The System Dynamics of Nuclear Energy in Singapore

In this article, a system dynamics model is developed to study the complex issues involving nuclear energy in Singapore by assessing four essential aspects, namely (1) Economic, (2) Environment, (3) Social, and (4) Political in various scenarios. The first factor juxtaposes the monetary benefit from deploying nuclear energy with the current situation. The second deals with carbon dioxide emission, nuclear waste, and thermal pollution from nuclear power plant. The third part discusses the safety and social acceptance toward nuclear project, and the last section analyzes the political stability in provision of nuclear energy advent. The proposed system dynamic model incorporates all four components that allow us to run sensitivity analysis based on various scenarios and enables us to gain insight in how each domain evolves with time. Based on the model, we present advantages and disadvantages of possessing nuclear power plants in Singapore and suggest remedies to rectify the drawbacks.     

RA-915^＋型测汞仪快速测定土壤中的总汞

本文采用RA-915＋型测汞仪建立了一种快速测定土壤中总汞的热解析冷原子吸收分光光度法。该方法使用土壤标准样品直接固体进样建立标准曲线,不需要任何样品前处理消解过程,可在几分钟内快速测量1个土壤样品中的总汞含量。采用该方法分析了ESS系列4个土壤标准样品和GSS系列15个土壤标准样品,并与原子荧光法比对分析了9个土壤实际样品,结果表明本方法具有快速、准确、简便和稳定性较高等优点。     

Causes and consequences of thermal runaway incidents—Will they ever be avoided?

A study of runaway incidents involving thermal chemical reactions in the UK over the past 25 years (1988–2013) has been carried out. The objective of this study is to determine possible causes of thermal runaway incidents. A statistical analysis of the underlying problems that led to thermal runaway incidents has been provided. A comparison of the current study on thermal runaway incidents with those identified prior to 1988 has been carried out. This study clearly shows that lessons have not been learnt from thermal runaway incidents caused by operator errors, management failures and lack of organised operating procedures. These factors have been the possible causes of about 77% of all the thermal runaway incidents analysed in this study. The number of fatalities and injuries as a result of thermal runaway incidents has increased by ∼325% and ∼279%, respectively, in the last 25 years even though the number of incidents was significantly less. On the basis of this analysis, several recommendations have been proposed that could help to minimise the risks associated with any thermal runaway incidents in the future.     

Speciation and quantification of vapor phases in soy biodiesel and waste cooking oil biodiesel

This study characterizes the compositions of two biodiesel vapors, soy biodiesel and waste cooking oil biodiesel, to provide a comprehensive understanding of biodiesels. Vapor phases were sampled by purging oil vapors through thermal desorption tubes which were then analyzed by the thermal desorption/GC/MS system. The results show that the compounds of biodiesel vapors can be divided into four groups. They include methyl esters (the main biodiesel components), oxygenated chemicals, alkanes and alkenes, and aromatics. The first two chemical groups are only found in biodiesel vapors, not in the diesel vapor emissions. The percentages of mean concentrations for methyl esters, oxygenated chemicals, alkanes and alkenes, and aromatics are 66.1%, 22.8%, 4.8% and 6.4%, respectively for soy biodiesel, and 35.8%, 35.9%, 27.9% and 0.3%, respectively for waste cooking oil biodiesel at a temperature of 25 ± 2 °C. These results show that biodiesels have fewer chemicals and lower concentrations in vapor phase than petroleum diesel, and the total emission rates are between one-sixteenth and one-sixth of that of diesel emission, corresponding to fuel evaporative emissions of loading losses of between 106 μg l⁻¹ and 283 μg l⁻¹. Although diesels generate more vapor phase emissions, biodiesels still generate considerable amount of vapor emissions, particularly the emissions from methyl esters and oxygenated chemicals. These two chemical groups are more reactive than alkanes and aromatics. Therefore, speciation and quantification of biodiesel vapor phases are important.     

Effects of ferric oxide on decompositions of methyl ethyl ketone peroxide

Methyl ethyl ketone peroxide (MEKPO) is a widely used initiator for polymerization reaction and hardener in glass-reinforced plastic. However, MEKPO is an unstable reactive chemical and has caused several serious accidents all over the world. This work studied the thermal stability of MEKPO in the presence of ferric oxide as the contaminant through calorimetric and kinetic studies. The calorimetry was performed using Automatic Pressure Tracking Adiabatic Calorimeter (APTAC) to identify the effects of ferric oxide (different concentration) on important reactive hazards such as onset temperature and pressure hazard. Kinetic modeling was then performed to study the kinetics of the runaway reaction and estimate important kinetic parameters. The results indicate that in the low concentration range (<0.3%), ferric oxide has no significant effect on the thermal stability of MEKPO. However, in the high and intermediate concentration range of ferric oxide (i.e., 10%), the negative effect on the thermal stability of MEKPO was observed. This result is in agreement with the kinetic study result that the activation energy and frequency factor decrease dramatically in the high ferric oxide concentration range. The results provide necessary process safety information for the handling of MEKPO and also technical basis for the further study in this area.     

Thermal risk analysis of cumene hydroperoxide in the presence of alkaline catalysts

Many studies have been performed to clarify the basic thermal runaway hazards and kinetics of cumene hydroperoxide (CHP) decomposition. However, materials that are incompatible with CHP have not been clearly identified. Alkaline solutions have been used as a catalyst to form dimethylphenyl carbinol (DMPC) and dicumyl peroxide (DCPO); however, these solutions also affect the reaction and storage temperature of CHP. In this study, thermal calorimeters, differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), were used to compare the effects of various bases on the decomposition of CHP in cumene. Specifically, the exothermic onset temperature, change in pressure over time, self-heating rate and heat of decomposition were evaluated. Moreover, to appraise the degree of hazard associated with the use of CHP, the compatibility of CHP with various substances was analyzed, and a risk matrix for thermal runaway reactions was obtained. The results of the present study could be used to design safety procedures for the production of CHP and its derivatives.     

Predicting the Thermal Effects of Dam Removal on the Klamath River

The Klamath River once supported large runs of anadromous salmonids. Water temperature associated with multiple mainstem hydropower facilities might be one of many factors responsible for depressing Klamath salmon stocks. We combined a water quantity model and a water quality model to predict how removing the series of dams below Upper Klamath Lake might affect water temperatures, and ultimately fish survival, in the spawning and rearing portions of the mainstem Klamath. We calibrated the water quantity and quality models and applied them for the hydrometeorological conditions during a 40-year postdam period. Then, we hypothetically removed the dams and their impoundments from the models and reestimated the rivers water temperatures. The principal thermal effect of dam and reservoir removal would be to restore the timing (phase) of the rivers seasonal thermal signature by shifting it approximately 18 days earlier in the year, resulting in river temperatures that more rapidly track ambient air temperatures. Such a shift would likely cool thermal habitat conditions for adult fall chinook (Oncorhynchus tshawytscha) during upstream migration and benefit mainstem spawning. By contrast, spring and early summer temperatures could be warmer without dams, potentially harming chinook rearing and outmigration in the mainstem. Dam removal might affect the rivers thermal regime during certain conditions for over 200 km of the mainstem.     

大型火力发电厂气体消防系统设计探讨

鉴于我国目前还未颁布烟烙尽 (INERGEN)和七氟丙烷 (FM - 2 0 0 )灭火系统设计规范 ,通过对大型火力发电厂气体消防系统进行分析 ,建议气体灭火系统设计中应做到 :有人值守的防护区域采用INERGEN或FM- 2 0 0灭火系统 ,防护区控制在 7个以内 ,不考虑备用量 ,减少其存储容积 ;无人值守的防护区域采用低压CO2 灭火系统 ,防止其较高灭火浓度对人体造成伤害。采用该设计方案可大大提高消防安全性和降低工程造价     

自反应性化学物质的热危险性评价方法

笔者进行的研究工作 ,给出了利用C80微量量热仪所测得的自反应性化学物质的热流速曲线 ,从而求解该物质的化学反应动力学参数 ,以及在Semenov模型下求解其自加速分解温度SADT(Self AcceleratingDecompositionTemperature)的方法 ,并将一些有机过氧化物、氧化剂和可燃剂的混合物的自加速分解温度的推算结果与实测值进行了比较。实验证明 ,该推算方法结论准确 ,是一种安全、简便、实用的反应性化学物质热危险性的评价方法     

池火特性参数计算及其热辐射危害评价

可燃性油品池火的火焰及其产生的热辐射 ,可能导致周围人员伤亡或设备设施损坏。笔者介绍了油品池火的质量燃烧速率、火焰长度、火焰倾角及火焰后拖量等特性参数的计算方法 ,提出了池火热辐射强度的预测模型 ,给出了热辐射伤害 /破坏准则 ,并进行了模拟计算和评价。