Loading pattern optimization for a PWR using Multi-Swarm Moth Flame Optimization Method with Predator

ABSTRACT

This paper aims to propose a new methodology for optimizing fuel loading pattern in a nuclear reactor which is important for its higher safety and economic efficiency. Previous researches have proposed various methodologies to decide better loading patterns automatically. However, the processes still require manual operations of engineers to automatically design actual loading patterns. Swarm intelligence algorithm has currently gained interest as a solution to seek the patterns. Although these methodologies generate better patterns, they sometimes struggle with getting out from local optima and fails to complete the optimization. Large and multimodal solution space sometimes captures worse solutions due to local optima. The conventional methodologies struggle with setting proper parameters to get out from local optima. This research focuses on Multi-Swarm Moth Flame Optimization with Predator (MSMFO-P), an improved Moth Flame Optimization (MFO) by applying the concepts of predator and multi-swarm, as new methodologies. The method of MSMFO-P was applied to solve a loading pattern problem and compared with the conventional optimization methods such as simulated annealing (SA), Hybrid genetic algorithm (GA), and particle swarm optimization (PSO). The results of our experimental works indicated that MSMO-P generates better loading patterns than the conventional methodologies.     

含有可燃毒物的压水堆核电站堆芯装料设计优化研究

含可燃毒物的压水堆装料优化是燃料管理优化研究中的难点,应用通常的脱耦方法和优化算法效率低、全局性差。研究提出局部脱耦方法用以简化问题规模、缩小搜索空间,选择特征统计算法进行优化方案的搜索。利用局部脱耦方法结合特征统计算法研制出压水堆核电站堆芯LP和BP耦合装料优化程序CSALPBP。使用该程序对大亚湾第10循环和第12循环进行了装料优化计算。结果表明CSALPBP程序在求解含可燃毒物的压水堆装料优化问题方面具有很高的搜索效率和很好的全局性,能够较好地解决含可燃毒物的压水堆堆芯装料优化难题。     

Comparison between Equilibrium Cycle and Successive Multicycle Optimization Methods for In-Core Fuel Management of Pressurized Water Reactors

Analyses of an equilibrium cycle are useful for evaluating newly designed fuels defining an envelope of core operating parameters, and so on. However, generation of a loading pattern for the equilibrium cycle is much more difficult than that of a single cycle. Therefore, a loading pattern optimization code for the equilibrium cycle of pressurized water reactors, OPAL, has been newly developed on the basis of the simulated annealing method. In order to verify the capability of the OPAL code, comparison with successive multicycle optimizations was performed while fixing the number of fresh fuel in each cycle. Through benchmark calculations, it was found that the result of the equilibrium cycle optimization was almost compatible with that of the successive multicycle optimization, when the definition of each objective function was similar. However, successive multicycle optimization includes some ambiguity due to limits on the number of calculated cycles, since it requires much computation time. Consequently, the equilibrium cycle optimization has advantages including the quantitative comparison of the core neutronic performances.     

模拟退火算法搜索优化布料方案的机理及效率

利用自行构造的已枚举所有布料方案并完成方案评价的压水堆布料优化基准问题,对应用较为普遍的以组件随机两两交换方式进行解域搜索的模拟退火算法进行了研究,揭示了算法的物理机理,并首次定量给出了算法的搜索效率.研究还表明,用组件"十"字平均k∞分布的约束来过滤非可行解十分有效,结合模拟退火算法使用可获得很高的搜索效率.     

Optimization of in-core fuel management strategy of Tehran Research Reactor (TRR) using MCNP-4C

In order to optimize fuel utilization in TRR, the method of fuel management is modified using MCNP-4C code system. An important parameter of fuel management is the uniformity of neutron flux distribution in the core region, which is obtained efficiently in the present strategy. This strategy is based on calculation of position factors and power densities utilizing MCNP simulations. This study shows that the core life time and average extracted burn up of spent fuel elements of TRR are improved significantly.     

PWR（U）乏燃料中超铀元素在混合堆快裂变包层内嬗变研究

从中子学角度对ＰＷＲ（Ｕ）乏燃料中的超铀元素（２３８Ｐｕ，２３９Ｐｕ，２４１Ｐｕ，２４１Ａｍ，２４３Ａｍ，２３７Ｎｐ，２４４Ｃｍ）在聚变－裂变混合堆快裂变包层内嬗变的可行性进了研究。利用一维中子输运和燃耗计算程序ＢＩＤＥＣＡＹ译不同燃料组分的四个快裂变包层进行分析计算。结果表明，在聚变－裂变混合堆快裂变包层内安全，高效地嬗变ＰＷＲ（Ｕ）乏燃料中的超铀元素是可能的。     

Optimization of fuel core loading pattern design in a VVER nuclear power reactors using Particle Swarm Optimization (PSO)

The two main goals in core fuel loading pattern design optimization are maximizing the core effective multiplication factor (K_eff) in order to extract the maximum energy, and keeping the local power peaking factor (P_q) lower than a predetermined value to maintain fuel integrity. In this research, a new strategy based on Particle Swarm Optimization (PSO) algorithm has been developed to optimize the fuel core loading pattern in a typical VVER. The PSO algorithm presents a simple social model by inspiration from bird collective behavior in finding food. A modified version of PSO algorithm for discrete variables has been developed and implemented successfully for the multi-objective optimization of fuel loading pattern design with constraints of keeping P_q lower than a predetermined value and maximizing K_eff. This strategy has been accomplished using WIMSD and CITATION calculation codes. Simulation results show that this algorithm can help in the acquisition of a new pattern without contravention of the constraints.     

Ensuring the possibility of using thorium as a fuel in a pressurized water reactor(PWR)

The possibility of utilizing thorium as a fuel in a pressurized water reactor(PWR)has been proven from the neutronic perspective in our previously published work without assessing the thermal hydraulic(TH)and solid structure performances.Therefore,the TH and solid structure performances must be studied to confirm these results and ensure the possibility of using a thorium-based fuel as an excellent accident-tolerant fuel.The TH and solid structure performances of thorium-based fuels were investigated and compared with those of U02.The radial and axial power peaking factors(PPFs)for U02,(232Th,235U)02,and(232Th,233U)02 were examined with a PWR assembly to determine the total PPF of each one.Both Gd203 and Er203 were tested as burnable absorbers(BAs)to manage the excess reactivity at the beginning of the fuel cycle(BOC)and reduce the total PPF.Er203 resulted in a more significant reduction to the total PPF and,therefore,a greater reduction to the temperature distribution compared to Gd203.Given these results,we analyzed the effects of adding Er203 to thorium-based fuels on their TH and solid structure performances.     

Development of advanced expansion due to compression (A-EDC) test method for safety evaluation of degraded nuclear fuel cladding materials

Expansion due to compression (EDC) test has been applied to evaluate the performance of nuclear fuel claddings where pellet-cladding mechanical interaction (PCMI) is introduced by swelling of fuel pellets and is triggered by the larger hoop deformation of the pellets, especially during accidental transients. The purpose of this study is to modify the EDC test to describe PCMI, specimen volume reduction and others. Ring-shaped specimens were cut from Zry-4 cladding tubes. Cylindrical metal pellets with 8 mm in diameter and 15 mm in maximum height were used as inner pellets. Expansion of the specimens due to the inner pellet compression was performed at room temperature. The experimental data were further analyzed by finite element method. Through the survey in the variation of the specimen and core, specimen size and inner pellet geometry were optimized. Excellent reproducibility with less error was confirmed. The uniaxial tension condition in the hoop direction up to the specimen failure was confirmed. Hoop stress–hoop strain curves were successfully derived.     

Non-linear dynamics of a two phase flow system in an evaporator: The effects of (i) a time varying pressure drop (ii) an axially varying heat flux

In this paper we study the phenomena of density wave oscillations (DWO) in a vertical heated channel. The homogeneous equilibrium model is used to simulate the flow in the two-phase region. The equations are solved numerically using a ‘shooting-method' technique. This in its turn employs an implicit backward finite difference scheme. The scheme can incorporate the movement of the interface. It is very elegant and does not involve storage of variables in large N×N matrices. This scheme is sufficiently general and can be used to simulate the dynamic behaviour when: (i) the heat flux imposed at the surface is non-constant, i.e. exhibits an axial variation; and (ii) the imposed pressure drop is varied periodically at a fixed frequency. A possible explanation for the conflicting reports of the effect of a periodic variation in heat flux is provided using a linear stability analysis and the D-partition method. The interaction of the natural frequency of the DWO and the fixed forcing frequency of the imposed pressure drop gives rise to various phenomena viz relaxation oscillations, sub-harmonic oscillations, quasi-periodic and chaotic solutions. To aid the experimentalist describe this infinite-dimensional system on the basis of his experimental results we discuss the characterisation using only the velocity time series data. This is done employing the method of delay coordinate embedding. The phase portraits, stroboscopic map and correlation dimension of the actual attractor are compared with that of the reconstructed attractor from the velocity time series.     

A study on selective precipitation ability of cyclic urea to U(VI) for developing reprocessing system based on precipitation method

We have proposed a new reprocessing system based on precipitation method. In order to find out precipitants with high selectivity to U(VI) and to investigate factors controlling precipitation ability to U(VI) and U(IV), properties of 3,4,5,6-tetrahydro-1,3-dimethyl-2(1H)-pyrimidinone (DMPU) as a precipitant have been examined by using U(VI), U(IV) as a simulant of Pu(IV), and simulated fission products (FPs). We have evaluated precipitation ratios (P.R.) for U(VI) and U(IV), solubility of U(VI) precipitates to 3.0 mol dm^?3 (M) HNO₃ solution, melting points (MPs) of U(VI) precipitates, log P (distribution ratio of a substance in 1-octanol/water biphasic system, a measure of hydrophobicity) of precipitants, and decontamination factors (DFs) of FPs. The properties of DMPU were compared with those in systems using N-n-butyl-2-pyrrolidone (NBP), N-cyclohexyl-2-pyrrolidone (NCP), and other pyrrolidone derivatives as the precipitant. The P.R. values of DMPU to U(VI) and U(IV) in 3.0 M HNO₃ solutions were around 99% at [DMPU]/[U(VI)] = 2.0 and 0% at [DMPU]/[U(IV)] = 5.0, respectively. In DMPU system, the DF values of the most of simulated FPs [Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Rh(III), La(III), Ce(III), Pr(III), Nd(III), and Sm(III)] used in the present study were found to be more than 100. Even in U(VI)–U(IV) coexisting system, the selectivity of DMPU to U(VI) was higher than those of NBP and NCP. This selective precipitation ability of DMPU to U(VI) was evaluated by the solubility of U(VI) precipitates on the basis of their MPs and the log P values of precipitants. As a result, it was found that the precipitants having low hydrophobicity and forming the U(VI) precipitates with high MPs have highly selective precipitation ability to U(VI).     

Simultaneous separation and recovery of Cs(I) and Sr(II) using a hybrid macrocyclic compounds loaded adsorbent. Kinetic,equilibrium and dynamic adsorption studies

In this study, simultaneous separation and recovery of Cs(I) and Sr(II) from nitric acid solution was investigated using a silica-based hybrid adsorbent. The adsorbent was prepared by successive impregnation and fixing of two supramolecular recognition agents namely, 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix[4]-arene(Calix[4]arene-R14) and 4',4' (5")-di(tert-butylcyclohexano)-18-crown-6, onto a silica-based polymer support(SiO₂-P). Uptake properties, characterization, equilibrium kinetics, and dynamic adsorption properties of Cs(I) and Sr(II) were then assessed. Distribution coefficients (K_d) higher than 10² cm³/g for Cs(I) and Sr(II) were obtained using 3 M HNO₃ at 298 K, and the K_d values decreased with increasing temperature. Adsorption kinetics and equilibrium studies fitted well with pseudo-second-order model and Redlich–Peterson isotherm model, respectively. The constant total organic carbon values in the aqueous phase were obtained after adding 10^?3 ～ 4 M HNO₃. Results of the dynamic adsorption/elution test indicated that Cs(I) and Sr(II) were efficiently and simultaneously captured and eluted even under a flow rate of 1.5 cm³/min.