Nuclear fuel rod diagram
High-performance alloys are widely used in some very important fields, such as the cladding used to protect the fuel in nuclear reactors. However, even the best alloys are gradually eroded in high temperature, radiation, and hydrogen rich environments in nuclear reactors. Now, MIT researchers in the United States have found a new method that can greatly reduce hydrogen damage to the alloy.
According to the official website of the Massachusetts Institute of Technology, the team mainly analyzed zirconium alloys widely used in the nuclear industry. When the water molecules in the nuclear reactor coolant split, hydrogen is released and these hydrogen elements enter and react with the zirconium alloy. This reduces the ductility of the zirconium alloy, making it brittle and failure ahead of time.
The researchers found that the first pass of hydrogen atoms into the zirconium alloy is the oxide layer on the surface. If this layer of oxide is carefully designed, it will prevent the hydrogen element from entering the interior of the alloy, or it will "drive away" the hydrogen again in the form of hydrogen.
Hydrogen will first dissolve in the oxide layer on its surface before it enters the interior of the zirconium alloy. Experiments have shown that the solubility of hydrogen can be controlled by incorporating other elements in the oxide layer, and its solubility changes as a U-shaped curve with the amount of electrons incorporated into the oxide layer. In other words, there is a type of doping element that minimizes the infiltration of hydrogen and prevents hydrogen from entering the oxide layer. Another type of doping element maximizes the bringing of electrons to the oxide layer and promotes the release of oxide layers. Out of hydrogen. Therefore, the key to designing a strong "barrier" for zirconium alloys is to find effective incorporation elements.
In view of this, the researchers found two effective strategies: one is â€œshoufuâ€ that aims to minimize the penetration of hydrogen elements, which can be achieved by incorporating chromium; the other is â€œdischargingâ€ in order to make The infiltrated hydrogen is maximally released and this can be achieved by incorporating helium. These doping elements can be added during the manufacture of zirconium alloys, incorporating an oxide layer on the surface of the zirconium alloy.
Professor Gary Vas, Professor of Sustainable Energy, Environment and Earth System Engineering at the University of Michigan, USA, commented that hydrogen's behavior has been regarded as the biggest potential challenge for nuclear reactors under normal operating conditions. This study is to understand hydrogen from a physical point of view. First attempt at behavior in zirconium alloys.
However, the researchers emphasized that these two strategies, or general methods that can be applied to a variety of alloys, have the potential to increase the life of the alloy in many important areas. (Reporter Liu Yuanyuan)
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