NSSC Approves Restart of Gori Unit 3 Reactor... Automatic Shutdown After Just Two Weeks

[Asia Economy Sejong=Reporter Dongwoo Lee] The Nuclear Safety and Security Commission announced on the 5th that it has completed the investigation of the automatically shut down Kori Unit 3 reactor last month and approved its restart.

According to the NSSC, on December 22nd last year at around 8:25 a.m., a ground fault (a phenomenon where current flows to the ground due to insulation damage, etc.) occurred at the generator excitation transformer cable connection, causing the turbine and generator, followed by the reactor, to automatically shut down. The excitation transformer is a facility that supplies power to the exciter, which magnetizes the generator rotor as an electromagnet.

The investigation confirmed that the ground fault occurred in a gap less than 1 mm caused by the heat shrink tube at the excitation transformer cable connection not being fully adhered to the insulation.

Accordingly, Korea Hydro & Nuclear Power replaced the problematic connection with an assembly type that does not require heat shrink, and the NSSC verified the installation suitability of this part and the soundness of other facilities using heat shrink tubes.

The NSSC stated that during the automatic shutdown process of the reactor, the nuclear power plant operators took actions according to relevant procedures, and safety equipment such as reactor cooling operated normally. There were no abnormalities in radiation levels inside and outside the power plant.

The NSSC said, "After approving the restart of Kori Unit 3, we plan to closely inspect the safety of the relevant facilities during the power increase process."

Gori Nuclear Power Plant Overview