As a clean and efficient power generation method, nuclear power has become an important strategic carrier to meet the national power demand, optimize the energy structure, ensure energy security, and promote sustainable economic development.
At the same time, it is an effective way to reduce environmental pollution and achieve economic and ecological development. In recent years, my country's nuclear power has developed rapidly, and nuclear power equipment in use continues to operate safely and stably, and the annual cumulative power generation has increased by 6.6% over the previous year.
While nuclear power has brought significant social and economic benefits, it has also caused many safety issues. Following the Fukushima nuclear accident, South Korea placed a high priority on nuclear safety issues. The treatment method of high-level radioactive waste has become an important issue urgently needed to be solved in the utilization of nuclear power, and it is also a key factor related to the sustainable generation of nuclear energy.
The world-recognized and most reasonable radioactive waste disposal method is to perform geological treatment on the solidified radioactive waste obtained after solidification of radioactive waste, so that high-level radioactive waste can be separated from the human living environment in a long-term and stable manner. Minimize or eliminate the effects of high-level radioactive waste on both nature and humans.
The high-level radioactive waste storage tank is a special vessel for the storage of solidified high-level radioactive waste. Vitrification of high-level radioactive waste is a treatment method that was first developed and has been used in practical engineering for more than 30 years, and the technology is relatively mature. In France, the United Kingdom, the United States, Japan, and other developed countries, it has been widely utilized. Our country is still in the process of conducting experimental research. 310S austenitic stainless steels are used to make the storage tank. When welding the tank, grains in the coarse-grained zone of the heat affected zone (CGHAZ) were found to be very rough. This results in a decrease in impact toughness, a decrease in crack propagation work, and an increase in the brittle transition temperature of austenitic stainless steel CGHAZ. Stress concentration will occur, particularly when the grain size is uneven, which can easily limit the use and application of austenitic stainless steel.
Three methods are currently used in practical industrial applications to reduce particle growth in the heat-affected zone of the weld. One is to adjust the welding process, that is, reduce the welding current and increase the welding speed to reduce the grain size of the welding heat-affected zone, but this method greatly reduces the welding quality and welding efficiency.
The second is phase transformation, that is, through heat treatment, the heat-affected wound of the weld seam undergoes phase transformation and transforms into a phase with a relatively small particle size. The structure cannot be adjusted by phase transformation because 310S austenitic stainless steels are completely austenitic from room temperature to a solid phase without any phase transformation.
Third, alloying elements are added on the basis of the base metal, so that the second phase particles and fine particles are precipitated at the interface, which plays a role in fixing the grain boundary. As a result, it hinders the movement of grain boundaries. This method is highly applicable and has a noticeable inhibitory effect. 310S austenitic stainless steels are a full austenitic stainless steel that contains 25% Cr and up to 20% Ni, ensuring corrosion resistance and mechanical properties.
As a result, the waste storage tank mainly uses 310S austenitic systems. Stainless steel. At present, the main grade of 310S steel of the domestic Baosteel Group and Taiyuan Iron and Steel Group is 06Cr25Ni20, and the American ASTM and UNS standard grades are 310S and S31008 respectively. The Korean KS standard grade is STS310S, and the EU BSEM standard grade. 1.4845 and Australian AS standard grades.
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