External Gelation 방법을 이용한 구형 UO3 Gel 입자제조 = Spherical UO3 Gel Preparation Using the External Gelation Method

다국어 초록 (Multilingual Abstract)

HTGR (High Temperature Gas-cooled Reactor) is spotlighted to next generation nuclear power plant for producing the clean hydrogen gas and the electricity. In this study, the spherical UO3 gel particles were prepared by the external gelation process, and the characteristics of these particles were analyzed the particle shape, composition of precipitate, and thermal decomposition characteristics with the Streoscope, FT-IR, and X-ray diffractometer. Raw material of the ADUN (Acid Deficient Uranyl Nitrate) solution, which has [NO3]/[U] mole ratio=1.75, was obtained from dissolution of the U3O8 powder with concentrated HNO3, and its concentration is 3.5 M-U/ℓ. The broth solution is prepared with the ADUN, urea, PVA, and THFA solution. The droplets of the broth solution was made through a nozzle system. From this study, we obtained the following results ; 1) an externel chemical gelation process is a suitable method in the spherical UO3 particle production, 2) the particle shape are changed by an urea mixing time, THFA volume, and the viscosity of the broth solution, 3) the amorphous UO3 particles obtained from these experiments was converted to U3O8 and then UO2 by heat treatment in hydrogen atmosphere at 600℃.

국문 초록 (Abstract)

차세대 수소생산을 위한 원자로로 고온가스로가 각광을 받고 있으며, 본 연구에서는 고온가스로 핵연료 중간매체로 예상되는 구형 UO3 gel 입자를 external gelation 공정을 이용해서 제조한 후, gel입자의 특성을 파악하고자하였다. 원료용액은 U3O8분말을 질산에 용해시켜 [NO3]/U mole ratio 1.75인 ADUN(Acid Deficient Uranyl Nitrate)용액을 제조한 후 우라늄 농도 3.5M/ℓ 인 초기용액에 urea 와 THFA(TetraHydroFurfurylAlcohol) 및 PVA(PolyVinylAlcohol)를 첨가하여 broth 용액을 제조하였다. 제조된 broth 용액을 미세 needle을 통해 공기, 암모니아 가스층을 통과시킨 후 암모니아 용액에서 구형 UO3 침전물을 얻었으며, Streoscope, X-ray, FT-IR 등을 이용해서 침전물의 입자모양, 구성성분 및 열분해 특성 등을 관찰하였다. 초기 broth 용액 제조과정에서 urea의 혼합시간, THFA의 적가량, PVA에 의한 점성등에 의해 입자의 모양과 크기가 다르게 나타났으며, 제조된 UO3 gel입자는 수소분위기에서 UO3→U3O8→UO2로 형태로 상변화가 진행되는 것을 알 수 있었다.

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