PRICO~?天然气液化技术在海上浮式装置上的应用

较之于岸上(陆地)天然气液化装置,海上浮式天然气液化(FLNG)装置具有投资低、建设周期短、便于迁移及可重复使用等优点,但也面临着易受海上工况及船体晃荡影响等诸多挑战。为此,借助于PRICO~?单循环混合冷剂(SMR)天然气液化工艺技术所具有的较大的灵活性,以及流程简单、易于操作、可满足不同客户的需求、成本更低等优势,运用模块化设计进行了FLNG装置的设备布置,针对海上操作环境对部分关键设备进行了改进,研发出了世界上第一个基于该工艺的浮式天然气液化装置——Exmar FLNG,并进行了现场调试及性能考核。应用效果表明:(1)PRICO~?天然气液化技术能够使FLNG从概念设计实现工程化,并获得更多的发展空间;(2)Exmar FLNG装置集合了天然气处理、天然气液化、LNG储存和装卸功能,工艺流程简短、装置设备数量少、操作简单,具有较短的开停车时间,能较好适应海上恶劣天气及原料气组成变化大的工况,其设计与建造完全符合船级社的相关规范和规定。结论认为,该技术为海洋石油伴生气处理、边际气田和深海气田开发利用提供了一种新的既安全又经济的解决方案。     

Risk‐reduction of passive decay heat removal system by using gallium‐water for UCFR and SMR

Employing a gallium‐based passive decay heat removal system (PDHRS), which enables the use of water as an ultimate heat sink, was proposed for the UCFR‐100. The gallium‐based PDHRS has replaced the previous sodium‐based PDHRS. To evaluate the safety and thermal performance of the gallium‐based PDHRS, safety analysis and heat exchanger tests were performed. The safety analysis, using both deterministic and probabilistic analyses methods, confirmed the unique safety feature of the UCFR‐100. The transient analysis for design basis accidents showed the rapid cooling characteristic of the gallium‐based PDHRS of the UCFR‐100. In addition, compared with the sodium‐based PDHRS, the probabilistic safety analysis, using the level‐1 Probabilistic Safety Assessments method, showed the significant decrease of the minimal cut sets and the significant reduction of the failure probability of the gallium‐based PDHRS of the UCFR‐100. Finally, compared with the sodium‐to‐air feature in the sodium‐based PDHRS, the gallium‐to‐water heat exchanger in the gallium‐based PDHRS enhanced the heat transfer performance and facilitated economic advantages to the entire system. In conclusion, the gallium‐water PDHRS represented risk reduction of the entire reactor system with the effective thermal performance. Copyright © 2016 John Wiley & Sons, Ltd.     

Hypertension incidence after tap-water implementation: a 13-year follow-up study in the arseniasis-endemic area of southwestern Taiwan

Hypertension is the leading cause of cardiovascular disease worldwide. Long-term arsenic exposure has been linked to increased risk for hypertension; however, little is known whether a previous exposure has lingering effects on hypertension after the exposure being reduced significantly for decades. The study cohort was established in 1990 in an arseniasis-endemic area of 3 villages — Homei, Fuhsin, and Hsinming in Putai Township located on the southwestern coast of Taiwan, where residents were exposed to artesian well water (median level = 700 to 930 μg/L) until early 1970s. The original cohort consisted of 490 non-hypertensive residents over 30-yrs-old and 352 of them were successfully followed up in 2002/03. Arsenic concentrations in the artesian well water consumed by residents during 1960s were used to indicate the previous exposure while urinary arsenic species measured in 2002/3 was used to represent current exposure. Hypertension incidences were 27.4, 65.6, and 69.1, per 1000 person-years for men aged 35-49, 50-64, and 65-74 years, respectively being higher than the corresponding rates of 25.1, 46.1, and 57.2 in a community-based longitudinal study. Cancer was the major cause of the total deaths (17/30 = 57%). Diastolic blood pressure was shown to increase with an increased cumulative arsenic ingestion from drinking water (β = 0.27, p < 0.001). The incidence was increased by 2.43-fold in subjects of As(V) ≥ 2.67 μg/g creatinine as compared to those of As(V) < 1.20 μg/g creatinine (the third vs. first tertile; p = 0.047) after adjustment for conventional risk factors. This study suggests that three decades after cessation of drinking artesian well water, residents of the endemic area are still at increased risk for developing hypertension, particularly those who excrete high amounts of As(V).     

Safety analysis for an inadvertent control rod withdrawal event during a power operation of an advanced integral reactor

To identify a safety margin in the case of an inadvertent control rod withdrawal event of a 65-MW_t advanced integral reactor, safety analysis has been carried out by using the Transients And Setpoint Simulation/System integrated Modular Reactor (TASS/SMR) code. The diverse initial conditions, various reactivity insertion rates into a core, different combinations of a reactivity feedback and three different speed modes of a main coolant pump (MCP) have been considered to identify the effect of each parameter on a critical heat flux ratio (CHFR) and the initial condition resulting in the worst consequences from the viewpoint of the minimum critical heat flux ratio. The analysis results show that the worst consequences occur when a reactivity of 17.61 pcm/s is inserted into a core at an initial condition of a 45% initial core power, high coolant temperature at the core inlet position, low system pressure and a thermal design flow. It is also assumed that the least negative fuel and moderator temperature coefficients are applied. The safety parameters such as the minimum critical heat flux ratio and the system pressure are maintained within the safety limits and the reactor is safely transferred to a safe condition by a functioning of the safety systems of the advanced integral reactor.     

The role of the reactor size for an investment in the nuclear sector: An evaluation of not-financial parameters

The literature presents many studies about the economics of new Nuclear Power Plants (NPPs). Such studies are based on Discounted Cash Flow (DCF) methods encompassing the accounts related to Construction, Operation & Maintenance, Fuel and Decommissioning. However the investment evaluation of a nuclear reactor should also include not-financial factors such as siting and grid constraints, impact on the national industrial system, etc.The Integrated model for the Competitiveness Assessment of SMRs (INCAS), developed by Politecnico di Milano cooperating with the IAEA, is designed to analyze the choice of the better Nuclear Power Plant size as a multidimensional problem. In particular the INCAS’s module “External Factors” evaluates the impact of the factors that are not considered in the traditional DCF methods.This paper presents a list of these factors, providing, for each one, the rationale and the quantification procedure; then each factor is quantified for the Italian case. The IRIS reactor has been chosen as SMR representative.The approach and the framework of the model can be applied to worldwide countries while the specific results apply to most of the European countries. The results show that SMRs have better performances than LRs with respect to the external factors, in general and in the Italian scenario in particular.     

SMR稳定性分类方法在大朝山水电站的应用

在大朝山水电站进水口高边坡专题研究时，采用了SMR稳定性分类方法，SMR是从RMR方法演变而来，它综合地考虑了影响边坡的实际因素，如结构面、边坡开挖方法等对边坡稳定的影响，并针对某一分类提出相应的处理措施，是一种较为合理的方法。     

Optimal design of a sleeve-type steam methane reforming reactor for hydrogen production from natural gas

The three-dimensional computational fluid dynamics (CFD) model was used in a sleeve-type steam methane reforming (SMR) reactor for H₂ production of 2.5 Nm³/h from natural gas. The feed and combustion gases acted as a counter-current heat exchange owing to a narrow sleeve equipped between the combustor and catalyst-bed. The CFD results were validated against the experimental data of the SMR reactor with a sleeve gap size of 3 mm. The effect of the sleeve gap size and the flame shape on process performances such as H₂ production rate, thermal efficiency, and uniformity of catalyst-bed temperature was investigated using the CFD model. The sleeve gap size influenced the gas velocity inside the sleeve gap and the convective heat transfer. The SMR reactor with a sleeve gap size of 7 mm showed the highest H₂ production rate and thermal efficiency when comparing six sleeve gap sizes ranging from 2 to 10 mm. A new flame shape for the SMR reactor with the sleeve gap size of 7 mm was proposed to improve the process performances.     

Lifecycle impacts of natural gas to hydrogen pathways on urban air quality

In this paper we examine the potential air quality impacts of hydrogen transportation fuel from a lifecycle analysis perspective, including impacts from fuel production, delivery, and vehicle use. We assume that hydrogen fuel cell vehicles are introduced in a specific region, Sacramento County, California. We consider two levels of market penetration where 9% or 20% of the light duty fleet are hydrogen fuel cell vehicles. The following three natural gas to hydrogen supply pathways are assessed in detail and compared in terms of emissions and the resulting changes in ambient air quality: (1) onsite hydrogen production; (2) centralized hydrogen production with gaseous hydrogen pipeline delivery systems; and (3) centralized hydrogen production with liquid hydrogen truck delivery systems. All the pathways examined use steam methane reforming (SMR) of natural gas to produce hydrogen. The source contributions to incremental air pollution are estimated and compared among hydrogen pathways. All of the hydrogen pathways result in extremely low contributions to ambient air concentrations of _NOx${\mathrm{NO}}_x$, CO, particulates, and _SOx${\mathrm{SO}}_x$, typically less than 0.1% of the current ambient pollution for both levels of market penetration. Among the hydrogen supply options, it is found that the central SMR with pipeline delivery systems is the lowest pollution option available provided the plant is located to avoid transport of pollutants into the city via prevailing winds. The onsite hydrogen pathway is comparable to the central hydrogen pathway with pipeline systems in terms of the resulting air pollution. The pathway with liquid hydrogen trucks has a greater impact on air quality relative to the other pathways due to emissions associated with diesel trucks and electricity consumption to liquefy hydrogen. However, all three hydrogen pathways result in negligible air pollution in the region.     

水电边坡岩体稳定性分级系统研究

 边坡岩体稳定性分级多源于地下工程,并未考虑边坡与地下工程岩体破坏机制的差异,为弥补这一缺陷,提出一种基于边坡破坏机制的分级方法。以水电边坡为样本,分析收集平面破坏模式下的边坡几何形态、岩石强度、岩体完整性、结构面特征、坡面与结构面组合关系、工程环境、气象条件及破坏历史8个岩体稳定性影响因素;运用多元线性回归探索影响因素和边坡岩体稳定性之间的关系,得到各因素的权值;剔除权值近于0的因素,建立边坡岩体稳定性分级系统。与已有边坡岩体分级系统(SMR,CSMR)的比较表明：SRSC的评价结果更接近于基于边坡实际稳定情况的经验评分,标准误差最小,评价准确率最高。另外,用12个水电边坡对该系统进行准确性及适用性分析,评价结果准确率为100%,表明SRSC分级系统的评判效果良好。因此,基于边坡破坏机制的SRSC系统是一种更优的边坡岩体分级方法。