페이지 정보2022.09.19 / 620
▶ Date: 2022. 09. 22(THU)
▶ Time: 4:30 ~ 5:30PM
▶ Venue : Research Building I, #310 / Offline
▶ Speaker: Dr. Byoungkoo Kim(KITECH)
▶ Title: Study of cobalt reduction of valve hardfacing for radiation exposure reduction in the primary system of PWR and DED 3D printed P21-STS316L functionally gradient material for nuclear applications
95% of the radiation dose of nuclear workers is from cobalt radiated from the primary system of nuclear power plants. International research to reduce radiation exposure by reducing cobalt in NSSS has been conducted since the 1980s, and research has been conducted in Korea since the 1990s. The main sources of radioactive cobalt in nuclear power plants are steam generator tube, valve hardfacings, CRDMs, main feed water pump shafts and nuclear fuel structures. Cobalt generation was reduced by replacing the steam generator tube material from IN600 to IN690 and replacing the nuclear fuel space grid material from Inconel to Zircaloy. For valve hardfacing, research is underway to change the material from cobalt base to low cobalt, nickel base, and iron base. We are conducting research to establish a high-temperature, high-pressure water chemical environment wear evaluation equipment which simulate the primary system of nuclear power plant, and to select and evaluate cobalt-reducing valve hardfacing materials.
Laser hardfacing technology shows the best combination of properties among hardfacing technologies. As laser devices have become popular in recent years, the application of laser welding technology is increasing. In particular, a multi-hopper DED 3D printer capable of producing alloys has been developed, which can produce laser-laminated blocks with different components depending on the location. We used a multi-hopper DED 3D printer to fabricate an FGM material whose composition gradually changed from P21 to SUS316L and evaluated its microstructure and mechanical properties. I introduce the applicability of FGM materials in nuclear power plant environments that require complex properties such as corrosion resistance and strength.