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This study investigates the impact of hybrid nanoparticles on the temperature of nuclear reactor coolant, with a focus on graphene nanoplatelet (GNP)‐based hybrid nanoparticles. Sixteen different hybrid nanofluids were analyzed, and their performance was compared with a standard water‐based coolant. The criticality values were obtained through MCNP modeling, revealing that higher nanoparticle ratios led to increased criticality, with the highest value of 1.3239 observed in GNP‐Fe3O4 + Al2O3 nanofluids (0.05 wt%) and the lowest value of 1.2935 in GNP–Fe3O4 + SiO2 nanofluids (0.001 wt%). Temperature variations showed that increasing nanoparticle concentrations resulted in slightly higher temperatures, with a maximum of 611.97 K for 0.05 vol.% GNP nanoparticles. Additionally, the departure from nucleate boiling ratio values were consistently above the safety threshold of 2.08, with the lowest value of 3.657 for GNP–Fe3O4 + SiO2 nanofluids (0.05 vol.%). These findings suggest that hybrid nanofluids, particularly those with higher nanoparticle ratios, can enhance the thermal performance and safety margins of nuclear reactor coolants, offering a promising avenue for future research and application. [ABSTRACT FROM AUTHOR]

In this paper, the author investigates particular disconjugate even‐order linear difference equations with two terms and classify them based on the properties of their recessive solutions at plus and minus infinity. The main theorem described states that the studied equation is (k−p+1)$(k-p+1)$‐critical whenever a specific second‐order linear difference equation is p$p$‐critical. In the proof, the author derived closed‐form solutions for the studied equation wherein the solutions of the said second‐order equation appear. Furthermore, the solutions were organized, in order to determine recessive solutions, into a linear chain by sequence ordering that compares the solutions at ±∞$\pm \infty$. [ABSTRACT FROM AUTHOR]

We analyze exciting recent measurements [Phys. Rev. Lett. 114 (2015) 037202] of the magnetization, differential susceptibility and specific heat on one dimensional Heisenberg antiferromagnet Cu(C4H4N2)(NO3)2 (CuPzN) subjected to strong magnetic fields. Using the mapping between magnons (bosons) in CuPzN and fermions, we demonstrate that magnetic field tunes the insulator towards quantum critical point related to so-called fermion condensation quantum phase transition (FCQPT) at which the resulting fermion effective mass diverges kinematically. We show that the FCQPT concept permits to reveal the scaling behavior of thermodynamic characteristics, describe the experimental results quantitatively, and derive for the first time the [ABSTRACT FROM AUTHOR]

This paper presents an advanced version of the failure mode effects and criticality analysis (FMECA), whose capabilities are enhanced; in that the criticality assessment takes into account possible interactions among the principal causes of failure. This is obtained by integrating FMECA and Analytic Network Process, a multi-criteria decision making technique. Severity, Occurrence and Detectability are split into sub-criteria and arranged in a hybrid (hierarchy/network) decision-structure that, at the lowest level, contains the causes of failure. Starting from this decision-structure, the Risk Priority Number is computed making pairwise comparisons, so that qualitative judgements and reliable quantitative data can be easily included in the analysis, without using vague and unreliable linguistic conversion tables. Pairwise comparison also facilitates the effort of the design/maintenance team, since it is easier to place comparative rather than absolute judgments, to quantify the importance of the causes of failure. In order to clarify and to make evident the rational of the final results, a graphical tool, similar to the House of Quality, is also presented. At the end of the paper, a case study, which confirms the quality of the approach and shows its capability to perform robust and comprehensive criticality analyses, is reported. Copyright © 2011 John Wiley and Sons Ltd. [ABSTRACT FROM AUTHOR]

Maintenance tasks and their application in the shipping industry have evolved significantly in the recent years. Particularly in the offshore industry, safety onboard, environmental protection and intensive operational activities necessitate the minimization of down-time and the preservation of an excellent performance ratio. The first step of an innovative ship maintenance strategy, which is proposed by the authors and is based on criticality and reliability assessment, is presented herein using the FTA tool with time-dependant dynamic gates so as to represent in an accurate and comprehensive way the interrelation of the components of a system. The paper also presents a review of the maintenance standards and procedures, such as the ALARP concept, the Key Programme 3-Asset Integrity (KP3) initiative, the OREDA handbook as well as the RCM and RBI principles. As part of the reliability assessment, the Birnbaum and Criticality reliability importance measures are utilized to validate the results of the analysis. A case study of a diving support vessel (DSV) illustrates the application of this strategy. The main systems examined are: the vessel's power plant, propulsion, water system, lifting, hauling and anchoring, diving and finally the safety system. The reliability of the main systems and subsystems as well as of their critical components is identified and suggestions of how to improve the overall reliability of the various systems both at a component, system and managerial level are also proposed. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

U isotope is used as a booster fissile fuel material in the form of mixed ThC/UC fuel in a Canada Deuterium Uranium (CANDU) fuel bundle in order to assure the initial criticality at startup. Three different fuel compositions have been used: (1) 97% ThC+3% UC, (2) 98% ThC+2% UC and (3) 99% ThC+1% UC. The temporal variation of the criticality k and the burn-up values of the reactor have been calculated by full-power operation for a period of 20 years. The criticality starts by k=1.541, 1.355 and 0.995 for modes of (1), (2) and (3) fuel compositions, respectively. A sharp decrease in the criticality has been observed in the first 2 years as a consequence of rapid U burnout fuelling with (1) and (2) modes. The criticality becomes quasi-constant after the second year and remains above k∼1.06 for 20 years. After the second year, the CANDU reactor begins to operate practically as a thorium burner. Very high burnup could be achieved with the same fuel materials (up to 500 000 MWday t), provided that the fuel rod claddings would be replaced periodically (after every 500 00 or 100 000 MWday t). The reactor criticality will be sufficient for fuelling with (1) and (2) modes until a great fraction of the thorium fuel is burnt up. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We examined the molecular mechanisms underlying the formation of the thalamocortical pathway in the cerebral neocortex of normal and reeler mutant mice. During normal development of the mouse neocortex, thalamic axons immunoreactive for the neural cell adhesion molecule L1 rarely invaded the cortical plate and ran centered in the subplate which is immunoreactive for neurocan, a brain-specific chondroitin sulfate proteoglycan. On the other hand, in homozygous reeler mutant mice, thalamic axons took an aberrant course to run obliquely through the cortical plate. Injection of bromodeoxyuridine at embryonic day 11 specifically labeled subplate neurons in normal mice, whilst in the reeler neocortex it labeled cells scattered in the cortical plate as well as in the superficial layer (superplate). Neurocan immunoreactivity was associated with the bromodeoxyuridine-positive cells in the superplate, as well as being present in oblique bands within the cortical plate, along which L1-bearing thalamic axons preferentially ran. The present results support our previous hypothesis proposed for normal rats that a heterophilic molecular interaction between L1 and neurocan is involved in determining the thalamocortical pathway within the neocortical anlage [T. Fukuda et al. (1997) Journal of Comparative Neurology, 382, 141–152]. [ABSTRACT FROM AUTHOR]

Criticality analysis is applied in risk and reliability studies to rank decisions on system design and operation. There is a wide variety of methods used to meet the requirements of different organizations. Most methods feature an initial assessment of the consequences of failure and its probability of occurrence; however, other factors may also be applied to provide a more robust analysis applicable to each specific situation. As well as assessing system criticality during the design phase, it is also necessary to continue to evaluate system and equipment criticality during operation so that availability can be maximized. Some alternatives to the well-known MILHBK 1629A approach are considered in this paper. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper will introduce a computer aided reliability analysis system, IRAS, which is a Unix-based software package. It provides the following features: a model builder, failure mode effect and criticality analysis (FMECA), fault tree synthesis and analysis (FTA) and real time fault location (RTFL). 1. The model builder allows the creation of reliability models for production systems, which are able to reflect the initiation and propagation of serious deviations outside the production and performance tolerances. The modelling procedure allows hierarchical modelling. 2. The failure mode effect and criticality analysis (FMECA) option uses the causal trees and cause-consequence diagrams that are created automatically from the IRAS model data base. The trees can be analysed by the user and the basic events can be grouped according to their criticality, probability and severity. 3. The fault tree analysis and synthesis (FTA) option enables the graphical analysis of fault trees. The generated tree can be trimmed automatically or by the user. It is also possible to extract the minimal cut-set from the complete tree. 4. RTFL enables the fast detection of the most probable fault locations in the system, during the continuous measuring of sensors of the production system and comparing the signals with the expected values of the stored operational vector. It alarms the user In case of serious deviations, thus reducing the out of work stage of the system by making quicker and more efficient reaction of the maintenance facility operators. The failure searching time reduction results in lower maintenance cost. [ABSTRACT FROM AUTHOR]

This paper examines the possibility of criticality in a nuclear waste repository. The estimated probabilities are rough bounds and do notentirely dismiss the possibility of a critical condition; however, they do point to the difficulty of creating conditions under which a critical mass could be assembled (i.e., corrosion of containers, separation of neutron absorbers from the fissile material and collapse or precipitation of the fissile material). In addition, should a criticality occur in or near a container, the bounding consequence calculations showed that fissions from one critical event are quite small (< ~1020 fissions, if similar to aqueous and metal accidents and experiments). Furthermore, a reasonable upper bound of total critical events of 1028 fissions corresponds to only 0.1% of the number of fissions represented by the spent nuclear fuel inventory in a repository containing 70,000 metric tons of heavy metal (MTHM) (the expected size for the proposed repository at Yucca Mountain, Nevada. [ABSTRACT FROM AUTHOR]