microphase separated structure in the block copolymer‐diaminotriazine mixtures has been confirmed by DSC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2338–2346, 2006