The solid-state chemistry of uranium is essential to the nuclear fuel cycle. Uranyl nitrate is a key compound that is produced at various stages of the nuclear fuel cycle, both in front-end and backend cycles. It is typically formed by dissolving spent nuclear fuel in nitric acid or through a wet conversion process for the preparation of UF6. Additionally, uranium oxides are a primary consideration in the nuclear fuel cycle because they are the most commonly used nuclear fuel in commercial nuclear reactors. Therefore, it is crucial to understand the oxidation and thermal behavior of uranium oxides and uranyl nitrates. Under the ‘2023 Nuclear Global Researcher Training Program for the Back-end Nuclear Fuel Cycle,’ supported by KONICOF, several experiments were conducted at IMRAM (Institute of Multidisciplinary Research for Advanced Materials) at Tohoku University. First, the recovery ratio of uranium was analyzed during the synthesis of uranyl nitrate by dissolving the actual radioisotope, U3O8, in a nitric acid solution. Second, thermogravimetric-differential thermal analysis (TG-DTA) of uranyl nitrate (UO2(NO3)2) and hyper-stoichiometric uranium dioxide (UO2+X) was performed. The enthalpy change was discussed to confirm the mechanism of thermal decomposition of uranyl nitrate under heating conditions and to determine the chemical hydrate form of uranyl nitrate. In the case of UO2+X, the value of ‘x’ was determined through the calculation of weight change data, and the initial form was verified using the phase diagram for the U-O system. Finally, the formation of a few UO2+X compounds was observed with heat treatment of uranyl nitrate and uranium dioxide at different temperature intervals (450°C-600°C). As a result of these studies, a deeper understanding of the thermal and chemical behavior of uranium compounds was achieved. This knowledge is vital for improving the efficiency and safety of nuclear fuel cycle processes and contributes to advancements in nuclear science and technology.

Many pronuclear stage eggs were used to generate transgenic mice (Tg) by microinjection. In this study, we used in vitro fertilized mouse eggs, followed by ultrarapid freezing to establish a simple procedure for production of Tg mice. We produced in vitro fertilized mouse eggs and cryopreserved them by ultrarapid freezing method. A total of 139 cryopreserved-thawed pronuclear eggs, of which 101 (72.6%) were survived following microinjection of chicken b-actin promoter-driven firefly improved luciferase cDNA (β-act/luc+) and were transferred into 5 recipients. All recipients became pregnant and gave birth to a total of 15 (14.8%) pups. As a control, same DNA construction (β- act/luc+) was also injected into 450 in vitro fertilized eggs, of which 338 (75.1%) were survived and then were transferred into 14 recipients. Eleven (78%) mice became pregnant and littered a total of 54 (19.1%) pups. Southern blotting analysis of Tg mice indicated that one (1/15, 6.6%) and three (3/54, 5.5%) transgenic mice were production from cryopreserved and in vitro fertilized eggs, respectively. All Tg mice produced from both eggs showed the expression of improved luciferase gene. These results indicated that efficiency of produced of Tg mice from cryopreserved eggs was comparable to that from in vitro fertilized eggs. Furthermore, it is suggested that microinjection of transgene into in vitro fertilized eggs cryopreserved by ultrarapid freezing is an easy and conveniently method for production of Tg mice.

Diglycidyl ether of bisphenol A(DGEBA)/4,4'-methylene dianiline(MDA)/phenyl glycidyl ether(PGE)-acetamide(AcAm)/carboxyl-terminated acrylonitrile butadiene copolymer(CTBN) 계의 열적 안정성을 평가하기 위해 열중량 분석법(TG)을 사용하였다. 활성화 에너지를 구하기 위해 Freeman & Carrol, kissinger, Flynn & Wall 식을 사용하였다. Freeman & Wall 식을 이용하여 구한 활성화 에너지는 112.9 kJ/mol, Kissinger 식에 의한 값은 151.5kJ/mol 이었으며, Flynn & Wall식에 의해 구한 값은 168.3 kJ/mol 이었다.

내분비계 교란물질은 환경으로 방출되어 다양한 경로를 통해 조직에 축적되며, 각종 형태의 교란을 일으킴으로써 생식 이상과 성장억제 등을 초래한다. 본 연구에서는 내분비계 교란물질로 분류되는 Phthalate 및 대체물질 안전성 평가를 위해 TG407 실험을 수행하였다. TG407에 따라 (8주령) 수컷 Mouse에 Sonde를 이용하여 Phthalate (DEHP, 양성대조군; 4, 400 mg/kg/day) 및 대체후보물질 2종 (ATEC; 4, 40, 400 mg/kg/day), (ATHC; 400 mg/kg/day)를 28일 동안 경구투여 하였으며, 경구투여 종료 후 Sampling, 혈당 측정, CBC 측정, 호르몬 측정을 수행하였다. CBC와 혈당, Insulin 측정 및 뇌, 뇌하수체, 심장, 부정소, 정낭의 무게 측정 결과, 대조군과의 차이를 보이지 않았으며, T4와 T3의 농도는 ATHC를 제외하고는 대조군과의 차이를 보이지 않았다. ATHC(400 mg/kg)를 처리한 경우, 대조군에 비해 T4가 높았으며, T3는 낮았다. 간의 경우 DEHP(400 mg/kg)을 처리했을 때 대조군에 비해 무게가 증가하였다. 신장의 경우, DEHP(400 mg/kg), ATHC(400 mg/kg)을 처리했을 때 대조군에 비해 무게가 증가하였으며, 부신의 경우, DEHP(400 mg/kg), ATEC(40, 400 mg/kg), ATHC(400 mg/kg)을 처리했을 때 대조군에 비해 무게가 증가하였다. 흉선의 경우 DEHP(400 mg/kg), ATHC(400 mg/kg)을 처리했을 때 대조군에 비해 무게가 증가하였으며, 비장의 경우, DEHP(400 mg/kg)을 처리했을 때 대조군에 비해 무게가 증가하였다. 정소의 경우, DEHP(400 mg/kg), ATEC(40, 400 mg/kg), ATHC(400 mg/kg)을 처리했을 때 대조군에 비해 무게가 증가하였으며, 전립선의 경우, DEHP(400 mg/kg), ATHC(400 mg/kg)을 처리했을 때 대조군에 비해 무게가 증가하였다. 간, 신장, 부신, 비장, 정소, 부정소, 전립선을 대상으로 조직학적 분석을 진행하였으며, 특이적인 소견을 보이지 않았다. 본 연구를 통해 ATEC가 가장 독성이 낮은 것으로 사료되며, 따라서 ATEC와 같은 대체소재가 향후 플라스틱 시장에서 Phthalate를 대체할 수 있을 것으로 생각된다.