Outer Cladding Research Articles

A comprehensive theoretical assessment of potential ‘tramp uranium’ isotopic evolution in BWR reactors

This paper presents calculation studies towards validation of a methodology for estimations of the mass of tramp uranium in a boiling water reactor (BWR) core from water chemistry measurements. The computational studies are carried out for a typical BWR fuel assembly with CASMO-5M and MCNPX. By approximating the evolution of fissile nuclides and the fraction of 235U fissions to total fissions in different zones of a fuel rod, including tramp uranium on the clad surface, it is found that Pu gives the dominant contribution to fissions for tramp uranium after an irradiation on the outer clad surface of at least one cycle. Thus, the use of the so-called “Pu-based model” for the determination of the tramp uranium mass (this means in particular using the yields for 239Pu fission) appears justified in the cases considered. On that basis, replacing the older “U-based model” by the “Pu-based model” is recommended.

Low confinement loss photonic crystal fibre capable of supporting 54 orbital angular momentum modes

ABSTRACTA novel structure photonic crystal fibre (PCF) supporting orbital angular momentum (OAM) modes is proposed. The transmission layer is a ring core with high refractive index, sandwiched between the inner air-hole cladding and the outer cladding composed of nonuniform air-holes periodically arranged in silica. The diameters of the air-holes in the outer cladding gradually increase in the radial direction. The simulation results show that the designed PCF is capable of supporting 54 OAM modes over the 650 nm bandwidth ranging from 1200 nm to 1850 nm, and possesses some advantages in low confinement loss and flat dispersion, that is, the confinement loss is low to the order of magnitude of and the dispersion slope is less than 0.2.

Slow light via stimulated Brillouin scattering in double-clad As2Se3 chalcogenide photonic crystal fibers

Slow light of stimulated Brillouin scattering in double-clad As2Se3 chalcogenide photonic crystal fibers was investigated theoretically. The influence of air hole size of the inner and outer cladding of the PCFs on Brillouin gain spectrum, Brillouin threshold time delay, and Brillouin gain by taking into account the contribution of the high-order acoustic mode was numerical simulated by full vectorial finite element method. The simulated results indicate that the properties of slow light are affected more obviously by varying the air filling fraction in the inner cladding and less affected by the air hole size of the outer cladding. We found that with the time delay up to 705ns, Brillouin gain up to 40dB can be achieved with pump power of only 10mW in a 1m long chalcogenide PCF when the air filling fraction in the inner cladding is 0.9. The pertinent results can be of great importance for studying and designing the optical devices or optical sensors based on this kind of PCF.

Influence of wavelength on the bandwidth of W-type plastic-clad silica optical fibers

The bandwidth and steady-state loss of multimode W-type plastic-clad silica optical fibers are investigated by solving the time-dependent power flow equation. The results show how the bandwidth of W-type plastic-clad silica optical fibers can be enhanced by shifting from the red to the infrared wavelength region for different intermediate layer widths and refractive indices of the outer cladding. Such characterization of these fibers is consistent with their manifest effectiveness in reducing modal dispersion and increasing bandwidth.

Sensitivity Enhancement in Long Period Gratings by Mode Transition in Uncoated Double Cladding Fibers

This work deals with long period gratings (LPGs) fabricated in double cladding fibers (DCFs) with W-type refractive index profile and analyzes their surrounding refractive index (SRI) sensitivity. The W-type fiber presents an outer cladding with refractive index higher than the inner one, thus some cladding modes can be guided in the ring-shaped outer cladding without interacting with the core mode. However, the transition phenomenon from outer- to inner-cladding of these modes can be induced, through the reduction of the external cladding thickness (i.e. fiber diameter). As a matter of fact, here we demonstrate for the first time the mode transition phenomenon without any additional coating on the fiber. The result is a significant enhancement of the SRI sensitivity, as well as the possibility to tune the SRI range with maximum sensitivity gain. It is illustrated by numerical analysis and experimentally verified by considering LPGs written in pure-silica core with F-doped inner cladding and silica outer cladding fiber, by means of the electric arc discharge technique. The case study is focused on the SRI sensitivity in water-like environment as for biological applications. Proof of concept results have demonstrated that, by proper selection of the outer diameter through chemical etching, the gain in SRI sensitivity reaches from 40 to 60 as compared with unetched fiber, with maximum sensitivity around 420 nm/RIU with water as surrounding material.

Exploiting of the aesthetic potential of hand knitting stitches in the implementation of contemporary designs for women cardigan

The art of hand knitting is one of the oldest arts are practiced by man , this art industry has developed through the ages, and so far continue to practice this art and employ it in line with the latest fashion lines in addition to the clothes produced by hand knitting stitches suit all age groups because of its characteristics Aesthetic and functional such as giving warmth and comfort to the body and freedom of movement. In spite of the variety and variety of studies dealing with knitting, it has not been taken advantage of the aesthetic potential of hand knitting stitches in women's outer clothing, especially cardigan, which is one of the newly models emerging and favored by the majority of women . Therefore, the current research aims to take advantage of the aesthetic potential of hand knitting stitches in enriching women cardigan functionally and aesthetically, identify the opinions of specialists in the suitability of models of cardigan implemented from the cloth with hand knitting and identify the views of consumables in the models of cardigan implemented using hand knitting stitches. The research follows the descriptive approach in the preparation of the theoretical framework of the research, through access to literature and previous studies and the construction of research tools and experimental method through the implementation of hand knitting pieces and employ different designs on women cardigan. (10) models of cardigan were implemented and hand knitting samples are implemented according to the design of each model were installed on the cardigan . The implemented models were presented to the specialists in the field of clothing and textile (9) in addition to a group of consumables (30) consumers from the age of (25 - 45) in order to evaluate them in terms of the required evaluation axes, and after processing the results using appropriate statistical methods show the success of the implemented models In obtaining high values ​​according to measured evaluation axes they are also accepted by arbitrators and consumers , The most important results of the research were that there are statistically significant differences between the implemented models in achieving aspects of evaluation as a whole (design bases - functional side - aesthetic side - innovative side) according to the opinions of the arbitrators, where the seventh model came from the best models implemented in achieving Aspects of the assessment as a whole according to the opinions of the arbitrators and at least the ninth model. Consumers' opinions are positive towards the use of the implemented models, where the seventh model came from the best models implemented according to the views of the consumables and the least model ninth .

Predicting crack patterns in SiC-based cladding for LWR applications using peridynamics

SiC continuous fibre reinforced SiC matrix (SiC-SiC) composites are a proposed material for accident tolerant fuel cladding. Thermomechanical models of SiC-based cladding under light water conditions indicate that microcracking in the radial direction of the tubing may lead to a loss of hermicity. SiC-based tubing is known to have anisotropic elastic properties but the effect of this anisotropy have not been incorporated into existing thermomechanical models of clad cracking. This work augments an existing isotropic 2D peridynamic model of cracking and damage in the r-θ plane of a SiC-based cladding to account for the orthotropic elastic properties of SiC-SiC composite tubing. Three SiC-based architectures are modelled under normal operating conditions of a UO2-fuelled pressurised water reactor (PWR). The results of the anisotropic SiC-cladding model are compared with the results of the isotropic model, and the sensitivity of results to material anisotropy, thermal conductivity, and applied linear power rating are analysed.The results of this analysis show that anisotropy has a significant effect on the damage and crack patterns observed in the r-θ plane of SiC-based cladding, if either an inner or outer monolith is present. The anisotropic model predicts more cracks in two layer clad with an inner monolith and higher levels of damage in a two layer clad with an outer monolith than the isotropic model. Under normal reactor conditions the outer monolith clad architecture was found to remain hermetic.

Design and coupling characteristics of terahertz dual-core anti-resonant fiber

The THz wave has good photonic and electronic properties, and has high penetration for non-polar materials, but its own photon energy is low. In addition, the THz wave also has characteristics such as wide bandwidth and large communication capacity, thereby making the THz wave possess important academic value and wide application prospects in the fields of non-destructive testing, biomedical imaging and communication. The development of THz technology requires not only high-performance THz waveguide technology for efficient transmission of THz waves, but also important optical devices such as optical switches, modulators, and couplers that are suitable for THz bands. With the in-depth study of THz waveguide technology, researchers have proposed many high-performance THz waveguide structures, such as metal hollow core tube waveguide, parallel metal plate waveguide, photonic crystal fiber and microstructure hollow core fibers, among which hollow-core photonic crystal fibers and hollow-core anti-resonant fibers (HC-ARF) have developed rapidly in recent years. So far, THz single-mode single-polarization fiber and high-birefringence fiber have been widely studied, but the researches on the fiber structure and devices that realize THz wave directional coupling are relatively rare. In this paper, we study the influences of the arrangement and distribution of the inner and outer claddings of HC-ARF on transmission characteristics, and thus design a new type of THz dual-core anti-resonant fiber. Compared with ordinary quartz fiber couplers and dual-core photonic crystal fibers, it can utilize a relatively simple structure and achieve directional coupling above 2 THz. Using the finite element analysis method to theoretically analyze the loss characteristics and coupling characteristics of the fiber, it is found that HC-ARF changes the periodic arrangement and distribution of the inner cladding tube within a certain range, which can achieve mode leakage without affecting the fiber transmission characteristics. So the THz dual-core anti-resonant fiber can be designed by using the mode leakage coupling mechanism. By changing the core distance and core gap size, the directional coupling with a coupling length of 0.72 m is realized at a transmission frequency of 2.5 THz. This terahertz dual-core anti-resonance fiber will have an important application value in terahertz optical devices such as terahertz optical switches, modulators and couplers.

Corrosion tests in water of fuel elements irradiated in the world’s first NPP reactor

Spent nuclear fuel (SNF) storage in reactor spent fuel pools (SFP) is one of the crucial stages of SNF management technology: it requires special measures to ensure nuclear and radiation safety. During long-term storage in water-filled SFPs, leak-tight canisters in which SFAs are usually placed can become unsealed, which will result in the development of corrosion processes in the fuel element (FE) claddings. We studied fragments of spent fuel elements of the AM reactor of the World’s First NPP during their long exposure in the aqueous medium. The aim of the study was to obtain experimental data on the corrosion changes in the FE claddings and fuel composition during storage as well as on the release of radioactive fission products from them. For the study, a laboratory facility for exposing fuel elements in the water was developed and experimental fragments of fuel elements were made. The study was carried out in the hot chamber of the SSC RF-IPPE. The change in the activity of the water was estimated by the γ-dose rate from the selected water sample. The diameter measurements and metallographic studies were carried out in various sections of FE fragments. Corrosion tests were carried out on fragments of spent fuel elements of the AM reactor of the World’s First NPP that were stored for a long time (more than 50 years – FEs with U-Mo fuel and ~ 20 years – FEs with UO2 fuel) using standard technology – first in SFP canisters filled with water and then in dry canisters in the air. Placing the fuel elements in the water did not lead to through damage to the FE claddings and a significant change in the size (diameter) of the outer cladding. Metallographic studies of the FE fragments after the corrosion tests showed the presence of intergranular and local frontal corrosion on the surface of the claddings, the depth of which exceeded the depth of the cladding corrosion defects before testing. The rate of radionuclide release from the fuel composition was estimated by the γ-dose rate of water samples taken from the glasses with FE fragments. Throughout the test period, the dose rate of water samples from the glasses with defect-free FEs remained constant. The dose rate from water samples taken from the glasses with the FE fragments with an artificial defect grew during storage.

Wavelength dependence of equilibrium mode distribution and steady state distribution in W-type plastic-clad silica fibers

Abstract Wavelength dependence of equilibrium mode distribution (EMD) and steady state distribution (SSD) in W-type plastic-clad silica fibers (PCSFs) is investigated in this paper for parametrically varied width of the fiber’s intermediate optical layer and refractive index of the outer cladding. We have shown that the W-type PCSF has better transmission characteristics at longer infrared wavelengths. This is explained by the rise of the leaky mode losses with increasing wavelength. This facilitates tailoring W-fibers to a specific application at hand in the infrared wavelength region.

Worst crosstalk analysis in heterogeneous and trench assisted heterogeneous multicore fiber for different core counts and layouts

In order to obtain appreciably low worst crosstalk level in high core count multicore fiber, heterogeneous MCF with different core configurations and layouts have been investigated analytically using coupled mode equation. The variations in worst crosstalk behavior with respect to the bending radius, core configurations, core layouts, and outer cladding thickness have been analyzed. Further, the core count dependent variations in worst crosstalk level, core pitch, and peak bending radius in different core layouts have been presented. It has been observed that the selection of core configuration, core layout, and outer cladding thickness have significant impact on the reduction in worst crosstalk level. For example, in 12-core normal-index heterogeneous MCF with SLS structure, the core Configuration 1 can provide the worst crosstalk level reduced by 7.09 dB and 16.92 dB in comparison to the other two core configurations, i.e., Configuration 2, and Configuration 3, respectively. Further, for the same core count with TA Configuration 1, SLS core layout can achieve the reduced worst crosstalk level in comparison with circular ORS and DRS, hexagonal ORS and DRS respectively by 24.62 dB, 25.86 dB, 28.87 dB and 30.64 dB.

PATHOPHYSIOLOGICAL ASPECTS OF COMPRESSION THERAPY USE FOR PREVENTION OF SCARS AFTER BURNS

Mechanical squeezing of a skin cover by knitted clothes or its details is considered as the basic technological principle of compressive therapy. The definition of a level of squeezing the body by medical pressure clothes and manufacturing of an individual pattern for it sewing is offered to be carried out on the basis of physiologically adequate criteria of blood microcirculating of patients with various anthropometrical and functional blood pressure parameters with the help of the device - electronic tension-meter. Ischemization of the connective tissue parts of the scar, which is clinically confirmed by the foliation of the skin under compression elastic clothing, leads to a decrease in the mass of connective tissue and accelerated subsidence of the processes of inflammation and maturation of scar tissue. At the same time, the object affected by the compression therapy is the connective tissue that is formed, keeping the collagen fibers and fibroblasts in disorder. Creating a compression in excess of 25 mm Hg per cm2 in the early stages leads to a reduction in interstitial edema and limitation of excess formation of granulation tissue capillaries. According to the results of experimental and preliminary clinical studies, it was found that the optimum mechanical compression of the body tissues with elastic clothing is achieved by mechanical compression, which in quantitative terms corresponds to half of the average dynamic blood pressure, adjusted to the level of development of subcutaneous adipose tissue of the patient. In addition to the anatomical and physiological features of the structure of subcutaneous adipose tissue in different parts of the body, according to the results of clinical observations in people with different levels of vascular tone, it became necessary to take into account not only the average dynamic but also diastolic pressure, that largely determines the conditions of transcapillary blood exchange, resulting in additional compression of their outer compression clothing that can not only affect the level of local blood flow, but also the ability of hemodynamic function. While wearing medical clothing for compression therapy, the patient subjectively felt compression of the tissues, and objectively this was accompanied by mechanical pressure on the pressure sensor, and therefore – by switching on a light indicator, which indicated the achievement of the necessary mechanical impact on the compression therapy of the tissue. Thus, the suggested method provides a technological and accurate removal of the pattern of clothing for compression therapy, which will help to produce the optimal clothing size, and therefore to achieve the desired therapeutic effect.

Metabolic rate and muscle activation level when wearing state-of-the-art cold-weather protective clothing during level and inclined walking

Use of cold-weather personal protective clothing (PPC) in cold climates is essential but can add metabolic cost to the wearer. This study measured the effect of wearing state-of-the-art PPC and personal protective equipment (PPE), with the possible effect of clothing layers and fit, on physiological responses including metabolic rate (MR) and muscle activation level. 19 male participants (80.2 ± 5.9 kg, 181.5 ± 5.1 cm) wore five different clothing ensembles during level (0°) and inclined (6°) walking. Compared to a base layer ensemble (388.7 ± 42.7 W/737.8 ± 57.9 W), wearing a 3-layer PPC ensemble (421.5 ± 44.7 W/811.7 ± 69.2 W) significantly increased MR, and adding PPE (458.3 ± 59.8 W/864.5 ± 71.2 W) further increased MR during level/inclined walking. Independent of the extra weight, adding a middle layer between base layer and outer clothing significantly increased MR during inclined walking only, and no effect of oversized outer clothing was measured.

Seismic Aspects Regards Overbuilding on Masonry Heritage Buildings

Nowadays, masonry heritage buildings usually experience changes during exploitation. In areas of emphasized seismic risk, in cases of extensions, alterations to the original dimensions, reconstruction (the removal of bearing elements, replacement of materials, introduction of new fittings), or the subsequent erection of properties close by, with a comparison of the foundation levels change of use, refurbishment, extension, or additional building to an existing building. It is necessary to analyze the seismic aspect of such interventions in seismic prone areas. At first, we’ll focus on the legal and technical regulations. For start we’ll look back at UNESCO’s Program on Masonry Heritage, then domestic and regional legal and technical regulations and with all of that we will define the first step of the process. Next step would be a detailed registration of the current condition of the building, and also determining the characteristics of the embedded materials. The load bearing structures of the building must also be accurately identified, with all relevant measurements and, in particular, a description of the building materials and their condition. This includes all detailed maps, plans, and details of the used materials, and especially detailed record of all the damages on the structure. Even at this early stage of investigative works it may prove necessary to secure certain structural elements, or even the entire building, to prevent it from collapsing. As a rule, this requires not only the removal of the outer cladding or even of parts of a wall to determine the depth of cracks but also, if there is any suggestion of subsidence, excavations around the building or to the depth of the foundations. Calculations, based on the planned and current condition of the building, will show whether the strengthening and rehabilitation are needed for the structure. The elements that need reinforcement or conservation can be identified during the initial visit, and provision can immediately be made to take the necessary steps to relieve the load. It is necessary to do all the steps regarding technical regulations, legal regulations, methods of approach, theoretical consideration, methods of calculation, and in the end to determine the needs of that building. Theoretical consideration regarding the determined condition of structure, from all the above aspects, is the next step to be done. This also includes evaluation of the viability of these interventions, based on experience. The most sensitive issue, without doubt, is determining the condition of the foundations. This should be addressed with the utmost care with the general opinion of the building’s stability in mind.

Benchmarking COMSOL Multiphysics Single-Subchannel Thermal-Hydraulic Analysis of a TRIGA Reactor with RELAP5 Results and Experimental Data

COMSOL Multiphysics has been used to conduct thermal-hydraulic analysis in multiple nuclear applications. The aim of this study is to benchmark the prediction accuracy of COMSOL Multiphysics in performing thermal-hydraulic analysis of TRIGA (Training, Research, Isotopes, General Atomics) reactors such as the Geological Survey TRIGA Reactor (GSTR) by comparing its predictions with RELAP5 (a widely used code in nuclear thermal-hydraulic analysis) results and experimental data. The GSTR type is Mark I with a full thermal power of 1 MW, and it resides at the Denver Federal Center (DFC) in Colorado. The numerical investigation of the present work is carried out by developing single-subchannel thermal-hydraulic models of the GSTR utilizing RELAP5 and COMSOL codes. The models estimate the temperatures (fuel, outer clad, and coolant) and water flow patterns in the core as well as fuel element powers at which void starts to form within the coolant subchannels. Then, these models’ predictions are quantitatively evaluated and compared with the measured data.

Dual-cladding high birefringence photonic crystal fiber with elliptical-core

A novel elliptical core photonic crystal fiber (EC-PCF) is proposed with a trapezoidal outer cladding and three different inner claddings in this paper. The material of proposed fiber is a combination of the background material of silica and core material of As2S3. Using the finite element method (FEM) with the boundary condition of the circular perfectly matched layer (C-PML), the effect of different inner cladding structures (ellipse plus circles, strip circles, and hexagonal circles) on birefringence and nonlinear coefficients is analyzed. Simulation results show that the inner cladding has revealed a high birefringence in the order of 3.3136 × 10-1 with strip circles, while the nonlinear coefficients for x- and y-polarization is 2.81 × 104 w−1/km and 2.09 × 104 w−1/km at an operation wavelength of 1.55 μm, respectively. The demonstration of our proposed fiber can supply a feasible method for optical communication and supercontinuum generation.

Calculation of the power of the field, peneting into the external environment of the weaknessing guide of a single-mode fiber

A regular circular weakly guiding double clad optical fiber is considered. For a single-mode regime of the waveguide, an expression for estimating the proportion of the mode field power penetrating into the outer continuous cladding is obtained using a standard approach and a Gaussian model. It is shown that a simpler and more transparent result is obtained in the Gaussian model, which can be used in practical applications, in particular, when designing this type of waveguides with a minimal proportion of power penetrating into the outer shell.

Clothing sets with thermoregulation function for mine rescuers

Mine rescuers’ work is associated with many extreme hazards, including difficult climatic conditions. At the same time, the clothing and cooling systems that they use are still too ineffective in terms of dissipating excess heat from the body, which sometimes leads to overheating and consequent death of a rescuer due to heat stroke. These factors constituted an impulse to undertake work towards the development of new, effective in terms of cooling and protective properties, clothing sets for mine rescuers. This publication presents two alternative clothing sets developed in the RESCLO project, made up of outer protective clothing, used along with one of the two underwear variants, ie. underwear with inserts with phase change material (PCM) or underwear with air-fed cooling system from the air receiver. These solutions ensure compatibility with the additional equipment of the rescuer and provide the possibility of ad hoc configuration of clothing sets depending on the conditions of the action and the threats. Laboratory tests have shown that depending on the tested variant, the thermoregulatory solutions used allow for heat dissipation from the rescuer's body at the level of up to 30 W/m2, which will have a positive effect on the safety of mine rescuers during the operation and extend their safe working time in the underground hot environment.

Tensile strength and failure behavior of bare single mode fibers

Abstract We have investigated systematically the tensile strength and failure behavior of bare single mode fibers (SMFs) prepared by mechanical stripping technique. The tensile strength of bare SMFs under different temperatures is analyzed based on Weibull statistics. At room temperature, the bare SMFs show lower tensile strength than the SMFs with coating. The Weibull modulus referring to the width of the tensile strength distribution decreases when the gauge length of bare SMFs increases. The fractographic examination indicates that the fracture initiates from the outer cladding surface. As testing temperature increases from room temperature to 900 °C, we find that the tensile strength of bare SMFs decreases for the reason of the structural surface relaxation of SMF. The Weibull modulus decreases firstly then increases. Such change of bare SMFs is due to the partial restoration of flaws on fiber surfaces as testing temperature increases. The obtained results could provide guidance for the application of bare SMF prepared by mechanical stripping technique in harsh environment.

Optical data signals in fiber optic communication links with fading

Introduction: This article is based on the recent research work in the field of two subjects: signal data parameters in fiber optic communication links, and dispersive properties of optical signals caused by non-homogeneous material phenomena and multimode propagation of optical signals in such kinds of wired links.Purpose: Studying multimode dispersion by analyzing the propagation of guiding optical waves along a fiber optic cable with various refractive index profiles of the inner optical cable (core) relative to the outer cladding, as well as dispersion properties of a fiber optic cable due to inhomogeneous nature of the cladding along the cable, for two types of signal code sequences transmitted via the cable: return-to-zero and non-return-to-zero ones.Methods: Dispersion properties of multimode propagation inside a fiber optic cable are analyzed with an advanced 3D model of optical wave propagation in a given guiding structure. The effects of multimodal dispersion and material dispersion causing the optical signal delay spread along the cable were investigated analytically and numerically.Results: Time dispersion properties were obtained and graphically illustrated for two kinds of fiber optic structures with different refractive index profiles. The dispersion was caused by multimode (e.g. multi-ray) propagation and by the inhomogeneous nature of the material along the cable. Their effect on the capacity and spectral efficiency of a data signal stream passing through such a guiding optical structure is illustrated for arbitrary refractive indices of the inner (core) and outer (cladding) elements of the optical cable. A new methodology is introduced for finding and evaluating the effects of time dispersion of optical signals propagating in fiber optic structures of various kinds. An algorithm is proposed for estimating the spectral efficiency loss measured in bits per second per Hertz per each kilometer along the cable, for arbitrary presentation of the code signals in the data stream, non-return-to zero or return-to-zero ones. All practical tests are illustrated by MATLAB utility.