 INES 2 |
Cs137 shielded radioactive source smelted in metal recycling facility |
On January 13 2004 an alarm was received from the radiation monitoring equipment installed to monitor the entering scrap metals, while a truck was leaving the facility. The truck was transporting dust pellets resulting from the deposition of the smelting process fumes. As a result of measurement performed by Fire Brigade and Regional Agency for Environmental Protection, the pellets resulted contaminated by Cs137. Then the truck was stopped inside the facility area, the smelting process was shutdown and the potentially contaminated areas interdicted to access. On the basis of measurements performed on the contaminated material it seems very likely that an heavily shielded radioactive source had been inadvertently smelted; an activity of the source in the range of 1,11×109 – 1,85×109 Bq was estimated as well. As a confirmation, some lead in excess was measured on products from the facility in the pertinent period of time.
A maximum contamination level in the dust resulting from the fumes treatment process of 25 Bq/g was measured, and a maximum contact dose rate of 5 microSv/h. Contaminated dust, with a maximum measured level of 10 Bq/g, was found in several portions of the fumes lines.
Measurements performed outside the facility showed dose rate values at background level, and no evidence of air or soil contamination was detected.
Detailed medical investigations, including whole body counter survey, were undertaken on eight workers identified as the critical group, because involved in the maintenance activities in the vicinity of the contaminated lines when the smelting event was thought to have occurred. Results of these investigations showed a very limited intake of Cs137 for only one worker, resulting in an estimated effective dose less than 3 microSv. For all the other workers no internal contamination was detected.
In summary, the event did not result in any significant consequences for workers, general public and environment, but heavy economic and social implications resulted, due to temporary shut down of the facility, in order to perform decontamination of the affected areas, currently in progress. It is envisaged that the resulting waste, once collected and properly confined, will be stored on the site.
The event calls for need of improved surveillance on radiation sources, in all phases, likely supported by adequate legislation improvement.
The event was at attention of local and national press for some days after the event.
Event date: Mon, 12-01-2004
