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Expert review finds fault with Ulsan demolition plan

Published: 11 Nov. 2025, 19:32 Updated: 11 Nov. 2025, 19:41

Operations take place to demolish boiler towers No. 4 and 6 at the Ulsan Thermal Power Plant site in Ulsan on Nov. 11. The disaster headquarters decided to go ahead with the demolition at noon in order to bring in heavier equipment to locate and rescue workers trapped under boiler tower No. 5. [SONG BONG-GEUN]

ULSAN — Two boiler towers at the Ulsan Thermal Power Plant were demolished Tuesday at noon to allow rescue workers to search for four people still buried under the rubble of a collapsed structure.

Soon after the demolition of boiler towers No. 4 and 6, which had obstructed efforts to locate four workers trapped in last week’s industrial collapse in Ulsan, rescuers resumed search operations. Authorities have confirmed the location of two of the four missing and believe both are dead. The whereabouts of the other two remain unknown.

Experts say the collapse of boiler tower No. 5 on Thursday was the result of flawed planning and insufficient structural analysis.

The collapse happened during pre-blast work known as “weakening,” which involves cutting parts of the steel frame to direct the fall. The failure resulted in deaths and injuries among workers on-site.

The JoongAng Ilbo obtained the safety guidelines for the boiler tower demolition project and commissioned a review by Prof. Ahn Hyung-joon of Konkuk University, former Korea Institute of Architecture and Technology Chairman Seo Gyu-seok, Prof. Sim Kyu-hyeong of Incheon University, Safety Professionals Association of Korea Head Lee Song-gyu and Prof. Kim Dae-geon of Dongseo University.

“It’s a patchwork of data compiled without proper on-site evaluation,” they said on Tuesday.

A boiler tower at the Ulsan Thermal Power Plant is seen collapsed in Nam District, Ulsan on Nov. 10. Fire authorities have suspended the search, with personnel dispatched, while conducting preliminary work to blast reactors No. 4 and 6, located on either side of the collapsed boiler tower, No. 5. [YONHAP]

Firefighters and cutting equipment are being deployed to the Ulsan Thermal Power Plant in Ulsan on Nov. 11. [YONHAP]

Their primary concern focused on the absence of a detailed structural survey before dismantling began.

The plan’s “On-site Characteristics Analysis” includes only three items: underground utilities, nearby structures and traffic conditions.

“The on-site characteristics analysis should include data on corrosion caused by salt exposure and aging for each boiler tower unit, but it contains none of that information,” Prof. Ahn said.

Records show the plan’s preparation and review cost 30 million won ($20,500), spent in February 2024, roughly one month after HJ Shipbuilding & Construction received the demolition contract from Korea East-West Power.

Firefighters prepare for rescue and search operations at the Ulsan Thermal Power Plant in Ulsan on Nov. 11. [NEWS1]

"A structural engineer would need at least three months to conduct an appropriate inspection and analysis," Seo said. “Spending 30 million won on the safety plan for a 52.3 billion won project is equivalent to rubber-stamping it.”

The experts identified execution during the weakening phase as a likely source of failure. The plan specifies cuts at two points on the steel columns, but does not provide exact locations or measurements for the gouging work done with oxygen torches.

“A lack of precise instructions increases the risk of error in the field,” Sim said.

HJ Shipbuilding & Construction previously experienced an unsuccessful demolition at the Seocheon Thermal Power Plant in March. That incident led to changes in its approach for the Ulsan project.

On the sixth day following the collapse of a boiler tower at the Ulsan Thermal Power Plant, boiler towers No. 4 and No. 6 are demolished with explosives on Nov. 11. Fire authorities plan to deploy eight teams comprising around 70 personnel to search the area surrounding tower No. 5, where the collapse occurred, immediately after the demolition. [YONHAP]

Korea Kacoh, the subcontractor that carried out the dismantling, said workers were conducting protective shielding work to prevent debris from scattering at the time of the collapse and followed procedures laid out in the plan. Fire officials said workers were operating at a height of 25 meters (82 feet) when the structure collapsed.

The exact sequence of events — particularly whether the collapse occurred during weakening or during shielding — remains under investigation.

Lee questioned why shielding work took place inside the structure rather than from the exterior.

“Using cranes or aerial platforms from outside would have been safer,” the safety association head said. “They appear to have worked from inside to reduce costs.”

HJ Shipbuilding & Construction has not responded to repeated requests for comment.

Korea East-West Power, which commissioned the project, said it "could not comment while the investigation is ongoing."

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.
BY LEE EUN-JI, WE SUNG-WOOK AND AN DAE-HUN [[email protected]]