Simulation of the VVER-1000 pump start-up experiment of the OECD V1000CT benchmark with CATHARE and TRAC-PF1

In the framework of joint effort between the Nuclear Energy Agency (NEA) of OECD, the United States Department of Energy (US DOE), and the Commissariat a l'Energie Atomique (CEA), France a coupled three-dimensional (3D) thermal-hydraulics/neutron kinetics benchmark for VVER-1000 was defined. The benchmark consists of calculation of a pump start-up experiment labelled V1000CT-1 (Phase 1), as well as a vessel mixing experiment and main steam line break (MSLB) transient labelled V1000CT-2 (Phase 2), respectively. The reference nuclear plant is Kozloduy-6 in Bulgaria. The overall objective is to assess computer codes used in the analysis of VVER-1000 reactivity transients. A specific objective is to assess the vessel mixing models used in system codes. Plant data are available for code validation consisting of one experiment of pump start-up (V1000CT-1) and one experiment of steam generator isolation (V1000CT-2). The validated codes can be used to calculate asymmetric MSLB transients involving similar mixing patterns. This paper summarizes a comparison of CATHARE and TRAC-PF1 system code results for V1000CT-1, Exercise 1, which is a full plant point kinetics simulation of a reactor coolant system (RCS) pump start-up experiment. The reference plant data include integral and sector average parameters. The comparison is made from the point of view of vessel mixing and full system simulation. CATHARE used a six-sector multiple 1D vessel thermal-hydraulic model with cross flows and TRAC used a six-sector, 18-channel coarse-mesh 3D vessel model. Good agreement in terms of integral parameters and inter-loop mixing is observed.     

Improvement of a Direct Method for Outer Solution of Linear Parametric Systems

Recently, a direct method for outer solution of linear parametric systems has been suggested for the general case where the elements of the system are nonlinear functions of independent interval parameters. In this paper, an improvement of the method is introduced which may lead to a narrower outer solution.     

A New Method for Global Solution of Systems of Non-Linear Equations

In this paper the problem of finding the set of all real solutions to a system of n non-linear equations contained in a given n-dimensional box (the global solution problem) is considered. A new method for solving the global solution problem is suggested. It is based on a transformation of the original system into a larger system of separable form. The global solution of the latter system is then found in a most efficient manner by a new interval method which exploits the separabily property. Numerical examples illustrating the efficiency of the method suggested are provided.     

Multigrid methods with space–time concurrency

Computing and Visualization in Science - We consider the comparison of multigrid methods for parabolic partial differential equations that allow space–time concurrency. With current trends in...     

Magnetic Properties of Nanosized Ba2Mg2Fe12O22 Powders Obtained by Auto-combustion

We studied the magnetic properties of nanosized Ba₂Mg₂Fe₁₂O₂₂ powder obtained by citrate auto-combustion synthesis. The powder consists of agglomerates with mean crystallite size of 100?nm. The magnetic properties of the powder were investigated at 4.2?K and at room temperature. The values measured of the magnetization M at a magnetic field of 60?kOe are 22.78?emu/g and 30.47?emu/g at room temperature and 4.2?K, respectively. The magnetic phase transition at 183 K is related to the ferromagnetic-to-spiral spin order and is a precondition for this material??s exhibiting multiferroic properties.     

Determining the Positive Definiteness Margin of Interval Matrices

A method for determining the positive definiteness margin of interval matrices is suggested. It is based on the use of outer interval bounds on the solution set of an interval eigenvalue problem. Three algorithms of the method are developed. It is shown that their numerical complexity is polynomial. Numerical examples illustrating the applicability of the method suggested are provided.     

Über die optimale Form von Füllkörpern für Kolonnen

Optimum Shape of Packings for Columns Packings, dumped and orderly arranged as well, are applied in an increasing amount for mass transfer processes for waste water and off gas purification in the field of technological environmental protection. The choice of suitable column internals is an important prerequisite for optimum operation of those plants. Based on the performance characteristics of modern packing internals the criteria will be discussed, which are decisive for optimum column choice.     

Computerized investigation of robust measurement systems

This paper deals with the development of software for investigating the robust properties of measurement systems and for their design and tuning in order to improve their robustness. The software constitutes Simulink models and m-files as extensions of the libraries of MATLAB. The investigations on continuous measurement systems (a self-balancing system) and discrete systems (ADCs) with improved robustness by using the internal model controller technique revealed new properties-fast dynamics, high accuracy, and discretization error reduction via multiple measurements     

Packing with Stamped Horizontal Lamellas Operating at Extremely Low Liquid Loads I. Hydrodynamics of a Single Plate

In the case of equilibrium absorption with low initial concentrations of very soluble absorbed gas, it can be seen from the material balance of the packed columns that the liquid superficial velocity must be very low to carry out the process in a counter current manner. Preceding investigations have shown that a packing made of separate short horizontal lamellas of very wettable sintered PVC is especially effective for mass transfer under these conditions. The construction of the packing of single lamellas is a difficult and expensive task. The aim of the present work is to investigate a new type of packing composed of many lamellas stamped in sheets of sintered PVC. The construction of the new more easily generated packing is described. It is shown that the irrigated packing is almost fully covered with a moving liquid film at extremely low liquid flow rates, ensuring very high radial spreading and uniform distribution of the liquid phase.     

An interval method for finding all operating points of non-linear resistive circuits

A new method for finding the set of all d.c. operating points of non-linear electronic circuits is suggested. it is applicable in the case where the circuit equations are written in the hybrid-representation form. In the general case, the non-linear elements involved may be described by non-monotone continuous characteristics. The method suggested is based on interval analysis techniques. Unlike other non-interval methods, this approach guarantees that all operating points will be found within prescribed accuracy in a finite number of steps. The computational efficiency of the present method is illustrated by a numerical example.