The watchdog's review looked into an array of safety issues, including the plant's passive autocatalytic recombiner (PAR), which is designed to prevent hydrogen explosions by reducing hydrogen concentration levels from the reactor's containment building during natural disasters.

South Korea has required the system to strengthen safety after multiple hydrogen explosions during Japan's Fukushima nuclear power plant disaster in 2011.

The Shin-Hanul plant's PAR system received intense scrutiny after environmental groups claimed that its effectiveness had been overstated.

Korea Hydro & Nuclear Power Corp., which built the plant, has argued that there is no problem with the system.

Commission members also requested more measures against potential terrorist attacks or aircraft crashes during the review.

The government plans to reduce nuclear energy to account for 23.9 percent of the country's total power generation by 2030 from around 30 percent last year. It targets to raise the proportion of renewable sources to 20 percent from 6.6 percent over the same period.

According to the KHNP, 16 of the country's 24 nuclear power plants are currently operational, with seven undergoing maintenance. The Shin-Kori No. 4 has halted operations since late May after a fire incident.

South Korea is expected to have 28 nuclear reactors by 2022, considering those already under construction, but the number will gradually drop to 14 by 2038 as aging plants shut down. (Yonhap)