基于光滑粒子与有限元耦合算法的放射性废液运输容器跌落分析

基于光滑粒子和有限元耦合算法,利用显式动力学分析软件LS-DYNA,对装载放射性废液的车载式废树脂接收装置在三种不同跌落方式下的跌落冲击过程进行了数值分析。以装置水平跌落为典型算例,对其在跌落过程中所受的动态激励、装置的压力变化和装置的应力状态进行了分析。结果表明,光滑粒子和有限元耦合算法对于解决装载放射性废液的运输容器在跌落冲击过程中流固耦合问题是有效的。同时,基于有限元分析结果,提出了一种按照RCC-M《压水堆核岛机械设备设计和建造规则》等规范对放射性物质运输容器跌落冲击过程进行应力强度评定的方法,并依据该方法对装置的结构强度进行了评定,结果显示装置在三种不同跌落方式下的应力强度均满足要求。     

Coupling of smooth particle hydrodynamics with the finite element method

A gridless technique called smooth particle hydrodynamics (SPH) has been coupled with the transient dynamics finite element code . In this paper, a new weighted residual derivation for the SPH method will be presented, and the methods used to embed SPH within will be outlined. Example SPH calculations will also be presented. One major difficulty associated with the Lagrangian finite element method is modeling materials with no shear strength; for example, gases, fluids and explosive biproducts. Typically, these materials can be modeled for only a short time with a Lagrangian finite element code. Large distortions cause tangling of the mesh, which will eventually lead to numerical difficulties, such as negative element area or “bow tie” elements. Remeshing will allow the problem to continue for a short while, but the large distortions can prevent a complete analysis. SPH is a gridless Lagrangian technique. Requiring no mesh, SPH has the potential to model material fracture, large shear flows and penetration. SPH computes the strain rate and the stress divergence based on the nearest neighbors of a particle, which are determined using an efficient particle-sorting technique. Embedding the SPH method within allows part of the problem to be modeled with quadrilateral finite elements, while other parts are modeled with the gridless SPH method. SPH elements are coupled to the quadrilateral elements through a contact-like algorithm.     

用多路望远镜探测器测量中子带电粒子核反应实验中的事例判选

介绍一个测量由中子引起的核反应的双微分截面实验的事例判选系统,由于反应截面非常小,而且本底相当大,为了最大程度地减少本底的影响,系统采用了二级硬件判选和一级软件判选。经过三级事例判选之后,可使本底计数降低４－５个数量级。     

Simulation of melt jet breakup experiments by JASMINE with an empirical correlation for melt particle size distribution

We modified JASMINE code, a fuel–coolant interaction simulation code developed at Japan Atomic Energy Agency (JAEA), to extend the applicability for ex-vessel melt coolability assessment. The modification included addition of a melt particle size distribution model based on an empirical correlation and a simple non-local radiation heat transfer model, improvement in the treatment of melt particle generation, and re-agglomeration of settled particles. The modified code was tested by simulating melt jet breakup experiments, namely selected cases of ALPHA/GPM series with alumina–zirconia mixture and steel melt by JAEA, and FARO experiments with urania–zirconia mixture by Joint Research Center Ispra. Simulation results showed that the code reproduces the experimental results well for the cases with a deep subcooled water pool where the melt breaks up completely. On the other hand, significant underestimation of heat removal from the melt and overestimation of agglomeration of settled melt was encountered for conditions with a shallow or saturation temperature water pool. The melt agglomeration behavior in the simulation was sensitive to model parameters on the agglomeration criterion and heat transfer depending on conditions.     

Interaction of imploding shock waves with expanding central plasma in spherical pinch experiments: Simulation analysis

In the spherical pinch scheme, the hot D-T plasma produced in the center of the high pressure spherical vessel is confined by means of imploding shock waves launched from the periphery of the vessel for a time sufficiently long to achieve break-even conditions for plasma fusion. Theoretical studies on spherical pinch made so far have been limited up to the conditions of substantial expansion of the central plasma and the well-defined time delay between the creation of central plasma and the launching of the peripheral shock which led to the conclusion that, in realistic situations of SP experiments, negative time delays should be adopted, i.e., the launching of the imploding shock wave should precede the formation of the central plasma. However, the interaction of converging shock wave with the central plasma causing an additional heating and compression of the central plasma favoring plasma fusion conditions was not taken into account. Starting from the hydrodynamic equations of the system, the proposed simulation code deals with the propagation of converging shock waves and its interaction with the expanding central plasma. Considering the above-mentioned interaction in a self-consistent manner, the temporal evolution of temperature of central plasma is studied. Some results of the numerical simulation on the dynamics of shock wave propagation are also compared with the predictions of point strong explosing theory.     

Dryout heat flux experiments with deep heterogeneous particle bed

A test facility has been constructed at Technical Research Centre of Finland (VTT) to simulate as accurately as possible the ex-vessel core particle bed in the conditions of Olkiluoto nuclear power plant. The STYX particle bed reproduces the anticipated depth of the bed and the size range of particles having irregular shape. The bed is immersed in water, creating top flooding conditions, and internally heated by an array of electrical resistance heating elements. Dryout tests have been successfully conducted at 0.1–0.7 MPa pressure for both uniformly mixed and stratified bed geometries. In all tests, including the stratified ones, the dry zone first formed near the bottom of the bed. The measured dryout heat fluxes increased with increasing pressure, from 232 kW/m² at near atmospheric pressure to 451 kW/m² at 0.7 MPa pressure. The data show some scatter even for the uniform bed. The tests with the stratified bed indicate a clear reduction of critical power due to the presence of a layer of small particles on top of the uniform bed. Comparison of data with various critical power (dryout heat flux) correlations for porous media shows that the most important parameter in the models is the effective particle diameter. Adiabatic debris bed flow resistance measurements were conducted to determine the most representative particle diameter. This diameter is close, but not equal, to the particle number-weighted average diameter of the bed material. With it, uniform bed data can be calculated to within an accuracy of 3–28% using Lipinski's 0-D model. In the stratified bed experiments, it appears that the top layer was partially fluidized, hence the measured critical power was significantly higher than calculated. Future experiments are being planned with denser top layer material to eliminate non-prototypic fluidization.     

Simulation of drop deposition process in annular mist flow using three-dimensional particle method

The three-dimensional moving particle semi-implicit (MPS) method is employed to simulate the deposition process of single droplet on the liquid film. The model accounts for the presence of inertial, gravitation, viscous and surface tension and is validated by comparison with experimental results. The parameters of liquid droplets and film are calculated by a one-dimensional mixture model in which correlations and methods on void fraction, entrainment fraction and droplet velocity and size distribution are employed. The simulation results are analyzed to study the effect of splash on the deposition and re-entrainment processes in annular-mist flow. It is found that splash plays an important role in the deposition and re-entrainment processes in high quality conditions of BWR.     

Extended table of angular-distribution coefficients for (gamma,particle) and (particle,gamma) reactions

Presented here is a tabulation of angular-distribution coefficients for photonuclear and radiative-capture reactions which extends the work of Carr and Baglin by listing cases involving M1 and E2 radiation not covered by the previous authors. In conjunction with the Carr and Baglin tabulation, the present work provides numerical values for reactions involving target and residual spins $\text{≤}\text{5}\text{2}$, positive-parity particles of spin, 0, $\text{1}\text{2}$, and 1, and radiation multipolarities through E2. Notation is identical to the earlier tabulation. Cross references are given.     

Surface channeling experiments on Pb(110)

Low energy ion scattering techniques at 2 keV with Ne⁴ are used to study the surface structure of Pb (110) around 400 K. Surface channeling reveals a phase transition at this temperature. Surface blocking shows that the surface phase transition is of the roughening type.     

强脉冲X射线辐照含间隙多层材料动力学效应的SPH模拟

脉冲X射线辐照材料时,会在材料中形成能量沉积并产生热击波。目前一般使用差分法对所形成的热击波进行数值模拟,但若考虑多层材料之间的间隙,差分法处理起来比较困难。本文使用SPH方法对脉冲X射线辐照含间隙多层材料进行了数值模拟。结果表明,各层材料之间的缝隙对热击波的强度具有一定的影响,而对表面气化反冲冲量没有影响。     

A computer method of particle identification

A particle identification method is presented, in which calculations of ΔE energy losses are stored in computer memory and compared with experimental event by event data.     

A two nuclide method for wear measurements with particle loss

A two nuclide method is proposed for tribological measurements with wear particle losses. The decisive advantage of this technique applied to the flow-through method is the following: the activity ratio of two nuclides generated by charged particle activation in a machine part under investigation is dependent only on the material depth from which the wear particles come and is independent of the particle mass. The complete collection of wear particles can be omitted with this method.     

Review of the experiments for energetic particle physics on HL-2A

This paper reviews the energetic particle(EP) experiments during electron cyclotron resonance heating(ECRH) and neutral beam injection in the HL-2 A tokamak.A number of important results are summarized,which relate to ITER physics,including the behavior of the multi-mode instability,the nonlinear interaction between wave–wave and wave–particles,the losses of EP induced by the instabilities,the effect of the EP instabilities on the thermal plasma confinement and the control of the EP instabilities by means of ECRH.Systematic experiments indicate that when the drive is great enough,the nonlinear effects and the multi-mode coexistence may play an important role,which affect the transport both of the EPs and the background plasma confinement,and these instabilities could be controlled.Some new phenomena about the EP induced instabilities discovered recently on the device,such as high frequency reversed shear Alfvén eigenmodes,Alfvénic ion temperature gradient modes,the geodesic acoustic mode induced by energetic electrons excited by interaction between tearing mode and beta induced Alfvén eigenmode and double e-fishbone in negative magnetic shear discharges etc,have also been presented in the paper.     

Optimization studies of fuel loading pattern for a typical Pressurized Water Reactor (PWR) using particle swarm method

A three dimensional multi-energy group computer model PRISHA, which solves the neutron diffusion equations using finite difference method is developed for Pressurized Water Reactor (PWR). This computer code can find an optimum loading of a group of fresh fuel assemblies along with fuel assemblies of different exposures. The successive line over relaxation (SLOR) method is used to solve neutron diffusion equations. After validation of this part of computer code against an IAEA – PWR benchmark problem with 177 fuel assemblies in the core, particle swarm optimization (PSO) method is incorporated in the code for finding the optimum fuel loading pattern. A typical PWR core with 157 fuel assemblies, where 289 fuel pins are arranged in 17 × 17 rectangular arrays in a fuel assembly, was analyzed using this computer model for two cycles using PSO method. Different numbers of particles and iterations were used in PSO method. The results are found to be not very sensitive to either the number of particles or the number of iterations used in PSO method for considered case. However, a number of experiments have to be performed to arrive at the best global fitness parameter. Reasonably low power peaking factors were obtained for both the cycles.     

Simulation and analysis of transient cooldown natural convection experiments

The characteristics of natural convection heat transfer during transient cooldown in 3-dimensional fluid layers and hemispherical cavity have been investigated by means of a finite-difference numerical method. It was found that the turbulent structure and heat transfer characteristics of the unstably-stratified upper wall region are similar for internal heating (IH) case and transient cooldown (TCD) case, except near the cooled bottom wall of fluid layer, and for a small region (φ≤15°) near the bottom of the hemispherical cavity. For most of the surface area of the hemispherical cavity, there is excellent agreement between the heat fluxes calculated for the IH and the TCD cases. Calculations also showed that pseudosteady-state natural convection (PSSNC) is a better model for simulation of volumetric energy sources.     

The FeSe2(cr) solubility determined by solubility experiments of Se co-existing with Fe

To determine the equilibrium constant for ferroselite (FeSe₂(cr)) dissolution reaction, FeSe₂(cr) solubility experiments were performed at 298 ± 1 K from both the over- and under-saturation directions with Fe–Se precipitates that were aged at 348 K. X-ray diffraction (XRD) analysis detected only FeSe₂(cr) as the Se solid phase in the equilibrated precipitates. The E_h values of the equilibrated suspensions ranged from ?188.6 to ?4.9 mV vs. standard hydrogen electrode (SHE) and the pH values ranged from 6.00 to 8.76. Based on the available thermodynamic data, Se₄^2? and Fe²⁺ are thermodynamically stable within this E_h–pH range. Agreement between the solubility data obtained from the over- and under-saturation directions lends credence to the attainment of equilibrium at 298 ± 1 K. The thermodynamic interpretations using the specific ion interaction theory (SIT) model showed that E_h values and the concentrations of Se and Fe are well represented by the 2FeSe₂(cr) solubility reaction (2FeSe₂(cr) ? 2Fe²⁺ + Se₄^2? + 2e^?) with log₁₀K^○ = ?17.09 ± 0.28. The obtained log₁₀K^○ value falls within the uncertainty limits of the log₁₀K^○ value calculated from the available thermodynamic data.     

Radiometric method of determining tritium activity in experiments

Moscow Physics Research Institute. Translated from Atomnaya Énergiya, Vol. 70, No. 6, pp. 394–396, June, 1991.     

粒子物理实验中的精密时间间隔测量

本文是关于粒子物理实验中精密时间间隔测量的电子学方法和技术的一个综述.描述了精密时间间隔测量在粒子物理实验中的作用,以及粒子物理实验对时间间隔测量系统的性能指标需求.讨论了时间间隔测量的基本电子学手段,并着重分析了时间内插技术的分类和实现方法.