Stabilization and termination of severe accidents in LWRs

The last 20 years of research on severe accident safety for light water reactors (LWRs) has resolved a number of issues. However, the issue of melt/debris coolability is still unresolved. At stake is the stabilization and termination of a severe accident, if ever it would occur. The stabilization and termination can be established only through the coolability of the melt or the particulate debris, which are found in-vessel, or ex-vessel, depending upon the extent of the progression of a postulated accident.This paper will review the state of the art of coolability during a severe accident for the current light water reactors (LWRs). It will also review whether the accident management actions will be effective in terminating a postulated severe accident. The attention paid to the stabilization and coolability in future LWRs will be discussed and the design solutions will be evaluated.     

Effect of laser irradiation on the electrical properties of amorphous germanium films

Amorphous films of germanium were grown using a vacuum evaporation technique, on glass substrates kept at room temperature. As-grown films were irradiated with Q-Switched Nd-YAG laser pulses (=1.06 m, 20nsec, 10 to 50Jcm^–2). The d.c. conductivity measurements were made in the temperature range 77 to 300 K. It was observed that the effect of laser irradiation was similar to the effect caused by the thermal annealing of the films. The d.c. conductivity data were analysed in the light of Mott's theory of a variable range hopping conduction process.     

A spatio‐temporal water quality assessment of the Beas and Sutlej Rivers at the Harike Wetland: A Ramsar site in Punjab,India

Lakes play a vital role in regulating water storage, flow of river water, and ultimately maintaining a balanced ecosystem. Spatial and temporal variations in physicochemical parameters of water in Harike Wetland, a Ramsar site in the northwestern state of Punjab, India, were studied. This study was conducted on a monthly basis from January to December 2015. The water quality was studied at ten locations from sites 1 to 10 upstream, central and downstream from Harike Lake for ten physicochemical parameters, including temperature, pH, electrical conductivity, turbidity, dissolved oxygen concentration biological oxygen demand, nitrate and phosphate concentrations and salinity. The findings of this study revealed that, except for temperature and pH, all parameters exhibited relatively higher values for the Sutlej River, compared with the Beas River, with sampling sites 5 to site 7 exhibiting intermediate results. The mean seasonal temperature variations ranged from 16.9 to 26.6 °C, the pH from 7.7 to 8.2, electrical conductivity from 223 to 303 μS cm^?1 and TDS concentration from 148.7 to 180.4 ppm. Correlation analysis was conducted to assess the relations between the variables. The electrical conductivity exhibited a high positive correlation with salinity and biological oxygen demand, whereas it correlated negatively with the dissolved oxygen concentration. Box and whisker plots were also plotted for the study results to better examine the data distribution.     

Geospatial technology applied to spatiotemporal assessment of Harike Wetland,Punjab

The Harike Wetland situated in Punjab is a Ramsar site and a wetland of national importance. The present study was undertaken to assess the spatiotemporal dynamics of the wetland on the basis of geospatial technology and ground‐based studies. Landsat images for the years 2002 and 2014 were acquired from the United States Geological Survey and classified digitally to generate landuse/land cover maps involving four classes (water, grassland (including water hyacinth), agriculture, built‐up (settlement), barren land). The total area of the Harike Wetland was found to be 8023.68 ha. Water sampling at eleven sites was carried out and evaluated for physicochemical parameters. The water quality at several sampling points was found to be severely degraded. Change detection analysis revealed the submerged area (area under water) and grassland (including water hyacinth) had decreased over the past 12 years, whereas that area under agriculture and built‐up land has increased, indicating a shrinkage in the total wetland area. The present study also indicated that the near‐infrared band is a good indicator of water quality parameters, as indicated by the significant positive correlation between the near‐infrared band and relevant water parameters. Because the wetland is important from both an ecological perspective and economic perspective, regular monitoring is recommended, for which geospatial technology has proven to be very useful.     

Epoxy‐tert‐butyl poly(cyanoarylene ether) blends: Phase morphology,fracture toughness,and mechanical properties

Tert‐butyl hydroquinone–based poly(cyanoarylene ether) (PENT) was synthesized by the nucleophilic aromatic substitution reaction of 2,6‐dichlorobenzonitrile with tert‐butyl hydroquinone using N‐methyl‐2‐pyrrolidone (NMP) as solvent in the presence of anhydrous potassium carbonate in a nitrogen atmosphere at 200°C. PENT‐toughened diglycidyl ether of bisphenol A epoxy resin (DGEBA) was developed using 4,4′‐diaminodiphenyl sulfone (DDS) as the curing agent. Scanning electron micrographs revealed that all blends had a two‐phase morphology. The morphology changed from dispersed PENT to a cocontinuous structure with an increase in PENT content in the blends from 5 to 15 phr. The viscoelastic properties of the blends were investigated using dynamic mechanical thermal analysis. The storage modulus of the blends was less than that of the unmodified resin, whereas the loss modulus of the blends was higher than that of the neat epoxy. The tensile strength of the blends improved slightly, whereas flexural strength remained the same as that of the unmodified resin. Fracture toughness was found to increase with an increase in PENT content in the blends. Toughening mechanisms like local plastic deformation of the matrix, crack path deflection, crack pinning, ductile tearing of thermoplastic, and particle bridging were evident from the scanning electron micrographs of failed specimens from the fracture toughness measurements. The thermal stability of the blends were comparable to that of the neat resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3536–3544, 2006     

Kinetics of esterification of cycloaliphatic epoxies with methacrylic acid

The esterification of cycloaliphatic epoxy resins CER I and CER II containing glycidyl and cyclohexane epoxy groups, respectively, as their reactive units was carried out using a 1 : 0.9 stoichiometric ratio of resin and methacrylic acid in the presence of triphenylphosphine. The reaction was performed at 80, 85, 90, 95, and 100°C and it followed second‐order kinetics. The specific rate constants, calculated by regression analysis, were found to obey an Arrhenius expression. Kinetic and thermodynamic parameters, activation energy, frequency factor, entropy, enthalpy, and free energy of the reaction, revealed that the reaction was spontaneous and irreversible and produced a highly ordered activated complex. The reactivity of CER II was found to be higher than that of CER I. The difference in the reactivity of the cycloaliphatic epoxies was explained by proposing a reaction mechanism. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3197–3204, 2002     

Phase Transitions on Fixed Connected Graphs and Random Graphs in the Presence of Noise

In this paper, we study the phase transition behavior emerging from the interactions among multiple agents in the presence of noise. We propose a simple discrete-time model in which a group of non-mobile agents form either a fixed connected graph or a random graph process, and each agent, taking bipolar value either +1 or -1, updates its value according to its previous value and the noisy measurements of the values of the agents connected to it. We present proofs for the occurrence of the following phase transition behavior: At a noise level higher than some threshold, the system generates symmetric behavior (vapor or melt of magnetization) or disagreement; whereas at a noise level lower than the threshold, the system exhibits spontaneous symmetry breaking (solid or magnetization) or consensus. The threshold is found analytically. The phase transition occurs for any dimension. Finally, we demonstrate the phase transition behavior and all analytic results using simulations. This result may be found useful in the study of the collective behavior of complex systems under communication constraints.     

Interleukin-6-type cytokines in vivo: regulated bioavailability

Investigators have traditionally thought of the class of inflammation- and injury-associated cytokines in large part as "free" entities in the peripheral circulation. In the case of interleukin-6 (IL-6), the cytokine can be found in blood in complexes of molecular mass 400-500, 150-200, and 25-35 kDa in association with binding proteins that can include soluble IL-6 receptor (sIL-6R), anti-IL-6, and anti-sIL-6R IgG, and others. Sustained high levels of different particular IL-6 complexes are observed in the human circulation in cancer patients subjected to particular active anticancer immunotherapy regimens. In the "chaperoned" state, circulating IL-6 complexes display differential immunoreactivity in different ELISAs and possess differential biological activity as assayed ex vivo. The discovery of "chaperoned" circulating IL-6 in humans points to a new level of modulation of cytokine function, that of regulated bioavailability of IL-6 in vivo.     

A study on fitness-for-service assessment for crack-like defects and corrosion in nuclear reactor pressure tubes

This paper looks forward to thoroughly assess zirconium alloy (Zr-2) pressure tubes used in nuclear power reactors for crack like and corrosion type defects. It emphasizes on the use of reliability concept for determining the probability of failure of zirconium alloy pressure tubes based on deuterium ingress. The in depth analysis carried out to calculate the reliability index for the above two problems is based on FORM approach. A steady state corrosion rate is assumed to estimate the growth in the dimensions of corrosion defects. The methodology suggested in this paper is useful for designers and plant engineers in timely detection of the cracks and leaks in the pressure tubes used in nuclear reactors and initiate suitable corrective actions based on their criticality.