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Obaidurrahman K.,Indian Atomic Energy Regulatory Board | Doshi J.B.,Indian Institute of Technology Bombay
Annals of Nuclear Energy | Year: 2011

A simple methodology has been developed to assess the spatial dynamic behavior of large PWRs against xenon spatial instability in different modes. Method of analysis aims to analyze xenon dynamic behavior against anticipated reactivity perturbations. Reactivity perturbations in different modes have been evaluated based on reactivity device movements as well as localized thermal variations in the core. Effect of individual core design and operating parameters on xenon spatial instability has been studied. Behavior of spatial stability index (SI) with core size is investigated. Based on SI-core size curve, a threshold core size has been determined beyond which a PWR core tends to become spatially unstable. Methodology has been used to assess the spatial xenon dynamic behavior of different modes of oscillations in VVER1000 and AP1000 reactor cores. © 2010 Elsevier Ltd. All rights reserved.

Chowdhury S.,Ultratech | Basu P.C.,Indian Atomic Energy Regulatory Board
ACI Materials Journal | Year: 2010

A new methodology to proportion self-consolidating concrete (SCC) suitable for high-volume ASTM Class F fly ash content is introduced. Ingredients are determined from explicit criteria on strength and rheology. The water-cementitious material ratio (w/cm) is derived from the model systematically developed for this study. The quantity of chemical admixture and fine aggregates are determined from the Theological requirement. Finally, the quantity of coarse aggregate is calculated using the absolute volume method and finalized by adjusting the volume fractions. The suitability of the method is examined by proportioning SCC mixtures with different powder composition and fine aggregate types. The workability and compressive strength as well as the split tensile strength of these mixtures are tested. The results suggested that the method was adequate to proportion SCC mixtures with ingredients used in this study, satisfying both of the requirements of strength and rheology. Copyright © 2010, American Concrete Institute. All rights reserved.

Chowdhury S.,Ultratech | Basu P.C.,Indian Atomic Energy Regulatory Board
ACI Materials Journal | Year: 2010

Under identical conditions of mixing, curing, compaction, and testing, the relationship between the compressive strength of concrete (fc) and water-cementitious material ratio (w/cm) is critical to proportion a workable concrete mixture for specified target properties. The relationship between strength and w/cm is developed in the generic format for fly ash-based concrete involving nondimensional parameters; strength ratio (fc/f m), and w/cm. The fc/fm is the ratio of f c and compressive strength of the standard mortar (fm). The standard mortar is proportioned with the cementitious material of the same composition and fine aggregates that will be used in the concrete mixture. The fm is tested following the standard procedure to test the compressive strength of cement. The hydration characteristics of cementitious materials are incorporated in the relation. The test results confirm the satisfactory performance of a new relation in proportioning a fly-ash-based concrete mixture. Copyright & 2010, American Concrete Institute. All rights reserved.

Bajaj S.S.,Indian Atomic Energy Regulatory Board
Energy Procedia | Year: 2011

Over the years, India has mastered all the stages of the nuclear fuel cycle, which include mining, processing & fabrication of nuclear fuel; design, construction, and operation of nuclear power reactors and research reactors; reprocessing of spent fuel and management of radioactive wastes. Ionising radiation is also used widely in medical, industrial and research areas. Since its inception, Department of Atomic Energy (DAE) was enforcing radiological safety in the country through in -house or ad-hoc committees, till a dedicated regulatory body (AERB) was set up 25 years ago. Today India is operating 19 nuclear power plants with different vintages (2 BWRs and 17 PHWRS) and another 8 (1 PFBR, 5 PHWRs and 2 PWRs) are in various stages of construction. Recently there are new evolutionary reactors (AHWRs) for which design has been completed and are on the threshold for consideration for construction. To match the rapid growth in the need for power India is also about to take up construction of large evolutionary PWRs of foreign design. This variety in the Indian nuclear power programme has come up due to a systematic evaluation and optimisation of the resources and technology available within the country. Added to this is the growing use of radiation in non -power applications. As the safety supervision of this huge programme is the responsibility of AERB, it faces various challenges, like, • Strategies for regulating wide variety of nuclear and radiation facilities with wide dispersal; • Meeting present day expectations with regard to nuclear and radiation safety and nuclear security; • The safety and security of large number of radioactive sources spread over such a vast country and of the associated import/export guidance; • Ensuring safety of old plants by periodic reviews and by prescribing adequate safety upgradation and ageing mana gement programme; • Adaptation of the regulatory system and of regulations to new and foreign design nuclear technologies and applications; • Developing competence in wide variety of technologies and different reactor designs; • Developing adequate human resource ready for safety supervision of this huge nuclear and radiation programme; • Approach to regulatory research related to new technologies. Apart from the above mentioned issues regulatory challenges may arise from policies to make all energy se ctors competitive. With growing competition, it is becoming increasingly important to reconcile commercial interests with safety requirements. For AERB, the first challenge will be to ensure that economic pressures do not erode nuclear safety. To maintain highest level of safety culture, AERB will also need to adapt to an increasingly market -oriented environment and new working relationships with utilities. Although it is a difficult task, the Board has also evolved systematically over the years and now has an efficient structure, which is capable of facing the current challenges. © 2011 Published by Elsevier Ltd.

Rani R.D.,Indian Atomic Energy Regulatory Board | Sasidhar P.,Indian Atomic Energy Regulatory Board
Environmental Earth Sciences | Year: 2012

The mobility of strontium in subsurface is largely influenced by sorption on to clay minerals. In the present study, kaolinite clay samples collected from the Kalpakkam nuclear plant site were employed to understand the sorption characteristics of strontium by batch method. The effect of several parameters such as time, strontium ion concentration, pH, temperature and ionic strength was investigated. The kinetic studies suggested pseudo-second-order mechanism. The experimental sorption data was fitted to Langmuir adsorption model for obtaining the sorption capacity of the sorbent. The maximum sorption capacity was 5. 77 mg/g at 298 K and was found to increase with an increase in temperature. It was observed that the distribution coefficient (K d) of strontium on clay increased as the pH of the solution increased. The distribution coefficient was found to decrease with an increase in concentration of Na + and Ca 2+ ions. This variation of K d suggests that cation exchange is the predominant sorption process. It was also observed that sorption process is endothermic. The thermodynamic parameters such as {increment}G 0, {increment}H 0 and {increment}S 0 were calculated. The negative values obtained for {increment}G 0 indicated that the sorption of strontium on clay was spontaneous at all studied concentrations. {increment}G 0 becomes more negative with an increase in temperature, suggests that the sorption process is more favorable at higher temperatures. © 2011 Springer-Verlag.

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