Vapor deposition of large area NpO2 and UO2 deposits

Deposition of NpO2 and UO2 thin films over an area of 7.5 to 10 cm diam has become a routine operation in preparation of fission chamber plates. Vacuum evaporation or electroplating has been used for this purpose. The ''paint brush'' technique has been used as well; however, uniformity requirements normally eliminate this procedure. Vapor deposition in vacuum appears to be the most suitable technique for preparing NpO2 and UO2 deposits of >200 cm2. This paper describes the procedures used in preparing uniform large area deposits of NpO2 (approximately 300 cm2) and UO2 (approximately 2000 cm2) by vacuum evaporation using electron bombardment heating and several substrate motion and heating methods to achieve uniformity and adhesion