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Single-phase natural circulation loops (SPNCL) finds application in district heating reactors and low-power pressurized water reactors. It is not only adopted as a backup operation mode during accidental scenarios but also as the normal operating mode in several small and medium-sized advanced nuclear power plants. Stable operation is desired in such plants for smooth power generation and hence, the stability analysis of single-phase natural circulation systems assumes significance. The horizontal heater and horizontal cooler combination produce a maximum flow rate for a specific heater power but also is the most unstable compared to other configurations. Out of many instability restraining techniques, the orifice plate has been targeted by very few. The present experimental study focuses on the effect of using orifice plates (β = 0.90, 0.77, 0.64, and 0.51) on the stability of the 38.89 mm diameter rectangular loop with a horizontal heater and cooler configuration. The various operating procedures (start-up from rest, power raise from a stable steady-state, and power step down from an unstable state) have shown different stability/instability thresholds. Further, a hysteresis phenomenon was observed between the operating procedure of power raise from a stable state and the power step down from an unstable state, both exhibiting different stability thresholds. The increase in the stability threshold for β = 0.9, 0.77, and 0.64 for the operating procedure of start-up from rest was 75%, 110%, and 225% respectively compared to without orifice. Since the heater power was limited to 1100 W, the orifice of β = 0.51 was seen to be completely stable for the entire range of all three operating procedures for the same cooler conditions. From the loss coefficient (K), the effective length of the loops for β = 0.9, 0.77, 0.64, and 0.51 increased by 0.36, 1.32, 4.72, and 21.8 m respectively. Accordingly, the steady-state analytical solution with and without orifice found a good agreement with the experimental results. Thus, the present experimental investigations show that with the judicious choice of the flow restrictor, an unstable natural circulation system can be stabilized although the steady-state flow decreases.

In order to design advanced nuclear reactors with enhanced safety systems such as passive decay heat removal system (PDHRS), a new design of Isolation Condenser (IC) has been proposed. The effect of inclination of condenser tube on sliding bubble dynamics and associated heat transfer has been studied for seven angles of tube inclination α (with respect to vertical direction), in the range 0°≤α≤90°. For this purpose, two phase transient 3D CFD simulations using mixture model (based on Euler–Euler approach) have been performed. The model considers different mechanisms such as single phase natural convection, latent heat transfer due to evaporation, transient conduction due to disruption of thermal boundary layer and enhanced liquid convection due to bubble sliding motion (quenching). The transient vapor fraction ( ϵ G ) contours and flow distribution enables to understand the mechanism of bubble formation and bubble sliding motion. The major heat transfer mechanism was found to be the liquid agitation caused by sliding bubbles on the tube surface. The heat transfer contribution due to evaporation was found to be very small because of highly sub cooled ( ∆ T sub = 70 K ) liquid inside the tank. Results show that the heat transfer was found to be maximum for α=75° and minimum for α=30°. The bubble sliding length at the tube top was found to decrease and at the tube bottom was found to increase with an increase in the inclination angle (α). The enhanced transfer at α=75° ensures excellent thermal mixing and hence results in reduction in thermal stratification. This paper is in continuation of our earlier two papers which employed 21 l ( Gandhi et al., 2013a ) and 200 l ( Gandhi et al., 2013b ) PDHRS whereas this paper presents the simulation of 10 l and 10,000 m3 PDHRS.

During the past years, several studies were focused on the instability of single-phase rectangular natural circulation systems. However, experimental identification of instability threshold and categorization of instability regimes is of prime interest in many industrial applications which have been addressed by very few researchers that too limited to lower diameter loops only. Hence, in the present study, a larger diameter rectangular loop with horizontal heater horizontal cooler (HHHC) configuration has been designed to generate single phase natural circulation data on the steady state and stability behavior. Effect of different operating procedures (i.e., start-up from rest, power raising from stable steady state, and power reduction from an unstable state) on stability behavior are studied. Most of the oscillatory regimes are identified and noticed that the operating procedure can influence the instability threshold. The instability threshold was found to increase with the lowering of the coolant temperature and increasing its flow rate. The operating procedures i.e., power raising from stable steady state and start-up from rest gave the maximum and minimum values of the stability threshold respectively. As opposed to this, the minimum instability threshold in smaller diameter loops was reported for the operating procedure with power reduction from an unstable state. The experimental results confirm the occurrence of the hysteresis phenomenon. Due to the larger diameter and lower Lt/D ratio of the loop, all the oscillatory behaviors were aperiodic in nature in contrast to the observations in smaller diameter loops.

The recent Fukushima accident has raised strong concern and apprehensions about the safety of reactors in case of a prolonged Station Black Out (SBO) continuing for several days. In view of this, a detailed study was performed simulating this condition in Advanced Heavy Water Reactor. In this study, a novel concept of moderator cooling by passive means has been introduced in the reactor design. The Passive Moderator Cooling System (PMCS) consists of a shell and tube heat exchanger designed to remove 2 MW heat from the moderator inside Calandria. The heat exchanger is located at a suitable elevation from the Calandria of the reactor, such that the hot moderator rises due to buoyancy into the heat exchanger and upon cooling from shell side water returns to Calandria forming a natural circulation loop. The shell side of the heat exchanger is also a natural circulation loop connected to an overhead large water reservoir, namely the GDWP. The objective of the PMCS is to remove the heat from the moderator in case of an SBO and maintaining its temperature below the permissible safe limit (100 °C) for at least 7 days. The paper first describes the concept of the PMCS. The concept has been assessed considering a prolonged SBO for at least 7 days, through an integrated analysis performed using the code RELAP5/MOD3.2 considering all the major components of the reactor. The analysis shows that the PMCS is able to maintain the moderator temperature below boiling conditions for 7 days.

Summary In this study, the effect of different vegetables baby corn, green pea, broccoli as filling ingredients along with yellowfin tuna (Thunnus albacares) on the heat penetration characteristics and quality changes were assessed. Heating and cooling lag factors (Jh and Jc) were least for tuna with broccoli and tuna without vegetables, respectively. Heating rate index was in the range of 13.5–19.3 min with least value for tuna with broccoli. Heat processing increased the hardness and chewiness of tuna significantly (P

Numerical simulation was performed to study the turbulent mixing behavior of two opposing flows inside as quare chim ney structure of ar esearch reactor .T he chimney design facilitates drawing pool water in the downwar dd irection and thereby suppresses the upward flow of radioactive water jet to limit the radiatio nf ield at the reactor pool top .A nalyses were car ried out considering am ass flow rate of 75 0k g/s for the upward flowing hot water from the core ,w hich corresponds to Reynolds number of 3 · 10 6 .M ass flow ratios of the downwar d flow and the upward flow were 0.0, 0.05, 0.1 and 0.15. Th ee ffects of mass flow ratio ,c himney height on the velocity and temperatur ed istribution inside three-dimensional chimney structur ew as evaluated using CFD code PHOENICS .T he effect of temperatur ed ifference between the opposing flows on velocity was also analysed. It is observed that increase in downward flow cause st he jet height to decrease due to the opposing momentu mo fd ownwar df low against the upward jet. The effects of chimney height and temperature difference on the jet height are found to be marginal because of dominating inertial force over buoyancy forc ef or the study. Numerische Simulation turbulenter Stromungsvermischung in eine rq uadratischen Kaminstruktur eines Forschungsreaktors. Fur einen quadratischen Stromungskanal eines Forschungsreaktors wurde nB erechnungen zur Vermischung zweier entgegengesetzt stromender turbulente Wassermengen durchgefuhrt. Dabei fliest das Poolwasser von oben nach unten, um den aufwarts gerichteten Wasserstrahl nach unten zu drangen und zu verhindern, dass das radioaktive Wasser des Strahls die Radioaktivitat an der Pooloberflache vergrosert. Die Berechnungen wurden mit dem CFD-Programm PHOENICS durchgefuhrt. Dabei wurde der Einfluss der Massenstromverhaltnisse, der Hohe des Stromungskamins auf die Geschwindigkeits- und Temperaturverteilung sowie der Temperaturunterschiede zwischen den beiden Stromen untersucht. Als ein Ergebnis wir d herausgestellt, dass die Grose des abwarts gerichteten Massenstroms den grosten Einfluss hat. Die Kaminhohe und die Temperaturdifferenz hingegeben haben vernachlassigbaren Einfluss auf die Vermischung.

The present work is an attempt to provide an overview, about the status of R&D and current trends in Hydrogen Production using High Temperature Reactors. Bibliographic references from the INIS database, the Science Direct database and the NTIS database were downloaded and analyzed. Ten year data on the subject, published between 2001 and 2010, was selected for the study. Appropriate qued ry formulations on these databases, resulted in the retrieval of 621 unique bibliographic records. Using the content analysis method, all the records were analyzed. Part One of the analysis details Scientometric RD B. European RD C. National Initiatives and Programmes for Nuclear Hydrogen Production; D. Reactor Technologies for Nuclear Hydrogen production; E. Fuel Developments; F. Hydrogen Production Processes using HTRs and G. Materials Consideration for Nuclear Hydrogen Production. The results of this analysis are summarized in the study.

The Advanced Heavy Water Reactor (AHWR) is a vertical pressure tube type reactor designed for utilizing thorium fuel with boiling light water as coolant and heavy water as moderator. The AHWR has several passive features, the major ones being heat removal through natural circulation, decay heat removal through passive means by the way of isolation condensers and a large heat sink in the form of gravity driven water pool. In the existing design of AHWR, the fuel rod cluster has solid fuel pins. The limitation on it is the Minimum Critical Heat Flux Ratio (MCHFR), which comes from coolant characteristics. In order to improve power output from the AHWR we are trying to design internally and externally cooled annular fuel rod cluster for AHWR. The fuel cluster design would have to be qualified from physics and thermal hydraulic behavior. In order to satisfy the design objectives, a detailed thermal hydraulics and physics simulation has been done.

Supercritical water (SCW) exhibits excellent heat transfer characteristics and a high volumetric expansion coefficient (hence high mass flow rates in natural circulation systems) near the critical temperature. SCW is being considered as a coolant in some advanced nuclear reactor designs on account of its potential to offer high thermal efficiency, compact size, and elimination of steam generator, separator, and dryer, making it economically competitive. The elimination of phase change results in elimination of the critical heat flux phenomenon. Cooling a reactor at full power with natural instead of forced circulation is generally considered an enhancement of passive safety. In view of this, it is essential to study natural circulation behavior at supercritical conditions. Carbon dioxide can be considered to be a good simulant of water for natural circulation at supercritical conditions, since the density and viscosity variation of carbon dioxide follows a curve parallel to that of water at supercritical ...

This paper critically assesses the usefulness of the “new-Orientalism” thesis in understanding the discourses around the idea of “terrorism” and of “the terrorist”. It observes that critiques of “new Orientalism” provide important insights into the ways in which “Islam”, “the Muslim” and “terrorist” have come to be constructed. However, it also argues for the importance of the density of historical context and specificity of locality in understanding how these categories are formulated. The case of Bombay cinema is particularly instructive here. The paper argues that Bombay cinema – which has engaged with these concerns in some form since its inception, and is going “global” in unprecedented ways – exemplifies both the play of these two distinct discursive tendencies and also the tensions that arise because they are not identical. Post-9/11 films like Aamir (2008) and New York (2009) manifest these discursive mechanics and the tensions that result from the play between “new Orientalism” and the local.

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 steamewater 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.

Three element Steam Drum (SD) Level Controller has been conventionally used for most of the boilers, Nuclear power plant steam generator & Boiling Water Reactor (BWRs). Based on the process dynamic studies it was found that this scheme does not work properly for an interacting, interconnected multiple loop boiling water system i.e., Advanced Heavy Water Reactor (AHWR). It is a pressure tube type light water cooled heavy water moderated Boiling Water Reactor (BWR). It has 4-inter-connected parallel loops with 113 × 4 = 452 boiling channels in the Main Heat Transport (MHT) system. These multiple (four) interconnected loops influences the Steam Drum (SD) level control adversely. Such a behavior has not been reported in the open literature. The open loop response is stable, non-oscillatory and non-diverging for a step change in the feed flow rates. Also it is not possible to maintain a steady level in all the SDs even without any external disturbance/perturbation with 4 conventional 3-element individual SD level controllers. To overcome these interactions it is proposed to interconnect all the four steam drums in the liquid & vapor regions respectively. This makes the 4 SDs behave like a single entity. The influence of the interconnect configuration & the level controller are studied in detail to find a robust solution. The response obtained for unsymmetrical core power, symmetrical power maneuvering and reactor trip transients shows that the SD levels do not diverge and quickly settle very near to the set points assigned with SD interconnect schemes.

Shrimp in curry medium (SICM) was prepared and thermally processed to three different F0 values, i.e., 5, 7 and 9. The total process time taken to reach the F0 value of 5, 7 and 9 for SICM was 20.09, 24.31 and 28.69 min, respectively. The cook value obtained during the thermal processing of SICM at F0 values of 5, 7 and 9 was 59.20, 67.45 and 69.73 min, respectively. The sensory textural parameters and instrumental textural parameter followed the same trend and showed very good correlation. The instrumental textural parameter like hardness correlated well with the shear force for all the products. The instrumental color parameters for thermally processed shrimp were measured for CIELAB values like L*, a* and b*. These instrumental color parameters correlated well with the sensory color parameters. PRACTICAL APPLICATIONS Texture is one of the important properties of thermally processed food. The present study was conducted to measure the changes in the textural parameters of retort pouch-processed Indian white shrimp in different F0 value and to correlate the sensory textural parameters with the instrumental one. It was observed from the result that there is a decrease in the hardness as well as shear force and an increase in the F0 values. Apart from this, the color of the products was also measured to know the effect of thermal processing on it. The color also followed the same trends as texture. This will help to standardize the F0 value to get optimum sensory characteristics for shrimp in curry medium in retort pouch processing.

Heat transfer and fluid flow studies related to spent fuel bundle of a research reactor in fuelling machine has been carried out. When the fuel is in reactor core, the heat generated in the fuel bundle is removed by heavy water under normal reactor operation. However, during the de-fuelling operation, the fuel bundle is exposed to air for some period called dry period. During this period, the decay heat from fuel bundle has to be removed by air flow. This flow of air is induced by natural convection only. In this period, the temperatures of fuel and clad rise. If clad temperature rises beyond a certain limit, structural failure may occur. This failure can result into release of fission products from fuel rod. Hence the temperature of clad has to be within specified limit under all conditions. The objective of this study is to estimate the clad temperature rise during the dry period. In the CFD simulation, the turbulent natural convection flow over fuel and radiation heat transfer are accounted. Standard k – ɛ model for turbulence, Boussinesq approximation for computing the natural convection flow and IMMERSOL model for radiation are used. The steady state and transient CFD simulation of flow and heat is performed, using the CFD code PHOENICS. The steady state analysis provides the maximum temperature the clad will attain if fuel bundle is left exposed to air for sufficiently long time. For safe operation, the clad temperature should be limited to a specified value. From steady state CFD analysis, it is found that steady state clad temperature for various decay powers is higher than the limiting value. Hence transient analysis is also performed. In the transient analysis, the variation of clad temperature with time is predicted for various decay powers. Safe dry time, i.e. the time required for clad to reach the limiting value, is predicted for various decay powers. Determination of safe dry time helps in deciding the time available to the operator to drop the bundle in light water pool for storage. The analysis is found useful in optimizing the de-fuelling process.

For AHWR (Advanced Heavy Water Reactor), a pressure tube type Boiling Water Reactor (BWR) with parallel inter-connected loops, the Steam Drum (SD) level control is closely related to Main Heat Transport (MHT) coolant inventory and sustained heat removal through natural circulation, hence overall safety of the power plant. The MHT configuration with multiple (four) interconnected loops influences the SD level control in a manner which has not been previously addressed. The MHT configuration has been chosen based on comprehensive overall design requirements and certain Postulated Initiated Event (PIEs) for Loss of Coolant Accident (LOCA), which postulates a double ended break in the four partitioned Emergency Core Cooling System (ECCS) header. A conventional individual three-element SD level controller can not account for the highly coupled and interacting behaviors, of the four SD levels. An innovative three-element SD level control scheme is proposed to overcome this situation. The response obtained for a variety of unsymmetrical disturbances shows that the SD levels do not diverge and quickly settle to the various new set points assigned. The proposed scheme also leads to enhanced safety margins for most of the PIEs considered with a little influence on the 100% full power steady-state design conditions.

The critical heat flux (CHF) is one of the important phenomena limiting the maximum rate of heat transfer and hence power rating of nuclear reactors. The thermal hydraulic phenomena like pressure drop, heat transfer, stability, etc. depends upon the flow pattern in the system. The CHF phenomenon is also closely related to the two-phase flow patterns. It is important to investigate the dependence of CHF on the flow pattern regimes to understand the underlying mechanisms. The present investigation reveals that CHF generally increases with mass flux in the churn/slug region. However, in the annular region the CHF decreases with increase in mass flux. Considering the dependency of the CHF trend on the flow pattern regime, it will be useful to develop CHF models, which are specific to the flow pattern regime. The data of CHF look-up table has been considered in this investigation since this approach is one of the most reliable methods for the prediction of CHF and is being used in several best-estimate thermal-hydraulic system codes, such as RELAP5, CATHARE and CATHENA. The pressure, mass flux and quality have been considered as important thermal hydraulic parameters to characterize the flow pattern during CHF under various operating condition.

Effect of the heater and cooler orientations on the single-phase natural circulation was studied in a rectangular loop. From steady state considerations, the maximum flow for a specified operating condition is achievable for the orientation with both the heater and the cooler horizontal. However, this orientation is found to be least stable and the orientation with both heater and cooler vertical is found to be most stable. Three oscillatory modes were observed in the experiments, two of which are observable only for certain heat addition paths. A hysteresis (conditionally stable) regime wherein stable or unstable flow can prevail depending on the operating procedure is also observed. Generalized steady state equation valid for all the orientations is possible whereas generalized stability equation is possible for a given orientation and flow direction. Steady state flow rate can be predicted with reasonable accuracy using the generalized equation. The stability map predicted by the generalized equation is found to be highly conservative in that its unstable zone is much larger than that observed in the experiments. Both the linear and the nonlinear stability analyses gave the same stability map for identical initial conditions. With nonlinear analysis, it was possible to reproduce the observed unstable oscillatory modes albeit at significantly different power levels. Also, the predicted limit cycles were significantly different in shape which is attributed to the multidimensional nature of the flow especially during the low flow part of the oscillation cycle.

Freshwater fish, rohu ( Labeo rohita) curry was prepared in a north Indian style, packed in polyestercoated tin free steel (TFS) cans in a 60:40 ratio (fish:curry) and thermal processed in a retort. Physical tests of the can such as double seam efficiency, lacquer integrity, sulphur resistance and food contact application showed that polyester-coated TFS cans can be used for canning fish products. F0 value of the product was 8.79 when the thermal processing was at 121°C for 46.42min, and cook value to achieve tenderness of the product was 102min. The processed product was found to be commercially sterile. The product was acceptable even after 6 months of storage at room temperature (28±2°C) and at 37°C with regard to all sensory attributes. Texture attributes such as hardness, chewiness, springiness and cohesiveness did not show marked variation in the samples stored at room temperature and at 37°C. There were no significant changes in chemical parameters during the storage period. The results showed that the polyester-coated TFS cans can be used for processing ready to serve fish products, which can be stored at room temperature for long periods.

The Critical Heat Flux (CHF) is an important parameter, which limits the thermal hydraulic performance of the nuclear fuel bundle. The tools available for the prediction of the CHF are empirical in nature and are valid for their experimental range only. However, the recently developed Look-Up Table (LUT) approach has emerged to be a promising tool for predicting CHF in a tubular geometry over a wide range of parameters, which can be extended to the rod bundle geometry considering correction factors for the rod bundle effects. The error statistics of the present assessment confirms the values provided with the LUT for the HBM approach for the tubular application. However, the error statistics by DSM (not provided with the LUT development) is found to be quite different from that of the HBM. It is found that CHF in the rod bundle can also be predicted with a good accuracy using the Heat Balance Method (HBM). The proposed correction factor is found to improve the prediction accuracy of the LUT for the rod bundle application. This paper deals with the assessment of the CHF prediction by LUT for the tubular and bundle geometry and evaluation of the correction factor for rod bundle at the normal operating pressure of BWR (70 bar) using the experimental data base.

Seer fish in curry medium packed in locally manufactured retort pouches, having a three-layer configuration of thickness 12.5 µm polyester/12.5 µm aluminium foil/80 µm cast polypropylene was processed in a steam/air mixture over a pressure retort. About 210 g fish curry, having 110 g fish slices, was packed in a retort pouch of size 17 cm × 15.5 cm, each fitted with a thermocouple. Time–temperature data were collected during heat processing using an Ellab data recorder FO and cook value integrator. The heat penetration characteristics were determined using a mathematical method. The fh value was 25 min with a FO value of 11.5 and cook value of 95 min. These samples remained in good condition for up to 24 months at room temperature. Copyright © 2002 John Wiley & Sons, Ltd.

Fish curry processed in metal cans is popular in the overseas markets. An important limitation with the use of metal cans is the undesirable taste imparted to the products on storage. Flexible pouches are an ideal alternative to metal cans. Extensive work carried out at Central Institute of Fisheries Technology has been able to identify indigenous pouches, which are as good as imported pouches. This has been done after collecting different types of indigenous and imported flexible pouches, analyzing their composition and conducting detailed studies on their physical and food contact application properties. Two indigenous pouches with composition 12 micron polyester/ 12 micron aluminium foil/ 87.5 micron cast polypropylene and 12 micron polyester/ 15 micron aluminium foil/ 70 micron cast polypropylene have been selected and got made by indigenous laminators and an imported one with configuration 12 micron polyester/ 15 micron aluminium foil/ 75 micron cast polypropylene were used for further experiment on processing fish curry. Traditional Kerala style mackerel fish curry was processed in the retort pouches of the above configurations. About 220 g fish curry was packed in each pouch (15.5 cm ×7 cm ) . Process requirements were worked out by measuring heat penetration using thermocouples introduced into the pouches. Fish curry processed to a F0 value of 8.43 gave an acceptable product with desired texture and sensory characteristics. The physical properties of the pouches studied showed that the indigenous pouches of the above configurations were good enough to give a shelf life of 1 year at room temperature. The curry remained sterile throughout the storage period at ambient temperature (25–30°C) and retained acceptable sensory characteristics.

Experiments carried out in three rectangular loops differing in diameter showed instability in the loop with the largest diameter. The observed oscillatory behavior involves repetitive flow reversals, the frequency of which is regular (periodic) at low powers and irregular (chaotic) at high powers. The flow reversal frequency increases with heater power. Due to the flow reversals the Reynolds number vary between +10 000 and −10 000 causing the flow to pass through the laminar and turbulent regime repetitively. Simulation of the oscillatory behavior using the computer code athlet did not show instability with a coarse nodalization. The nodalization was then progressively refined and with a fine nodalization athlet was able to predict the instability behavior and to reproduce all the essential characteristics of the observed oscillatory behavior.