Nuclear Research Institute "Solving the Issue of Damage to SFR Reactor Nuclear Fuel Cladding"

Domestic researchers have found a clue to solving the cladding tube damage problem of the Sodium Fast Reactor (Sodium Fast cooled Reactor, hereinafter SFR). SFR is evaluated as the most technologically advanced type among next-generation reactors.

Schematic of pulse-reverse current method for nuclear fuel cladding coating technology. Provided by Korea Atomic Energy Research Institute

The Korea Atomic Energy Research Institute announced on the 24th that it has developed a technology to uniformly coat chromium (Cr) inside the SFR nuclear fuel cladding tube without impurities, blocking chemical reactions between the nuclear fuel and the cladding tube.

The metal nuclear fuel and cladding tube of the SFR can be damaged due to degradation caused by Fuel-Cladding Chemical Interaction (FCCI).

To prevent this, a chromium-containing aqueous solution is typically introduced inside the cladding tube, and a coating layer is formed on the cladding tube by an electroplating process.

However, the conventional electroplating methods using Direct Current (DC) and Pulse Current caused problems where hydrogen or impurities generated by water decomposition flowed in one direction and were included in the coating layer. This created cracks in the coating layer and caused FCCI reactions between the nuclear fuel and the cladding tube.

To solve this problem, Dr. Seunghwan Yeo’s research team at the Advanced Nuclear Fuel Technology Development Division applied a ‘Pulse-Reverse Current electroplating method,’ which changes the current direction repeatedly at a speed of more than 100 times per second, developing a technology to coat the inside of the cladding tube with chromium at 55 degrees Celsius for 30 minutes.

Researchers at the Korea Atomic Energy Research Institute are testing a pulse-reverse current coating technology that protects SFR nuclear fuel cladding tubes. Photo by Korea Atomic Energy Research Institute

This technology rapidly changes the current direction to prevent impurities from adhering to the coating layer, enabling the formation of a pure chromium coating layer.

Through this, the research team succeeded in creating a uniform coating layer with a thickness of 20㎛, reducing the coating thickness error to one-third compared to the conventional method.

The Korea Atomic Energy Research Institute has completed domestic patent applications for the developed technology and plans to transfer the technology to related companies in the future.

Kim Junhwan, head of the Advanced Nuclear Fuel Technology Development Division, said, “The pulse-reverse current electroplating process for nuclear fuel cladding tubes developed by the research team will become a core technology for manufacturing materials for SFR reactors,” adding, “The Korea Atomic Energy Research Institute will continue to focus on developing nuclear fuel systems to enhance the safety of next-generation reactors.”

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