Hydrofluoric acid was allegedly leaked Saturday evening from the LG Siltron plant in Gumi, North Gyeongsang Province, according to police.

The leakage was reported to local authorities on Sunday morning, 16 hours after the initial leak was detected at 8:34 p.m. on Saturday, raising suspicions of a cover up. 

According to police, some 30 to 60 liters of mixed hydrofluoric, nitric and acetic acid was leaked from the Gumi plant 2 of LG Siltron, a producer of wafers used in semiconductor manufacturing. 

The police investigation found that the liquid was discharged during a trial run around 6 p.m. that was conducted after the plant mended a small crack found on a filter cap around 10:30 a.m. on the same day.

The statement released from the plant said they evacuated 11 workers on site after a leak was detected and contained the situation using a neutralizing agent around 4:30 a.m. Sunday.

According to police reports, the liquid, which was 55 percent nitric acid, 21 percent hydrofluoric acid and 24 percent acetic acid, was made by a subcontractor and delivered to the LG Siltron plant.

Samsung Electronics’ semiconductor plant in Hwaseong was under fire for delay in reporting hydrofluoric acid leakage on Jan. 28, which killed one worker and injured four others.

By Lee Woo-young
(wylee@heraldcorp.com)