Study of rationalized safety design based on the seismic PSA for an LMFBR

Seismic PSA was carried out for a typical liquid metal cooled fast breeder reactor (LMFBR) in order to study the rationalized seismic design, maintaining and/or improving safety during seismic event. The seismic sequence quantification identifies the dominant structures, systems and components (SSCs) to the seismic core damage frequency (CDF). The sensitivity analyses by reducing or increasing the seismic capacity for SSCs are used to examine the optimized seismic design in view of safety and economical aspects. The LMFBR-specific risk-significant SSCs are reactor coolant boundary, decay heat removal coolant path and reactor control rod, which are different from those of light water reactors (LWRs). The electrical power supply system has a minor contribution to the seismic CDF. The sensitivity study shows that passive safety features of LMFBRs are important to maintain and/or enhance seismic capacity. The passive safety includes the decay heat removal capability via natural circulation and safety measures without depending on the support systems such as alternating current (AC) electrical power, for example. On the course of seismic sequence quantification, a methodology to evaluate the probability of seismic-induced multiple failure has been developed and applied to the decay heat removal function. The results suggest the multiplicity of the triply redundant system is to be considered for the significant components such as the decay heat removal path when one considers the difference in the seismic response.     

Statistical aspects of best estimate method—I

In former years, thermal hydraulics phenomena have been analyzed mostly by means of conservative models. Recently there is a tendency to revert to best estimate safety analysis of thermal hydraulics phenomena in a nuclear power plant. In a best estimate analysis we have to know the uncertainty of the estimated values. We investigate two aspects of the error analysis. Firstly, we define a black box model of the thermal hydraulic calculation and derive the precise number of sample calculations needed for a given tolerance level even for several statistically dependent output variables. Then we point out possible chaotic behavior of calculation along with suggesting methods for recognizing the appearance of chaos.     

Dynamic analysis of a bistable actuator for digital hydraulics

A fast and small electromagnetic actuator, which requires a small amount of work to switch between two stable positions, for the use in digital hydraulics, is presented. A dynamic study of the bistable actuator as part of a new kind of hydraulic on/off valve is carried out. A prototype is built and measured to verify the analysis. The results show that with careful elaboration the design is feasible. Furthermore, the response times depend on driving frequencies and an optimal current density for minimal energy consumption in cyclic action can be found. A single on/off valve is a critical part of a digital hydraulic system.     

Inherent safety concepts in nuclear power reactors

Different inherent safety concepts being considered in fast and thermal reactors are presented after outlining the basic goals of nuclear reactor safety, the ‘defence in depth’ philosophy to achieve these goals and the characteristics affecting the safety of liquid metal fast breeder and light water reactors. The inherent safety potential of fast reactors with respect to different sizes and types of fuel is also discussed. Finally, the approach proposed for the Indian Prototype Fast Breeder Reactor (Pfbr), which is in the detailed design stage, is also presented.     

SCWR for Future LargeScale Nuclear Power Generation

The ambitious nuclear power program motivates the Chinese nuclear community to develop advanced reactor concepts of generation IV, in order to ensure the longterm, stable and sustainable development of nuclear power. The supercritical watercooled reactor (SCWR) has favorable features in economics, sustainability and technology availability. It is the logical extension of the existing PWR technology and has very promising perspectives in largescale power generation in China. This paper describes the main features of SCWR. New designs of SCWR core structure and fuel assemblies are proposed. Preliminary analysis using a coupled neutronphysics/thermalhydraulics method is carried out and shows a good feasibility of the new design proposal.     

卫生型离心泵水力性能的参数化研究

为给卫生型离心泵过流部件结构的优化设计提供依据,采用CFD分析软件Fluent对卫生型离心泵内部流场流动进行了数值模拟和水力性能的参数化分析.给出了建模和流场分析方法,分析了泵内流体速度和压力的分布特性,基于流动模拟结果预测了水力性能.性能预测结果与试验结果吻合较好.关键结构参数对水力性能影响的计算结果表明,叶轮轴向间隙、叶片宽度、叶轮与蜗壳直径比等参数均存在最优值.研究结果对卫生型离心泵的结构改进和性能提高具有参考价值.     

Flow boiling in microgravity condition investigation using inverse techniques

The objective is to provide a method to obtain local heat transfer coefficients in small channels when flow boiling occurs. The experimental device has been developed to perform investigations in parabolic flights campaigns on board A300-ZéroG. Simultaneously flow visualization and thermo-hydraulic measurements are carried out to investigate the two phase flow and heat transfer in minichannels. The experiments are conducted with HFE-7100 in several operating conditions for three hydraulic diameters. The investigations concern flow pattern and the associated heat transfer coefficient during convective for several gravity levels. We mainly on the thermal measurements which consists in inversing experimental temperature measurements (thermocouples) to derive the local surface temperature and heat flux. For the investigated operating conditions, the heat transfer coefficient is found to vary along the flow axis especially at the channel entrance zone.     

Thermal-hydraulic CFD study in louvered fin-and-flat-tube heat exchangers

Heat transfer performance prediction by CFD codes is of major interest. Usually air-side heat transfer characteristics of fin-and-tube heat exchangers are determined from limited experimental data. The ability of CFD code to predict flow patterns and thermal fields allows determining the heat transfer characteristics by performing ‘numerical experiments’. CFD calculations of a 1-row automotive condenser are compared to experimental results and correlations of the literature matching the fin design and the flow conditions. Calculations are performed for different air frontal velocities. 2D models, with uniformly constant fin temperature overestimate significantly the heat transfer coefficient. 3D models, taking into account tube effects, conjugate heat transfer and conduction through the fin are in better agreement with the experimental results. However, even if an offset in noticed between CFD calculations and the experimental results, the trends are comparable and CFD study permits to reach local information, leading to better understanding of the physical phenomena involved in compact heat exchangers. An attempt for 2D unsteady flow has also been performed. Results are discussed in terms of flow pattern and heat transfer coefficient behaviour.     

Equation of state of refractory materials at very high temperatures—theoretical and experimental studies

This paper describes some of the theoretical and experimental studies being carried out at IGCAR on the equation of state of refractory materials like reactor fuels at high temperatures (>3000 K). The equation of state is primarily calculated by the principle of corresponding states. The influence of these equations of state on energy release in a hypothetical core disruptive accident in a fast breeder reactor is indicated. Details of an experimental facility based on laser induced vapourization mass spectrometry, which is being developed to measure the vapour pressures of materials at high temperatures is presented. Possible applications of this facility in other fields of materials research are indicated.     

Multifunctional design of prismatic cellular materials

Low density, prismatic cellular materials have a combination of properties that make them suitable for multifunctional or multi-physics applications such as ultralight load-bearing combined with energy absorption and heat transfer. In this work, non-uniform, graded cellular materials are designed to achieve superior thermal and structural performance. A general multifunctional design approach is presented that integrates multiobjective decision-making with multi-physics analysis tools of structural and heat transfer performance. Approximate analysis models for heat transfer and elastic stiffness are utilized to analyze designs efficiently. Search/solution algorithms are used to solve multiobjective decisions by interfacing with customized and commercial software. During the design process, cell topology is assumed to be rectangular, but aspect ratios and dimensions of cells and cell walls are varied. Two design scenarios are considered – maximum convective heat transfer and in-plane elastic stiffness in the first case and maximum convective heat transfer and elastic buckling strength in the second case. A portfolio of heat exchanger designs is generated with both periodic and functionally graded cells. Both single- and multi-objective performance are considered, and trade-offs are assessed between thermal and structural performance. Generalization of this approach is discussed for broader materials design applications in which material structures and processing paths are designed to achieve targeted properties and performance characteristics within a larger overall systems design process, and process-structure-property-performance relations are manifested on a hierarchy of length and time scales.     

Hardening neutron spectrum for advanced actinide transmutation experiments in the ATR

The most effective method for transmuting long-lived isotopes contained in spent nuclear fuel into shorter-lived fission products is in a fast neutron spectrum reactor. In the absence of a fast test reactor in the United States, initial irradiation testing of candidate fuels can be performed in a thermal test reactor that has been modified to produce a test region with a hardened neutron spectrum. Such a test facility, with a spectrum similar but somewhat softer than that of the liquid-metal fast breeder reactor (LMFBR), has been constructed in the INEEL's Advanced Test Reactor (ATR). The radial fission power distribution of the actinide fuel pin, which is an important parameter in fission gas release modelling, needs to be accurately predicted and the hardened neutron spectrum in the ATR and the LMFBR fast neutron spectrum is compared. The comparison analyses in this study are performed using MCWO, a well-developed tool that couples the Monte Carlo transport code MCNP with the isotope depletion and build-up code ORIGEN-2. MCWO analysis yields time-dependent and neutron-spectrum-dependent minor actinide and Pu concentrations and detailed radial fission power profile calculations for a typical fast reactor (LMFBR) neutron spectrum and the hardened neutron spectrum test region in the ATR. The MCWO-calculated results indicate that the cadmium basket used in the advanced fuel test assembly in the ATR can effectively depress the linear heat generation rate in the experimental fuels and harden the neutron spectrum in the test region.     

Numerical study on effect of CuO-water nanofluid on cooling performance of two different cross-sectional heat sinks

In this paper, effect of CuO nanoparticles in distilled water on heat dissipation from electronic components is investigated numerically. Computational Fluid Dynamics (CFD) simulations are carried out to study the rectangular and circular cross-sectional shaped heat sinks, and influence of their sectional geometry on the flow and heat transfer characteristics. The three-dimensional governing equations for fluid flow and heat transfer are solved using finite volume method. The two-phase and single-phase models are used to simulate the nanofluid flow. Comparisons of the numerical results with corresponding experimental data show that the two-phase model is more accurate than the single-phase model. Also, effect of various nanoparticle volume fraction on thermal and hydrodynamic characteristics of the heat sink are discussed in details for two different geometry of channel. The results show that the heat sink with nanofluid has better heat transfer rate in comparison with the water-cooled heat sink. A comparison between rectangular and circular channels at the same Reynolds number and cross section area shows that the heat sink with rectangular channels has lower thermal resistance.     

CFD技术在板翅式换热器设计开发中的应用

介绍CFD软件的应用领域及特点,阐述CFD技术在板翅式换热器设计中进行数值模拟的理论基础、传热与流动分析,指出CFD技术在板翅式换热器设计开发中的研究发展状况。同时,总结了对流体流动进行CFD技术数值模拟的一般步骤,并提出了CFD技术在板翅式换热器优化设计及开发方面的前景与方向。     

Failure Analysis of Motorized Bellow-Sealed Valve of Sodium Loop in Fast Breeder Test Reactor

Journal of Failure Analysis and Prevention - A motorized bellow-sealed valve in the steam generator leak detection circuit of fast breeder test reactor developed sodium leak while carrying out...     

MODELING OF PURE AND IN SITU DOPED POLYCRYSTALLINE SILICON DEPOSITION UN LPCVD REACTORS

A global mathematical model of Low Pressure Chemical Vapor Deposition (LPCVD) reactors has been developed. The use of the model can be of practical interest for both the choice of operating conditions and reactor design. Calculations of the wafer temperature have been carried out providing better insights in the radiation heat transfer phenomena, occurring inside the reactor. The presence of injectors, often used in the industrial practice, has also been taken into account. This model turned out to be successful for predicting growth rates of pure and in situ boron doped polycrystalline silicon. The case of in situ phosphorus doped poly-Si, involving complex homogeneous chemistry and a consequent radial nonuniformity, needs a more appropriate local approach, which is briefly discussed.     

Numerical analysis of grid plate melting after a severe accident in a Fast-Breeder Reactor (FBR)

Fast breeder reactors (FBRs) are provided with redundant and diverse plant protection systems with a very low failure probability (<?10^???6/reactor year), making core disruptive accident (CDA), a beyond design basis event (BDBE). Nevertheless, safety analysis is carried out even for such events with a view to mitigate their consequences by providing engineered safeguards like the in-vessel core catcher. During a CDA, a significant fraction of the hot molten fuel moves downwards and gets relocated to the lower plate of grid plate. The ability of this plate to resist or delay relocation of core melt further has been investigated by developing appropriate mathematical models and translating them into a computer code HEATRAN-1. The core melt is a time dependent volumetric heat source because of the radioactive decay of the fission products which it contains. The code solves the nonlinear heat conduction equation including phase change. The analysis reveals that if the bottom of grid plate is considered to be adiabatic, melt-through of grid plate (i.e., melting of the entire thickness of the plate) occurs between 800 s and 1000 s depending upon the initial conditions. Knowledge of this time estimate is essential for defining the initial thermal load on the core catcher plate. If heat transfer from the bottom of grid plate to the underlying sodium is taken into account, then melt-through does not take place, but the temperature of grid plate is high enough to cause creep failure.     

Coatings for fast breeder reactor components

Several types of metallurgical coatings are used in the unique environments of the fast breeder reactor. Most of the coatings have been developed for tribological applications, but some also serve as corrosion barriers, diffusion barriers or radionuclide traps.The tribological coatings must meet a variety of performance criteria for friction coefficients, wear rates, galling resistance and self-welding resistance in liquid sodium. In addition, most applications require the coating to exhibit long-term resistance to sodium corrosion, resistance to damage by thermal cycling at temperatures up to 625°C and, for core applications, resistance to irradiation damage to neutron fluences of 6 × 10²² neutrons cm^-2 or more.The materials that have consistently given the best performance as tribological coatings in the breeder reactor environments have been coatings based on chromium carbide, nickel aluminide or Tribaloy 700 (trademark of Cabot Corporation) (a nickel-base hardfacing alloy). Other coatings that have been qualified for limited applications include chromium plating for low temperature galling protection and nickel plating for radionuclide trapping.Processes now employed include detonation gun coating, diffusion coating, electrospark deposition coating and electroplating. Several plasma spray processes, sputtering and chemical vapor depositions have been candidates for use on some reactor components, but did not pass the required qualification tests or were not economically competitive with alternative coating methods.     

Development of process for aluminising nickel alloy 718 strips for tube bundle support structures in liquid sodium–water steam generators

Abstract

The tubes in liquid sodium–water steam generators of the Indian prototype fast breeder reactor (PFBR) will be supported by corrugated nickel alloy 718 strips. Aluminisation of nickel alloy 718 strips has been chosen for this application because of the excellent performance of aluminide coatings in reducing impact fretting wear of the tubes due to flow induced vibrations and compatibility of the coating with liquid sodium at the operating temperature of the steam generators. Aluminisation of nickel alloy 718 strips for steam generator tube bundle support structures has been developed using a procedure involving thermal spraying of aluminium followed by diffusion heat treatment in vacuum atmosphere. One of the advantages of the technique is that it will coat only the desired surfaces of the strips, whereas in conventional pack cementation process, significant precautions have to be ensured. Furthermore, this process has enabled aluminisation to be carried out at a much lower cost than the conventional process of pack aluminising. The problems encountered during the initial trials and technology development, such as coating thickness and distortion, are discussed. A process flow chart for this procedure to take the job on an industrial scale is also reported. This process (under patenting) has been adopted for the aluminisation of corrugated strips for the support structures of one steam generator module and the steam generator for a test facility during the technology development phase, as also of all the steam generators being fabricated for the PFBR.     

150MD24Z7.5高速电主轴多场耦合模型与动态性能预测

电主轴是机电一体化产品,充分考虑并预测其动态特性是机床主轴系统优化设计的前提。本文基于电主轴内部磁场、电场、温度场、结构场间的耦合关系,建立了150MD24Z7.5高速电主轴多场耦合有限元模型,通过电主轴电机电磁损耗及轴承摩擦生热计算,仿真电主轴温度场及结构场变化,讨论电主轴热态特性与振动特性之间耦合关系,分析电主轴温升热膨胀后气隙变化对振动特性的影响并通过实验加以验证。研究结果表明,电主轴温升形变对振动幅值影响较大,其中由气隙变化引起的电磁力幅值增加12.1%。利用该多场耦合模型可预测电主轴振动幅值,预测误差为10.2%。     

Mixed plutonium-uranium carbide fuel in fast breeder test reactor

This paper describes the development of the indigenous plutonium-uranium mixed carbide nuclear fuel for the fast breeder test reactor. The fuel has performed satisfactorily and produced, for the first time in our country, nuclear electricity from a fast reactor. The experience and knowledge gained in the fuel development has provided great confidence for undertaking a programme on utilization of fast reactor technology for power production.