The Nuclear Safety and Security Commission (NSSC) released findings on the radiation exposure incident involving a radiation worker at the National Cancer Center that occurred in October on the 20th. The incident was attributed to a lack of safety awareness and insufficient management and supervision, and it was found that the exposure dose of the affected person was within legal limits.
Earlier, on Oct. 7 at 12:50 p.m., an incident occurred where a worker at the National Cancer Center was exposed while in the linear accelerator room during maintenance work by a technician who activated the linear accelerator. Immediately after the incident, the NSSC assessed the details of the incident and conducted an exposure dose evaluation.
According to the investigation results, the technician from the accelerator vendor began maintenance work on the accelerator at 10 a.m. On that day, around 12:35 p.m., the affected worker entered the accelerator room to prepare for treatment and take a break, turning off the power to 4 out of 6 closed-circuit television (CCTV) monitors in the control room. Subsequently, at around 12:50 p.m., the technician saw that the 2 remaining CCTV monitors were on and judged that there were no unusual circumstances, then activated the accelerator. The affected worker immediately heard the activation sound and came out, causing the safety device to activate and stop the operation of the accelerator.
The technician reported the situation to the vendor at 1:35 p.m., and the vendor conveyed the incident details to the technical team at the National Cancer Center at around 4:30 p.m. The radiation safety manager at the National Cancer Center verbally reported to the NSSC at 5:21 p.m. after interviewing the affected worker. This was 4.5 hours after the incident occurred.
As a result of analyses conducted by the Nuclear Medicine Institute and the Korea Institute of Nuclear Safety (KINS), the effective dose of the affected worker was determined to be 10 mSv (millisievert, a unit representing radiation exposure dose), while the equivalent dose, indicating radiation effects on the human body, was 44 mSv for the lens and 69 mSv for the localized skin (crown area). These levels are below the dose limits of 50 mSv for effective dose, 150 mSv for lens, and 500 mSv for skin (crown area).
However, the NSSC noted that the accelerator room with a radiation-generating device for treatment purposes must be strictly managed, but the incident occurred due to a lack of awareness regarding radiation safety and insufficient management and supervision during the accelerator maintenance process. Consequently, they decided to impose fines of 7 million won for violations of related nuclear safety laws.
The NSSC plans to establish measures to prevent recurrence at the National Cancer Center and will continuously monitor the implementation status of these measures.