[en] An argon-atmosphere glovebox was constructed in order to treat samples for analysis of oxygen, nitrogen and carbon in U-Pu mixed carbide fuel. In addition to safe handling of plutonium, the glovebox is designed to maintain the highly pure argon atmosphere in order to avoid the contamination from oxygen and water. The leak rates of oxygen and water vapor into the glovebox are 1.6 x 10^-4 and 3.1 x 10^-4 atm cc/sec respectively. These impurities enter the glovebox mainly through four pairs of Hypalon gloves. The purity of argon gas in the glovebox is kept at less than 1 ppm each of oxygen and water. When uranium carbide powder was in the glovebox for 5 hr, the amount of carbon decreased by 7.5 x 10^-3 w/o, and of oxygen increased by 1.0 x 10^-2 w/o. This composition change is negligibly small for analysis of carbon and oxygen. Test operation with uranium carbide powder showed that the glovebox satisfy its design specifications of safety, operation and argon gas purity. (auth.)