Reactor Safety Division

BARC, India

Reactor Safety Division

BARC, India

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Gopalan A.,Bhabha Atomic Research Center | Samal M.K.,Reactor Safety Division | Chakravartty J.K.,Bhabha Atomic Research Center
Journal of Nuclear Materials | Year: 2015

In this work, fracture behaviour of 20MnMoNi55 reactor pressure vessel (RPV) steel in the ductile to brittle transition regime (DBTT) is characterised. Compact tension (CT) and single edged notched bend (SENB) specimens of two different sizes were tested in the DBTT regime. Reference temperature 'T0' was evaluated according to the ASTM E1921 standard. The effect of size and geometry on the T0 was studied and T0 was found to be lower for SENB geometry. In order to understand the fracture behaviour numerically, finite element (FE) simulations were performed using Beremin's model for cleavage and Rousselier's model for ductile failure mechanisms. The simulated fracture behaviour was found to be in good agreement with the experiment. © 2015 Elsevier B.V. All rights reserved.


Naveen Kumar N.,Bhabha Atomic Research Center | Tewari R.,Materials Science Division | Durgaprasad P.V.,Reactor Safety Division | Dutta B.K.,Reactor Safety Division | Dey G.K.,Materials Science Division
Computational Materials Science | Year: 2013

Molecular dynamics (MD) simulations of nanoindentation of alpha-iron (α-Fe) have shown that all previously observed slip plane families i.e. {1 1 0}, {1 1 2} and {1 2 3} were active in the system. The slip plane families, {1 1 0} and {1 2 3}, were more are less equally active whereas {1 1 2} family was the least active. A small fraction of dislocation density was observed on {1 0 0} slip planes arising due to the formation of a 〈1 0 0 junctions because of the interaction of a/2 〈1 1 1⌠family of dislocations. It was also shown that the line character of dislocations varied uniformly from edge to screw character without any biasing towards a single character of dislocation at temperatures less than 300 K. These results were found to be consistent even with changing the size of domains, shape of the indenter and rate of loading. Present study has shown that for the prediction of deformation behaviour in α-Fe dislocation activities on {1 2 3} slip planes should also be considered along with the activities of {1 1 0} and {1 1 2} slip planes. © 2013 Elsevier B.V. All rights reserved.


Goyal P.,Reactor Safety Division | Sharma P.K.,Reactor Safety Division | Markandeya S.G.,Planning and Coordination Division | Ghosh A.K.,Bhabha Atomic Research Center
Kerntechnik | Year: 2012

A computational model was developed earlier for 2 units of Nuclear Power Plants (NPPs) operational at Kaiga Atomic Power Station (KAPS) to understand the thermal plume behaviour in the Kadra reservoir wherein the hot water from the plant condensers is discharged. The model was successfully validated against the site data. The same model has now been extended for analyzing the thermal plume bahaviour in case of 4 NPP units as well as 6 NPP units operational at the same site. The present paper briefly describes details of the studies along with the results of earlier study to understand the overall behavior of thermal plume in Kadra reservoir. © Carl Hanser Verlag, München.


Muralidhara S.,BMS College of Engineering | Muralidhara S.,Indian Institute of Science | Eskandari H.,Kharazmi University | Prasad B.K.R.,Indian Institute of Science | Singh R.K.,Reactor Safety Division
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2011

In seismology, Gutenberg-Richter relationship log 10N=a-bM is an empirical relationship between the magnitude of earthquake and its recurrence frequency. The constant 'b ', is called the b-value and is the log linear slope of frequency-magnitude distribution. An analogy is drawn between earthquake and failure process in concrete. During the failure process of concrete, Acoustic emission (AE) energy is released in the form of energy waves having certain peak amplitudes. While estimating the b-value during fracture in concrete, peak amplitudes of the AE signals are used. Right from the onset of micro-cracks till failure, the AE events are recorded with their peak amplitudes and AE energies. Interestingly, the AE energy release has been observed to be in "packets" or bursts. These energy packets have been called by the authors as AE quanta. In the estimation of b-value, peak amplitudes of events of groups having a definite number are used. Instead of using amplitudes of arbitrary group of events, quanta are utilized as groups for obtaining the b-value,. Unlike in seismology, wherein the b-value could be nearly unity, it is found that the b-value from quanta is much less than that obtained from the amplitudes. ©2010 Society for Experimental Mechanics Inc.


Muralidhara S.,BMS College of Engineering | Raghu Prasad B.K.,Indian Institute of Science | Singh R.K.,Reactor Safety Division
Engineering Fracture Mechanics | Year: 2013

Size independent fracture energy and size effect on fracture energy are the key concerns for characterization of concrete fracture. Although there have been inconsistencies in results, a consensual fact is that the fracture energy from a large specimen is size independent. The fracture energy is proportional to the size of the fracture process zone (FPZ). FPZ size increases with size of the specimen, but the rate of increase of FPZ size decreases with increase in specimen size [1] implying that rate of increase of fracture energy decreases with increase in specimen size, more appropriately with increase in un-cracked ligament length. The ratio of fracture energy to the un-cracked ligament length almost becomes a constant at larger un-cracked ligament lengths. In the present study an attempt is made to obtain size independent fracture energy from fracture energy release rate. © 2012 Elsevier Ltd.


Muralidhara S.,BMS College of Engineering | Muralidhara S.,Indian Institute of Science | Raghu Prasad B.K.,Indian Institute of Science | Karihaloo B.L.,University of Cardiff | Singh R.K.,Reactor Safety Division
Construction and Building Materials | Year: 2011

The boundary effect or the size effect on the fracture properties of concrete has been studied assuming a bi-linear model for the distribution of local fracture energy concept. Boundary effect is observed not only near the back boundary but also near the notch tip, where a fictitious boundary seems to exist, separating the linear and non-linear fracture zones. In this paper a tri-linear function is assumed for the local fracture energy distribution along the ligament and expressions relating RILEM fracture energy and the size-independent fracture energy are developed. Transition ligament length measurements based on the acoustic emission (AE) histogram of events are used to obtain size-independent fracture energy. Length of the fracture process zone is identified in the AE histogram and compared with the value obtained from softening beam model. There seems to be a good agreement between the results. © 2011 Elsevier Ltd. All rights reserved.


Rahim A.,Indian Institute of Technology Roorkee | Sharma U.K.,Indian Institute of Technology Roorkee | Murugesan K.,Indian Institute of Technology Roorkee | Sharma A.,Reactor Safety Division | Arora P.,Reactor Safety Division
Construction and Building Materials | Year: 2013

This paper presents results of an experimental study undertaken to optimize the residual compressive strength of heated high performance concrete using the Taguchi off-line method and the utility concept. The design of experiments (DoEs) was first carried out by Taguchi method using a standard L 9(34) orthogonal array (OA) of four factors with three material parameter levels. The factors considered in the context of high performance concrete were cement content, fly ash content, super-plasticizer content and fine aggregate content. The cube specimens were cast and heated up to 200 °C, 400 °C, 600 °C and 800 °C target temperatures. They were subsequently tested under axial compressive loads in cooled conditions. Based on the results, the material parameter responses were analyzed by utility concept to reduce the multi-characteristic response and to obtain single setting of optimized parameters in order to maximize the post-fire residual compressive strength of concrete. The results indicate that the best level of control factors paid their own contribution for compressive strength at various elevated temperatures. The cement content was found to be the most influencing parameter followed by fine aggregate content and fly ash dosage. The role of chemical admixture dosage was observed to be relatively less marked on the residual compressive strength of high performance concrete. The confirmation tests corroborated the theoretical optimum test conditions. © 2012 Elsevier Ltd. All rights reserved.


Rahim A.,Indian Institute of Technology Roorkee | Sharma U.K.,Indian Institute of Technology Roorkee | Murugesan K.,Indian Institute of Technology Roorkee | Arora P.,Reactor Safety Division
MATEC Web of Conferences | Year: 2013

The present experimental program was planned to investigate the effect of type of mineral admixture, pre-load and the presence of confining reinforcement on the spalling behaviour of heated high performance concrete (HPC). Reinforced concrete cylindrical short columns were cast and exposed to four different target temperatures. A compressive preload equal to 25% of the ultimate load capacity of column was maintained on the specimens during heating and cooling. The test results mainly focus on the influence of above said variables on spalling behaviour of reinforced HPC columns. Interesting observations have been made in the paper on the subject matter of the workshop. © Owned by the authors, published by EDP Sciences, 2013.


Sharma A.,Reactor Safety Division | Sharma A.,University of Stuttgart | Reddy G.R.,Reactor Safety Division | Eligehausen R.,University of Stuttgart | Vaze K.K.,Reactor Safety Division
Nuclear Engineering and Design | Year: 2011

Every nuclear facility consists of various structures of varying importance. Standards and design guidelines recommend categorization of these structures based on their importance, safety function that they have to perform, hazard class, etc. In order to economize the designs, the structures that pose only industrial risk are recommended to be designed following the national practice. This paper presents the results of experiments performed on the beam-column joints of such structures to verify their seismic performances. The specimens were full-scale replicas of the joints of the original non safety related structures such as turbine buildings, intake structures and office buildings. The beam-column connections in the original structures either had non-seismic detailing or seismic detailing, but in order to have a comparison, every joint was tested with both types of detailing. The strength and ductility obtained from the experiments for both types was compared with the codal recommended values by different national standards. Conclusions and comments on the suggested values of allowable stresses, assumed ductility values and corresponding strength reduction factors have been made. © 2011 Elsevier B.V. All rights reserved.


Rahim A.,Indian Institute of Technology Roorkee | Sharma U.K.,Indian Institute of Technology Roorkee | Murugesan K.,Indian Institute of Technology Roorkee | Sharma A.,Reactor Safety Division | Arora P.,Reactor Safety Division
Journal of Structural Fire Engineering | Year: 2012

This paper presents results of an experimental study undertaken to optimize the residual compressive strength of heated concrete with respect to various mix design parameters using the Taguchi method. The design of experiments (DoE) was carried out by standard L9 (34) orthogonal array (OA) of four factors with three material parameter levels. The factors considered were water-cement ratio, cement content, super-plasticizer dosage and fine aggregate content. The specimens were heated up to 200°C, 400°C, 600°C and 800°C target temperatures and were subsequently tested under axial compressive loads in cooled condition. Based on the results, the material parameter responses of optimum performance characteristics were analyzed by statistical analysis of signal to noise ratio (S/N) and analysis of variance (ANOVA) techniques to maximize the post-fire residual compressive strength of concrete. The results indicate that the best level of control factors paid their own contribution of compressive strength at various elevated temperatures. The confirmation tests corroborated the theoretical optimum test conditions.

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