Scientists and government safety experts spent 48 days handling an accident involving a highly dangerous radioactive substance near a densely populated area of Guangzhou's Panyu district.
A technical glitch at the Guangzhou Research and Development Centre for Irradiation Technology on October 12 led to cancer-causing cobalt-60 leaking in an irradiation chamber. The government published a report on the incident two days after it happened, and provided short updates in official media during the operation.
However, the announcements failed to explain to residents the extent of the problem, and a report by The Southern Metropolis News yesterday caused widespread panic. The story was released on the newspaper's website yesterday afternoon, later than is normal. The laboratory is close to Clifford Estate, home to many Hongkongers.
The centre is one of the biggest commercial irradiation facilities on the mainland. Irradiation is the process of exposing an object to radiation. It uses gamma rays to kill germs and viruses in industrial products, such as pharmaceuticals, cosmetics, medical equipment and food.
On October 12, about 30 containers of seasoning and herbal medicine were brought into the irradiation chamber. But one of the container lids became dislodged and blocked the well containing water used to cool the cobalt-60.
The amount of radiation in the room was extremely high, meaning staff at the centre could not enter to remove the container lid.
Guangdong environmental authorities received a report two days later, and Vice-Premier Li Keqiang ordered the Ministry of Environmental Protection to take over the handling of the incident.
A team of robotics experts were summoned from an unspecified institute and began working on October 19. However, that night a fire broke out in the irradiation chamber and destroyed their equipment.
Two more robotic systems were brought in, and by November 26 they had removed the container cover. Two days later, the radiation source returned to the well. According to authorities, no cobalt-60 leaked out of the chamber during the period.
A senior nuclear-safety engineer of a Fortune 500 energy company said cobalt-60 could not cause widespread radioactive contamination like nuclear material, and evacuation of residents was unnecessary.
'As long as human beings stay out of the irradiation room, they should be fine. Cobalt-60 radiates like the sun - it's just stronger,' said the engineer, who would not give his name.
'Unlike a neutron source [such as nuclear material], which can make objects near it radioactive as well, cobalt-60 does instant harm but leaves no damage behind.'
The government only gave brief accounts of the incident and most local residents did not know the nature of the radioactive material, prompting anger at authorities.
'It is a scandal - it is terrifying. The government treats citizens like white rats,' said an internet user on py168.com, a forum for Panyu residents.
Lian Yue, a well-known internet commentator, said the government should have been more forthcoming. 'News should be an alert, telling residents of dangers that might happen. News should not be an obituary, describing a tragedy that has already happened.'