IASTA-2010

IT–1

ISRO-Geosphere Biosphere Programme (GBP) Perspectives

CBS Dutt

Indian Space Research Organisation, Bangalore

gbp@isro.gov.in

Land-Air-Ocean interactions are delicately in equilibrium and sustain the life supporting environment to our Planet Earth. These interactive forces modulate equilibrium in the weather and climate. The indiscriminate land use practices, fossil fuel burning, increased vehicular traffic, loss of vegetation cover, etc. are exerting changes in the radiative forcing reaching the earth’s surface. The elevated levels of trace gases, and altered absorption efficiency of the land cover are interactively summarizes the forcing to pronounce changes in climate on a short, medium and long term scales which operate at micro, meso and synoptic spatial scales. The temporal and spatial scales of changing Earth’s climate result in aberrations on natural cycles of monsoon, vagaries in the natural disasters, increased temperatures both on surface and oceans, loss of soil moisture, decrease in the extent of snow/glaciers, changes in plant productivity etc cumulatively inflict irrecoverable changes to our climate.

Realizing the importance of temporal and spatial scales in Geosphere and Biospheric exchange processes ISRO focused its objectives mainly on large-scale issues contributing to the understanding of parameters responsible for climate change. Towards this Specific Atmospheric Assessment Projects (SAAP) viz. 1) Aerosol Radiative Forcing over India – on a periodic basis is contemplated through the establishment of MWR network in the country for possible uses in the assimilation to our numerical weather forecasting. 2) Atmospheric Trace Gases composition and Transport over India –envisages to apportion the sources and sinks of the trace gases and their residence time of transporting to other regions and to identify ecological hotpots. 3) Atmospheric Dust Composition and Transport

– through establishment of aerosols dust composition observatory network and the transport of atmospheric dust from the continental and extra continental regions to understand the intra-annual variability of our atmospheric composition and the possible role of dust in regulating radiative forcing. 4) Atmospheric Boundary Layer Characterization – through establishment of boundary layer Lidars is envisaged. 5) Energy and Mass Exchanges in Vegetative Systems – a project planned to understand the exchanges of energy and water use during the growing season of our major agricultural systems to possibly assimilate into the crop production and protection models.

The Integrated Land Ecosystem and Atmospheric Projects (ILEAP) viz. 1) Land Use Land Cover Dynamics and Impact of Human Dimensions in the Indian River Basis over the last 30 years is proposed to analyze the issues causing concerns on our dwindling hydrological regime. 2) The Multi-proxy Quantitative Paleo monsoon reconstruction for past 21,000 years BP and Regional Climate Modeling efforts are integral part of the past and future predictions of our changing Indian climate on a scientific basis.

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AEROSOLS & CLOUDS : CLIMATE CHANGE PERSPECTIVES

As far as atmospheric CO2 and its flux is concerned there are no primary databases or reliable observations available for use in the carbon dynamics studies. Towards this GBP is planning for Intense Observational Projects (IOP) related to 1) Vegetation Carbon Pool Assessment and 2) Soil Carbon Pool Assessment.

In addition to the above, ISRO-GBP periodically designs and develop major national experimental campaigns to understand the large scale atmospheric phenomena using multi-institutional, multi-platform observations over land, ocean and vertical profiles of atmosphere using aerial and balloon platforms. Some of the major experiments on land campaigns (LC-1 & LC-2) and ICARB & ICARB-W as well as the forthcoming RAWEX- GVAX are some of the major experiments significantly contributing to the overall growth of climate research in India.

Besides the above, the most significant observational networks being established, which are of vital importance both to atmospheric and biospheric scientists, are 1) ARFI network 2) Trace Gas Network 3) Agro Meteorological Stations Network 4) Flux Network and 5) Atmospheric Boundary Layer Network.

ISRO-GBP’s climate change research programme envisages the development of small satellites capable of measuring and monitoring of trace and greenhouse gases and atmospheric aerosol characterization etc. The satellite based observations eventually be integrated with ground observational network of ISRO-GBP and attempt to make it operational to implement the climate scenario of Indian continent in the near future.

The ISRO-GBP projects would thus provide enhanced understanding of India’s regional climate and its atmospheric composition.

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IASTA-2010

IT–2

Regional Aerosol Source-receptor Relationships in the Climate

Context

Chandra Venkataraman

Department of Chemical Engineering, Indian Institute of Technology,Bombay

Powai, Mumbai 400 076

E-mail : chandra@iitb.ac.in

How good is our understanding of aerosol source-receptor relationships on regional scales over India? What relevance does this bear to our understanding of climate perturbation by aerosols? Extensive observational campaigns in the last decade in the south Asian region have furthered an understanding of regional aerosol composition and its influences on atmospheric extinction, lower atmospheric heating and reduction of radiation flux at the surface. Modeling studies have estimated large increases in atmospheric radiative flux mediated by seasonal variability in aerosols. Some modeling studies have indicated the potential of aerosols to perturb precipitation in the region and ongoing research programs seek to understand the extent to which human activities, including anthropogenic aerosol emissions, modulate the Asian monsoon climate. There are several unanswered questions regarding the origin of south Asian aerosols, i.e., the relative influence of emissions arising from nearby and distant geographical regions, the relative influence of surface sources (industry, transport, residential energy, agricultural burning) and elevated sources (thermal power, forest burning) and the influence of megacity emissions on regional scales. These govern our ability to predict aerosol surface concentrations and vertical structure, along with consequent changes in the atmospheric radiation balance and precipitation. This talk will discuss a combined chemical transport and receptor modeling approach towards understanding source receptor relationships over India using examples from recent observational campaigns in the region. Findings will be discussed on sources that affect surface and columnar aerosols on campaign and episode time scales. Source influence on aerosol loading, optical depth and radiative forcing will be discussed on different receptor domains in the subcontinent. Future research needs will be highlighted to integrate such findings into climate modeling and assessment frameworks.

References

Bhanuprasad, S.G., C. Venkataraman and M. Bhushan (2008) Source identification using positive matrix factorization and trajectory modelling: A new look at the INDOEX ship-observations, Atmospheric Environment, 42 (2008) 4836–4852, doi:10.1016/ j.atmosenv.2008.02.041.

Verma, S. C. Venkataraman and O. Boucher (2008), Origin of surface and columnar INDOEX aerosols using source- and region-tagged emissions transport in a general circulation model, Journal of Geophysical Research, 113, D24211, doi:10.1029/2007JD009538.

Verma, S., C. Venkataraman and O. Boucher (2010), Aerosol radiative forcing during the Indian winter monsoon from natural and anthropogenic sources based on geographical origin, Journal of Geophysical Research, in preparation.

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Mehta, B., C. Venkataraman, M. Bhushan and S.N. Tripathi (2009) Identification of sources affecting fog formation at Kanpur (80°22’E, 26°26’N), India: Combining positive matrix factorization and trajectory modeling with quantitative emission estimates, Atmospheric Environment, 43 (2009) 1288–1295, doi:10.1016/j.atmosenv.2008.11.041.

Cherian, R., C. Venkataraman and S. Ramachandran (2009), Temporal variability in emission category influence on organic matter aerosols in the Indian region, Geophysical Research Letters, 36, L06809, doi:10.1029/ 2008GL036311.

Cherian, R., C. Venkataraman, S. Ramachandran, A. Kumar, A.K. Sudheer and M.M. Sarin (2010) Origin of regional-scale absorbing aerosols: Integrating PMF and PSCF with emission inventories and satellite observations, Journal of Geophysical Research, submitted.

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IASTA-2010

IT-3

Aerosols & Clouds : Climate Change Perspectives

A. Jayaraman

National Atmospheric Research Laboratory

Gadanki-517 112, Andhra Pradesh, India

E-mail : jayaraman@narl.gov.in

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AEROSOLS & CLOUDS : CLIMATE CHANGE PERSPECTIVES

IT–4

Extreme Heat Events and Human Health

P K Nag

National Institute of Occupational Health

Ahmedabad 380 016, India

E-mail : pranabnag@yahoo.com

Climate change being real, there is a growing concern that teeming millions might be at greater risk of death, disease and disability due to extreme heat events in the tropics and other regions. Risks of heat induced human illnesses prevail, with relative vulnerability to children, elderly, pregnant mothers, and those with pre-existing medical conditions, such as obesity, cardiovascular and neurological diseases. The population vulnerability assessment depends on multiple determinants, including biological, environmental, behavioural, social, and economic dimensions. In heat wave episodes witnessed in Europe and northern America in the recent time, most of the victims were elderly who stayed isolated in indoor environment. In contrast, the vast labouring population in the tropical countries are subjected to extreme heat exposures outdoor. Urban and rural poor dwelling in the slums and pavement, outdoor construction workers, and others, face adverse health effects, due to their low physiological adaptive capacity, lack of awareness of the risks, as well as non-feasibility of adopting any mitigation measures.

Unpredictable heat waves may change geographic risk in certain regions. Integration of geo-spatial and enviro-climatic information, socio-economic data, and health outcome and wellbeing measures has been emphasized in planning response to heat wave. An example may be drawn that the environmental warmth depends on the environmental characteristics and anthropogenic activities, and the relationships between the environmental, physiological and biophysical descriptors yield dimensions of stress and disorders of the population involved. Prediction of sweating response of a vulnerable population group in a heat-prone region can be an indication to introduce, for example, fluid supplementation programme in a region, in order to avoid dehydration and heat exhaustion of the exposed population.

The extent to which the climatic change factors may prove determinants of health impairments, safety consequences and productivity impacts in our diverse occupational spheres now or in the future remains speculative. The roles of the Government, regulatory and standards agencies, employer organizations have been delineated to take up measures for mitigation towards rural and urban area development, housing and shelters, industrial hotspots, transport systems, public health care services. The environmental health researchers have obvious targets to generate experimental data from the heat exposed population from the community and work environment, with reference to morbidity of heat disorders and impacts on productivity. To this, our own commitment to the challenge to accomplish the research agenda in bringing better adaptation and mitigation measures to protect all those at risk bears significance.

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IASTA-2010

IT–5

Campaign-mode Studies on Atmospheric Aerosols over Indian Region

Prabha R Nair

Space Physics Laboratory, Vikram Sarabhai Space Centre,

Trivandrum – 695 022,Kerala, India

E-mail : prabha_nair@vssc.gov.in

Atmospheric aerosols play crucial roles in climate change, air pollution, public health, remote sensing and atmospheric chemistry. Aerosols originate from a variety of natural and anthropogenic sources on the Earth’s surface or in the atmosphere and are composed of a wide variety of inorganic and organic particles with their size spectrum lying in the range 10-3 m to 102 m. Major natural sources of aerosols include sea spray, wind-blown soil dust, extra terrestrial dust, vegetation, forest fires, etc. The main anthropogenic sources include fossil fuel combustion, industrial activities, automobiles, biomass burning etc. Due to the large diversity in their sources and production mechanisms, aerosols are highly heterogeneous in their physical and chemical properties. On global scale, the natural aerosols amount 4-5 times larger than the anthropogenic aerosols. But on regional scales the contribution of anthropogenic aerosols sometimes exceeds that of natural aerosols several times. The spatial and temporal variations in aerosol properties induce largest uncertainty in the prediction of global climate forcing [IPCC, 2007] and in assessing environmental/biological impacts. The large heterogeneities in aerosol sources and the influence of meteorological conditions in modifying their physical and chemical properties demand characterization of aerosols on regional basis and at short time scales. Such studies will also reveal the perturbations in the aerosol loading of the atmosphere due to human activities and subsequent impact on regional climate and ecosystems. For the past few decades our knowledge on the role of atmospheric aerosols in the regional climate forcing as well as in their environmental/biological impacts has increased significantly owing to the well-focused efforts from the scientific community all over the world. Network-based observations, long-term measurements from fixed locations and thematic field campaigns have contributed significantly to our present understanding on atmospheric aerosols and their impacts on the geosphere-biosphere system.

The Indian subcontinent with its varied topography, geographic features and climatic patterns is one of the prime regions where aerosol characterization is essential on regional scale and on short-term basis. But, scientific data on aerosols and trace gases have been scarce over the Indian region till late 1990s. However, for the last fifteen years, studies on aerosols have gained momentum. Several networks of stations have been set up and a number of field campaigns have been conceived and conducted in Indian region for aerosol characterization. The Campaign mode observations conducted as part of Indian Ocean Experiment (INDOEX) in 1998-1999 and Arabian Sea Monsoon Experiment (ARMEX) have brought out the spatial features of aerosol characteristics in the marine

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AEROSOLS & CLOUDS : CLIMATE CHANGE PERSPECTIVES

environments of Arabian Sea (AS) and Indian Ocean (IO) and the role of long-range transport in establishing these patterns. The Geosphere Biosphere Programme (GBP) of Indian Space Research Organization (ISRO) –ISRO-GBP- has several projects with the objective of complete characterization of aerosols and deriving the spatial maps of various aerosol parameters and their radiative forcing. In addition to the network observations covering geographically different locations, two land campaigns were also conducted under ISRO-GBP. While Land Campaign I (LCI) focused on the coastal, inland, semi-arid and high altitude locations over the Indian land mass, Land Campaign II (LCII) focused on the Indo-Gangetic Plains extending from 22°N to 30°N over a longitude region 75°E to 87°E, where occurrence of fog is frequent during winter. Integrated Campaign for Aerosols gases & Radiation Budget (ICARB) under the ISRO-GBP forms the largest campaign conducted in the Indian region with the major objective of mapping the characteristics of aerosols and trace gases over Indian landmass and adjoining oceanic environments and to quantify their radiative impacts. It has been a multi-platform, multi-instrumented and multi-institutional field programme. The first campaign in this series (ICARB-I) has been conducted in March-May, 2006 and second (ICARB-W) during winter months of December 2008 to Jan 2009. During ICARB-I ship-borne observations were carried out over both Bay of Bengal (BoB) and AS and during ICARB-W over BoB with vast spatial coverage. Based on measurements through a national network of Multi-Wavelength Radiometers under the ARFI project of ISRO-GBP, spatial maps of the aerosol optical depth (AOD) could be generated. The long-term trends in AOD could also be examined for several locations. In addition, satellite derived AOD is used to investigate the spatial features in detail and to examine their long-term trends. This presentation gives the high lights of the various campaigns conducted over the Indian region and the results obtained. Aerosol mass loading, number density and columnar aerosol optical depth show significant spatial variations due to varying source characteristics, transport processes and prevailing meteorology. Information on chemical composition of aerosols is used as a potential tool in identifying the sources. Another major outcome of these campaigns is the evolution of first-cut aerosol chemical models for different environments over Indian landmass and surrounding oceanic regions. Using measured aerosol parameters realistic estimates of radiative forcing also are made. Future scope of the campaign-based studies also will be discussed.

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IASTA-2010

IT–6

An Overview of Twenty Years of Optical Remote Sensing Studies of Tropical Atmospheric Aerosols, Gases and Clouds at IITM, Pune

P.C.S. Devara and P. Ernest Raj

Indian Institute of Tropical Meteorology, Pashan, Pune 411 008, India

E-Mail : devara@tropmet.res.in

The impact of aerosols, gases and clouds, through scattering and absorption of solar and terrestrial radiation, on global/regional/local weather and climate, satellite remote sensing, air and water quality has been the subject of numerous investigations in recent years. Efficient methods for real time monitoring of these parameters over longer period are of great interest in the programs connected with impact, assessment, control and forecast of anthropogenic activities on climate system. Compared to direct measuring techniques, which provide reasonably reliable information with good time resolution at a specific location, more representative information can be obtained with remote sensing techniques. Of the latest optical remote sensing techniques, laser radar or LIDAR (active remote sensing) and solar radiometry (passive remote sensing) have been recognized to be powerful and versatile tools for atmospheric diagnostics. A variety of lidar and radiometric techniques, operating for the past several years, at the Indian Institute of Tropical Meteorology (IITM), Pune, India and the multi-year, multi-institutional, poly-platform, vertical profile / columnar distributions of aerosols, gases and clouds archived with these facilities and the data archival and analysis procedures, and salient results are reviewed. With the advent of recent technological developments, the advanced sun-sky radiometers and autonomous Dual Polarization Micro Pulse Lidar (DPMPL), installed at the Institute in the recent past for understanding the direct and indirect aerosol effects, particularly of anthropogenic origin, will be discussed. Some stimulating results, bringing insight into the complex interactions and feedback processes underlying aerosols, boundary-layer, clouds and precipitation using these advanced light scattering techniques from land and oceanic regions, documenting the impact of aerosols on weather and climate are presented. Future directions of atmospheric remote sensing, and scientific joint collaborations to fill the research gaps and address the key cross-cutting issues among the above parameters in different time scales will be highlighted.

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AEROSOLS & CLOUDS : CLIMATE CHANGE PERSPECTIVES

IT–7

Impact of Anthropogenic Sources on Chemical Composition of Aerosols over Bay of Bengal

Bikkina Srinivas, M.M.Sarin and A.Kumar

Physical Research Laboratory, Navrangpura,

Ahmedabad, India – 380 009

E-mail : sarin@prl.res.in

Introduction

The long-range transport of atmospheric fine particulate matter, derived from natural and anthropogenic sources, has profound impact on the marine atmospheric boundary layer (MABL) and subsequent deposition of chemical constituents across the air–sea interface. For open ocean regions, it is increasingly recognized that atmospheric supply of trace metals (such as Fe) and nutrient species (NO3-, NH4+) can enhance the surface primary production, thus, leading to increased sequestration of atmospheric CO2. Recently, a two-fold increase in the atmospheric deposition of anthropogenic nitrogen species in the marine areas around south-east Asia has been suggested (Duce et al., 2008). However, there have been very few systematic studies from the perspective of atmospheric transport of mineral dust and pollutants from south and south-east Asia to the MABL of Arabian Sea and Bay of Bengal (Lelieveld et al, 2001; Kumar et al., 2008a, b; Sudheer and Sarin, 2008). As a part of the national efforts (under ICARB-Programme sponsored by ISRO- GBP), aerosol samples were collected from the MABL of Bay of Bengal in order to assess the impact of the long-range transport of anthropogenic species and heterogeneous phase chemistry.

Aerosol Sampling and Analysis

The size-segregated (PM2.5 & PM10) aerosols were collected (during 27th Dec’08 to 30th Jan’09) on Tissuquartz filters(220 x 210 mm2), by simultaneously operating two high- volume samplers (flow-rate: 1.13m3/min) onboard ORV Sagar Kanya, and analyzed for water-soluble ions (Cl-, NO3 , SO42- & Na+, NH4+,K+,Ca2+, Mg2+), carbonaceous species (EC, OC), crustal elements ( Fe, Al, Ca and Mg ) and combustion derived trace metals (Cd, Pb). The water-soluble ions (extracted in Milli-Q water) were measured on Dionex-500 Ion- Chromatograph equipped with suppressed conductivity detection. The acid digested samples (in distilled HF and HNO3) were measured for crustal elements (Al, Fe, Ca and Mg) on ICP-AES and for heavy metals (Cd, Pb) on GF-AAS.

Results and Discussion

The mass concentrations of PM2.5 and PM10 varied as 2.0 to 76.7 and 6.0 to 108 μg.m-3, respectively. The average chemical composition of the two-size fractions is summarized in

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IASTA-2010

Fig1. Analysis of these results suggests that MABL of Bay of Bengal is significantly influenced by pollutants derived from anthropogenic sources (fossil- fuel combustion and biomass burning). The anthropogenic fraction of water-soluble ionic species (ANTH = NO3- + nss- SO42- + NH4+) is most abundant in PM2.5.

Figure 1. Average chemical composition of PM2.5 & PM10 in the MABL of Bay of Bengal. EC = Elemental Carbon, OM = Organic Matter (Organic carbon * 1.6), ANTH = anthropogenic fraction of water-soluble ions (nss-SO42- + NO3- + NH4+).

Total carbonaceous aerosol mass concentration (TCA= OM+EC) is the second most abundant fraction in PM2.5 aerosols. These results, together with OC/EC ratio of = 3.0, suggest that chemical composition of fine fraction is dominated by emissions from fossil- fuel combustion sources. The temporal variability in OC/EC ratio in PM2.5 and PM10 is presented in Fig 2. The impact of anthropogenic sources is also evident from large-scale chloride depletion in sea-salt aerosols and high enrichment factors of heavy metals (Cd, Pb).

Figure 2. Temporal variability of OC/EC ratio in PM2.5 and PM10.

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References

1)J. Lelieveld et al., 2001. The Indian Ocean Experiment: Widespread Air Pollution from South and Southeast Asia. Science, 9 February, 291: 1031-1036.

2)R.A.Duce et al., 2008. Impacts of Atmospheric Anthropogenic Nitrogen on the Open Ocean. Science 16 May 2008 320: 893-897.

3)Kumar, A., Sudheer and A.K., Sarin, M.M., 2008a. Chemical characteristics of aerosols in MABL of Bay of Bengal and Arabian Sea during spring inter-monsoon: a comparative study. July 2008. J. Earth Syst. Sci. 117 (S1), 325–332.

4)Kumar, A., Sarin, M.M. and Sudheer, A.K., 2008b. Mineral and anthropogenic aerosols in Arabian sea- atmospheric boundary layer during inter-monsoon: sources and spatial variability. Atmos. Environ. 42, 5169–5181. doi:10.1016/j.atmosenv.2008.03.004.

5)A.K.Sudheer and M.M.Sarin, 2008. Carbonaceous aerosols in MABL of Bay of Bengal: Influence of continental outflow. Atmos. Environ. 42, 4089–4100.

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IASTA-2010

IT–8

Cosmic Ray – Cloud Connection

Sanjay K. Ghosh

Centre for Astroparticle Physics & Space Science

Bose Institute, Kolkata, India

E-mail : sanjay@bosemain.boseinst.ac.in

The research at Centre for Astroparticle Physics & Space Science encompasses both the Astroparticle Physics, specifically Cosmic Ray physics and Atmospheric Science. On the observational side, we have already started work to set up a large-scale array of both passive and active detectors at high mountain altitude to study the exotic components in Cosmic Ray. The goal of space science research at Darjeeling is aimed to use a holistic approach in which all (or most of) the interactive systems from biosphere to space are covered. At present, we are engaged in the understanding of atmospheric chemistry and chemical weather. We are also pursuing radiometric studies which would provide information on the interplay of rain, liquid water in cloud and atmospheric water vapour.

The present set up provides an ideal opportunity to study the cosmoclimatology, a new field proposed only a few years back. In this talk I would summarise the recent trends in this field.

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AEROSOLS & CLOUDS : CLIMATE CHANGE PERSPECTIVES

IT–9

Anthropogenic Emissions of Carbonaceous Aerosol and Gaseous Pollutants and Associated Climatic Changes

Gufran Beig and S.K. Sahu

Indian Institute of Tropical Meteorology

Pune-411008

E-mail : beig@tropmet.res.in

To understand how weather and chemical climate may vary based on changes in emissions of fine aerosol and gaseous pollutants for particular decades and from differences in emission inventories used, we made various simulations using coupled on- line aerosol chemistry-transport model. Aerosols scheme includes sulphates and carbonaceous aerosols (organic matter and BC) whereas gaseous pollutant includes NOx, CO and HCs. We used the recent emissions inventory from India developed by us that differ from EDGAR and other global emissions widely used by global community for India. The decadal growth rate of BC emissions over the Indian region is around 61%. The impact of increased fossil /bio-fuel BC emissions indicates an increase in summer precipitation for the eastern parts of India with a decline in most other areas for 1990s. For the future projection (2000s), the decrease is confined to the north-central and southern parts.

Impact of uncertainty in Indian emission is not only affecting Indian region but almost all of south Asia. The variations in the concentration of ozone and CO obtained by using 2 different emission inventories are found to be 5-10%. The decadal growth in ozone is of the order of 5-15%.

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IASTA-2010

IT–10

Aerosol Studies Towards Fast Reactor Safety

R.Baskaran

Radiological Safety Division,Safety group

Indira Gandhi Center for Atomic Research

Kalpakkam – 603 102, India

E-mail : rb@igcar.gov.in

In the context of safety studies on Fast Reactor, the physical and chemical characteristics of sodium aerosols are very important. The detailed scenario on the formation of sodium aerosols and their consequences, during normal operation as well as in the accidental conditions of the fast reactors, are described as follows: (i) In the normal operation of the fast reactors, evaporation of sodium from the hot pool surface and subsequent condensation results in the formation of sodium aerosol within the cover gas space. These sodium aerosols play a significant role in heat and mass transfer across the cover gas space due to temperature difference of the pool surface and the reactor top plug. (ii) In the unlikely event of Core Disruptive Accident (CDA), the sodium slug may impact the reactor top plug. This provides a pathway for the escape of radioactive material (fission products and fuel material) and sodium into the reactor containment building (RCB) volume. Fuel and fission product vapors will condense and form aerosols. Thus RCB is bottled-up with large amount of sodium, fuel and fission product aerosols. There exists a possibility of release of these aerosols from the stack, duct and pores of the containment building to the environment due to pressure build up in the containment. The longer the time as the aerosols remain suspended in RCB volume, the more would be the environmental source term leads to higher radiological impact. (iii) In the secondary loop, sodium leak can occur due to cracks developed in fluid carrying pipes and eventually, sodium may get in contact with atmosphere. The hot sodium burns in air and give rise to large amount of aerosols. The sodium aerosols pose serious problems such as chemical toxicity, corrosion of building materials and equipments. In order to have realistic estimation of environmental source term on reactor accident condition, the sodium fire consequences, and the role of sodium aerosol in cover gas have to be studied, since the available experimental data on aerosol characteristics are very limited.

In IGCAR, an aerosol test facility, having 1 m3 volume with controlled humidity, for carrying out physical and chemical characteristics of sodium and fission products aerosols, is in operation. Studies such as: (i) initial size distribution of sodium aerosols, (ii) coagulation of sodium aerosols under the influence of gamma radiation field, (iii) chemical speciation of sodium aerosol formed due to sodium fire, and (iv) co-agglomeration of sodium aerosols with fission product aerosols have been completed. The studies on aerosol physical properties (Shape factor, density, deposition velocity etc.) for sodium and fission product aerosols, parametric studies on sodium aerosol chemical conversion and aerosol charging by gamma irradiation are being carried out. A Mini Na Fire Facility (MINA) has been commissioned recently to undertake sodium Fire studies (pool and Spray fires). A sodium

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cover gas experimental facility is being constructed for studying the role of sodium aerosols on heat and mass transfer effect to the top shield in particular, in the presence of gamma radiation. A Sodium Fire Experimental Facility (SFEF), having 540 m3 volumes, for carrying out large-scale sodium fire experiments is under construction.

In this lecture, sources and consequences of aerosols in fast reactor, details of aerosol test facility (ATF), the studies carried out in ATF and their results along with the upcoming facility in IGCAR are presented.

Acknowledgement

Aerosol Group members, RSD, Safety Group, IGCAR are acknowledged for their continuous effort. Dr. P. Chellapandi, Director, Safety Group is acknowledged for his encouragement and guidance.

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IASTA-2010

IT–11

Nuclear Aerosol Test Facility Studies in the context of Indian Pressurised Heavy Water Reactors

B.K. Sapra

Radiological Physics and Advisory Division

Bhabha Atomic Research Centre Mumbai – 4000 085.

Email : bsapra@barc.gov.in

During a nuclear reactor core melt down accident, radioactive fission products are released from the fuel elements and carried into the containment. In order to assess the potential radioactivity releases from the containment to the environment, the behaviour of fission products in the containment must be known. Since most of the important radionuclides are present in the form of aerosols, it is of vital importance to understand the aerosol behaviour in the containment atmosphere. This constitutes the source term for the atmospheric dispersion and is a potential dose hazard in the public domain. Several theoretical and experimental studies have been carried out the world over to understand the complex mechanisms of particle dynamics and thermal hydraulics, which govern aerosol behaviour under accident conditions. Bhabha Atomic Research Center (BARC) has established a comprehensive research test facility called Nuclear Aerosol Test Facility (NATF) to investigate the transport and deposition behavior of aerosols in the containment, to validate the existing computer codes and develop in-house computer models which estimate the aerosol behavior in the containment. Systematic experiments have been carried out in a 10 m3 vessel with simulated reactor accident aerosols under quiescent and turbulent flow conditions. Results of these experiments have been compared with a computer code NAUA Mod 5. The code was suitably modified to include inertial deposition in the presence of turbulence. Extensive comparisons carried out between the experimental results and the code predictions have been satisfactory. As a test case, a simulated reactor accident scenario in the TAPS 3 & 4 reactor has been postulated and the aerosol behavior in the containment has been predicted. These results will be presented.

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