CURRENT PRACTICES IN INDIA FOR MANAGEMENT OF DISUSED RADIATION SOURCES

In India, the various isotopes are being used all over the country in large numbers in hospitals, industries and research institutions. In hospitals, these are mainly used for radiotherapy and diagnostic investigations. Some of the industries using radiation sources are steel, paper, petroleum, cement, fertiliser, metal refineries and thermal power stations. Radiation sources are also used in various electronic instruments and radiography. Research institutions normally use radiotracers and irradiators for studying materials. Some sources are used for calibration of nucleonic instruments. The majority of these isotopes are produced in India and few are imported. Dedicated facilities are existing for converting these isotopes, into usable form and shape. These radiation sources are supplied by Board of Radiation & Isotope Technology (BRIT) or routed through BRIT if imported from another country. To keep a proper inventory and control over the use of these radioisotopes all relevant information pertaining to these sources are available with Atomic Energy Regulatory Authority (AERB), AERB also provides guidance with respect to the management of sources. Sources are normally sealed in stainless steel capsule or impregnated in materials with adequate mechanical strength and are loaded in the respective gadgets. These gadgets with good locking mechanism can be unloaded only by authorised persons specially trained for such works, with special tools and usually in hot cell. Such facility is available in Bhabha Atomic Research Centre (BARC) at Trombay and Kalpakkam. Strength of source varies from instrument to instrument and depends upon the operational requirements. Normally level and thickness gauges are loaded with 37-MBq to 370-MBq of Co-60. However for higher material thickness measurement, sources with strength up to 111-GBq are used. Teletherapy units with 78-TBq of Co-60 and 40-TBq of Co-60 are in use. The source is replenished with new source and the depleted sources are sent as solid waste. Some of the depleted sources may be suitable for other kind of applications and are put to reuse. Due to failure or malfunctioning of gauge’s mechanism, nucleonic gauges as such become un-serviceable and such gauges are also treated as solid wastes. Small sources are packed in container with sufficient shielding. For example, radium needles used in hospitals are placed in SS capsules and impregnated in wax; the capsule is then loaded in lead transport cask. The transport cask is again packed in a wooden crate with all information about the source. The wooden crate is labelled with radiation symbol, sender’s and consigner’s address etc. The sources from equipment like radiography unit and nuclear gauge are not decasked at user’s premises but are packed in wooden crate or metal container having all information and labelled as mentioned earlier. The necessary radiation shielding is provided to keep the contact dose on the package as low as 0.01 to 0.02 mGy/hr. The package is sent by railway or by road preferably on door–to–door delivery basis, to avoid repeated handling, misplacing, pilferage and delay in transport. The radioactive sources loaded in radiography units or in gauges are decasked and relocated in small steel container. The void between source and the container is filled with cement grout. If required this processing is carried out in shielded glow box having remote handling facilities. At BARC Trombay, in