Assembly homogenization techniques for light water reactor analysis

Recent progress in development and application of advanced assembly homogenization methods for light water reactor analysis is reviewed. Practical difficulties arising from conventional flux-weighting approximations are discussed and numerical examples given. The mathematical foundations for homogenization methods are outlined. Two methods, Equivalence Theory and Generalized Equivalence Theory which are theoretically capable of eliminating homogenization error are reviewed. Practical means of obtaining approximate homogenized parameters are presented and numerical examples are used to contrast the two methods.

Applications of these techniques to PWR baffle/reflector homogenization and BWR bundle homogenization are discussed. Nodal solutions to realistic reactor problems are compared to fine-mesh PDQ calculations, and the accuracy of the advanced homogenization methods is established. Remaining problem areas are investigated, and directions for future research are suggested.     

Basic principles and proposals for rehabilitation of radioactively contaminated objects and grounds of the kirovo-chepetsk chemical works

The results of an examination of objects and grounds of the Kirovo-Chepetsk Chemical Works are presented. The methods used to perform a radiation survey are described briefly. The data obtained are used as a basis for a concept of rehabilitation of radioactively contaminated objects and grounds of the works. The radwaste volumes are determined for each object and possible ways to handle them are proposed. The technologies for handling radwastes are examined. The primary problems that must be solved without delay are determined.     

Salvaging the Lepse tender

The basic problems of salvaging the Lepse tender of the Murmansk Shipping Company are examined. The main sources of nuclear and radiation danger are determined, the characteristics of their structural features which prevent the appearance of a spontaneous reaction are given, the consequences of long-time storage of spent fuel assemblies are described, and different variants of their removal from storage are proposed. A computational validation of the required degree of subcriticality of the spent nculear fuel and an assessment of possible accidents, including accidents accompanying sinking of the vessel at its permanent base, are given. The salvaging steps are described, the bottlenecks are determined, schemes for handling the vessel are validated, and the radiation load on the workers is estimated. __________ Translated from Atomnaya énergiya, Vol. 101, No. 1, pp. 65–69, July, 2006.     

The pumping performances of the turbomoleculae pump simulated by direct simulation monte carlo method

Turbomolecular pumps (TMPs) are used extensively in several highly important areas of industry and research. The performances of TMP are evaluated by maximum throughput and maximum pressure ratio. In this paper, they are investigated by DSMC method. A 3D analysis in a rotating reference frame is proposed to simulate this flow field. Considering the Coriolis and centrifugal accelerations, the equations about the molecular velocities and position are deduced. The VSS model and NTC collision schemes are used to calculate the intermolecular collisions. The diffuse reflection is employed on the molecular reflection from the surfaces of boundary. The procedures for establishment of the correct collision rate are based on the cells, while individual collision pairs are chosen from the sub-cells. The pump performances of one stage TMP under the different kinds of gas, different heights, and different blade angles are simulated and the results are analyzed. Numerical results agree well with the existing experiment data.     

高能P-P对撞中的μ子探测——模拟探测

对一种适用于未来高能P-P对撞机上的探测器模型和质心能在16和40TeV的P-P对撞事例中进行了模拟。并把模拟的物理事例引进了模拟的探测器。 本文重点叙述了如何把物理事例和探测器衔接起来,如何利用该模拟系统“探测”粒子和测量它们的物理量。特别是对μ子的探测和测量。     

The Space Radiation Environment

The particle space radiation environment is reviewed and some of the latest models for the various phenomena are presented. The properties of the solar wind and interplanetary magnetic fields based on recent satellite measurements are given and solar proton events are discussed. The magnetospheric cavity and the character of the boundary between it and the solar wind based on Imp 1 results are shown. Flux maps and energy spectra for the inner and outer radiation zones are given and examples of temporal variations are shown.     

氢气还原金属氧化物

叙述的氢气还原金属氧化物的过程,装置和工艺过程,研究了若干种氧化物的还原温度和还原时间对还原效率的影响,采用特殊的滚轧技术,将还原的金属制备成较薄的靶膜。     

北京G120型Q3D磁谱仪焦面探测器系统

根据HI－13串列加速器及Q3D磁谱仪的特点和物理研究课题的要求，提出了与谱仪配用的焦面探测器的重要技术性能的要求。对磁谱仪和焦面探测器的联合系统的离子鉴别方法予以较详细的讨论。提出了模型设计的参数，并估算了各种可能的贡献及最后可获得的性能及修正方法。最后给出了运行中的轻、重离子探测器的性能的实验结果。     

Software Strategies and Hardware Upgrades to the PPL Data Acquisition System (DAS)

This paper describes upgrades to the Data Acquisition System for the Experimental Projects Department at PPPL, especially in support of the PBX-M upgrade to be completed this year. Hardware and software maintenance problems with the old configuration, consisting of a DEC KL-10 and eight PDP-11's, are described. The real-time software and hardware performance requirements and projections for CAMAC I/O and data analysis and display are presented. Described are three applications that have realtime requirements and are located on separate processors, connected to PPPL's VAX Cluster by an Ethernet link. Building upon a previous large software base, general-purpose subroutine libraries and utilities are being emphasized. The most useful of these are described. The use of software packages from DEC, third-party vendors, and the fusion community, is also described. The new approaches to software development that are being incorporated into the DAS efforts are discussed. Specific future challenges are also described.     

Calculation of equivalent static loads and its application

All the forces in the real world act dynamically on structures. Since dynamic loads are extremely difficult to handle in analysis and design, static loads are usually utilized with dynamic factors. Generally, the dynamic factors are determined from design codes or experience. Therefore, static loads may not give accurate solutions in analysis and design and structural engineers often come up with unreliable solutions. Two different methods are proposed for the transformation of dynamic loads into equivalent static loads (ESLs). One is an analytical method for exact ESLs and the other is an approximation method. The exact ESLs are calculated to generate identical response fields such as displacement and stress with those from dynamic loads at a certain time. Some approximation methods are proposed in engineering applications, which generate similar response fields from dynamic loads. They are divided into the displacement-based approach and the stress-based approach. The process is derived and evaluated mathematically. Standard examples are selected and solved by the proposed method and error analyses are conducted. Applications of the method to structural optimization are discussed.     

Vapor Species over Na2O-B2O3-SiO2-Cs2O Glass

Methods for suppression and control of the axisymmetric vertical positional instability are described on the basis of conceptural design studies with the International Tokamak Reactor (INTOR). The shell effect is well known to be useful for suppression of the fast instability. Here shell structures are presented and their usefulness is assessed. Included in the assessments are required modellings of the plasma current for determination of mutual inductances between the plasma and the inductive components around it. Three kinds of models are described and their features are compared to the shell effect. Two kinds of simplified reactor structures are described and studied by comparing them with some control characteristics of the slow instability by a pair of control coils. Their structures are selected so as to result in different shell effects between them, and are consequently found to produce different capacities of power supply, too.     

Accident loads for a VVER-440/213 containment

Specific features of the VVER-440/213 containment are the subdivided rectangular building and the localization system including the bubbler trays and air traps. Accident loads are calculated for a large break loss of coolant accident (LBLOCA). The maximum pressure and temperature loads are calculated with different codes during the blowdown phase of the LBLOCA. The uncertainty margins of the maximum pressure are given in this case. Sensitivity studies are performed for different leakage rates and hydraulic data of the containment. The effects of the active and passive spray systems on the depressurization are presented in this paper. The maximum pressure loads are also examined in case of degraded conditions of the localization system.     

Nuclear data sheets for A = 138

Detailed level schemes and the experimental reaction and decay data on which they are based are presented for all the nuclei with mass number A = 138. The experimental data are evaluated; inconsistencies and discrepancies are noted; and adopted values for level and gamma-ray energies, gamma intensities, and other nuclear properties are given. All data received before December 1975 have been included.     

Design and analysis of multicavity prestressed concrete reactor vessels

A critical state-of-the-art review of multicavity prestressed concrete reactor vessel (PCRV) design and analysis practice is presented. Included are discussions of basic design concepts, the behavior of liners and penetrations, and the various tests required and/or employed to demonstrate acceptance of new vessel geometries and innovations. Brief reviews are given of the influences of design codes such as ACI/ASME Section III, Division 2, and BS4975; analysis methods including elastic, inelastic, and time-dependent techniques; the constituve equations that are essential to the satisfactory use of these techniques; and semi-empirical methods for calculating ultimate strengths of multicavity vessels.Tests conducted on liner plates, liner anchorage systems, and cooling tubes are reviewed together with the methods of analysis used in the design of anchorage systems. The adequacy and economy of present liner systems are considered and possible modifications in design are suggested.Design code requirements and methods of analysis for penetrations are discussed. The various types of closure designs that have been proposed and in some cases employed are evaluated on the basis of overall PCRV design philosophy. Several methods of prestressing PCRVs are considered with respect to relative advantages and disadvantages; existing overall vessel in-service inspection requirements are evaluated.     

Extended MHD Modelling with the Ten-Moment Equations

High-order moment fluid equations for simulation of plasmas are presented. The ten-moment equations are a two-fluid model in which time dependent equations are used to advance the pressure tensor. With the inclusion of the full pressure tensor Finite Larmor Radius (FLR) effects are captured. Further, Hall-effects are captured correctly by including the full electron momentum equation. Hall and FLR effects are important to understand stability of compact toroids like Field Reversed Configurations (FRCs) and also to detailed understanding of small scale instabilities in current carrying plasmas. The effects of collisions are discussed. Solutions to a Riemann problem for the ten-moment equations are presented. The ten-moment equations show complex dispersive solutions which come about from the source terms. The model is validated with the GEM fast magnetic reconnection challenge problem.     

Solution of the neutron diffusion equation in hexagonal geometries

Various ways to solve the neutron diffusion equation in hexagonal geometries are known in the literature. In this paper it is aimed to unify these approaches from different points of view. First conditions are developed for consistency and uniqueness of the various approximations; they are then used to derive estimates of the order of the corresponding rates of convergence. Then several approximations are formulated explicitly and related to the theoretical considerations, and their mutual dependencies are shown. Finally, numerical experiments are reported which support the theoretical findings.     

Application and development of the pulsed plasma thruster

The application and development of pulsed plasma thrusters(PPTs) in recent years are reviewed in this paper. The advantages of PPTs are discussed. The schematics, propulsion performance parameters and key physical processes of PPTs are described. Some representative PPT products and flight systems developed in recent years are presented to show the performance of the PPT.Studies about how electrode structures, discharge circuits, propellant materials, energy discharge method, propellant feed method, ignition method and number of thruster heads influence the PPT performance are presented and analyzed. The ignitor design method, ignition process and propellant carbonization are introduced to discuss the reliability and lifetime issues in PPTs. The modeling methods of the discharge circuit, as well as ablation, ionization and acceleration in PPTs are presented. Finally, the application of PPTs in the future is analyzed and some suggestions for PPT development are proposed.     

Moisture migration and drying properties of hardened cement paste and mortar

The moisture migration and drying properties of hardened cement paste and mortar are studied experimentally and analytically. Thin-wall cylindrical specimens with a thickness of about 1.0 mm are used to reduce hygral gradients. The specimens are loaded with different compressive stresses in the range 0–11 MPa. Two test series are perfirmed: loss of water (test 1) and migration of moisture through the thin wall of the specimens (test 2) are measured: Furthermore, the experimental results are analyzed as a non-linear diffusion process, by means of the finite element method. The effects of the compressive stress and aggregates are discussed, referring to the diffusion coeffients obtained.     

AFA3G定位格架条带技术研究

介绍了目前国外燃料组件高燃耗、长周期、低泄漏的发展方向;阐述了研制高燃耗燃料组件定位格架的必要性和可行性。提出了定位格架研究中的主要技术指标、研究方案和实施途径。明确了定位格架条带的研制内容和模具制造中的技术难点;给出了总体实施方案,并确定了研究目标及技术性能指标。最后对格架研制中的关键技术和实施方案及格架研制中的相关配套条件进行了分析。