Neutron embrittlement of VVER reactor pressure vessels—recent results, open issues and new developments

Decisions regarding the verification of design plant lifetime involve a determination of the component and circuit condition. Neutron embrittlement of reactor pressure vessels (RPV) becomes a crucial consideration for continued safe plant operation. Since 1991, the European Commission (EC) has financed a significant number of projects in this area, in particular through the TACIS and PHARE programmes. In Nuclear Safety support programmes the countries mainly concerned are Russia, Ukraine, Armenia, and Kazakhstan for the TACIS programme, and Bulgaria, Czech Republic, Hungary, Slovak Republic, Lithuania, Romania and Slovenia for the PHARE programme. The corresponding results of these projects on neutron embrittlement have contributed to a better understanding of the available data and their uncertainties. Recent confirmations of the irradiation temperatures of the surveillance specimens in the operating VVER nuclear power plants show that the surveillance specimens can be used further for the validation of the current and the expected neutron embrittlement. Taking into account the latest results as a baseline for the development of the necessary material data to be used for upgraded RPV integrity assessment, two new TACIS projects are being launched, jointly with Russia and Ukraine, whose scope is:

• Upgrading the surveillance databases.

• Acquisition of new impact test and toughness results on reconstituted surveillance specimens, including the evaluation of the Mater Curve Approach.

• Further validation tests of the shape of the fracture toughness curve and the base and weld metal and characterization of the cladding.

• Preparation of some selected upgraded RPV integrity assessments, with insights on the latest approved methodology.

The paper summarizes the major conclusions of the recent completed EC projects, reviews the remaining major open issues in the field of reliable determination of fracture toughness properties of the operating VVER RPVs, and details the scope of the new projects.     

Analysis of a BMAP/D/1-Timer Multiplexer

In this paper we introduce and analyze a model of a multiplexer queue with a batch Markovian arrival process and a special, timer based, non-work-conserving service discipline. We show that the embedded process at departures is an M/G/1 type process with proper state partitioning, which can be efficiently analyzed by matrix geometric methods. We derive the expressions to compute the distribution of the waiting time. The paper ends with numerical experiments, and points out some interesting features of the system.     

Speckle correlation method used to measure object's in-plane velocity

We present a measurement of an object's in-plane velocity in one direction by the use of the speckle correlation method. Numerical correlations of speckle patterns recorded periodically during motion of the object under investigation give information used to evaluate the object's in-plane velocity. The proposed optical setup uses a detection plane in the image field and enables one to detect the object's velocity within the interval (10-150) microm x s(-1). Simulation analysis shows a way of controlling the measuring range. The presented theory, simulation analysis, and setup are verified through an experiment of measurement of the velocity profile of an object.     

Anomalous celestial polarization caused by forest fire smoke: why do some insects become visually disoriented under smoky skies?

The effects of forest fire smoke on sky polarization and animal orientation are practically unknown. Using full-sky imaging polarimetry, we therefore measured the celestial polarization pattern under a smoky sky in Fairbanks, Alaska, during the forest fire season in August 2005. It is quantitatively documented here that the celestial polarization, a sky attribute that is necessary for orientation of many polarization-sensitive animal species, above Fairbanks on 17 August 2005 was in several aspects anomalous due to the forest fire smoke: (i) The pattern of the degree of linear polarization p of the reddish smoky sky differed considerably from that of the corresponding clear blue sky. (ii) Due to the smoke, p of skylight was drastically reduced (p(max)相似文献   

Evaluation of Pheromones and a New Trap for Monitoring <Emphasis Type="Italic">Agriotes lineatus</Emphasis> and <Emphasis Type="Italic">Agriotes obscurus</Emphasis> in the Fraser Valley of British Columbia

A prototype ground-based pheromone trap design, baited with various pheromone lures, was field tested for effectiveness in trapping male Agriotes obscurus and Agriotes lineatus click beetles in British Columbia. Pheromone dispensers containing geranyl octanoate and geranyl hexanoate in a 1:1 ratio caught the greatest numbers of A. obscurus, whereas those containing geranyl octanoate and geranyl butanoate in a 9 or 10:1 ratio caught high numbers of A. lineatus. Some differences in A. obscurus attraction to traps were observed between dispensers according to the manufacturer and the number of dispensers deployed in traps. The trap design and optimal pheromone dispensers tested would be suitable for monitoring or surveying A. obscurus and A. lineatus populations in North America.     

Preparation of CO-tolerant anode electrocatalysts for polymer electrolyte membrane fuel cells

The preparation and the thorough characterization of 40 wt% Pt electrocatalysts supported on Ti_(1?x)M_xO₂-C (M = W, Mo; x = 0.3–0.4) composite materials with enhanced stability and efficiency is presented.W-containing composite supported catalyst with different structural characteristics were compared in order to explore the influence of the nature of the W species on the electrocatalytic performance. The assessment of the electrochemical properties of the novel catalysts revealed a correlation between the degree of W incorporation, the hydrogen spillover effect and the stability against initial leaching which influences the activity and CO tolerance of the catalysts.A preparation route for Ti_0.7Mo_0.3O₂-C composite with high extent of Mo incorporation was developed. No significant difference was observed in the activity, stability and CO tolerance of the W- or Mo-containing composite supported Pt catalysts with almost complete incorporation of the oxophilic dopant. Better performance of the Pt/Ti_0.7M_0.3O₂-C (M = W, Mo) electrocatalysts in a single cell test device using hydrogen containing 100 ppm CO compared to the reference Pt/C and PtRu/C (Quintech) catalysts was also demonstrated.     

Surface changes of corona‐discharge‐treated polyethylene films

Morphological and chemical changes of the surface of low‐density polyethylene (LDPE), linear middle‐density polyethylene (L‐MDPE), and their 80/20 blend were studied by different techniques after corona‐discharge treatment in air and subsequent annealing. The surface tension was determined by wetting; the roughness was measured by atomic force microscope (AFM), and the surface chemical composition was analyzed by X‐ray photoelectron spectroscopy (XPS), whereas the low‐molecular‐mass fraction washed off by chloroform by FTIR. The surface tension of the films increases with the electrode current. The surface roughness depends primarily on the polymer type and is less affected by the corona treatment. At the initial stage of annealing, posttreatment‐type oxidation and hydrophobic recovery are competing. The former is more pronounced in L‐MDPE, the latter in LDPE. After annealing at 50°C for 160 days, hydrophobic recovery becomes predominant in each film studied, which is accompanied by significant smoothening of the surface. According to XPS and FTIR results, this is due to the migration of low‐molecular‐mass components (oligomers, oxidized polymer fractions, and additives) to the surface. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1529–1541, 2000     

Challenges in Analyzing Functional Epigenetic Data in Perspective of Adolescent Psychiatric Health

The formative period of adolescence plays a crucial role in the development of skills and abilities for adulthood. Adolescents who are affected by mental health conditions are at risk of suicide and social and academic impairments. Gene–environment complementary contributions to the molecular mechanisms involved in psychiatric disorders have emphasized the need to analyze epigenetic marks such as DNA methylation (DNAm) and non-coding RNAs. However, the large and diverse bioinformatic and statistical methods, referring to the confounders of the statistical models, application of multiple-testing adjustment methods, questions regarding the correlation of DNAm across tissues, and sex-dependent differences in results, have raised challenges regarding the interpretation of the results. Based on the example of generalized anxiety disorder (GAD) and depressive disorder (MDD), we shed light on the current knowledge and usage of methodological tools in analyzing epigenetics. Statistical robustness is an essential prerequisite for a better understanding and interpretation of epigenetic modifications and helps to find novel targets for personalized therapeutics in psychiatric diseases.     

Gold nanoparticles: effect of treatment on structure and catalytic activity of Au/Fe2O3 catalyst prepared by co‐precipitation

1 wt% Au/Fe₂O₃ catalyst was prepared by a co‐precipitation method. The structure of the sample in the as prepared, oxidized and reduced states was investigated by means of X‐ray photoelectron spectroscopy (XPS), transition electron microscopy (TEM), electron diffraction (ED) and X‐ray diffraction (XRD). The structure of the samples after various treatments and their activity in the CO oxidation were compared. The results show the stability of the gold particle size during the treatments. However, after oxidation, a slight shift in the Au 4f binding energy towards lower values points to the formation of an electron‐rich state of the metallic gold particles compared to that revealed in the as prepared sample. Simultaneously, a goethite phase in the Fe₂O₃ support is present, which is not observed in the “as prepared” and reduced samples. In the reduced sample the presence of a crystalline maghemite‐c phase indicates a change in the support morphology. In the CO oxidation the oxidized sample shows the highest activity and it might be the result of the cooperative effect of goethite, FeO and the electron‐rich metallic gold nanoparticles. We suggest that a structural transformation occurs along the gold/support perimeter during the treatments and we propose a possible mechanism for the effect of the oxidation treatment. This revised version was published online in July 2006 with corrections to the Cover Date.