Conventionally, shielded-metal arc welding (SMAW) process has been applied to join
pipes of reactor coolant loop, which caused defects and lot of loss in time and cost due to excessive
heat input in joining section. Recently, narrow-gap welding (NGW) process was introduced to
overcome the disadvantages of SMAW. However, the application of NGW to nuclear power plant is
not yet commonly used, because safety of NGW process is not fully proven. In the present paper,
welded coupons are made of stainless steel. They are manufactured under different processes; general
welding (GW), and repair welding after GW. Performed are various mechanical tests to investigate
microstructure, tensile strength and so on. It is verified that the mechanical properties of stainless steel
are slightly changed after repair welding process. It is also found from stress corrosion cracking tests
that the failure time of repair welding is shorter than that of general welding.
Recent accident at Fukushima nuclear power plant in Japan raised a great concern about the safety of nuclear power plants and the radiological consequences. About twenty percent of the operating power plants in the world are located in north-east Asia. Nuclear accident is not a domestic matter but an international matter especially among neighboring countries. The purpose of this study is to understand the general behavior of the radiological materials and the radiation dose in Korea resulted from a nuclear accident in neighboring countries of Korea. We selected a nuclear power plant unit respectively from China and Japan. We suppose a severe accident releasing radiological materials to the environment and performed a plume dispersion simulation using HYSPLIT4, considering the seasonal weather. The results show that the radiation exposure doses in the most pessimistic case could reach the nuclear emergency level in Korea, such as the indoor sheltering and the restriction on food consumption and drinking water for the public, which is based on the ICRP recommendation. The long-range plume dispersion model for the decision supportive system should be established and improved in near future.
Conventionally, shield metal arc welding (SMAW) process was applied to join pipes of RCL, which caused lot of loss in time and cost due to excessive heat input and defects in joining section. Recently, narrow-gap welding (NGW) process was introduced to overcome the disadvantages of SMAW. However, the application of NGW to nuclear power plant is not yet common because safety of NGW process is not proven. In present paper, the welded coupons are manufactured under different welding processes in carbon steel. Then, microstructure observations and various mechanical tests are performed. It is verified that the mechanical properties of carbon steel are greatly changed after repair welding process due to applied heat flux, and that the effect of post-welding heat treatment is beneficial.
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