[en] The Computational Fluid Dynamics (CFD) code FLUBOX is developed at GRS for the multidimensional simulation of two-phase flows. The single-pressure two-fluid model is used as basis of the simulation. A basic mathematical property of the two-fluid model of FLUBOX is the hyperbolic character of the convection. The numerical solution methods of FLUBOX make explicit use of the hyperbolic structure of the coefficient matrices. The simulation of two-phase flow phenomena needs, apart from the conservation equations for each phase, an additional transport equation for the interfacial area concentration. The concentration of the interfacial area is one of the key parameters for the modelling of interfacial friction forces and interfacial transfer terms. A new transport equation for the interfacial area concentration is in development. It describes the dynamic change of the interfacial area concentration due to mass exchange and a force balance at the phase boundary. Results from FLUBOX calculations for different experiments of two-phase flows in vertical tubes are presented as part of the validation. (authors)

[en] Experimental evidence indicates a polygenic control of mutagenesis in Drosophila melanogaster. In oocytes chromosome aberrations detected as half-translocations or dominant lethals depend on a repair system which in a number of genetically nonrelated strains shows different repair capacities. Sister chromatid exchanges are easily studied as ring chromosome losses. They develop through a genotype controlled mechanism from, premutational lesions. Stocks with particular pairs of third chromosomes were discovered in which increased sensitivity of larvae to the toxic effects of a monofunctional alkylating agent correlates with high frequencies of x-ray induced SCE's. Sex-linked mutagen-sensitive mutants could be shown to control mutation fixation: pronounced maternal effects were found when sperm carrying particular types of premutational lesions were introduced into different types of mutant oocytes. The mutant mus(1)101D1 was found to be unable to process lesions induced by the crosslinking agent nitrogen mustard into point mutations. Alkylation damage leads to increased point mutation frequencies in the excision repair deficient mutant mei-9L1, but to reduced frequencies in the post-replication repair deficient mutant mei-41D5. It became clear that the study of maternal effects on mutagenized sperm represents an efficient tool to analyze the gentic control of mutagenesis in the eukaryotic genome of Drosophila melanogaster

[en] The project RS1184 „Thermal-hydraulic Calculation Methods for Transients and Accidents of the Reactor Cooling System Under Special Consideration of Multi-Dimensional Flows (ATHLET, FLUBOX, CFX)'' consists of four work packages: 1. Further development of the computer code ATHLET 2. Termination of FLUBOX development and development of an ATHLET-internal 3D module 3. Coupling of ATHLET and CFD code ANSYS CFX as well as CFX model development to simulate three-dimensional flows in the reactor coolant system 4. Prediction capability of computer code ATHLET. One of the superior objectives of the project is to improve the prediction capability of the thermal-hydraulic system code ATHLET, including the simulation of multi-dimensional flow in the reactor vessel. The constitutive equations in ATHLET, especially the momentum equations in ATHLET, are written in one-dimensional form. It was planned to develop the 2D/3D module FLUBOX further and couple it with ATHLET. Due to reasons given in chapter 3, the FLUBOX development was terminated. Instead, the decision was made to develop a fast running internal ATHLET-module. The 2D/3D equations for ATHLET have been derived and were implemented. That strategy allows using all ATHLET models and the ATHLET code structure. An additional advantage is that different numerical schemes of different codes, and consequently a loss of efficiency, will be avoided. A second possibility is the coupling of ATHLET with the CFD code ANSYS CFX. Such a coupled code system will be used in those cases when a part of the simulation area is needed to be calculated with high resolution. Such a detailed modelling cannot be provided by ATHLET-3D. A complete representation of the cooling system by a CFD code cannot be performed due to calculation time. In order to calculate the complete system behavior still with ATHLET, that part to be investigated in more detail, will be replaced by a CFX model. Several new models and improvements of existing models have been developed in the frame of further development of ATHLET. The descriptions of these models are provided in the report. The commercial CFX code solves the three-dimensional conservation equations for mass, momentum and energy. The most important physical models in a CFD code for reactor safety applications are the turbulence and multi-phase models. In order to calculate the turbulent transport terms in the averaged conservation equations for momentum and energy, many turbulence models are available. The variety of physical models, to be selected by the code user, range from turbulent one-phase flows up to two-phase flows and mass and heat transfer at the interface. Within this project, available turbulence and two-phase models in ANSYS CFX suitable for reactor-typical transients and detached flows combined with heat transfer were validated and adjusted. If necessary, new models were implemented and tested. The method for uncertainty evaluation of computer code results proposed by GRS is used in many countries and organisations in the meantime. The method is also applied in many licensing cases of nuclear plants. Some extensions of the method were investigated and are proposed. These address two problem areas: 1. Treatment of epistemic and aleatory uncertainties 2. Uncertainty and sensitivity analysis under special consideration of dependences between uncertain input parameters. In the frame of the international OECD/CSNI programme ''Safety Margin Application and Assessment (SM2A)'', GRS performed uncertainty and sensitivity analyses of the results of the thermal-hydraulic computer code ATHLET. The investigated scenario was a steam line break of the pressurized water reactor Zion in USA. The effect of variations of uncertain input parameters on the maximum cladding temperature is significant for the identified relevant event sequences. That result demonstrates the importance of uncertainty analyses.

[en] Radioisotope and radiation techniques are largely applied in industry since many years. Not only real analytical methods but also indirect analytical methods such as nuclear gauges make use of beta, gamma and neutron radiation for measuring densities, thickness and moisture content of different material. An application which analyses moisture content and density of construction materials, soil, asphalt and more will be illustrated hereafter. (author)

[en] X-ray induced premutational lesions persist in mature gametes of drosophila until fertilization. Repairable lesions in sperm and oocyte chromosomes are repaired exclusively by maternal repair systems in the inseminated egg. Interactions between irradiated genomes in inseminated eggs might result in additional lethality if breaks induced in separate nuclei, which would normally be repaired, could interact to form dicentric chromosomes. Adult drosophila flies were X-irradiated (up to 5 kR), individual females crossed to three or four males, and the dose-response curves for dominant lethals (embryonic lethality) compared. The results indicate thet the potentially lethal damage present in irradiated sperm chromosomes was expressed independently of whether or not the oocyte was also irradiated. There were no (or only very few) interactions between maternal and paternal chromosome complements, and the maternal repair systems acting on radiation-induced chromosome breaks in sperm were resistant to X-rays. (U.K.)

[en] Short communication

[en] A combination of several numerical methods is used to construct a procedure for effective calculation of complex three-dimensional fluid flow problems. The split coefficient matrix (SCM) method is used so that the differenced equations of the hyperbolic system do not disturb correct signal propagation. The semi-discretisation of the equations of the SCM method is done with the asymmetric, separated region, weighted residual (ASWR) method to give accurate solutions on a relatively coarse mesh. For the resulting system of ordinary differential equations, a general-purpose ordinary differential equation solver is used in conjunction with a method of fractional steps for an economic solution of the large system of linear equations. (orig.)

[en] X ray fluorescence (XRF) spectroscopy is recognized as a very accurate non-destructive testing method for measuring the element composition of a material by irradiating a sample with high energy photons such as γ rays and observing the resulting XRF radiation emitted by the sample. Handheld devices can be used for lead detection in painted surfaces, dust and soil, or for general analysis of soil or rock. The most important elements are lead, arsenic, chrome and cadmium. XRF spectrometers consist of a source of excitation radiation (an X ray tube for fixed systems or a radioisotope for portable systems), a radiation detector to detect the stimulated radiation from the sample and a display of the spectral output. In portable systems, built-in isotope identification software helps in comparing the wavelength of the stimulated X rays with known data. For further analysis, computers often are used

[en] A dynamic grid adaption method has been developed for use with the ASWR-method. The method automatically adapts the number and position of the spatial meshpoints as the solution of hyperbolic or parabolic vector partial differential equations progresses in time. The mesh selection algorithm is based on the minimization of the L₂-norm of the spatial discretization error. The method permits accurate calculation of the evolution of inhomogenities like wave fronts, shock layers and other sharp transitions, while generally using a coarse computational grid. The number of required mesh points is significantly reduced, relative to a fixed Eulerian grid. Since the mesh selection algorithm is computationally inexpensive, a corresponding reduction of computing time results

[en] The numerical solution of multi-dimensional partial differential equations poses extremely high demands on computing capacity. For the solution of the 3-dimensional partial differential equations of the fluiddynamics a semidiscrete solution technique (discrete in space, continuous in time) is used. The resulting large system of ordinary differential equations (10³ - 10⁵ unknowns) may be oscillatory stiff which requires for its efficient solution an ODE-solver of high order which is A (α) - stable, with α > 89⁰. The ODE-solver FEBE is presented which can make use of parallel processing on the subroutine level. Parallelisation is possible on the level of the general ODE-solver algorithm and on the level of solving the implicit matrix equation. For the solution of the implicit matrix equation system a fractional step method is used which is well qualified for parallel computing