Ho Chi Minh City Mr. Phan Phuoc Thang (39 years old) has performed radioactive source loading 4 times and still cannot forget the feeling of trembling the first time he did this job.
Phuoc Thang has been working at the Radiation Technology Research and Development Center (Vinagamma) in Thu Duc City, Ho Chi Minh City since 2008. Young people like Thang at that time were given priority to perform the source loading at a distance of 6 m from the radioactive source at the bottom of the water tank. With 6 m of water shielding, the staff doing this job was guaranteed an environment similar to the outside, and the radiation dose received on the body (radiation dose rate) was low.
Thang said that in the unit, everyone usually shares the work. Older employees who have families often take on the task of moving Co-60 from outside to the source loading area. "Uncles who have wives and children will be in charge of transporting the source," Thang said, adding that many people believe that being too close to the radioactive source will result in a higher radiation dose, which will affect fertility.
Mr. Phan Phuoc Thang wears a radiation dose measuring device while working near the irradiator at Vinagamma. Photo: Ha An
The sources are transported in a multi-layered protected container. This box has a volume of about 1 m3, weighs 5 tons, and is usually transported by forklift in a zigzag path to enter the irradiation chamber area. The container is lifted by a crane into a 6 m deep water tank area and lowered to the bottom.
After opening the protective cover, the person in charge of this step must control the grippers at the bottom of the tank to grip the power bars into each power module of the device.
Thang shared that the most frightening thing about picking up the source is that it will fall off the table at the bottom of the tank. If it falls, it will be very difficult and time-consuming to operate. Therefore, it requires employees to have sharp eyes, with the support of a magnifying glass and a flashlight to operate. The person loading the source must be both precise and fast, because the longer they stay close, the higher the radiation dose they will receive.
Here, every 2 years, employees must refill the Cobalt-60 (Co-60) radioactive source for the industrial irradiation system. This source emits gamma rays used for the service of killing harmful microorganisms in food, fruit, medical equipment...
Every two years, a group of 10-12 Vinagamma technicians recharges the radioactive source in the radiation chamber for 2-3 days. The reason is that Co-60 is an unstable isotope that can continuously decay and emit gamma rays. After 5.25 years, the radioactive source will be reduced by half due to its half-life, so it must be replenished to maintain its activity.
Due to close contact with radioactive sources, the staff here will have to receive direct radiation doses to their bodies. Therefore, each time they perform the procedure, each staff member will have to wear a dose measuring device to know if their body is within the allowable threshold.
To ensure that no one person gets an overdose, the staff at Vinagamma do not let one person do the job of loading the radioactive source for a long time but have to rotate. "I have been doing this job for many years but now I feel my health is normal," said Mr. Thang.
Irradiator status indicator light and radiation warning board at Vinagamma. Photo: Ha An
Mr. Nguyen Thanh Cuong, Director of Vinagamma, said that the unit currently has 26 technical staff and 92 workers. Equipment operators must have a certificate of knowledge on radiation safety. According to regulations, they must be trained once every two years and have this certificate renewed. Every three months, the dosimeter attached to the employee must be sent to check the radiation dose they receive.
Regarding the design of the irradiation house, Mr. Cuong said that it must be calculated and simulated with thick enough concrete walls that can be shielded, so that the radiation background of the outermost wall will be almost the same as that of the environment. When the irradiator stops working or has any problems, or when outsiders enter, the radiation source will be moved down to the water tank to ensure safety along with many other layers of protection. "The safety principle is the first requirement," Mr. Cuong said.
According to the Department of Nuclear and Radiation Safety, there are currently more than 600 facilities nationwide using and managing radioactive sources with a total of 5,400 radioactive sources. Of these, 2,000 sources are in use and more than 3,000 sources are being temporarily stored.
Ha An
Source link
Comment (0)