Role of Passive Safety Features in Prevention and Mitigation of Severe Plant Conditions in Indian Advanced Heavy Water Reactor

Vikas Jain,A. K. Nayak,M. Dhiman,P.P. KULKARNI,P. K. Vijayan,K.K. Vaze 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.5

Pressing demands of economic competitiveness, the need for large-scale deployment, minimizing the need of human intervention, and experience from the past events and incidents at operating reactors have guided the evolution and innovations in reactor technologies. Indian innovative reactor ‘AHWR’ is a pressure-tube type natural circulation based boiling water reactor that is designed to meet such requirements, which essentially reflect the needs of next generation reactors. The reactor employs various passive features to prevent and mitigate accidental conditions, like a slightly negative void reactivity coefficient, passive poison injection to scram the reactor in event of failure of the wired shutdown systems, a large elevated pool of water as a heat sink inside the containment, passive decay heat removal based on natural circulation and passive valves, passive ECC injection, etc. It is designed to meet the fundamental safety requirements of safe shutdown, safe decay heat removal and confinement of activity with no impact in public domain, and hence, no need for emergency planning under all conceivable scenarios. This paper examines the role of the various passive safety systems in prevention and mitigation of severe plant conditions that may arise in event of multiple failures. For the purpose of demonstration of the effectiveness of its passive features, postulated scenarios on the lines of three major severe accidents in the history of nuclear power reactors are considered, namely; the Three Mile Island (TMI), Chernobyl and Fukushima accidents. Severe plant conditions along the lines of these scenarios are postulated to the extent conceivable in the reactor under consideration and analyzed using best estimate system thermal-hydraulics code RELAP5/Mod3.2. It is found that the various passive systems incorporated enable the reactor to tolerate the postulated accident conditions without causing severe plant conditions and core degradation.

Design and Characterization of Colon-specific Drug Delivery System Containing Paracetamol Microsponges

Vikas Jain,Ranjit Singh 대한약학회 2011 Archives of Pharmacal Research Vol.34 No.5

The present work was aimed at designing microsponge based colon specific drug delivery system containing paracetamol. Eudragit S-100 based microsponges containing drug in varying amounts were prepared using quasi-emulsion solvent diffusion method. The microsponges were prepared by optimizing various process parameters. DSC and FTIR studies indicated compatibility of the drug in various formulations. Shape and surface morphology of the microsponges were examined using scanning electron microscopy. The formulations were subjected to in vitro release studies and the results were evaluated kinetically and statistically. The in vitro release data showed a bi-phasic pattern with an initial burst effect. In the first hour drug release from microsponges was found to be between 18-30%. The cumulative percent release at the end of 12th hour was noted to be between 74-98%. The release kinetics showed that the data followed Higuchi model and the main mechanism of drug release was diffusion. The colon specific tablets were prepared by compressing the microsponges followed by coating with pectin: hydroxypropylmethyl cellulose (HPMC) mixture. In vitro release studies exhibited that compression coated colon specific tablet formulations started releasing the drug at 6th hour corresponding to the arrival time at proximal colon. The study presents a new approach for colon specific drug delivery.

ppGpp: Stringent Response and Survival

Jain Vikas,Kumar Manish,Chatterji Dipankar The Microbiological Society of Korea 2006 The journal of microbiology Vol.44 No.1

Adaptation to any undesirable change in the environment dictates the survivability of many microorganisms, with such changes generating a quick and suitable response, which guides the physiology of bacteria. During nutritional deprivation, bacteria show a stringent response, as characterized by the accumulation of (p)ppGpp, resulting in the repression of stable RNA species, such as rRNA and tRNA, with a concomitant change in colony morphology. However, genes involved in amino acid biosynthesis become over-expressed to help bacteria survive under such conditions. The survivability of pathogenic bacteria inside a host cell also depends upon the stringent response demonstrated. Therefore, an understanding of the physiology of stringent conditions becomes very interesting in regulation of the growth and persistence of such invading pathogens.

ROLE OF PASSIVE SAFETY FEATURES IN PREVENTION AND MITIGATION OF SEVERE PLANT CONDITIONS IN INDIAN ADVANCED HEAVY WATER REACTOR

Jain, Vikas,Nayak, A.K.,Dhiman, M.,Kulkarni, P.P.,Vijayan, P.K.,Vaze, K.K. Korean Nuclear Society 2013 Nuclear Engineering and Technology Vol.45 No.5

Pressing demands of economic competitiveness, the need for large-scale deployment, minimizing the need of human intervention, and experience from the past events and incidents at operating reactors have guided the evolution and innovations in reactor technologies. Indian innovative reactor 'AHWR' is a pressure-tube type natural circulation based boiling water reactor that is designed to meet such requirements, which essentially reflect the needs of next generation reactors. The reactor employs various passive features to prevent and mitigate accidental conditions, like a slightly negative void reactivity coefficient, passive poison injection to scram the reactor in event of failure of the wired shutdown systems, a large elevated pool of water as a heat sink inside the containment, passive decay heat removal based on natural circulation and passive valves, passive ECC injection, etc. It is designed to meet the fundamental safety requirements of safe shutdown, safe decay heat removal and confinement of activity with no impact in public domain, and hence, no need for emergency planning under all conceivable scenarios. This paper examines the role of the various passive safety systems in prevention and mitigation of severe plant conditions that may arise in event of multiple failures. For the purpose of demonstration of the effectiveness of its passive features, postulated scenarios on the lines of three major severe accidents in the history of nuclear power reactors are considered, namely; the Three Mile Island (TMI), Chernobyl and Fukushima accidents. Severe plant conditions along the lines of these scenarios are postulated to the extent conceivable in the reactor under consideration and analyzed using best estimate system thermal-hydraulics code RELAP5/Mod3.2. It is found that the various passive systems incorporated enable the reactor to tolerate the postulated accident conditions without causing severe plant conditions and core degradation.

Multi-Objective Optimization of Cascade Refrigeration System Using the Concept of Modified and Advanced Exergy, Risk Level and Thermal Inventory

Vaibhav Jain,Rajiv Rawat,Gulshan Sachdeva,Vikas Kumar 대한설비공학회 2020 International Journal of Air-Conditioning and Refr Vol.28 No.4

This work conceives the performance of vapor compression cascaded refrigeration system (CRS) from the exergy, safety and thermal inventory points of view employing the theory of effective temperature (T eff )Teff) than environment temperature (To) in Gouy–Stodola equation. Comparative results show that the actual irreversible loss in CRS is 8.1% higher. Further, advanced exergy analysis results showed that 17.985 kW irreversible loss (out of 33.737 kW irreversible loss) in the system is evadable with improvement in the system design. Besides, the vulnerability of toxic fluid R717 is reported in terms of the total risk level. Moreover, the economy matter is expressed in terms of its total thermal inventory. At the base case, total risk level and total thermal inventory are determined to be 454.3 US$ and 48.86 kW/K, respectively. First, sensitivity analysis is carried out to evaluate the variation in irreversible loss, total risk level and thermal inventory at different evaporator and condenser temperatures with different degrees of overlap (decision variables). A total of nine simulations are designed using the Taguchi technique. Later, multi-objective optimization is employed. The optimization process reduced the total irreversibility and annual risk level of CRS by 10.2% and 8.9%, respectively, with 6.8% increase in thermal inventory.

A young man with acute respiratory distress syndrome: eosinophilia is not always “benign”

Ankur Jain,Pankaj Malhotra,Vikas Suri,Ritesh Agarwal,Amanjit Bal,Subhash Varma 대한혈액학회 2017 Blood Research Vol.52 No.4

An Experimental Investigation on Vapor Compression Refrigeration System Cascaded with Ejector Refrigeration System

Kumar Vikas,Sachdeva Gulshan,Tiwari Sandeep,Anuradha Parinam,Jain Vaibhav 대한설비공학회 2021 International Journal Of Air-Conditioning and Refr Vol.29 No.3

A conventional vapor compression refrigeration system (VCRS) cascaded with a heat-assisted ejector refrigeration system (ERS) has been experimentally analyzed. Cascading allows the VCRS to operate at lower condenser temperatures and thus achieve a higher coefficient of performance. In this cascaded system, the condenser of the vapor compression system does not dissipate its heat directly to the evaporator of the ERS; instead, water circulates between the condenser of VCRS and the evaporator of ERS to exchange the heat. Seven ejectors of different geometries have been used in the ERS; however, all the ejectors could not maintain thermal equilibrium at the desired operating conditions. The compressor of the cascaded VCRS consumed 1.3 times less power than the noncascaded VCRS. Furthermore, the cascaded system provided a maximum 87.74% improvement in COP over the noncascaded system for the same operating conditions. The performance of the system remained constant until the critical condenser pressure of the ERS.

A young man with acute respiratory distress syndrome: eosinophilia is not always “benign”

Ankur Jain,Pankaj Malhotra,Vikas Suri,Ritesh Agarwal,Amanjit Bal,Subhash Varma 대한혈액학회 2017 Blood Research Vol.51 No.4

Rheological investigations of water based drilling fluid system developed using synthesized nanocomposite

Rajat Jain,Triveni K. Mahto,Vikas Mahto 한국유변학회 2016 Korea-Australia rheology journal Vol.28 No.1

In the present study, polyacrylamide grafted xanthan gum/multiwalled carbon nanotubes (PA-g-XG/ MWCNT) nanocomposite was synthesized by free radical polymerization technique using potassium persulfate as an initiator. The polyacrylamide was grafted on xanthan gum backbone in the presence of MWCNT. The synthesized nanocomposite was characterized by X-ray diffraction technique (XRD), and Fourier transform infrared spectroscopy analysis (FT-IR). The morphological characteristics of the nanocomposite were analyzed by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) analyses. Also, its temperature resistance property was observed with Thermogravimetric analysis (TGA). The effect of nanocomposite on the rheological properties of the developed drilling fluid system was analyzed with a strain controlled rheometer and Fann viscometer. Flow curves were drawn for the developed water based drilling fluid system at elevated temperatures. The experimental data were fitted to Bingham, power-law, and Herschel Bulkley flow models. It was observed that the Herschel Bulkley flow model predict the flow behavior of the developed system more accurately. Further, nanocomposite exhibited non-Newtonian shear thinning flow behavior in the developed drilling fluid system. Nanocomposite showed high temperature stability and had a significant effect on the rheological properties of the developed drilling fluid system as compared to conventionally used partially hydrolyzed polyacrylamide (PHPA) polymer.

ppGpp: Stringent Response and Survival

Dipankar Chatterji,Vikas Jain,Manish Kumar 한국미생물학회 2006 The journal of microbiology Vol.44 No.1

Adaptation to any undesirable change in the environment dictates the survivability of many microorganisms, with such changes generating a quick and suitable response, which guides the physiology of bacteria. During nutritional deprivation, bacteria show a stringent response, as characterized by the accumulation of (p)ppGpp, resulting in the repression of stable RNA species, such as rRNA and tRNA, with a concomitant change in colony morphology. However, genes involved in amino acid biosynthesis become over-expressed to help bacteria survive under such conditions. The survivability of pathogenic bacteria inside a host cell also depends upon the stringent response demonstrated. Therefore, an understanding of the physiology of stringent conditions becomes very interesting in regulation of the growth and persistence of such invading pathogens.