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Abstract: In this paper, photonic crystal (PhC) based on two dimensional (2D) square and hexagonal lattice periodic arrays of Silicon Carbide (SiC) rods in air structure have been investigated using plane wave expansion (PWE) method. The PhC designs have been optimized for telecommunication wavelength (λ =1.55μm) by varying the radius of the rods and lattice constant. The result obtained shows that a photonic band gap (PBG) exists for TE-mode propagation. First, the effect of temperature on the width of the photonic band gap in the 2D SiC PhC structure has been investigated and compared with Silicon (Si) PhC. Further, a cavity has been created in the proposed SiC PhC and carried out temperature resiliency study of the defect modes. The dispersion relation for the TE mode of a point defect A1 cavity for both SiC and Si PhC has been plotted. Quality factor (Q) for both these structures have been calculated using finite difference time domain (FDTD) method and found a maximum Q value of 224 for SiC and 213 for Si PhC cavity structures. These analyses are important for fabricating novel PhC cavity designs that may find application in temperature resilient devices. [Copyright &y& Elsevier]

In this research, a series of Dy3+ ions doped Sr 9 Y 2 W 4 O 24 (SYWO) phosphors was prepared for the application in white-LEDs and display devices. The structure, surface, and photo-luminescent (PL) behaviour of the samples were studied. X-ray diffraction (XRD) and Fourier Transform Infra-Red (FT-IR) spectroscopy indicated the formation of single phase particles with no contaminants with various vibrational bands present in the host lattice. The synthesised powders showed agglomeration with the average crystallite size to be in the range of 22–27 nm. The optical band gaps were estimated using diffuse reflectance spectral (DRS) data. The emission spectra of SYWO: xDy3+ (1.0, 2.0, 3.0, 4.0, & 5.0 mol%) have been obtained at different excitation wavelengths of 354, 367, and 391 nm. The SYWO phosphors emit intense blue and yellow colors at 491 nm (4F 9/2 → 6H 15/2), 576 nm (4F 9/2 → 6H 13/2) & 679 nm (4F 9/2 → 6H 11/2), respectively. Furthermore, from the CIE 1931 diagram, it is evident that the emission from these Dy3+ doped phosphors lies in the white region. The lifetime of excited Dy3+ ions decreased with increasing Dy3+ concentration as seen in the luminescence decay graphs. Finally, to determine the phosphor's luminescence thermal stability, temperature dependent photoluminescence (TD-PL) was recorded and the activation energy calculated from this study was found to be 0.231 eV. In the light of aforementioned results, we can conclude that Dy3+ doped Sr 9 Y 2 W 4 O 24 phosphors could be used in construction of w-LEDs or as white-emitting luminescent materials in various photonic devices and other photonic applications. • Solid state reaction technique was utilised to synthesise SYWO: Dy3+ ions doped phosphors. • The phase identification done by using XRD analysis of un-doped & doped SYWO phosphors. • SYW: Dy3+ ions doped phosphors emit blue, yellow & red emission on 367 nm excitation. • CIE coordinates are located in the white area under 367 nm excitation. • SYWO: Dy3+ phosphors show relatively high thermal stability. [ABSTRACT FROM AUTHOR]

Abstract: We report the design of an AND optical logic gate based on two dimensional triangular lattice of air holes in Si. The proposed structure consists of Y-branch waveguide without nonlinear materials and optical amplifiers. The simulation results show that the proposed all optical structure could really function as an AND logic gate. This structure is favorable for large scale optical integration and can potentially be used in on-chip photonic logic integrated circuits. [Copyright &y& Elsevier]

Abstract: Critical Heat Flux (CHF) is an important parameter for the thermal design of any heat generating system, most importantly, nuclear reactors. Owing to the complex mechanisms of CHF there has been a large proliferation of the correlations, each having narrow range of validity, which shows that the empirical correlation is not an appropriate approach for the CHF prediction for a wide range of validity. This limitation has led to the development of the phenomenological approach of the CHF prediction. The film dryout mechanism is applicable to the high quality CHF corresponding to the annular flow pattern in which the progressive depletion of the liquid film leads to dryout. The basic concern in the prediction of dryout is the accuracy in the evaluation of the droplet deposition and entrainment. There are various models for the estimation of the entrainment and deposition of droplets. However, most of these models are based on the air-water data at the atmospheric conditions and hence their applicability to the BWR conditions needs to be confirmed. Some of the models are based on the steam–water data which needs to be validated for the dryout prediction under BWR conditions. In this paper, the film dryout modelling has been carried out for the prediction of CHF using appropriate models for entrainment fraction and deposition coefficient. The results have been compared with the CHF data generated to substantiate the appropriateness of the selected models under BWR conditions. [Copyright &y& Elsevier]

Abstract: It is now mandatory to seismically qualify the safety-related structures and components used in the nuclear power plants. Among several qualification approaches the qualification by the analysis using finite element (FE) method is the most common approach used in practice. However, the estimated dynamic behaviour by FE model of a structure is known to show significant deviations from the dynamic behaviour of the ‘as-installed’ structure in many cases. Considering such limitations, few researchers have advocated re-qualification of such structures after their installation at site to enhance the confidence in qualification vis-à-vis plant safety. For such an exercise, validation of FE model with experimental modal data is important. A validated FE model can be obtained by the model updating methods in conjugation with the in situ experimental modal data. Such a model can then be used for qualification. However, for the reactor in-core components such a modal testing and FE model updating may not be straightforward. Hence, the complication involved in the reliable seismic qualification of in-core components and the advantage of using the FE model updating has been brought out in the paper through an example of a typical in-core component—a perforated horizontal tube recently installed in a nuclear reactor in India. [Copyright &y& Elsevier]

Abstract: Both cholesteryl oleate (CO) and cholesteryl oleyl carbonate (COC) are thermotropic mesogens with a general cooling phase sequence: isotropic→cholesteric→smectic→crystal. They are almost identical with respect to molecular structure and the central location of molecular dipole. However, the orientation of the latter is axial for CO and transverse for COC. A eutectic mixture of these components shows a phase sequence like the above but involving an induced smectic-C* phase. We explain this discovery on the basis of computer simulation results involving rigid core-dipole-flexible tail model of a mesogen and argue in favor of a ferroelectric liquid crystal model of the induced phase. [Copyright &y& Elsevier]

Abstract: Experimentally it is evident that the nature of the flow-induced excitation in a pipe conveying fluid is a broadband frequency excitation. It is also observed that the amplitude of excitation decreases with increase in frequency. However, there is no method to estimate such forces. The measurement of excitation force all along the length of a pipe using the pressure transducers may be difficult or perhaps impossible. Another possibility is to measure the structural responses using vibration transducers all along the pipe length and then estimate the flow-induced excitation forces (both amplitude and phase) using a finite element (FE) model of the pipe. However, the measured degree of freedoms (dofs) are always much smaller than the dofs in FE model, hence a method has been developed that uses non-linear optimization method involving the limited measured responses together with FE model to predict the excitation forces (both amplitude and phase) acting all along the pipe conveying fluid. The predicted excitation forces can then be used to perform safety related study by assessing the pipe responses at any location whether accessible or not. The theory of the proposed method and its validation has been presented in the paper through a long straight pipe conveying fluid. Typical applications of the proposed method are also discussed. [Copyright &y& Elsevier]

The subject of finite element (FE) model updating has advanced significantly and has emerged as a useful tool in the modelling of structures particularly in the field of structural dynamics. However, to enhance the confidence in the updated model, presently emphasis of researches is to demonstrate the prediction capabilities of the updated model in case of any structural change in future. This has been shown by several researchers on the benchmark and on small laboratory scaled models. In the present paper a prediction capability of the updated model of a full scale set up of the perforated tube used in nuclear power reactor is presented as a case study. [Copyright &y& Elsevier]

A theoretical model has been developed to study the local heat transfer coefficient of a condensing vapour in the presence of a noncondensable gas, where the gas/vapour mixture is flowing downward inside a vertical tube. The two-phase heat transfer is analysed using an annular flow pattern with a liquid film at the tube wall and a turbulent gas/vapour core. The gas/vapour core is modeled using the analogy between heat and mass transfer. The model incorporates Nusselt equation with McAdams modifier and Blangetti model for calculating the film heat transfer coefficient, Moody and Wallis correlations to account for film waviness effect on gas/vapour boundary layer. The suction effect due to condensation, developing flow and property variation of the gas phase is also considered. A comparative study of heat transfer coefficient and vapour mass flow rate has been made with various models to account for condensate film resistance and condensate film roughness. Results show that for very high Reynolds number, the condensation heat transfer coefficient is higher than the film heat transfer coefficient. [Copyright &y& Elsevier]

5,7-Diamino-4,6-dinitrobenzofuroxan (CL-14) has been synthesized by a cost-effective method. CL-14 was characterized by spectral data (IR, NMR and mass) and elemental analysis. The compound was evaluated in plastic bonded explosives (PBX) using polyurethane (PU) as binder. The thermal, mechanical and explosive properties of PBX composition from preliminary tests are also reported. Good thermal stability as well as good insensitiveness are indicated. [Copyright &y& Elsevier]

Ohmic heating power supply is used in ADITYA Tokamak for plasma breakdown and current drive. Presently the ohmic coils store a magnetic flux of 0.40 V s and high di/dt is created for the required loop voltage. After the plasma breakdown the plasma current control is made active with the difference of reference plasma current and measured plasma current to drive the PI regulator, which regulates the ohmic falling current. The vertical field current is also made proportional to plasma current by feedback control at appropriate time. The control scheme adopted and the results with the feedback control are described in this paper. We could improve the plasma current as well as plasma current flattop by employing the plasma current feed back control. Further to correct the radial position in fast time scale, four-quadrant transistor switched bridge inverter power supply by plasma position feedback control is proposed. On line ±ΔX (by position coils) position signal is given to PI control and polarity detector accordingly the current is amplified by the bridge inverter and fed to the four set of feedback coils which shifts the plasma position on radial directions. [Copyright &y& Elsevier]

In this paper, the power penalty analysis for approximate and realistic weight functions has been presented for combating the pulse broadening effects of group-velocity dispersion in a fiber-optic communication link using differential time delay method including higher-order dispersion terms. The expressions for root mean square (RMS) phase deviation, optimum chirp factor and figure of merit have been evaluated for approximate and realistic systems. We show that the optimum value of chirp factor corresponds to dispersion compensation. The power penalty graphs for second-, third-, and fourth-order dispersion and their combinations have been presented for distance up to 300 km for this chirp factor for different weight functions. It is observed that the power penalty for realistic weight functions is less in comparison with the approximated weight function. It has also been shown that it is possible for a short pulse to propagate without significant broadening over the lengths many times longer than the usual dispersion length of fiber. [Copyright &y& Elsevier]

We herein demonstrate polypyrrole decorated micro-porous laboratory filter paper (PFP) as photoanode (PA) for efficient and stable water splitting. The straddling band position with water redox and the measured band gap of ~1.98 eV, make these PFP-PAs effective for water splitting reactions. The results manifest excellent photo-anodic PEC activity of these PFP-PAs, yielding a photocurrent density of ~9.5 mA/cm2 (at 1.23 V vs. RHE) in a three-electrode configuration. The incident photon-to-current efficiency (IPCE) and applied bias photon-to-current efficiency (ABPE) was measured to be 43.19% and ~1%, respectively. Moreover, the robustness of these flexible PFP-PAs was visualized by the provided stability for more than ~160 min in alkaline conditions. The current study provides a proof-of-concept for the realization of a cost-effective, flexible, and efficient paper-based artificial catalyst (like a natural leaf) for solar-driven water splitting. Image 1 • In-situ fabricated polypyrrole based flexible filter paper photo electrode (PFP-PEs). • Exhibit a bandgap of ~1.98 eV and reported as PEs for water splitting. • Photocurrent density of ~9.5 mA/cm2 (at 1.23 V vs. RHE) in 3-electrode system. • IPCE and ABPE was measured to be 43.19% and ~1%, respectively. • PFP-PEs stable for 160 min in alkaline conditions for PEC water splitting. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for renewable and clean energy sources has prompted the development of novel materials for photoelectrochemical (PEC) water splitting, but efficient solar to hydrogen conversion remains a big challenge. In this work, we report a bio-nanohybrid strategy in a photo-system to simultaneously enhance the charge separation and water splitting efficiency of photoanode (PA) by introducing Bacteriorhodopsin (bR), a natural proton pumping photosystem and GaN nanowall network (NWN), a direct band gap and corrosion-resistant semiconductor. The experimental study reveals that this combination of bR and GaN NWN has huge potential as a light-activated sensitizer as well as proton pumping source to achieve enhance photocurrent density in hydrogen evolution reaction (HER). Consequently, this synergistic effect in bR/GaN NWN PA gives rise to largely enhanced applied bias photon-to-current efficiency (ABPE) ~7.8% and photocurrent density (28.74 mA/cm2 at 1.0 V vs RHE). It is worth mentioning that the photocurrent density of bR/GaN NWN, to the best of our knowledge, is superior to previously reported bR-based PAs and bio-photoelectric devices reported till today for solar-to-hydrogen fuel generation. Image 1 • First report on GaN NWN as photoanode with bR into electrolyte. • Measured photocurrent density is 28.74 mA/cm2 at 1.0 V (vs RHE). • Largely enhanced applied bias photon-to-current efficiency (ABPE) ~7.8%. [ABSTRACT FROM AUTHOR]

• Green synthesized Au and Ag loaded TiO 2 nanofiber photoanodes for solar water splitting. • One step green synthesis of Ag and Au nanostructures using green synthesized carbon dots. • Highest photocurrent density achieved with Au@CNL/TNF based photoanodes. • Waste to Value added approach derived photoanodes for solar hydrogen production. We herein present the Au and Ag NPs synthesized via chemical reduction with green synthesized carbon nano lights (CNL) as a visible light photosensitizer for TiO 2 nanofibers (TNFs) towards photoelectrochemical water splitting. The synthesized photoanodes (PA1: TNFs, PA2: Ag@CNLs/TNFs and PA3: Au@CNLs/TNFs) were probed ex-situ for morphological, structural, optical and electronic properties before being used for the PEC experiments. We first show the efficient photocatalytic activity of these photoanodes for the degradation of methylene blue under visible light irradiation. Followed by the photoelectrochemical (PEC) water splitting investigation, which reveals the substantially improved photocurrent density to 13 mA/cm2 and 18 mA/cm2, for PA2 and PA3, respectively under simulated AM 1.5 solar illumination at 1.36 V vs RHE, ~15 fold enhancement compared to that obtained for a PA1. This improvement we attributed to the synergic consequence, improved absorption and effective charge carrier separation & transport due to surface plasmonic effect, which is well evident in the decrease of measured charge transfer resistance (R ct), for PA2 (15.1 Ω) and PA3 (6.71 Ω), as compared to PA1 (139 Ω). [ABSTRACT FROM AUTHOR]

We show a flux dependence changes in structural, optical and electronic properties of In x Ga 1-x N nanostructures (NSs) namely nanocolumns (NCs), nanoflakes (NFs) and nanowall network (NWN) grown directly on Si(111) surface. Field emission scanning electron microscopy (FESEM) images were recorded to see morphological changes from NFs to NCs and NWNc etc, while high-resolution X-ray diffraction (HRXRD) ω−2θ scans were used to determine In incorporation. The maximum In incorporation was observed to be 20, 33 and 38% for the sharp transition from NFs to NCs and NWNs, respectively. The charge carrier dynamics of these grown NSs were probed using Ultrafast Femtosecond Transient Absorption Spectroscopy (UFTAS) with excitation at 350 nm pump wavelength. The UFTAS studies show the comparative charge carriers dynamics of the NWS, NCs and NFs. The charge carrier studies show a higher lifetime in NWNs as compare to NCs and NFs. Further, to examine electronic structure and level of degeneracy of these NSs, core-level and valence band spectra were analyzed by X-ray photoelectron spectroscopy (XPS), which manifest the upward band bending ranging from 0.2 eV to 0.4 eV. [ABSTRACT FROM AUTHOR]

We investigated the morphological, structural, optical, electrical and carrier relaxation dynamic changes on the self-assembled grown InGaN nanocolumns (NCs) directly on p -Si(111) substrate at two different substrate temperature, namely 580 °C (A) and 500 °C (B). The emission wavelength of comparably low temperature (LT) grown NCs was red-shifted from 3.2eV to 2.4eV. First observations on the charge carrier dynamics of these directly grown NCs show comparable broad excited state absorption (ESA) for LT gown NCs, which manifest bi-exponential decay due to the radiative defects generated during the coalescence of these NCs. [ABSTRACT FROM AUTHOR]

In the context of Indian nuclear power programme, thorium has always had a prominent place due to its unique resource position with large thorium deposits and limited uranium reserves. A three-stage programme has been devised to efficiently utilise the available resources in a sustainable manner. Work on thorium fuel cycle has therefore been carried out right from the inception of Indian nuclear power programme. Engineering scale studies have been carried out on all aspects of the thorium fuel cycle - mining and extraction, fuel fabrication, utilisation in different reactor systems, evaluation of its various properties and irradiation behaviour, reprocessing and recycling. To provide impetus to these studies and to embark on a large-scale programme, the thorium fuel cycle based Advanced Heavy Water Reactor (AHWR) is being developed. The large-scale deployment of thorium based reactors will also require several additional features such as economic competitiveness, practically no impact on public domain, and enhanced safety which has several technological challenges to be overcome. The paper brings out the design aspects of the AHWR besides the ongoing work on other thorium based reactors such as the High Temperature Reactor (HTR) and the Molten Salt Reactor (MSR). [ABSTRACT FROM AUTHOR]

In this paper, the design of all-optical logic gates using the combination of universal NAND gates has been proposed. The photonic crystal structure consists of triangular lattice arrangement of air holes in silicon. Initially, the all optical NAND gate has been designed and optimized. Further, the optimized NAND gates have been used and arranged in a combination such that the combined structure behaves as an all-optical logic gate specifically, NOT, AND, OR, XOR and XNOR. The truth table for the designed all-optical logic gates has been verified at an operating wavelength of 1.55 μm. The proposed all optical gates exhibit a response period of 2.168 ps with a bit rate of 0.461 Tb/sec. Further, the contrast ratio for the designed gates has also been obtained. [ABSTRACT FROM AUTHOR]

Experiments were carried out to determine the minimum material volume in the gauge section of miniature tensile test specimens required to get mechanical properties data comparable to those from standard test specimens. The experimental results were verified and aided by numerical and metallurgical analysis simultaneously. In order to generalize the results, three different materials, having large variation in their mechanical properties, were selected for the study. [ABSTRACT FROM AUTHOR]

The present work elucidates the synthesis of Dy 3+ doped barium silicate glasses, along with the subsequent studies performed to evaluate its viability in solid state lighting applications. The synthesized photonic glasses were investigated via X-Ray Diffraction, Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy. The photoluminescence properties were examined under ultraviolet (UV)/near UV (NUV) excitation. Photoluminescence spectrum exhibited characteristic emission bands at λ em =483 nm (blue) and λ em =576 nm (yellow) which are ascribed to the 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions of Dy 3+ ion, respectively. The chromaticity coordinates under excitation of λ ex =348 nm are (0.31, 0.34), which lies in the white region of CIE 1931 chromaticity diagram and are in excellent proximity with the standard equal energy white illuminant (0.333, 0.333). The calculated correlated color temperature and the yellow to blue ( Y / B ) ratio are found to be 6602 K and 1.12, respectively for the optimized sample. The synthesized photonic glass also offered the possibility of tuning the color as exemplified through the variation in CIE coordinates, correlated color temperature and the Y / B ratio. The results confirm the possibility of color tunability from the proposed glass and may be useful for various photonic device applications. [ABSTRACT FROM AUTHOR]

This review presents the work carried out by the international community in the area of sheet explosive formulations and its applications in various systems. The sheet explosive is also named as PBXs and is a composite material in which solid explosive particles like RDX, HMX or PETN are dispersed in a polymeric matrix, forms a flexible material that can be rolled/cut into sheet form which can be applied to any complex contour. The designed sheet explosive must possess characteristic properties such as flexible, cuttable, water proof, easily initiable, and safe handling. The sheet explosives are being used for protecting tanks (ERA), light combat vehicle and futuristic infantry carrier vehicle from different attacking war heads etc. Besides, sheet explosives find wide applications in demolition of bridges, ships, cutting and metal cladding. This review also covers the aspects such as risks and hazard analysis during the processing of sheet explosive formulations, effect of ageing on sheet explosives, detection and analysis of sheet explosive ingredients and the R&D efforts of Indian researchers in the development of sheet explosive formulations. To the best of our knowledge, there has been no review article published in the literature in the area of sheet explosives. [ABSTRACT FROM AUTHOR]

A design of equiangular spiral photonic crystal fiber (PCF) in As2Se3chalcogenide glass is reported for mid-infrared supercontinuum generation. Supercontinuum covering the 1.2–15 μm molecular fingerprint region is achieved using only 8 mm long designed PCF pumped with 50 fs laser pulses of 500 W peak power. The structural parameters have been tailored for all-normal dispersion characteristic. Proposed structure has high nonlinearity (γ = 12474 W−1 km−1) at 3.5 μm with very low and flat dispersion −2.9 [ps/(nm × km)]. Supercontinuum with such broadening and high coherence degree is applicable for mid-infrared spectroscopy, gas sensing, early cancer diagnostics and free space communication. [ABSTRACT FROM AUTHOR]

Correlations for evaluation of Ultimate Tensile Strength (UTS) using Miniature Disk Bend Test (MDBT) or Small Punch Test (SPT) has been an open issue since the development of the techniques. The larger plastic strains, in tri-axial state of stress during SPT, make the translation to the equivalent uniaxial parameter less certain. Correlations based on P max of load–displacement curve are also in disagreement as the point corresponding to P max does not represent a necking situation as in case of UTS, in a uniaxial tensile test. In present work, an attempt has been made for locating necking zone, which appears prior to P max , through experiments and FEM analyses. Experimental results on disk specimens from 20MnMoNi55, CrMoV ferritic steel and SS304LN materials along with FEM analyses found that load corresponding to 0.48 mm displacement is to be very close to the necking zone, and gives best fit for a UTS correlation. [ABSTRACT FROM AUTHOR]

The recent Fukushima accident has resulted in an increased need for passive safety systems in upcoming advanced reactors. In order to enhance the global contribution and acceptability of nuclear energy, proven evidence is required to show that it is not only green but also safe, in case of extreme natural events. To achieve and establish this fact, we need to design, demonstrate and incorporate reliable ‘passive safety systems’ in our advanced reactor designs. In Nuclear Power Plants (NPPs), the use of passive safety systems such as accumulators, condensing and evaporative heat exchangers and gravity driven cooling systems provide enhanced safety and reliability. In addition, they eliminate the huge costs associated with the installation, maintenance and operation of active safety systems that require multiple pumps with independent and redundant electric power supplies. As a result, passive safety systems are preferred for numerous advanced reactor concepts. In current NPPs, passive safety systems which are not participating in day to day operation, are kept isolated, and require a signal and external energy source to open the valve. It is proposed to replace these valves by passive components and devices such as self-acting valves, rupture disks, etc. Some of these innovative passive valves, which do not require external power, have been recently designed, developed and tested at rated conditions. These valves are proposed to be used for various passive safety systems of an upcoming Nuclear Power Plant being designed by India. For example, the Hot Shutdown Passive Valves (HSPV), developed for the decay heat removal system keep the main heat transport system under hot conditions by passively sensing and controlling the system pressure. Another crucial and important valve which has been successfully developed is the Poison Injection Passive Valve (PIPV) for the Passive Poison Injection System. It not only provides higher reliability, but also ensures safe shutdown of the reactor in case of insider threats or malevolent acts in disabling active shutdown system of the reactor. Recently, an innovative valve called the Accumulator Isolation Passive Valve (AIPV) has been developed for the Emergency Core Cooling System (ECCS), which is engineered to mitigate the consequences of Loss of Coolant Accident (LOCA). During normal operation of the reactor, the pressurized accumulators (55 bar) are kept isolated from the reactor core (70 bar) by means of AIPVs. In case of a LOCA, these passive valves open when the main heat transport system pressure falls to a desired value. For prolonged cooling of the core, these passive valves regulate the discharge in a desired manner. These are non-standard, high pressure and high temperature valves, which are unavailable commercially and hence have to be indigenously designed and developed. This paper primarily deals with the design, development and testing of Accumulator Isolation Passive Valves (AIPV) proposed to be used in the ECCS. A 25 NB size AIPV has been designed and successfully tested at Integral Test Loop (ITL) under simulated reactor conditions. It is a self-acting, ANSI 600 rating valve, which requires no external energy (i.e., neither air nor electrical power). It not only provides passive isolation but also passively controls high pressure liquid discharge through it. The design concept of the valve, functional performance, in situ valve testing methodology and the test results at simulated conditions are discussed. [ABSTRACT FROM AUTHOR]

Thermal contact conductance (TCC) is one of the most important parameters in determining the temperature distribution in contacting structures. Thermal contact conductance between the contacting structures depends on the mechanical properties of underlying materials, thermo-physical properties of the interstitial fluid and surface condition of the structures coming in contact. During a postulated accident scenario of loss of coolant with coincident loss of emergency core cooling system in a tube type heavy water nuclear reactor, the pressure tube is expected to sag/balloon and come in contact with outer cooler calandria tube to dissipate away the heat generated to the moderator. The amount of heat thus transferred is a function of thermal contact conductance and the nature of contact between the two tubes. An experimental facility was designed, fabricated and commissioned to measure thermal contact conductance between pressure tube and calandria tube specimens. Experiments were conducted on disc shaped specimens under axial contact pressure in between mandrels. Experimental results of TCC and a linear correlation as a function of contact pressure have been reported in this paper. [ABSTRACT FROM AUTHOR]

Highlights: [•] An ANN model is developed to predict the in-reactor diametral creep in Zr–2.5%Nb. [•] Database from pressure tubes of Indian PHWRs have been used. [•] The developed ANN model can efficiently predict diametral creep of pressure tubes. [•] O cont and mech properties play important role in determining diametral creep rate. [Copyright &y& Elsevier]

Abstract: Under a postulated accident scenario of loss of cooling medium in an Indian Pressurised Heavy Water Reactor (IPHWR), temperature of the pressure tubes can rise and lead to large deformations. In order to investigate the modes of deformation of pressure tube – calandria tube assembly, material property data defining the flow behaviour over a temperature range from room temperature (RT) to 800̊C are needed. It is of practical importance to formulate mathematical equations to describe the stress–strain relationships of a material for a variety of reasons, such as the analysis of forming operations and the assessment of component's performance in service. A number of constitutive relations of empirical nature have been proposed and they have been found very suitable to describe the behaviour of a material. Although these relations are of empirical nature, various metallurgical factors appear to decide applicability of each of these relations. For example, grain size influences mainly the friction stress while the strain hardening is governed by dislocation density. In a recent work, tensile deformation behaviour of pressure tube material of IPHWR has been carried out over a range of temperature and strain rates (Dureja et al., 2011). It has been found that the strength parameters (yield and ultimate tensile strength) vary along the length of the tube with higher strength at the trailing end as compared to the leading end. This stems from cooling of the billet during the extrusion process which results in the variation of microstructure, texture and dislocation density from the leading to the trailing end. In addition, the variation in metallurgical parameters is also expected to influence the work hardening behaviour, which is known to control the plastic instability (related to uniform strain). In the present investigation, the tensile flow and work-hardening behaviour of a cold worked Zr–2.5Nb pressure tube material of IPHWRs has been studied over the temperature range of 30–600̊C. The stress strain data have been analysed in terms of stress–strain relations proposed by Hollomon (1945), Voce (1948) and Ramberg–Osgood (RO) (Ramberg and Osgood, 1943). The relative efficacies of these relations has been examined by fitting the appropriate equation to the experimentally obtained true stress–true strain data. The quality of fit of these empirical relations is quantified using square root of co-efficient of determination, i.e. R value (in %). The results have been discussed in terms of the correlation coefficient and in error in the estimation of UTS and uniform strain. Of the various relations employed, the Voce's relation has been found to describe the stress–strain behaviour most precisely up to 300̊C. Hollomon's relation describes the strain–stress behaviour of the material over the entire temperature range but with over-estimation of UTS. RO relation does not fit well in the initial stage but satisfactorily models the uniform elongation regime till UTS for temperatures up to 500̊C. [Copyright &y& Elsevier]

Abstract: Pulsed neutrons emitted from a plasma focus (PF) device have been used for the first time for the non-destructive assay of 235U content in different chemical forms (oxide and metal). The PF device generates (1.2±0.3)×109 D–D fusion neutrons per shot with a pulse width of 46±5ns. The method involves the measurement of delayed neutrons from an irradiated sample 50ms after exposure to the neutron pulse for a time of about 100s in the multichannel scaling (MCS) mode. The calibration of the active interrogation delayed neutron counter (AIDNEC) system was carried out by irradiating U3O8 samples of varying amounts (0.1–40g) containing enriched 235U (14.8%) in the device. The delayed neutrons were monitored using a bank of six 3He detectors. The sensitivity of the system was found to be about 100counts/s/g over the accumulation time of 25s per neutron pulse of ∼109. The detection limit of the system is estimated to be 18mg of 235U. The system can be suitably modified for applications toward non-destructive assay of fissile content in waste packets. [Copyright &y& Elsevier]