High-Temperature Gas Reactors Emerge as 'Carbon Neutrality Solution' for Steel and Petrochemical Industries [Digging Energy]

Greater Safety Than Generation III Reactors...
Used for Hydrogen Production and Industrial Processes
Major Corporations Like POSCO, SK, and Lotte Also Take Notice
China Has Already Commercialized... U.S. Also Accelerating
Nuclear Hydrogen

Performance test device for helium loop high-temperature water electrolysis module installed at the Korea Atomic Energy Research Institute. In September 2024, the Korea Atomic Energy Research Institute, together with POSCO Holdings, successfully conducted a test simulating a high-temperature gas furnace to produce hydrogen using the heat of helium gas in a high-temperature water electrolysis facility. Korea Atomic Energy Research Institute

"This is a prototype of TRISO (Tri-Structural Isotropic) coated particles used in high-temperature gas reactors (HTGR). It was produced in the laboratory of the Korea Atomic Energy Research Institute."

On April 17, in a laboratory at the Korea Atomic Energy Research Institute in Daejeon, Chansu Kim, Head of the High-Temperature Reactor Development Department (Ph.D.), shook a transparent plastic container filled with tiny black granules and showed it to the reporter.

A prototype of triso-coated particles produced by the Korea Atomic Energy Research Institute. Korea Atomic Energy Research Institute

TRISO (Tri-Structural Isotropic) coated particles are about 1mm in diameter and are triple-coated with silicon carbide ceramic. HTGR, which is one of the fourth-generation reactors, uses these TRISO coated particle nuclear fuels. Silicon carbide is an extremely stable material that can withstand temperatures up to 1,600 degrees Celsius, enabling the nuclear fuel to remain stable. Because the nuclear fuel is coated with ceramic, it is difficult to reprocess, making it hard for terrorists to misuse it even if it falls into the wrong hands.

Cross-section of TRISO coated particle. Korea Atomic Energy Research Institute.

Greater Safety Compared to Generation III Reactors... Utilized for Hydrogen Production and Industrial Processes

Generation III light-water reactors, which are currently in commercial operation in Korea, use water as both a moderator and coolant. In contrast, HTGR uses graphite as a moderator and helium gas as a coolant.

Helium is a stable substance that does not undergo oxidation reactions and does not react with neutrons. Even if it leaks, it escapes into the atmosphere, so the risk of radioactive leakage is low. In the event of a loss-of-coolant accident, the graphite core of the HTGR absorbs decay heat, slowing the progression of the accident. Due to these characteristics, HTGR can significantly enhance safety compared to light-water reactors. Kim explained, "Generation III reactors are also designed to be sufficiently safe. However, HTGR has its own strong inherent safety characteristics."

The greatest advantage of HTGR is its ability to produce high-temperature heat. While light-water reactors have an outlet temperature of around 300 degrees Celsius, HTGR can generate heat at temperatures between 700 and 950 degrees Celsius. This heat can be used for hydrogen production or industrial processes such as petrochemicals. It can also be utilized for seawater desalination or district heating. Whereas current reactors are mainly focused on 'power generation,' HTGR is specialized in 'heat.'

Chansu Kim, Head of the High-Temperature Reactor Development Department at the Korea Atomic Energy Research Institute, is being interviewed by Asia Economy. Korea Atomic Energy Research Institute

The industrial sector expects HTGR to play a key role in achieving carbon neutrality in carbon-intensive industries such as steel and petrochemicals.

For the steel industry, which accounted for about 15% of Korea's carbon dioxide emissions in 2022, the introduction of hydrogen-based direct reduction is essential for carbon neutrality. The most urgent task is to lower the cost of hydrogen production. With the current price system, where hydrogen costs nearly 10,000 won per kilogram, hydrogen-based direct reduction cannot be economically viable. By using HTGR, hydrogen can be produced more cheaply through the Solid Oxide Electrolysis Cell (SOEC) method. SOEC utilizes high-temperature steam at 850 degrees Celsius, and at high temperatures, hydrogen can be produced with less electricity than at lower temperatures.

The petrochemical industry, along with steel, is one of Korea's two largest carbon-emitting industries, accounting for about 10% of greenhouse gas emissions. To produce petrochemical products by cracking naphtha, steam at temperatures above 800 degrees Celsius is required. Currently, petrochemical complexes use liquefied natural gas (LNG) as fuel to generate high-temperature steam. If the boilers using fossil fuels are replaced with steam from HTGR, the carbon emissions of petrochemical complexes can be significantly reduced.

Major Corporations Like POSCO, SK, and Lotte Also Take Notice

The industrial sector is paying close attention to the potential of HTGR and is actively engaging in research and development (R&D). The public-private HTGR development project, launched by the Ministry of Science and ICT in July 2024, includes seven companies in addition to the lead institution, the Korea Atomic Energy Research Institute: POSCO E&C, Daewoo Engineering & Construction, SK Ecoplant, Lotte Chemical, POSCO International, Donghwa Entec, and Smart Power. The Korea Atomic Energy Research Institute is responsible for reactor design, while POSCO E&C, Daewoo Engineering & Construction, and Smart Power are participating in plant construction design. Donghwa Entec is expected to be in charge of designing the reactor's heat exchanger.

SK Ecoplant is researching hydrogen production using high-temperature electrolysis, while Lotte Chemical is studying commercialization plans such as utilizing process heat in petrochemical operations. POSCO International plans to develop a nuclear fuel supply strategy. POSCO E&C and POSCO International are also researching new industry creation strategies linked to POSCO Group's steel business. Kim explained, "The goal is to complete the design by 2027." If R&D proceeds smoothly, it is expected that design certification will be completed and preparations for commercialization will begin by the early 2030s.

HTGR is planned to be designed as a small modular reactor (SMR) with a capacity of less than 100 MW. Because it is small, it can be built close to demand sites that require heat or steam. The Korea Atomic Energy Research Institute has named Korea's first HTGR "HECTAR" (Helium Cooled Thermal Application Reactor). The name carries a double meaning, as the site area can be reduced to hectares, which is significantly smaller than that of large nuclear power plants.

A bird's-eye view of 'HECTAR,' a high-temperature gas reactor being developed by the public and private sectors starting July 2024. The site area is planned to be designed in hectares, significantly smaller compared to large nuclear power plants. Korea Atomic Energy Research Institute.

In December 2024, the Korea Atomic Energy Research Institute, together with POSCO Holdings, completed a demonstration of hydrogen gas production using high-temperature electrolysis with helium gas. High-temperature helium gas was used to generate steam above 700 degrees Celsius, which was then supplied to a high-temperature electrolysis module to produce hydrogen. In this experiment, 1.9 Nm³ of hydrogen was produced using less than 36 kWh of electricity per kilogram of hydrogen.

China Has Already Commercialized... U.S. Also Accelerating

Other countries are progressing faster than Korea. In March 2025, global chemical company Dow Chemical and X-energy submitted an application for HTGR construction approval to the U.S. Nuclear Regulatory Commission (NRC). Previously, in March 2023, Dow Chemical and X-energy signed a joint development agreement (JD) to jointly promote the development and demonstration of the Xe-100, an HTGR-type SMR. The Xe-100 consists of four 80 MW-class reactors (320 MW in total).

The actual project is being carried out by Longmont Energy, a wholly owned subsidiary of Dow Chemical. The company plans to build the Xe-100 reactor at Dow Chemical's site in Seadrift, Texas. The electricity and steam produced by the Xe-100 will be used in Dow Chemical's production processes. Dow Chemical expects to begin construction in the late 2020s and start reactor operation in the early 2030s.

The U.S. government is also providing active support. The U.S. Department of Energy plans to invest $1.6 billion over seven years in the Xe-100, including an initial $80 million, as part of the Advanced Reactor Demonstration Program (ARDP). X-energy is also working with Korean companies Doosan Enerbility and DL E&C, which have invested in the project. In October 2024, Amazon announced a $500 million investment in X-energy.

China has already begun commercial operation of the HTGR "HTR-PM," which consists of two 250 MW reactors, in December 2023. Built in the Shidaowan area of Shandong Province, HTR-PM supplies district heating to 1,850 households. Construction began in December 2012, and it received its operating license in August 2021. The Chinese government explains that HTR-PM can replace 3,700 tons of coal and reduce 6,700 tons of carbon dioxide emissions annually. The HTR-PM consortium consists of China Huaneng Group (47.5%), China National Nuclear Corporation (32.5%), and Tsinghua University (20%).

The Japan Atomic Energy Agency built the HTGR test reactor HTTR in 2010 and has been conducting demonstration research on hydrogen production. HTTR was shut down after the Fukushima nuclear accident but resumed operation in 2021. HTTR is conducting research on hydrogen production by natural gas and steam reforming together with Japanese steel company Mitsubishi. Mitsubishi plans to use this for hydrogen-based direct reduction steelmaking.

<Glossary> Nuclear Hydrogen

A technology that produces hydrogen using the heat and electricity generated by a nuclear reactor. Utilizing nuclear power plants enables large-scale hydrogen production without carbon emissions. Nuclear hydrogen production technologies include low-temperature electrolysis (alkaline, PEM, etc.) using electricity from nuclear power plants, high-temperature electrolysis (SOEC) using both electricity and heat from nuclear power plants, and thermochemical methods using ultra-high temperature heat from nuclear reactors. Currently, low-temperature electrolysis is commercialized, while high-temperature electrolysis is at the demonstration stage. Thermochemical processes will require considerable time before commercialization.