Experimental qualification of subassembly design for Prototype Fast Breeder Reactor

The Prototype Fast Breeder Reactor (PFBR) which is under construction at Kalpakkam, India, is a 500 MWe sodium cooled pool type reactor. The core of the PFBR consists of 1758 free standing subassemblies supported on the grid plate. The entire core is divided into 15 different flow zones and the flow rate required through each zone is calculated based on the fission heat generation. The coolant sodium flows from the bottom of the subassembly to top and the design of the subassembly for each flow zone is quite complex. There are 181 fuel subassemblies in PFBR core with 217 fuel pins in each subassembly, vertically held in the form of bundle within a hexagonal wrapper tube. The pins are separated by spacer wires wound around the pins helically. Analytical prediction of subassembly pressure drop, vibration and determination of inception of cavitation for this complex geometry is very difficult. So experiments were conducted extensively to get a more accurate evaluation of the design and for its qualification for the use in PFBR, which is designed for 40 years of operation.Pressure drop and cavitation experiments were carried out in water on full scale (1:1) subassemblies of all flow zones. The overall pressure drop of the subassembly determines the ratings of the pump. Cavitation of the pressure drop devices lead to erosion damage of fuelpins and may also result in reactivity fluctuation due to sodium-void effect. So it is essential to confirm that the subassembly is not cavitating in the operating regime of the reactor. Subassembly can vibrate in cantilever mode due to the turbulence in the flow and can result in reactivity fluctuation, reactor control problem and can even lead to the failure of the fuel pins. So vibration measurements were carried out in water on the maximum rated subassembly. This paper discusses various experiments carried out on PFBR subassembly, the similarity criteria followed, instrumentation, results and conclusion.     

Steam condenser optimization using Real-parameter Genetic Algorithm for Prototype Fast Breeder Reactor

This work explores the use of Real-parameter Genetic Algorithm and analyses its performance in the steam condenser (or Circulating Water System) optimization study of a 500 MW fast breeder nuclear reactor. Choice of optimum design parameters for condenser for a power plant from among a large number of technically viable combination is a complex task. This is primarily due to the conflicting nature of the economic implications of the different system parameters for maximizing the capitalized profit. In order to find the optimum design parameters a Real-parameter Genetic Algorithm model is developed and applied. The results obtained are validated with the reference study results.     

我国的快堆技术发展和实验快堆

随着我国核电技术的发展,自主研制钠冷快中子增殖堆十分必要。本文介绍了我国在研究开发快堆技术方面的历史和实验快堆的设计原则、设计简介和安全特性。     

Dynamic model of Fast Breeder Test Reactor

Fast Breeder Test Reactor (FBTR) is a 40 M Wt/13.2 MWe sodium cooled reactor operating since 1985. It is a loop type reactor. As part of the safety analysis the response of the plant to various transients is needed. In this connection a computer code named DYNAM was developed to model the reactor core, the intermediate heat exchanger, steam generator, piping, etc. This paper deals with the mathematical model of the various components of FBTR, the numerical techniques to solve the model, and comparison of the predictions of the code with plant measurements. Also presented is the benign response of the plant to a station blackout condition, which brings out the role of the various reactivity feedback mechanisms combined with a gradual coast down of reactor sodium flow.     

Application of Gas-Cooled Reactor Technology to the Fast Breeder Concept

Presently discernible limitations to the extent of low-cost uranium resources provide an obvious incentive for seeking better utilization of fissile material, which may well become dominating by the end of the century. The high degree of world interest in breeder reactors, which could produce more fissile material than they consume, is thus very understandable, for the substantial conversion of fertile into fissile material thereby offered would greatly increase the effective energy yield of the mined fuel. However, the large-scale use of fast breeders which would be necessary for substantial impact on resource conservation would also require that these reactors be entirely acceptable also in other ways. Particularly they would have to compete with other routes to nuclear power in areas of capital cost, maintainability, and siting flexibility. Such considerations have stimulated the evolution of the gas-cooled fast breeder and the contemplation of combinations of fast breeders and advanced high temperature converter reactors aimed at taking best advantage of the special merits of each type. Predominant influences here are the enhanced importance of breeding ratio to the effectiveness of such a combination, the special worth of U233 as a thermal reactor fuel and the value of the high temperature capability, both directly and as a factor broadening the options available to power plant design.     

铅冷快堆固有安全性的分析

为了研究铅冷快堆的固有安全性。本文完成了25MW铅冷快堆物理和热工水力初步设计，并进行了铅的充排放实验和铅的自封性实验。在此基础上，依据核反应堆固有安全性的理论，详细地分析和比较了铅冷快堆所具有的固有安全性。分析结果表明，铅冷快堆是一种很有发展的先进核动力堆堆型。     

Neutronics and Core Design Studies on Fast Breeder Reactor

Briefly reviewed were recent R&D activities and achievements in Japan in the area of neutronics, core design and shielding studies on fast breeder reactor.     

Thermal hydraulics in the hot pool of Fast Breeder Test Reactor

Sodium cooled Fast Breeder Test Reactor (FBTR) of 40 MWt/13 MWe capacity is in operation at Kalpakkam, near Chennai. Presently it is operating with a core of 10.5 MWt. Knowledge of temperatures and flow pattern in the hot pool of FBTR is essential to assess the thermal stresses in the hot pool. While theoretical analysis of the hot pool has been conducted by a three-dimensional code to access the temperature profile, it involves tuning due to complex geometry, thermal stresses and vibration. With this in view, an experimental model was fabricated in 1/4 scale using acrylic material and tests were conducted in water. Initially hydraulic studies were conducted with ambient water maintaining Froude number similarity. After that thermal studies were conducted using hot and cold water maintaining Richardson similitude. In both cases Euler similarity was also maintained.     

池式快堆主容器地震响应分析

试图对池式快堆结构作较大简化,使计算简图既能反应堆结构的动力特性,又能使计算简便可行。从而把一个复杂的结构用一个简单的弹簧－质量体系来近似地等效代替。引入容器的变形假设和确定的液动压力假设,应用虚位移原理可获得体系在水平地震作用下的运动方程,而后考察其地震动响应。     

Postirradiation Annealing of Boron Carbide Pellet Irradiated in Fast Breeder Reactor

This paper reports some irradiation effects and recovery behavior of neutron irradiated boron carbide pellets that were used as control rod elements in the Enrico Fermi Fast Breeder Reactor. Measurements were carried out on changes in lattice parameters, thermal expansion, helium release, elastic moduli and microstructure observations by annealing the irradiated pellets at elevated temperatures. The increase in unit cell volume of B₄C upon irradiation was found to be 0.22%. The recovery in lattice parameter began at around 500°C and completed at 1,000°C. It was found that the pellet showed a sharp increase in a dimensional change at about 700 to 800°C with a large amount of helium release, and the pellet which showed larger swelling released smaller amount of helium.     

钠冷快中子增殖堆安全监管重要关注点探讨

钠冷快中子增殖堆(钠冷快堆)是一种最成熟、最具商业化前途的快堆堆型。但由于其材料、冷却剂安全性及经济竞争力等方面的原因,国内仍处于实验堆运行阶段。由于缺乏钠冷快堆安全监管方面的法规、标准、技术及经验,监管工作面临巨大挑战。本文将钠冷快堆与压水堆进行比较,并将钠冷快堆的特点与监管工作的特点相结合,从堆芯、系统及设备等方面提出15个监管重要关注点,并给出一系列相关建议。     

钠冷快堆钠池火事故数值模拟

为了估计和预测钠火事故的后果，构建了以“有火焰薄层”为理论基础的燃烧模型和热传输模型，给出了程序计算结果与试验值的比较。比较结果证实，该计算结果可信、模型合理。程序可用来分析和预测钠池火事故。     

可增殖快谱超临界水冷堆物理初步设计计算

建立改进型快谱超临界水冷堆(SCFR-M)堆芯模型,探讨点火区燃料棒直径和增殖区水棒直径对堆芯转换比的影响,得到合理的燃料组件设计形式。设计并计算6种不同堆芯布置的反应堆增殖特性和空泡反应性,并分析燃料中235U和239Pu成分对堆芯转换比和空泡系数的影响,提高了转换比;研究燃料成分对堆芯转换比的影响。结果表明:减小氢原子数与重金属原子数之比(H/HM),增加堆芯增殖燃料组件数目并采用合理布置可满足堆芯负空泡反应系数,且可以提高堆芯转换比;降低燃料中Pu同位素质量分数可以使堆芯转换比大幅增加,同时使堆芯的空泡反应性系数负值更大;当点火燃料组件采用Pu同位素质量分数为20.8%的MOX燃料,增殖燃料组件采用0.2%富集度235U的贫铀燃料,6号设计方案可以使堆芯的初始转换比达到1.03128,且空泡反应性系数为负,初步达到超临界水冷快堆的增殖要求。进一步对堆芯的缓发中子有效份额、能谱、中子注量率、功率分布进行计算,分析研究增殖堆芯的物理特性。     

日本文殊原型快堆堆芯出口腔室热分层现象数值模拟

本文利用商业CFD程序STAR-CCM+,采用合理的网格生成技术及物理模型,对日本文殊原型快堆堆芯出口腔室建立近似1∶1的模型,模拟分析40%额定功率停堆过程中堆芯出口腔室的瞬态工况,获得腔室内较为完整的热分层进程。结果表明：停堆2 min后腔室内出现稳定热分层现象;10～21 min时热分层通过上升桶桶顶位置;10～140 min热分层处于上升筒顶端位置附近期间,腔室内流型不稳定;140 min后热分层完全处于上升桶顶,桶内流型稳定且接近于停堆前。模拟结果与实验数据对比表明,停堆初期4 min内两者符合较好,表明本文模拟方法适用于停堆工况堆芯出口腔室热分层进程模拟;之后模拟进程明显快于实验,分析其偏差主要来自模拟边界及结构与实际的差异。     

Evolution in the design and development of the in-service inspection device for the Indian 500 MWe Fast Breeder Reactor

In-service inspection (ISI) plays a major role in monitoring the condition of nuclear power plant structures and components. Based on the information gathered during inspection and the studies carried out, it is possible to assess the extent of damage and take corrective measures to keep effects of ageing under control. In nuclear power plants comprehensive ISI is dictated by issues of increased safety to personnel and equipment, and efficiently enhances the plant life. A special emphasis has been laid on the development of robotic devices for the ISI of the indigenous Indian 500 MWe Prototype Fast Breeder Reactor (FBR) components. This paper traces the experiments and simulations in the key developments of a robotic device, for the ISI of main vessel and safety vessel of FBRs, carried out at Indira Gandhi Centre for Atomic Research, India.     

快堆堆芯水平抗震分析的单组件初步分析

快堆堆芯抗震分析是堆芯设计的重要组成部分，它将为堆芯在地震作用下的结构完整性评价和堆芯反应性变化分析提供必要的数据，同时为控制棒的可插入性评价提供参考。本文采用日本有限元程序FINAS，以中国实验快堆为例，对快堆堆芯水平抗震的计算方法和模型进行了研究，完成了单组件预分析，其中包括模态分析、自由振动分析和与刚性墙壁的碰撞分析，为堆芯多组件水平抗震分析作好了准备。     

Distribution of liquid sodium in the inlet plenum of steam generator in a Fast Breeder Reactor

Experimental and Computational Fluid Dynamics (CFD) investigations have been carried out on a 1/5th scale model of the inlet plenum of steam generator (SG) used in the Fast Breeder Reactor (FBR) technology. The distribution of liquid sodium in the inlet plenum of the steam generator strongly affects the thermal as well as mechanical performance of the steam generator. In the present work, flow distribution in a scaled down model has been investigated. Various strategies adopted for obtaining uniform flow distribution have been evaluated. Experiments have been conducted to measure the axial and radial velocity distributions using Ultrasonic Velocity Profiler (UVP) under a variety of geometries. Computational Fluid Dynamics (CFD) studies have been carried out for various geometries. On the basis of these experiments and CFD simulations, various flow distribution devices have been compared.     

Development of an ISI Robot for the Fast Breeder Reactor MONJU Primary Heat Transfer System Piping

This paper describes the development of a new inspection robot for the In-Service Inspection of the heat transfer system of the Fast Breeder Reactor MONJU. The inspection was carried out using a tire-type ultrasonic sensor for volumetric tests at high temperature (atmosphere, 55°C; piping surface, 80°C) and radiation exposure condition (dose rate, 10 mGy/h; piping surface dose rate, 15 mGy/h). An inspection robot using a new tire type for the ultrasonic testing sensor and a new control method was developed. A signal-to-noise ratio S/N over 2 was obtained during the functional test for a calibration defect with a depth of 50%t (from the tube wall thickness). In the automatic inspection test, an EDM slit with a depth of 9% from the pipe thickness was detectable and with an S/N ratio = 4.0 (12.0 dB).