Reactivity study of combustion for coals and their chars in relation to volatile content

To determine the effect of volatile matter on combustion reactivity, the pyrolysis and combustion behavior of a set of four (R, C, M and K coals) coals and their chars has been investigated in a TGA (SDT Q600). The maximum reaction temperatures and maximum reaction rates of the coals and their chars with different heating rates (5–20 °C/min) were analyzed and compared as well as their weight loss rates. The volatile matter had influence on decreasing the maximum reactivity temperature of low and medium rank coals (R, C and M coals), which have relatively high volatiles (9.5–43.0%), but for high rank coal (K coal) the maximum reactivity temperature was affected by reaction surface area rather than by its volatiles (3.9%). When the maximum reaction rates of a set of four coals were compared with those of their chars, the slopes of the maximum reaction rates for the medium rank coals (C and M coals) changed largely rather than those for the high and low rank coals (R and K coals) with increasing heating rates. This means that the fluidity of C and M coals was larger than that of their chars during combustion reaction. Consequently, for C and M coals, the activation energies are lower (24.5–28.1 kcal/mol) than their chars (29.3–35.9 kcal/mol), while the activation energies of R and K coals are higher (25.0-29.4 kcal/mol) than those of their chars (24.1–28.9 kcal/mol).     

Stable isotope characterization of olive oils. I—Compositional and carbon-13 profiles of fatty acids

Nearly 200 olive oils produced in the Mediterranean basin, mainly in Greece, during 4 yr from 1993 to 1996, were studied by gas chromatography (GC) and on-line GC-isotope ratio mass spectrometry (GC-C-IRMS). The composition of the oils in the more abundant fatty acids (C_16:0, C_16:1, C_18:0, C_18:1, C_18:2, and C_18:3) was obtained by GC after transesterification of the triglycerides into methyl esters. Using the hyphenated GC-C-IRMS technique, the ¹³C contents of the three most abundant acids, C_16:0, C_18:1, and C_18:2, were measured with satisfactory accuracy. The results, analyzed in terms of geographical, temporal, and botanical factors, provide new criteria for the authentication of olive oils.     

核反馈实时模拟程序

为了在堆外实验中实现核反馈实时模拟,用C 语言开发了核反馈模拟程序.该程序由3个主要模块组成:反应性反馈模拟、功率控制系统模拟及反应堆模拟.采用的主要物理模型有:点堆模型、一维均匀流体模型、瞬态导热模型等;堆功率控制系统模拟方案为平均温度控制方案;其他辅助计算包括物性参数、几何参数的计算.用Retran-02计算分析数据对模拟程序进行了测试,结果表明,模拟程序的数学模拟正确,运算速度快,计算准确.     

Preliminary safety analysis on loss of flow accidents and external source transients for LBE cooled ADSR core

In this paper, preliminary safety studies on the 800 MWth accelerator-driven system (ADS) proposed by Xi'an Jiaotong university are presented. The system is a pool type facility coupling a proton accelerator with current in the range of 17–23 mA and a sub-critical core by means of a spallation target. The RELAP5/MOD3.3 code is selected as a base tool. In order to simulate the system, the point kinetics model is modified and the property of lead-bismuth is implemented to meet the requirement of ADS analysis. This paper focuses on the assessment of its response to the loss of flow events. The first part is originated from the failure of the pump and the second part derives from the significant flow blockage at a fuel assembly inlet. The reactivity insertion accidents are caused by the change of the proton beam current. The results show that the safety and criteria are satisfied and the system is tolerant to the loss of flow accidents and proton beam doubled accident and is sensitive to the external neutron changing.     

Sensitivity analyses of the use of different reflector materials on the neutronics parameters of Tehran research reactor

In this paper, the effect of changes in neutron reflector type on neutronics parameters of Tehran research reactor is analyzed. In this study, at first, calculations for the HEU and LEU fuel configurations of the reactor core in which the light water is used as a neutron reflector in the core is done. Then, by using the reflectors such as graphite, beryllium and heavy water, changes on the neutronic parameters are examined. The results show that by altering the reflector, at HEU core configuration (compared with LEU), more changes appear in parameters such as neutron multiplication factor, average fast and thermal neutron flux, excess reactivity and shut down margin. Moreover, at LEU core configuration, changes are tangible specifically on parameters of cycle length and power peaking factor. In addition, the evaluated fuel temperature coefficient of reactivity is greater at HEU than LEU, while the temperature alteration of fuels represented greater influence on reactivity at LEU configuration.     

An efficient technique for the point reactor kinetics equations with Newtonian temperature feedback effects

The point reactor kinetics equations of multi-group of delayed neutrons in the presence Newtonian temperature feedback effects are a system of stiff nonlinear ordinary differential equations which have not any exact analytical solution. The efficient technique for this nonlinear system is based on changing this nonlinear system to a linear system by the predicted value of reactivity and solving this linear system using the fundamental matrix of the homogenous linear differential equations. The nonlinear point reactor kinetics equations are rewritten in the matrix form. The solution of this matrix form is introduced. This solution contains the exponential function of a variable coefficient matrix. This coefficient matrix contains the unknown variable, reactivity. The predicted values of reactivity in the explicit form are determined replacing the exponential function of the coefficient matrix by two kinds, Backward Euler and Crank Nicholson, of the rational approximations. The nonlinear point kinetics equations changed to a linear system of the homogenous differential equations. The fundamental matrix of this linear system is calculated using the eigenvalues and the corresponding eigenvectors of the coefficient matrix. Stability of the efficient technique is defined and discussed. The efficient technique is applied to the point kinetics equations of six-groups of delayed neutrons with step, ramp, sinusoidal and the temperature feedback reactivities. The results of these efficient techniques are compared with the traditional methods.     

An Interval Bound Algorithm of optimizing reactor core loading pattern by using reactivity interval schema

In order to optimize the core loading pattern in Nuclear Power Plants, the paper presents a new optimization method – Interval Bound Algorithm (IBA). Similar to the typical population based algorithms, e.g. genetic algorithm, IBA maintains a population of solutions and evolves them during the optimization process. IBA acquires the solution by statistical learning and sampling the control variable intervals of the population in each iteration. The control variables are the transforms of the reactivity of fuel assemblies or the worth of burnable poisons, which are the crucial heuristic information for loading pattern optimization problems. IBA can deal with the relationship between the dependent variables by defining the control variables. Based on the IBA algorithm, a parallel Loading Pattern Optimization code, named IBALPO, has been developed. To deal with multiple objectives and constraints, the Dynamic Discontinuous Weight Factors (DDWF) for the fitness function have been used in IBALPO. Finally, the code system has been used to solve a realistic reloading problem and a better pattern has been obtained compared with the ones searched by engineers and genetic algorithm, thus the performance of the code is proved.     

A simplified method of computing the effectiveness of tests in selection.

The Taylor-Russell method of predicting the number of successful workers, for various validities and selection ratios, is compared with a direct method in which the number successful is predicted from the data used to obtain the validity coefficient. Four sets of data are presented in which the predicted percent successful is compared with the percent actually successful, as determined from follow-up groups. "While the average errors of the Taylor-Russell method were… slightly less than the average errors of the direct method, the differences were small." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Al2O3 and Mn/Al2O3 sorbents highly utilized in destructive sorption of NF3

NF₃ is commonly used as an etching and cleaning gas in semiconductor industry,however it is a strongly greenhouse gas.Therefore,the destruction of disposal NF₃ is an urgent task to migrate the greenhouse effect.Among the technologies for NF₃ abatement,the destructive sorption of NF₃ over metal oxides sorbents is an effective way.Thus,the search for a highly reactive and utilized sorbent for NF₃ destruction is in great demand.In this work,Al OOH supported on carbon-sphere （Al OOH/CS） as precursors were synthesized hydrothermally and heat-treated to prepare the Al₂O₃ sorbents.The influence of Al OOH/CS hydrothermal temperatures on the reactivity of derived Al₂O₃ sorbents for NF₃ destruction was investigated,and it is shown that the Al₂O₃ from Al OOH/CS hydro-thermalized at 120℃ is superior to others.Subsequently,the optimized Al₂O₃ was covered by Mn（OH）_xto prepare Mn/Al₂O₃ sorbents via changing hydrothermal temperatures and Mn loadings.The results show that the Mn/Al₂O₃ sorbents are more utilized than bare Al₂O₃ in NF₃ destructive sorption due to the promotional effect of Mn₂O₃ as surface layer on the fluorination of Al₂O₃ as substrate,especially the optimal 5%Mn/Al₂O₃ （160℃） exhibits a utilization percentage as high as 90.4%,and remarkably exceeds all the sorbents reported so far.These findings are beneficial to develop more efficient sorbents for the destruction of NF₃ .