Structural integrity issues with Gen IV proposals: fast reactors and PBMR

Abstract

Structural integrity issues are discussed for two generation IV reactor concepts: the fast reactor and the high temperature reactor, more specifically, the pebble bed modular reactor. The pebble bed modular reactor and other designs of high temperature reactor are claimed to possess built-in safety features leading to safe shutdown: they do, however, involve >8% enrichment of ²³⁵U. Many high temperature creep, creep–fatigue and stress relaxation issues remain to be addressed. With lead/lead–bismuth cooled fast reactors running at ～500°C, there appear to have been none of the issues in the steam generator experienced with sodium cooling. The aspiration of both reactor types is to operate at high temperatures and to produce hydrogen from water thermochemically. A view has been expressed that temperatures up to 900°C could be achieved using metallic alloys (with ceramics for higher temperatures), but it is concluded that something of the order of 750°C represents a more realistic upper limit for economic service lives.     

Fabrication of a Li4SiO4–Pb tritium breeding material

PbO₂-doped Li₄SiO₄ pebbles were successfully fabricated by a liquid-atmosphere sintering process. Those pebbles sintered at 1000 °C under atmospheric conditions were found to have an average diameter of 1.05 mm, a sphericity of 98%, a theoretical density of 90.9%, an average crush load of 24.3 N, and a main phase structure of Li₄SiO₄ with a small percentage of Li₈PbO₆. Subsequent optimization of this fabrication process yielded ceramic pebbles suitable for tritium breeding in a test blanket module (TBM).     

Fabrication of beryllide pebble as advanced neutron multiplier

Fusion reactors require advanced neutron multipliers with great stability at high temperatures. Beryllium intermetallic compounds, called beryllides such as Be₁₂Ti, are the most promising materials for use as advanced neutron multipliers. However, few studies have been conducted on the development of mass production methods for beryllide pebbles. A granulation process for beryllide needs to have both low cost and high efficiency. To fabricate beryllide pebbles, a new granulation process is established in this research by combining a plasma sintering method for beryllide synthesis and a rotating electrode method using a plasma-sintered electrode for granulation. The fabrication process of the beryllide electrode is investigated and optimized for mass production. The optimized beryllide electrode exhibits higher ductility and can be sintered at a lower temperature for a shorter time, indicating that it is more suitable not only for withstanding the thermal shock from arc-discharge during granulation but also for producing the beryllide pebbles on a large scale. Accordingly, because these optimization results can reduce the time required for electrode fabrication by 40%, they suggest the possibility of great reductions in time and cost for mass production of beryllide pebbles.     

SABC碎磨工艺在多宝山铜业的应用实践

多宝山铜业二期选矿厂建设结合了一期选矿厂3CB碎磨系统扩建改造,创新地设计Ⅰ系列3.0万吨/天SABC工艺和Ⅱ系列2.5万吨/天3CB工艺相结合的碎磨流程, SABC工艺与3CB工艺互通互联,整个生产系统既具有两种碎磨工艺的优势特点和设备功效,又实现了协同互补,有利于降低碎磨能耗、保障设备运转率。本文主要阐述了多宝山SABC碎磨工艺的生产调试、技改、提产等过程,总结了SABC流程的重要影响因素、不足及优点。结合生产实际情况,通过采取顽石独立破碎技改、一期细碎筛分分流破碎技改、粗矿堆联通技改、二期Ⅰ、Ⅱ系列磨矿分级互通互调技改等优化改造措施,最终实践探索出较优的作业流程和工作参数,使多宝山选矿厂整体产能提升达到7700t/d,碎磨整体电耗下降2.63Kwh/t,钢球单耗下降0.03kg/t,经济效益非常显著。     

提高柳钢4号高炉风温的技术措施

柳钢4号高炉配置了4座大型顶燃式球式热风炉。通过采取富化焦炉煤气烧炉、更换使用新型耐火球、优化球式热风炉操作工艺、杜绝高炉风口直吹管发红烧穿现象、提高高炉接受高风温的能力等有效措施,高炉入炉风温由1064℃提高到1200℃左右,最高可达1220℃。     

Pebble bed-oil thermal energy storage for solar thermo-electric power systems

Results of a study to examine the operating characteristics of a 100 kWh thermal energy storage (TES) system suitable for solar thermo electric applications is described. The system chosen consisted of a pebble bed as the primary storage medium and oil as the heat transfer cum storage medium. The operating temperatures considered were between 230 and 250°C with a 20 deg C swing. A full-size unit consisting of a steel tank of volume 10 m³ with 50 mm pebbles, suitable instrumentation and facility for heating the oil was built. The important operating variables and characteristics of the system studied included the transient behaviour of the bed, namely the thermal wave front characteristics. Results of the theoretical analysis of the transient bed behaviour were compared with the experimental data on the wave front propogation characteristics and the comparisons are discussed. The uniformity of flow distribution is also examined.     

球床模块堆停堆后自然对流传热特性数值研究

对冷却流体在球床模块堆内燃料颗粒填充区域中的流动和传热过程进行了研究.数值模拟突然停堆后燃料颗粒区在温差作用下的自然对流过程,分析了瑞利数Ra对燃料填充区域内流场、温度场和局部努塞尔数Nu以及壁面摩擦阻力系数的影响.计算结果表明:当球床模块堆突然停堆时燃料填充区域可形成加热壁面流体上升流动、冷却壁面下降流动的自然循环流动;随着Ra数增大,回流中心向上移动;沿轴向壁面局部Nusselt数和摩擦阻力系数存在极值,并且极值点随Ra数增大而向上移动;与氮气相比,氦气作为冷却介质停堆后具有更均匀的堆芯轴向温度分布.     

Fabrication of Li2TiO3 pebbles by water-based sol-gel method

Fabrication of Li₂TiO₃ pebbles by wet process received great attention for their convenience to realize mass production and good performances. Li₂TiO₃ pebbles with about 1.4 mm in diameter were prepared by a water-based sol-gel method using Ti(C₄H₉O)₄ and LiNO₃ as raw materials. This process is simple and has not been reported previously. Phase analysis, thermal analysis and morphological observation were carried out with the pebbles. The experimental results showed that a large amount of pores were presented on the surface of the pebbles and the density of the pebbles was sensitive to the sintering temperature. The pebbles sintered at 1200 °C for 10 h reached a density of ∼68%T.D. The shape of the pebbles was favorable with an average sphericity of about 1.08.