Monitoring procedures for all medical and industrial sources of radioactivity will be strengthened by authorities in Jiangsu province.
The use of radioactive testing equipment will also be suspended in Nanjing, the provincial capital, in August after inspection equipment containing iridium-192 was lost for three days.
A bracelet-shaped loop containing the radioactive material, known as Ir-192, was mislaid by workmen during routine inspections at a construction site in Nanjing's Luhe district on May 7. Authorities said the workmen failed to observe safety procedures while packing equipment.
The loss prompted a major police search and led to a construction site cleaner being hospitalized.
The silvery-white metal is used widely in industrial radiography to check for flaws in metal welds and castings, and in medicine, especially during interior radiotherapy procedures.
The workmen, from Tianjin Hongdi Engineering Inspection Development Co, a division of oil refiner Sinopec, didn't notice the bracelet was missing until the evening of May 8, when they tried to use the equipment and found it was malfunctioning.
The bracelet was found on Saturday afternoon by Yu Jianjun, director of the Getang Community Office in Luhe, who was assisting police and environmental experts in the search. When he discovered the bracelet, which contained a soybean-sized piece of ir-192, Yu sealed it in a plastic box before rushing to show it to the experts. The bracelet was then sealed in a lead-lined container and taken away for disposal.
"I've never run so fast. I can't say I wasn't afraid, but the material had to be recovered ... someone had to do it," Yu said.
The bracelet had been discarded near the community office by a construction site cleaner called Wang, who found it as he was sweeping the floor of the construction company's welding workshop at 8 am on May 7.
Wang said he slipped the bracelet into his pocket because he thought it would make a good key chain, but during his lunch break three hours later, he decided he didn't want it and threw the object into his front yard.
However, after learning that the police were searching for a piece of radioactive material lost at the site, he became afraid, so he wrapped the bracelet in a plastic bag and threw it into bushes near his home at 5 am on May 10.
Wang was later diagnosed with acute, short-term radiation sickness and is now being treated at the Second Affiliated Hospital of Soochow University in Suzhou.
A series of incidents
Although the bracelet was recovered without loss of life or severe damage to the environment, it wasn't China's first potentially disastrous incident involving ir-192.
In January 1996, 21-year-old Song Xuewen found a key-chain-shaped source of ir-192 at a construction company in Jilin province. He kept it in his pocket for 10 hours and later suffered radiation sickness. He underwent seven operations in the following two years, in which both of his legs and an arm were amputated.
In April 2005, when two policemen in Liaoyang, Liao-ning province, detained a man suspected of stabbing his girlfriend, they discovered an unusual metal chain, which they took to the police station and placed in a cupboard. A few days later, three officers who worked in the office began to lose their hair, vomited frequently and discovered large amounts of blood in their faeces. All three men, in their early 30s, were later diagnosed with radiation sickness and found to be infertile.
The assailant, who later died of radiation sickness, admitted he had "borrowed" the chain, which contained ir-192, from an inspection company with the help of friends, and had planned to injure his girlfriend by exposing her to radioactivity.
In June 2005, 117 people in a residential community in Harbin, Heilongjiang province, were exposed to ir-192 after a source was thrown into a garbage disposal unit. Six people were diagnosed with health problems and one person died. The radioactive material bore no code - in contravention of the law - and wasn't registered with the monitoring authorities.
In October 2009, residents of Panyu in Guangdong province panicked after news broke that an irradiator at a local technical research centre had been emitting radiation continuously for 48 days because of an operational error.
In 2004, China's leading environmental protection authorities, health authorities and public security departments conducted a survey that revealed that more than 10,000 agencies across the country possessed more than 140,000 sources of radioactivity.
The survey estimated that the number of sources was growing at 5 to 10 per cent annually, and that more than 2,000 sources had gone missing.
According to the Case Compilation of China's Radiological Accidents 1988-1998, a report compiled in 2001 by the ministries of health and public security, the period had seen 332 accidents involving 966 people. The report said 584 sources of radioactivity had been reported as lost, and that 256 of them were still missing.
"Most radioactivity-related accidents happened in the last century or at the very beginning of this one," said Pan Ziqiang, an expert on nuclear radiation prevention and control at the Chinese Academy of Engineering.
"No one has died in an accident of this nature since 2005, when new radiation safety and prevention regulations came into effect that required departments involved in accidents related to radioactivity to assume legal, administrative and economic responsibility. Supervision has been strengthened, but it's hard to completely avoid accidents involving radioactive sources," he said.
According to Pan, 10 people have died from radiation poisoning emitted by radioactive sources and in industries in which nuclear techniques are used, accounting for 17.2 per cent of the global total. No one has died or contracted radiation sickness in the nuclear military industry or nuclear power plants.
Lack of expertise
Tang Shuangling, director of the radiation prevention and environmental protection department at Nanjing University of Science and Technology, said a lack of professional expertise among workers, poor management by related agencies, and the large number of radioactive sources have contributed to the high accident rate.
The health authorities used to monitor sources of radioactivity in China, but widespread industrial use of radioactive materials meant they were no longer able to undertake those duties, resulting in the environmental authorities assuming responsibility from 2003.
"Radioactive materials are widely used in hospitals, industry, agricultural colleges and research institutions," said Tang. "Although China has formulated strict monitoring regulations, the enforcement mechanism still requires improvement."
Lu Jigen, head of Jiangsu's Nuclear and Radiation Safety Supervision Management Bureau, said each source is strictly monitored during use. The province has 8,627 sources of radioactivity, the largest number in the country, at 5,257 agencies.
"Each source is given a unique code when it's produced," Lu said. "If an agency wants to transfer a source, the move must be approved by the monitoring department, and the vehicles and containers that carry the sources must meet strict requirements."
"When the sources are no longer needed, they are taken to the provincial urban radioactive waste site to be destroyed," he added.
According to Pan, the country's third national radioactive waste disposal site, Feifengshan, or Flying Phoenix, in Sichuan province, will become operational later this year or early in 2015.
China's first national disposal site, which was put into use in 1999, is located in Gansu province, while the second, which began operations in 2000, is in Guangdong province.
"Although every province has established its own disposal site, greater efforts are required to meet the huge demand," Pan said, adding that China will establish a disposal site for high-level radioactive waste before 2050. Sites are under consideration in several provinces, including Shandong and Guangdong.
Tang said it's essential that public understanding of the uses and potential risks of radioactive materials are heightened.
"Nuclear technology will be applied to people's daily lives ever more frequently as the economy develops. The technology has already been widely adopted in the fields of food irradiation, medical examinations and industrial testing. The public needs to improve its knowledge of radioactivity and nuclear materials."