SIGNAL GROUPING FOR CONDITION MONITORING OF NUCLEAR POWER PLANT COMPONENTS

International audienceThe present work investigates the possibility of building a condition monitoring model by splitting the usually very large number of signals measured by the sensors into subgroups and building a specialized model for each subgroup. Different criteria are considered for selecting the signal groups, such as the location of the measurements (i.e., signals measured in the same area of the plant belong to the same group) and their correlation (i.e., correlated signals are grouped together). A real case study concerning 48 signals selected between those used to monitor the reactor coolant pump of a Pressurized Water Reactor (PWR) is considered in order to verify the monitoring performance of different grouping criteria. Performance metrics measuring accuracy, robustness and spill-over effect have been considered in the evaluation. Key Words: Condition Monitoring, Empirical Modeling, Power Plants, Safety Critical Nuclear Instrumentation, Autoassociative models

Genetic Algorithm-based Wrapper Approach for Grouping Condition Monitoring Signal of Nuclear Power Plant Components

Equipment condition monitoring of nuclear power plants requires to optimally group the usually very large number of signals and to develop for each identified group a separate condition monitoring model. In this paper we propose an approach to optimally group the signals. We use a Genetic Algorithm (GA) for the optimization of the groups; the decision variables of the optimization problem relate to the composition of the groups (i.e., which signals they contain) and the objective function (fitness) driving the search for the optimal grouping is constructed in terms of quantitative indicators of the performances of the condition monitoring models themselves: in this sense, the GA search engine is a wrapper around the condition monitoring models. A real case study is considered, concerning the condition monitoring of the Reactor Coolant Pump (RCP) of a Pressurized Water Reactor (PWR). The optimization results are evaluated with respect to the accuracy and robustness of the monitored signals estimates. The condition monitoring models built on the groups found by the proposed approach outperform the model which uses all available signals, whereas they perform similarly to the models built on groups based on signal correlation. However, these latter do not guarantee the robustness of the reconstruction in case of abnormal conditions and require to a priori fix characteristics of the groups, such as the desired minimum correlation value in a group

Controlling the Decoration of the Reduced Graphene Oxide Surface with Pyrene-Functionalized Gold Nanoparticles

We exploited a non‐covalent approach based on π‐stacking interactions to address the formation of hybrids between pyrene‐functionalized gold nanoparticles (PyAuNPs) and reduced graphene oxide (RGO), in which the former are distributed homogeneously on the surface of the latter with a high degree of coverage. We used water soluble PyAuNPs of two different average dimensions, namely 2 and 8 nm, in which the pendant pyrene moieties were introduced within a mixed monolayer with a choline derivative. The combination with RGO originates highly insoluble materials, in which microscopy evidences a complete adhesion of the PyAuNPs onto the carbon nanomaterial layers in a highly homogeneous fashion, with no traces of free particles, confirming the high affinity between pyrene‐functionalized species and conjugated carbon nanostructure surfaces

Photocatalytic Fe-doped n-TiO2: From synthesis to utilization of in vitro cell models for screening human and environmental nanosafety

The utilization of different types nanomaterials (NMs) in environmental remediation and wastewatertreatment requires information on the potential harmful effects on human and environmental health. Inthis light, the utilization of human cell models together with cells from lower organisms, representativeof different environmental compartments, could represent a valuable tool for the in vitro screening of thepotential toxicity of different NMs used in nanoremediation. Among NMs, n-TiO2, because of its peculiaroptical and chemical properties, is widely applied for photosensitized UV oxidation of organic pollutants.Moreover, development in design of metal- and non metal- doped TiO2 with extended photocatalyticactivity in the visible region represents the subject of ongoing research

Vibrio cholerae interactions with Mytilus galloprovincialis hemocytes mediated by serum components

Edible bivalves (e.g., mussels, oysters) can accumulate large amount of bacteria in their tissues and act as passive carriers of pathogens to humans. Bacterial persistence inside bivalves depends, at least in part, on hemolymph anti-bacterial activity that is exerted by both serum soluble factors and phagocytic cells (i.e., the hemocytes). It was previously shown that Mytilus galloprovincialis hemolymph serum contains opsonins that mediate D-mannose-sensitive interactions between hemocytes and Vibrio cholerae O1 El Tor bacteria that carry the mannose-sensitive hemagglutinin (MSHA). These opsonins enhance phagocytosis and killing of vibrios by facilitating their binding to hemocytes. Since V. cholerae strains not carrying the MSHA ligand (O1 classical, non-O1/O139) are present in coastal water and can be entrapped by mussels, we studied whether in mussel serum, in addition to opsonins directed toward MSHA, other components can mediate opsonization of these bacteria. By comparing interactions of O1 classical and non-O1/O139 strains with hemocytes in artificial sea water and serum, it was found that M. galloprovincialis serum contains components that increase by at approximately twofold their adhesion to, association with, and killing by hemocytes. Experiments conducted with high and low molecular mass fractions obtained by serum ultrafiltration indicated that these compounds have molecular mass higher than 5000 Da. Serum exposure to high temperature (80°C) abolished its opsonizing capability suggesting that the involved serum active components are of protein nature. Further studies are needed to define the chemical properties and specificity of both the involved bacterial ligands and hemolymph opsonins. This information will be central not only to better understand V. cholerae ecology, but also to improve current bivalve depuration practices and properly protect human health

Comparison of intermittent and continuous exposures to inorganic mercury in the mussel, Mytilus edulis: accumulation and sub-lethal physiological effects.

Aquatic organisms are often subject to intermittent exposure to pollutants in real ecosystems. This study aimed to compare mercury accumulation and the physiological responses of mussels, Mytilus edulis during continuous and intermittent exposure to the metal. Mussels were treated in a semi-static, triplicated design to either a control (no added Hg) or 50 µg l(-1) Hg as HgCl2 in continuous (daily) or intermittent (2 day exposure, 2 days in clean seawater alternately) exposure for 14 days. A time-dependent increase in Hg accumulation was observed in the continuous exposure, while the intermittent treatment showed step-wise changes in Hg concentrations with the exposure profile, especially in the gills. At the end of the experiment, tissue Hg concentrations were significantly increased in the continuous compared to the intermittent exposure for digestive gland (4 fold), gonad and remaining soft tissue (>2 fold), but not for the gill and adductor muscle. There was no observed oxidative damage at the end of the experiment as measured by the thiobarbituric acid reactive substances (TBARS) concentrations in tissues from all treatments. However, total glutathione was significantly decreased in the gill and digestive gland of both the continuous and intermittent exposure by the end of the experiment. The neutral red retention ability of the haemocytes was not affected, but total haemocyte counts were significantly decreased (<2 fold) in the intermittent compared to the continuous exposure. Histopathological examinations showed less pathology in the gill, but more inflammation in the digestive gland of mussels for the intermittent compared to the continuous exposure. Overall, the results showed that Hg accumulation from intermittent exposure was less than that of the continuous exposure regime, but the sub-lethal responses are sometimes more severe than expected in the former

Effects of nanomaterials on marine invertebrates

The development of nanotechnology will inevitably lead to the release of consistent amounts of nanomaterials (NMs) and nanoparticles (NPs) into marine ecosystems. Ecotoxicological studies have been carried out to identify potential biological targets of NPs, and suitable models for predicting their impact on the health of the marine environment. Recent studies in invertebrates mainly focused on NP accumulation and sub-lethal effects, rather than acute toxicity. Among marine invertebrates, bivalves represent by large the most studied group, with polychaetes and echinoderms also emerging as significant targets of NPs. However, major scientific gaps still need to be filled. In this work, factors affecting the fate of NPs in the marine environment, and their consequent uptake/accumulation/toxicity in marine invertebrates will be summarized. The results show that in different model species, NP accumulation mainly occurs in digestive tract and gills. Data on sub-lethal effects and modes of action of different types of NPs (mainly metal oxides and metal based NPs) in marine invertebrates will be reviewed, in particular on immune function, oxidative stress and embryo development. Moreover, the possibility that such effects may be influenced by NP interactions with biomolecules in both external and internal environment will be introduced. In natural environmental media, NP interactions with polysaccharides, proteins and colloids may affect their agglomeration/aggregation and consequent bioavailability. Moreover, once within the organism, NPs are known to interact with plasma proteins, forming a protein corona that can affect particle uptake and toxicity in target cells in a physiological environment. These interactions, leading to the formation of eco-bio-coronas, may be crucial in determining particle behavior and effects also in marine biota. In order to classify NPs into groups and predict the implications of their release into the marine environment, information on their intrinsic properties is clearly insufficient, and a deeper understanding of NP eco/bio-interactions is required

Specificity of innate immunity in bivalves: a lesson from bacteria

Bivalves are a relevant ecological group, widespread in freshwater, estuarine, and marine ecosystems, with many edible species, such as oysters, mussels, and clams. Bivalves are endowed with an effective and complex innate immune system (humoral and cellular defenses). Bivalve immunity displays a wide variety of sensitive receptors, selective effectors, and synergistic genetic regulatory networks that afford protection in a fluctuating environment.As filter feeders, bivalves accumulate large numbers of microorganisms, mainly bacteria, that can either establish a commensal relationship with the host or proliferate and invade soft tissues, resulting in a high mortality of bivalve juveniles and adults. In this framework, understanding the relationship between the bivalve immune system and bacteria has important implications not only for the protection of economically important species but also for human health concerns. Available data underlying the specificity of bivalve immune responses to bacterial challenges will be summarized. \ua92016 Elsevier Inc. All rights reserved

New multiresponsive chromic soft materials: dynamic interconversion of short 2,7-dicyanomethylenecarbazole-based biradicaloid and the corresponding cyclophane tetramer

This work reports on a quinodimethane-type molecule, 2,7-dicyanomethylene-9-(2-ethylhexyl)carbazole (1), one of the shortest π-conjugated biradicaloids reported to be stable in solution under ambient conditions. This carbazole-based quinoidal precursor is able to form a macrocyclic σ-bonded tetramer (2). The resolved single-crystal X-ray structure of tetramer 2 shows that four molecules of 1 are linked together through four long (CN)2C−C(CN)2 bonds (1.631 Å) resulting from coupling of the unpaired electrons in biradicaloid 1. Dynamic interconversion between monomer 1 and cyclophane tetramer 2 is achieved by reversible cleavage and recovery of the four (CN)2C−C(CN)2 bonds upon soft external stimuli (light absorption, temperature and pressure), which is accompanied by significant color changes. These novel photo-, thermo-, and mechanochromic properties expand the versatility of π-conjugated biradicaloid compounds as novel functional materials that, in combination with spin chemistry and dynamic covalent chemistry, can be relevant in molecular machines, sensors, and switches

Estrogenic compounds as exogenous modulators of physiological functions in molluscs: Signaling pathways and biological responses

Molluscs have been widely utilized to evaluate the effects of estrogenic compounds, one of the most widespread classes of Endocrine Disrupting Chemicals-EDCs. However, knowledge on steroid signaling and metabolism in molluscs has considerably increased in the last decade: from these studies, a considerable debate emerged on the role of 'natural' steroids in physiology, in particular in reproduction, of this invertebrate group. In this work, available information on the effects and mechanisms of action of estrogens in molluscs will be reviewed, with particular emphasis on bivalves that, widespread in aquatic ecosystems, are most likely affected by exposure to estrogenic EDCs. Recent advances in steroid uptake and metabolism, and estrogen receptors-ERs in molluscs, as well as in estrogen signaling in vertebrates, will be considered. The results so far obtained with 17\u3b2-estradiol and different estrogenic compounds in the model bivalve Mytilus spp., demonstrate specific effects on immune function, development and metabolism. Transcriptomic data reveal non genomic estrogen signaling pathways in mussel tissues that are supported by new observations at the cellular level. In vitro and in vivo data show, through independent lines of evidence, that estrogens act through non-genomic signaling pathways in bivalves. In this light, regardless of whether molluscs synthesize estrogens de novo or not, and despite their ERs are not directly activated by ligand binding, estrogens can interact with multiple signaling components, leading to modulation of different physiological functions. Increasing knowledge in endocrine physiology of molluscs will provide a framework for a better evaluation and interpretation of data on the impact of estrogenic EDCs in this invertebrate group