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Nithyadevi R.,Bhabha Atomic Research Center | Thilagam L.,AERB Safety Research Institute | Karthikeyan R.,Bhabha Atomic Research Center | Pal U.,Bhabha Atomic Research Center
Annals of Nuclear Energy | Year: 2016

Advances in reactor physics have led to the development of new computational technologies and upgraded cross-section libraries so as to produce an accurate approximation to the true solution for the problem. Thus it is necessary to revisit the benchmark problems with the advanced computational code system and upgraded cross-section libraries to see how far they are in agreement with the earlier reported values. Present study is one such analysis with the DRAGON code employing advanced self shielding models like USS and 172 energy group 'JEFF3.1' cross-section library in DRAGLIB format. Although DRAGON code has already demonstrated its capability for heavy water moderator systems, it is now tested for light water reactor (LWR) and fast reactor systems. As a part of validation of DRAGON for LWR, a VVER computational benchmark titled "Neutronics Benchmarks for the Utilization of Mixed-Oxide Fuel-Volume 3" submitted by the Russian Federation has been taken up. Presently, pincell and assembly calculations are carried out considering variation in fuel temperature (both fresh and spent), moderator temperatures and boron content in the moderator. Various parameters such as infinite neutron multiplication (k∞ ) factor, one group integrated flux, few group homogenized cross-sections (absorption, nu-fission) and reaction rates (absorption, nu-fission) of individual isotopic nuclides are calculated for different reactor states. Comparisons of results are made with the reported Monte Carlo (MCU) values of the benchmark. Maximum deviation of 1.8% in k∞ is observed for variants with spent fuel and for the states with control rod whereas all the other results are in par with the results reported in the benchmark document. The few and multi-group macroscopic cross-sections and flux of all the nuclides also compare well with the benchmark results except for the 11B macroscopic absorption cross section, which is further compared with the XNWLUP software. Inter-comparison of results with the generalized self-shielding model SHI of DRAGON code employing the traditional WIMSD formatted 172 group cross-section library has also been made to highlight the improvements made in computational schemes and cross-section library format. © 2016 Elsevier Ltd.

Seshadri H.,AERB Safety Research Institute | Sinha P.K.,Bhabha Atomic Research Center
Journal of Radioanalytical and Nuclear Chemistry | Year: 2012

Nanostructures of β-Ga 2O 3 were prepared by solution combustion route using urea as the fuel. Transmission electron microscopic measurements and powder X-ray diffraction measurements confirmed the crystalline nature of β-Ga 2O 3 with particle size in the range of 10-15 nm. Surface area measurements indicated that the synthesized semiconductor catalyst had a specific surface area of 30 m 2/g. In this work, photocatalytic degradation studies of tri-n-butyl phosphate using nano sized β-Ga is presented. A cylindrical photoreactor was used for the degradation studies and gas chromatographic estimation was adopted to follow the extent of degradation. Complete degradation of tributyl phosphate could be achieved in less than 40 min using 10 mg of photocatalyst and 0.5 mL of H 2O 2 for 1000 mL of 400 ppm TBP. Degradation of TBP was found to follow pseudo first order kinetics and the rate of TBP degradation was found to be superior for β-Ga 2O 3 photocatalyst compared to P-25 TiO 2. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Hassija V.,Bhabha Atomic Research Center | Senthil Kumar C.,AERB Safety Research Institute | Velusamy K.,Bhabha Atomic Research Center
Annals of Nuclear Energy | Year: 2014

Safety systems deployed in nuclear industry are generally required to operate for a particular mission time. Most of such systems employ redundancy to ensure their high availability over the stipulated mission time. However, availability of a system with redundant configuration depends upon success criteria and is application-specific. The Safety Grade Decay Heat Removal System of Indian Prototype Fast Breeder Reactor is required to operate with different success criteria during the specified mission time on account of steady decline in decay heat produced by the reactor core. In this paper, Markov analysis is carried out to evaluate the availability of the system under both continuous and periodic monitoring schemes. The study estimates the upper bound and lower bound for mean unavailability of SGDHR system for the specified mission time. Sensitivity analysis of the system attributable to important parameters is also carried out. The study provides a comprehensive approach to model scenarios with time dependent success criteria and provides an insight on the factors affecting availability of such systems. © 2014 Elsevier Ltd. All rights reserved.

Hassija V.,Bhabha Atomic Research Center | Hassija V.,AERB Safety Research Institute | Senthil Kumar C.,AERB Safety Research Institute | Velusamy K.,Bhabha Atomic Research Center
Annals of Nuclear Energy | Year: 2014

Most of the modern technological systems are deployed with high redundancy but still they fail mainly on account of common cause failures (CCF). Various models such as Beta Factor, Multiple Greek Letter, Binomial Failure Rate and Alpha Factor exists for estimation of risk from common cause failures. Amongst all, alpha factor model is considered most suitable for high redundant systems as it arrives at common cause failure probabilities from a set of ratios of failures and the total component failure probability QT. In the present study, alpha factor model is applied for the assessment of CCF of safety systems deployed at two nuclear power plants. A method to overcome the difficulties in estimation of the coefficients viz., alpha factors in the model, importance of deriving plant specific alpha factors and sensitivity of common cause contribution to the total system failure probability with respect to hazard imposed by various CCF events is highlighted. An approach described in NUREG/CR-5500 is extended in this study to provide more explicit guidance for a statistical approach to derive plant specific coefficients for CCF analysis especially for high redundant systems. The procedure is expected to aid regulators for independent safety assessment. © 2013 Elsevier Ltd. All rights reserved.

Hassija V.,Bhabha Atomic Research Center | Senthil Kumar C.,AERB Safety Research Institute | Velusamy K.,Bhabha Atomic Research Center
Journal of Loss Prevention in the Process Industries | Year: 2014

Multi-unit safety assessment has gained global importance after the Fukushima disaster in 2011. Most of the nuclear sites in the world have more than one reactor and hence it is important to evolve a methodology to systematically assess the safety of the multi-unit site. In this paper, unique features to be addressed in multi-unit safety assessment are discussed and an integrated approach is developed to assess the risk contribution of multiple nuclear plants at the site. The paper highlights the importance of risks for multi-unit sites arising from shared system, common cause failures, failure correlations, cliff-edge effects, etc. from different hazards. Though the main emphasis on multi-unit safety is on external hazards, the proposed approach also includes risk from random internal events. The approach developed not only quantifies the frequency of multiple core damage for a multi-unit site but also evaluates site core damage frequency which is the frequency of at least single core damage per site per year. © 2014 Elsevier Ltd.

Seshadri H.,AERB Safety Research Institute | Cheralathan M.,Bhabha Atomic Research Center | Sinha P.K.,Bhabha Atomic Research Center
Research on Chemical Intermediates | Year: 2013

Nanostructures of β and γ-Ga2O3 were prepared by the solution combustion route using urea as fuel. The synthesized nano photocatalysts were characterized by use of XRD, FT-IR, BET, TEM, TGA-DTA, DRS, and Raman spectroscopy. XRD and TEM investigations confirmed the nanostructures; particle size was in the range 3-5 nm for γ-Ga 2O3 and 40-50 nm for β-Ga2O3. The specific surface area of γ-Ga2O3 was 91 m 2 g-1 and that of β-Ga2O3 was 24.3 m2 g-1. The polymorphs of gallium oxide were used as photocatalysts for decomposition of 1,000 mg/l 1,4-dioxane. More than 90 % of the 1,4-dioxane could be degraded in less than 180 min by use of 10 mg/l photocatalyst + 0.5 ml H2O2. The efficiency of photocatalytic degradation of 1,4-dioxane by the synthesized photocatalysts was compared with that of P-25 TiO2 and followed the order γ-Ga2O3 ≥ β-Ga2O3 > P-25 TiO2. The degradation was found to follow pseudo first-order kinetics. © 2012 Springer Science+Business Media B.V.

Sajith Mathews T.,AERB Safety Research Institute | John Arul A.,Indira Gandhi Center for Atomic Research | Parthasarathy U.,Indira Gandhi Center for Atomic Research | Senthil Kumar C.,AERB Safety Research Institute | And 2 more authors.
Nuclear Engineering and Design | Year: 2011

Innovative nuclear reactor designs include passive means to achieve high reliability in accomplishing safety functions. Functional reliability analyses of passive systems include Monte Carlo sampling of system uncertainties, followed by propagation through mechanistic system models. For complex passive safety systems of high reliability, Monte Carlo simulations using mechanistic codes are computationally expensive and often become prohibitive. Passive system reliability analysis using recently proposed Response Conditioning Method, which incorporates the insights obtained from approximate solutions like response surfaces in simulations to obtain computationally efficient and consistent probability estimates, is presented in this paper. The method is applied to evaluate the reliability of passive Decay Heat Removal (DHR) system of Indian Prototype Fast Breeder Reactor (PFBR). The accuracy as well as efficiency of the method is compared with direct Monte Carlo simulation. The variability of the reliability values is estimated using bootstrap technique. The system abilities, to prevent critical structural damage as well as to ensure operational safety, are quantitatively ascertained. The system functional failure probabilities are integrated with hardware failure probabilities and the inclusion of passive system unreliability in Probabilistic Safety Assessment is demonstrated. © 2011 Elsevier B.V. All rights reserved.

Christopher J.,Indira Gandhi Center for Atomic Research | Christopher J.,AERB Safety Research Institute | Choudhary B.K.,Indira Gandhi Center for Atomic Research | Isaac Samuel E.,Indira Gandhi Center for Atomic Research | And 2 more authors.
Journal of Nuclear Materials | Year: 2012

Tensile flow behaviour of P9 steel with different silicon content has been examined in the framework of Hollomon, Ludwik, Swift, Ludwigson and Voce relationships for a wide temperature range (300-873 K) at a strain rate of 1.3 × 10 -3 s -1. Ludwigson equation described true stress (σ)-true plastic strain () data most accurately in the range 300-723 K. At high temperatures (773-873 K), Ludwigson equation reduces to Hollomon equation. The variations of instantaneous work hardening rate (θ = dσ/d) and θσ with stress indicated two-stage work hardening behaviour. True stress-true plastic strain, flow parameters, θ vs. σ and θσ vs. σ with respect to temperature exhibited three distinct temperature regimes and displayed anomalous behaviour due to dynamic strain ageing at intermediate temperatures. Rapid decrease in flow stress and flow parameters, and rapid shift in θ-σ and θσ-σ towards lower stresses with increase in temperature indicated dominance of dynamic recovery at high temperatures. © 2011 Elsevier B.V. All rights reserved.

Choudhary B.K.,Indira Gandhi Center for Atomic Research | Christopher J.,AERB Safety Research Institute | Isaac Samuel E.,Indira Gandhi Center for Atomic Research
Materials Science and Technology (United Kingdom) | Year: 2012

Work hardening behaviour of P9 steel in the temperature range 300-873 K has been examined inthe framework of Kocks-Mecking (K-M) approach. At all temperatures, P9 steel exhibited twostagework hardening behaviour characterised by a rapid decrease in instantaneous workhardening rate (i.e. h5ds/d, where α is the true stress and e is the true plastic strain) with stressat low stresses (transient stage) followed by a gradual decrease at high stresses (stage III). StageIII work hardening of P9 steel was adequately described by K-M approach. The variations of workhardening parameters associated with K-M approach for stage III with temperature indicatedthree distinct temperature regimes. At all temperatures, good correlations between the respectivework hardening parameters evaluated using K-M approach and from Voce equation and itsderivative have been obtained for P9 steel. © 2012 Institute of Materials, Minerals and Mining.

Kota S.B.,AERB Safety Research Institute | Subramani A.,General Electric | Jayanti S.,Indian Institute of Technology Madras
Combustion and Flame | Year: 2016

Due to their high reactivity, alkali metals pose a fire hazard as spontaneous ignition in air is possible in several high temperature applications. In the present study, the ignition and burning rates of a hot, shallow potassium pool of 0.06 and 0.10m diameter have been studied experimentally. Thermodynamic equilibrium calculations of K-air system show that vapour phase combustion of potassium is possible. This has been verified experimentally. Over much of the duration of fire, the pool temperature is found to be in the 900-1000K range; therefore, the oxides formed as a result of combustion would be molten and solid residues are formed only at the end of the fire, unlike in the case of sodium and lithium. Burning rate of potassium has been found to be in the range of 30-60kg/m2s for various conditions and is typically lower than that of sodium and lithium under similar conditions. Auto-ignition temperatures lie in the range of 500-650K, the higher temperatures occurring in smaller pools and low oxygen concentrations. Using different mass transfer scenarios, it is shown experimentally that the burning rate of potassium pool is limited by mass of transfer of oxidant. © 2016 The Combustion Institute.

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