The corrosion of mild and stainless steel in alkaline anaerobic conditions representing the Belgian “supercontainer” concept and the Swiss L/ILW repository

Deep geological repositories for radioactive waste contain metallic materials, either used to construct disposal canisters or as low-/intermediate-level waste (L/ILW). The safety relevance of corrosion is linked to canister lifetime in the former case and gas generation in the latter. More specifically, the Belgian “supercontainer” concept envisages mild steel for the used fuel disposal canister, and in the case of the Swiss L/ILW repository, mild steels are the largest metallic waste component due to the decommissioning of civilian power-generating facilities. For these circumstances, the corrosion environment is dominated by the chemistry of cement, which is used as buffer or backfill material. The corrosion behaviour of mild steel in anoxic environments was studied through the analysis of the hydrogen end-product. Hydrogen analysis was conducted by periodically purging the cell head-space and analysing the gas using a solid-state hydrogen sensor. While this method is limited to providing only uniform corrosion rates averaged over periods of time, ranging from weeks to months, it provides excellent resolution and sensitivity. The test cell environments were matched against the anticipated Belgian high-level waste and Swiss L/ILW repository environments, and also against experiments that have been conducted by other researchers for comparative purposes. Samples were exposed to synthetic cement pore waters, representing fresh and degraded cement. In young cement waters, the formation of initial corrosion products resulted in steel wire corrosion rates of the order of µm/year, which, at 80°C rapidly declined to ∼10 nm/year. In contrast, SA516 grade 70 steel plate corroded much more slowly under similar conditions. In aged cement waters, initial corrosion rates were higher but declined faster towards a longer-term rate of ∼10 nm/year. 316L stainless steel, embedded in cementitious material, corroded at a rate of <1 nm/year at 50°C.     

Old-age Care Modes and Facility Planning Based on the Concept of “Continuum of Care”

Through the comparative analysis on the theories and practical experience of the development of old-age care (OAC) in both China and other countries,and based on the interview and questionnaire survey in Zhejiang Province and Hangzhou City,this paper proposes the research and analysis framework for the old-age service system,i.e.,"OAC mode-OAC service system-OAC facility system." The paper argues that,oriented by OAC mode of "taking community-and home-based care as the main body and institution-based care as supplement," China should build an OAC facility system and planning thoughts that take "continuum of care" as concept and long-term care system as core.Taking Zhejiang Province and Hangzhou City as examples,the paper conducts the optimization research on current OAC facilities planning in terms of hierarchical system,scale,and differentiation,so as to formulate more systematic and operable planning standards for OAC facilities.     

A Comparative Study of Urban Planning System Between Wuhan and Macao

This paper makes a comparative study of urban planning system between Wuhan and Macao,including the legislation system,administration system,and operation system of planning.Meanwhile,it also explores how to improve the current planning systems.     

切削数据库的最新研究进展

<正>1引言自1964年美国开发第一个切削数据库CUTDA-TA以来,经过近半个世纪的发展,切削数据库的理念已全面拓展。将计算机应用技术的最新成果与之结合,全面渗透到工程应用的各个领域。本文阐述最新计算机技术成果应用到切削数据库开发的最新进展情况。     

拍卖——无线频谱管理的有效手段

无线通信、尤其是移动通信的迅速发展，使原本有限的无线频谱资源越来越显得珍贵。保证无线频谱资源合理有效地利用，特别是要保证有利于新技术的发展，就必须具有有效的管理。本文从这一角度出发，先简单介绍美国和新西兰利用经济手段拍卖无线频谱的情况，又指出了像俄罗斯这样刚考虑引入“竞拍”方法来分配频率的国家应解决的问题。     

Ash Vaporization and Condensation During Combustion of a Suspended Coal Particle

The results of a theoretical study of the formation and growth of the submicron flyash aerosol around a single burning coal particle are presented. The vaporization of ash and subsequent aerosol formation near the coal particle are studied because the local combustion environment influences these processes strongly. A mathematical model is developed that describes the transport of ash vapor and and the growth of the aerosol. The ash aerosol calculation is superimposed on an existing solution to the combustion problem. Included in the model are the effects of convective transport and of both homogeneous and heterogeneous condensation of the ash vapor. The results of the calculations show that refractory compounds with low surface tension, like silica, nucleate very near the coal particle's surface and produce a substantial mass loading of aerosol. The presence of the aerosol does not greatly affect the ash vaporization rate, which is primarily a function of combustion conditions. The size and amount of the submicron ash aerosol are determined by both the local combustion conditions and the ash's physical properties.