Coming on the eve of next week's Nuclear Security Summit, the news of people being sickened by cobalt-60 in a Delhi market is an embarrassing reminder of weaknesses in the Indian system of tracking minor radioactive substances.

In the wake of heightened international fears about terrorists making ‘dirty bombs' with radioactive or radiological material or even acquiring atomic weapons, the April 12-13 meeting in Washington, DC, on nuclear security — defined by the IAEA to include radiological security as well — will focus on institutionalising best practices so that such material does not fall into the wrong hands.

Prime Minister Manmohan Singh, who leaves for the U.S. on Saturday morning, will join President Barack Obama and 45 other world leaders for the two-day summit.

Though far less dangerous than plutonium or enriched uranium — the raw material for making nuclear bombs — the cobalt isotope which leaked when a worker cut open a piece of metal that his employer had acquired as scrap is one of those substances that countries are supposed to keep strict track of.

Cobalt-60 is used for medical purposes and by the food processing industry for irradiation purposes. Like other radioactive material with industrial applications, the isotope is normally housed in a sealed container within whatever equipment it forms part of. The Atomic Energy Regulatory Board (AERB) is meant to maintain a ‘cradle to grave' system to keep track of such equipment, including through on-site inspections. But given its manpower limitations, radioactive material does get ‘orphaned,' eventually finding its way to the scrap market.

India is not alone in facing this problem. The U.S. Nuclear Regulatory Commission has reported losing track of over 1500 sealed sources since 1996, with more than half the number untraceable.

Compared with earlier incidents involving radioactive sources, the latest case in Delhi appears far more serious. From the reported symptoms of one of the patients, the incident is clearly one of Acute Radiation. This implies the source must have been a high intensity one. Such Co-60 sources are used, for example, in radiography equipment in industry, though it has been so extensively hammered and damaged that it is difficult to tell whether it was an industrial or medical source.

If the source was imported as part of a larger scrap consignment, the lapse is serious since all ports and airports are supposed to be equipped with geiger counters.

Though India has a good record as far as physical security of its nuclear premises and materials accounting are concerned, its system for tracking sealed radioactive sources is one area which needs strengthening. For example, of the 1485 institutions in which the 7850 nucleonic gauges are located, the AERB conducted just 16 inspections in 2008-09. Similarly, for 505 industrial radiography units, only 39 inspections were done.

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