Hanbit Unit 4 Restarted After 5 Years... Power Generation Resumes on the 11th

[Image source=Yonhap News]

[Asia Economy Sejong=Reporter Dongwoo Lee] Hanbit Unit 4 in Yeonggwang-gun, Jeollanam-do is set to resume operation. It has been five years since it stopped operating due to defects in the reactor containment building.

The Nuclear Safety and Security Commission (NSSC) announced on the 9th that it has approved the criticality (restart) of Hanbit Unit 4 in Yeonggwang-gun, Jeollanam-do.

Criticality refers to the state in a reactor where the number of neutrons produced by continuous nuclear fission chain reactions equals the number of neutrons lost, achieving neutron population equilibrium.

At the 168th NSSC meeting held the day before, the commission stated, "All items to be checked before restart have been confirmed, and the conducted gap inspections and structural integrity assessments so far are appropriate, confirming the safety of nuclear power plant operation."

Korea Hydro & Nuclear Power (KHNP) plans to increase the output of Hanbit Unit 4 starting today and connect it to the power grid on the 11th to begin power generation and supply.

Previously, Hanbit Unit 4 was shut down for over five years since May 2017 after 140 concrete gaps (holes), including some up to 157 cm deep, were found. After receiving a structural integrity evaluation from the regulatory agency in July, confirming the repair plan was appropriate, repair work on the gaps began in August.

KHNP repaired the containment building’s internal steel plates and gap areas by maintaining the radiation leakage prevention plates (CLP) below the standard thickness (5.4 mm), and repaired 140 gap locations and 23 exposed rebar sites found on the building’s exterior walls.

In October, a Integrated Leakage Rate Test (ILRT) was conducted to verify that the gap repairs were properly completed. The ILRT pressurizes the containment building to the design basis maximum accident pressure of 51.1 psig and measures the overall leakage rate of the containment building. During the regular inspection period, the steam generator was replaced with one using corrosion-resistant tubing, and safety was confirmed through manufacturing and installation processes, piping weld inspections, and non-destructive testing of the tubing.

A KHNP official said, "Hanbit Unit 4 will proceed with the remaining follow-up tests, including output increase tests, to fully enter commercial operation."