The Nuclear Safety and Security Commission allowed the restart of the reactor at Hanul Unit 3.
The Nuclear Safety and Security Commission said that after conducting a regular inspection of Hanul Unit 3 since Feb. 13, it verified the safety of 86 inspection items that must be checked before reaching criticality and allowed criticality on the 28th.
Criticality refers to a state in which a nuclear fission chain reaction is sustained in a reactor. It is the stage where the number of newly generated neutrons and the number of disappearing neutrons are in balance.
This regular inspection covers a total of 96 items, of which checks on 86 items that must be performed before criticality have been completed. The Nuclear Safety and Security Commission, after compiling the inspection results, determined that the reactor at Hanul Unit 3 can achieve criticality safely.
During the inspection period, the reactor head was also replaced. The newly installed reactor head is made of a material with a low likelihood of stress corrosion cracking, and the Nuclear Safety and Security Commission confirmed through pressure tests and other checks that the replacement work was performed in accordance with relevant technical standards.
Along with this, it also reviewed the adequacy of replacing aging parts such as the main generator breaker. For fire protection areas important to safety, it checked fire prevention management conditions and the integrity of fire protection equipment.
Based on the results of the regular inspection to date, the Nuclear Safety and Security Commission allowed criticality at Hanul Unit 3 and plans to confirm the plant's safety definitively through 10 remaining follow-up tests, including a power ascension test.