Clean-up has continued in the Indian market hit by contamination from lost cobalt-60 sources, almost six weeks after the incident came to light.
On 7 April a Mayapuri scrap dealer presented himself to a hospital with radiation-related symptoms, triggering an immediate survey of the man's shop and surrounding market area that uncovered a number of fragments of radioactive cobalt-60. Clean-up ensued and the area was "declared safe" by the Atomic Energy Regulatory Board and the Department of Energy on the morning of 9 April because "radiation levels were confirmed to be at natural background levels."
In following days six further people were admitted to hospital in relation to the incident, which was rated at Level 4 on the International Nuclear Event Scale - an 'accident with local consequences'. The original patient died on 26 April due to multiple organ failure.
|Greenpeace conducting a survey at Mayapuri (Image: Greenpeace)
The AERB has been continuing work to reduce some remaining radiation in the market area, engaging on the matter with local shopkeepers. However, a survey carried out by Greenpeace on 14 May identified several 'hotspots' where doses to a person squatting on the ground would have been between 200 and 500 μSv per hour. While this is far below levels that would cause noticeable detriment to health, it nevertheless means a person could receive in excess of the annual public dose limit of 1000 μSv year within hours. For comparison, the original patient received 3700 times the annual limit and others in hospital all received over 400 times the limit.
The AERB did not comment on Greenpeace's work, but removed "some traces of dust or particles of cobalt-60" from the market area on 15 and 16 May. The regulator said these could have come from the cutting of pieces already recovered. Jan Vande Putte of Greenpeace complained that, "So far authorities have not followed international standards to ensure the highest levels of safety. The AERB must publish a comprehensive assessment of the situation and its plans for further decontamination."
Cobalt-60 has significant uses in medicine and industry but the potential danger it poses dictates that its use and disposal be tightly controlled. In India this is under two sets of Atomic Energy Rules, one covering radiation protection and another on the safe disposal of radioactive waste.
The pieces found in Mayapuri came from the Chemistry Department of Delhi University, which had improperly disposed of a gamma cell containing decayed cobalt-60 sources. The university has been ordered by the AERB to explain the violations and to suspend all work with radioactive sources in the meantime.
Having compared the fragments to the known inventory of the gamma cell, AERB is confident that all of the source has been recovered. The pieces are being held by the Department of Atomic Energy at Narora Atomic Power Station "for safe and secure storage and further inspection."
Researched and written
by World Nuclear News