Revealing the 'Oxidation Principle' of Nuclear Power Plant Cladding Tubes... Enhancing Safety

A graph showing the change in the zirconium content ratio of ZIRLO cladding tubes adsorbing water according to temperature changes

[Asia Economy Reporter Junho Hwang] Domestic researchers have unveiled the oxidation mechanism of nuclear fuel cladding tubes used in nuclear power generation. This study is expected to contribute to improving the safety of nuclear fuel cladding tubes, which are constantly in contact with high-temperature, high-pressure coolant water in nuclear power plants.

The Korea Atomic Energy Research Institute announced on the 1st that a joint research team led by Dr. Sangho Lim of the Radiochemistry Research Laboratory and Professor Youngsang Yoon of Yeungnam University identified the oxidation mechanism of nuclear fuel cladding tubes that adsorb water, publishing their findings in Scientific Reports, a sister journal of Nature.

The research team conducted underwater oxidation reaction experiments on 'zirconium alloy cladding tubes,' the third-generation light nuclear fuel cladding tubes used worldwide, including in domestic pressurized water reactors, to elucidate the principles of the oxidation reaction. They observed that the proportion of zirconium metal on the cladding surface adsorbing water at room temperature decreased (46.4% → 43.1%) after oxidation, confirming the formation of zirconium oxide due to oxidation. However, when the cladding with zirconium oxide formed on its surface was heated to high temperatures, they confirmed that the zirconium oxide decomposed and a large amount of water desorbed simultaneously. During this process, the oxidized cladding surface was observed to revert back to metal.

Nuclear fuel cladding tubes are primarily made of corrosion-resistant zirconium alloy, safely enclosing the nuclear fuel inside the reactor. However, since they are exposed to high-temperature, high-pressure water and the thermal energy of the nuclear fuel, oxidation inevitably occurs on the surface.

The research team emphasized that since the oxidation of cladding tubes affects nuclear power plant safety and the performance of nuclear fuel, it must be considered from the design stage of the cladding tubes. They expect that utilizing the data revealed in this study will enable the manufacture of safe, high-performance cladding tubes.

Dr. Sangho Lim of the Korea Atomic Energy Research Institute stated, "This study is the world’s first to analyze the water adsorption mechanism of cladding tubes using synchrotron radiation-based high-resolution photoelectron emission spectroscopy, and we expect it to help create safer nuclear power plants."

ZIRLO Clad Tubes Used in the Experiment

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