The essential components of this facility are the 10 m 3 stainless steel test vessel, Plasma Torch Aerosol Generator (PTAG), the associated instrumentation for monitoring the temperature and pressure in various parts of the test vessel and aerosol instrumentation to study the aerosol characteristics.

An SSNTD in the membrane filter chamber registers the tracks due to radon gas, while one in the glass fibre filter chamber records the tracks due to both radon and thoron gases. The third SSNTD placed outside the chamber in the bare mode, registers the tracks due to radon and thoron gases and their progenies. The track densities recorded in these three SSNTDs are used to deduce the concentration of the progenies through the use of appropriate calibration factors. These calibration factors are obtained by a series of experiments conducted in a calibration chamber under well-defined conditions of gas concentrations and aerosol concentrations . These dosimeters have been widely used for the countrywide mapping of radon and thoron.

The environmental modelling and collection and analysis of meteorological data at Trombay using modern instruments like SODAR, Wind Profiler, meteorological tower and scintillometer are routinely done. The environmental modelling domain includes atmosphere, surface water and groundwater and the objective is to predict the transport and dispersion of radioactive and conventional pollutants in the environment. The collection and analysis of meteorological data form an important source for the safe operation of the nuclear facilities. The atmospheric modes developed include the Gaussian Plume Model (GPM), Equidistant Puff Model (EDPUFF), Particle Trajectory Model (PTM) and Atmospheric Dispersion Over Complex Terrain Model (ADOCT). These different models show a progressive development in modelling capabilities to achieve more realistic scenarios by negating simplified assumptions.

A number of hydrological models have been developed to evaluate the radionuclide concentrations in different aquatic media such as river, lake, coastal sea, deep ocean and sub sea sediment due to planned as well as assumed accidental releases of radioactivity. The Shallow Land Burial Model (SLBM) is a safety assessment model, which can be applied to near surface radioactive waste disposal facilities. The Risk Evaluation Model for Shallow Land Burial Facilities (REMS) is a probabilistic safety assessment model based on the failure rates of different natural and man-made barriers. The Environmental Heat Transfer Model (EHTM) has been developed to obtain the flow field and temperature field in the vicinity of thermal discharge outfalls located in coastal seas.

Countrywide environmental radiation/radioactivity monitoring network for the assessment of natural and fallout radioactivity has been established through a network called IERMON (Indian Environmental Radiation Monitoring Network) consisting of 29 stations across the country. The stations are equipped with automated systems with data communication facilities. T he environmental samples received from various stations are analysed at the Low Level Counting Laboratories .

The need was felt the world over for permanent monitoring networks. WHO  and  UNEP  jointly  promoted  the  Global   Environmental   Radiation   Monitoring   Network  (GERMON) Programme.  India was  a  member  country  and  a  member  of  the  scientific  advisory  committee of GERMON. Under this programme, data from a few selected stations would be made available to GERMON Head Quarters (called Coordinating and Collaborating Center (CCC)), situated in Paris, on a quarterly basis. Under the GERMON Programme, BARC has established a countrywide environmental radiation monitoring  network with 25 stations across the country. Though  GERMON as  such is not active now, most of the countries are operating their own countrywide monitoring networks with varying degree of sophistication.

Chairman,  Atomic  Energy  Commission  has  re-named Indian  GERMON as  IERMON  (Indian    Environmental   Radiation Monitoring Network) with effect from April, 2002.

A solar powered Environmental Radiation Monitor (ERM) for open field installation with wireless data communication using Short Message Service (SMS) of GSM Cellular Network has been developed for deployment at various stations of the IERMON.

BARC'S programme in isotope hydrology and hydraulics started in 1959 with the first ever radioisotope tracer investigation on sediment transport on the sea bed in the Bombay port. It has since grown from strength to strength and today covers the entire hydrological cycle with a veritable arsenal of isotope tools. These include the naturally occurring environmental stable isotopic species of water, cosmic ray produced radioisotopes in the environment (tritium and carbon-14) and reactor produced radioisotopes ( 82Br as NH 4Br; 198Au as HAuCl 4; 46Sc as scandium glass etc). Over the last three decades or so, BARC has had an active programme of developing relevant isotope technique and providing service to water resources management in the country.

Some of the important development work/services that were carried out include:

1. Study on salinisation/pollution of groundwater in coastal Minjur (Tamil Nadu), Midnapur (West Bengal), Mahanadhi Delta (Orissa), Purna River Basin (Maharashtra), Raipur City (Madhya Pradesh) and arsenic pollution of aquifers in some parts of West Bengal

2. Location of source of seepages during tunneling (Jammu & Kashmir) and during construction of hydel power tail race canal (Haryana), studies on seepages in Chilla hydel channels (Uttar Pradesh) and seepage loses from unlined canals (Uttar Pradesh)

3. Seepage investigation in the basement of buildings in some parts of Jodhpur city (Rajasthan)

• Cause and source of water logging in the basement of buildings

4. Investigation of seepage in dams/reservoirs ( Maharashtra, Andhra Pradesh, Tamil Nadu etc.)

5. Sediment transport in major ports and harbours of India (Kolkatta, Chennai, Kandla, Mumbai etc) for harbour development programmes

6. Dispersion of sewage/waste in marine environment (Mumbai, Mangalore)

7. Flow measurements in fast flowing hilly streams ( Sikkim, Kerala etc) wherein the conventional methods fail due to

8. Soil erosion and reservoir/lake sedimentation (Uttranchal, Kerala etc)

9. Efficacy of percolation tanks (Maharshtra)

10. Groundwater recharge studies in

11. Origin and flow dynamics of geothermal waters in

12. Ganga river-aquifer interconnection (Uttar Pradesh), aquifer-aquifer interconnections in Cauvery Delta (Tamil Nadu) and Lake Nainital-groundwater interaction (Uttranchal)

As can be seen from the above, the Isotope Hydrology programme yielded rich dividends in the area of management of natural water resources. Today no programme on water resources management is deemed complete without isotope inputs. The Central Water Commission (CWC), Central Board of Irrigation and Power (CBIP), Central Groundwater Board (CGWB), National Environmental Engineering Research Institute (NEERI), National Institute of Oceanography (NIO) and various port/dam authorities and a host of institutions in the country call upon the expertise in BARC to find solutions to a variety of water resource problems. In addition, the International Atomic Energy Agency, which has a large isotope hydrology programme in, the developing world often calls upon BARC expertise for a variety of assignments. BARC has also been providing training facilities for scientists and engineers from India and abroad in the area of isotope methods in hydrology. Isotope Applications Division, BARC provides group training covering all aspects of isotope hydrology for Asia/Pacific region.

BARC has carried out a number of isotope (both, environmental and artificial) based tracer studies to investigate seepage in dams and reservoirs, as well as sedimentation in lakes and reservoirs. The objectives of studying seepage in dams and reservoirs has been one or more of the following: