[en] A statistical method for determining safety margin of nuclear power plants has been developed. Each nuclear plant has a number of characteristic parameters, defining nuclear safety, for example, neutron life time, reactivity margin or dropping time of scram system rods. For the parameters determined were their characteristic limiting values. To determine the nuclear safety dependence on characteristic parameters the distribution density was calculated. The results obtained were compared to the data on 60 safety parameters and on 15 characteristic parameters of approximately 400 research reactors. A possibility of calculated estimation of reactor safety is proved on the basis of statistical treatement of literature data. The method developed permits to formulate the recommendations for substantiation many parameters of reactor nuclear safety, which are more cancrete and objective as compared to the ones at present. It is noted, that because of insufficient statistics its general application is limited

[en] The long-term measurement of a local radiation dose with neutrons was the basis for estimating doses, received while carrying out typical assignments for various groups of personnel operating research and power reactors. Shown is the order of calculating the maximum contribution of neutrons into a maximum permissible radiation dose for these groups with account of the dose rate and the average working time. The calculation is made that research and power reactors do not require individual neutron dosimetry. However, the use of neutron emergency dosimeters is considered to be necessary when working at reactors of both types

[en] Up to now it is impossible to calculate completely the safety of nuclear reactors. Therefore the authors have collected and employed a number of at a high degree independent safety parameters for mathematical evaluation of the reactor safety. By means of computer programs such parameters from about 400 research reactors have been analysed and the fluctuation ranges of their greatest density were determined. The limits of these fluctuation ranges are quickly available and can be used as recommended values for the layout and for the safety estimation of research reactors. A comparison of the existing layout recommendations and the determined fluctuation ranges in most cases shows a good agreement. In some cases corrections and new layout recommendations have been proposed. The determined fluctuation ranges found their first practical application in the estimation of the Rossendorf Equipment for Critical Experiments (RAKE). (author)

[en] The characterisation of the microstructure is an important factor in understanding the complex relationships between the microstructure and the superconducting properties of the new high temperature superconducting oxide materials. With the aid of a number of examples, the techniques of preparation and their use in practice in the light microscopic analysis of the microstructure of sintered ceramic and composite wire specimens, is illustrated. (orig.)

[en] Bronchioloalveolar cell carcinoma may cause three main patterns on CT: solitary nodule, parenchymal consolidation, and multicentric disease. The nodules usually have spiculated margins and frequently contain bubble-like lucencies or pseudocavitation. When presenting as consolidation, this is due mainly to mucin secretion and results in areas of lower attenuation than soft tissue. Multicentric disease is characterized by the presence of multiple nodules which may mimic metastatic disease. Although bronchioloalveolar cell carcinoma may cause different patterns on high-resolution CT, certain CT findings are sufficiently characteristic to suggest the underlying diagnosis. (authors). 12 refs., 7 figs

[en] The Ordinance on the Implementation of Atomic Safety and Radiation Protection of the GDR requires that the managers of plants where nuclear facilities are operated appoint Control Officers for the fields of radiation protection, nuclear safety, physical protection, and accounting for and control of nuclear materials. The Control Officers are staff members of the operating organization but their appointment is subject to approval by the National Board and requires adequate qualification. The main task of the Control Officers as specialists is to give advice to the plant manager who retains responsibility for the safety of nuclear facilities, and to verify on his behalf that all requirements within their competence are met by the operating group. For this reason the Control Officer has to be absolutely independent of the head of the operating group. To enable the Control Officers to accomplish all necessary control activities and to guarantee independence from the head of the operating group, the plant manager has to establish adequate regulations of operation. As a pattern for such regulations the National Board has issued a Recommendation for the Appointment of Nuclear Safety Control Officers for Research Reactors, which provides a comprehensive survey of the requisite qualification features as well as the duties and rights of these Control Officers. This recommendation will be dealt with in the presentation

[en] Focal vertebral artery tortuosity has been periodically reported as a rare cause of cervical vertebral body and foraminal erosion. Almost all reported cases are unilateral. A case of bilateral vertebral artery tortuosity, its possible pathogenesis as well as the computed tomography and magnetic resonance appearances are described. Axial computed tomography was performed and demonstrated expanded transverse foramina with concomitant erosion of the vertebral body. Magnetic resonance angiography performed using a three-dimensional time-of-flight technique appear to be an accurate, non-invasive method of confirming the diagnosis. 8 refs., 3 figs

[en] The bond dissociation energies for the molecules and the molecule ions of alkyl vanadates, especially for the triethyl vanadate were determined by mass spectrometric and thermodynamic measurements. A relative loosening of the Csub(α) bonds in the molecule ions corresponds to the interaction reactions observed. The stabilization of the V - O and O - C bonds is connected with the absence of several typical fragmentation reactions. Both effects are in accordance with the donoracceptor conception of Gutmann. (author)

[en] Cultured cells from individuals affected with Fanconi anemia (FA) exhibit spontaneous chromosome breakage and hypersensitivity to the cell killing and clastogenic effects of the difunctional alkylating agent diepoxybutane (DEB). The authors report here the correction of both of these DEB-hypersensitivity phenotypes of FA cells achieved by cotransfection of normal placental of Chinese hamster lung cell DNA and the plasmid pSV2-neo-SVgpt. Transfectants were selected for clonogenic survival after treatment with DEB at a dose of 5 μgml. At this dose of DEB, the clonogenicity of normal fibroblasts was reduced to 50% and that of FA fibroblasts was reduced to zero. DEB-resistant (DEB/sup r/) colonies selected in this system exhibited a normal response to DEB-induced chromosome breakage and resistance to repeated DEB treatment. The neo and gpt sequences were detected by Southern blot analysis of DNA from one of four DEB/sup r/ colonies independently derived from transfection of human DNA and one of three DEB/sup r/ colonies independently derived from transfection of Chinese hamster DNA. The results demonstrate that DNA sequences that complement the two hallmark cellular phenotypes (cellular and chromosomal hypersensitivity to alkylating agents) of FA are present in human as well as Chinese hamster DNA. The cloning of these genes using transfection strategies can be expected to enable molecular characterization of FA

[en] The influence of constitutive overproduction of the recA protein on the expression of SOS functions as measured by UV induction of mutations and prophage Λ was investigated. Constitutive high-level synthesis of the recA protein was achieved using the recombinant multicopy Co1E1 plasmid pLC 17-43, which carries the recA gene region of the E. coli chromosome. High cellular concentration of the recA protein did not result in an enhancement of either spontaneous or UV-induced mutagenesis or prophage Λ release, indicating that a high level of the recA protein is not sufficient for SOS expression. Obviously the recA protein requires, in addition to a high rate of synthesis a specific activation to trigger SOS responses. (author)