Process for the Production of Uranium Trifluoride

United States Patent im [in 3,964,965 Tagawa [45] June 24, 1976

[54] PROCESS FOR THE PRODUCTION OF URANIUM TRIFLUORIDE [56] References Cited [75] Inventor: Hiroaki Tagawa, Tokaimura, Japan UNITED STATES PATENTS [73] Assignee: Japan Atomic Energy Research 3,034,855 5/1962 Jenkins et al 423/258 Institute, Tokyo, Japan [22] Filed: Dec. 20, 1973 Primary Examiner—Stephen J. Lechert, Jr. Attorney, Agent, or Firm—Stevens, Davis, Miller & [21] Appl. No.: 426,593 Mosher

[30] Foreign Application Priority Data [57] ABSTRACT Dec. 26, 1972 Japan 47-129560 A novel method is disclosed for producing a pure uranium trifluoride efficiently. Said method is character- [52] U.S. CI 423/258; 423/259; ized by heating a mixture of uranium tetrafluoride and 252/301.1 R uranium nitride in an inert gas stream or under [51] Int. CI.2. C01G 43/06 vacuum. [58] Field of Search 423/258, 259; 252/301.1 R 2 Claims, No Drawings 3,976, 1 2

PROCESS FOR THE PRODUCTION OF URANIUM DETAILED DESCRIPTION OF INVENTION TRIFLUORIDE According to the present invention, uranium trifluoride is produced by heating a mixture of uranium tetra- BACKGROUND OF THE INVENTION 5 fluoride and uranium nitride in the form of powder or 1. Field of the Invention molding in a stream of inert gas or under vacuum. In The present invention relates to a method for pro- this invention, uranium sesquinitride (U2N3) or ura- duction of pure uranium trifluoride characterized by nium mononitride (UN) can be used for the starting heating a mixture of uranium tetrafluoride and uranium material. nitride in an inert gas stream or under vacuum. 1hydrogen gas free from The reaction for the preparation of uranium trifluo- oxygen and moisture to reduce the UF4 to UF:l. And the ride from uranium tetrafluoride and uranium sesquini- other is characterized by heating a uranium metal in a tride is shown in Eq. 2: stream of hydrogen gas to convert the uranium metal to 20 uranium hydride, decomposing the uranium hydride to 3LTH + ViU,N.n = 4UF-, + %N, L-q. 2 finely divide uranium metal powder under additional elevation of temperature and then fusing the mixture of The nitrogen gas formed is released outside the sys- UF, and the finely divided uranium metal powder to tem. The invention of this application can be worked at form UF:, in a stream of argon gas at high ignition temperatures. Each of these two methods has its own de- 25 temperatures in the range of 700°- 1000°C; however, merit as noted below. it is preferably worked at temperatures ranging from In the former case, because the hydrogen fluoride 900°C to 950°C. Since uranium tetrafluoride evapo- rates at temperatures above 1000°C, the reaction tem- formed along with UF:) is highly corrosive, it is very difficult to find materials for a reactor which are resis- peratures should be selected from the range below tant to the corrosive effect of the hydrogen fluoride at 30 1000°C. high temperatures. The same results can be obtained if the reaction is In the latter case, the finely divided uranium metal worked either under vacuum or in a stream of inert gas, powder is very hard to handle and is apt to be contami- e.g. He, Ar, etc. nated with impurities, e.g. oxygen. In addition, the In accordance with this invention, uranium trifluo- uranium metal powder itself is easily sintered, and 35 ride can be produced at a commercially practicable therefore the reaction is rarely completed satisfacto- reaction rate. rily. Since both the starting materials (uranium tetrafluo- Those skilled in the art have so far believed that ride and uranium nitride) used in this invention can be uranium tetrafluoride does not react with uranium produced in a state of high purity, a minimum amount nitride. 40 of impurities is left in the uranium trifluoride produced. However, I, the inventor of this invention have found The impurity content of the finished product does not that uranium trifluoride can be easily produced by exceed that of the starting materials. heating a mixture of uranium tetrafluoride and uranium And furthermore, since no corrosive gases are pro- nitride in a stream of inert gas (rare gas) or under duced by this invention, this invention can be worked vacuum. 45 easily at high temperatures. This invention will be further described by reference BRIEF SUMMARY OF INVENTION to the following specific examples, It should be under- Therefore, the main object of the present invention is stood, however, that although these examples may to provide uranium trifluoride in a state of high purity. describe in detail certain preferred operating condi- Another object of this invention is to provide a sim- 30 tions and/or materials and/or proportions, they are pie, efficient and economical process for production of provided primarily for the purpose of illustration and uranium trifluoride. the invention, in its broader aspects, is not limited An additional object of this invention is to provide an thereto. uranium trifluoride prepared by heating a mixture of EXAMPLE 1 uranium tetrafluoride and uranium nitride in a stream 55 of inert gas. Both uranium tetrafluoride (UF4) and uranium A further object of this invention is to provide a mononitride (UN) containing 5.53 percent nitrogen by uranium trifluoride prepared by heating a mixture of weight were finely powdered and passed through a uranium tetrafluoride and uranium nitride under vac- sieve of 200 mesh. 60 uum. And then, the powdered uranium tetrafluoride (UF4) A still further object of this invention is to provide a and uranium mononitride (UN) were mixed together, process for the production of uranium trifluoride char- the proportions of UF4 to UN being 3.74:1 by weight, acterized by heating a mixture of uranium tetrafluoride and molded into pellets. The pellets were then placed and uranium nitride in a stream of inert gas or under in a quartz crucible lined with a nickel plate, and there- vacuum. after, the quartz crucible was placed in a quartz reac- These and other objects and advantages of this invention tube, which was then evacuated to 1()~5 mmHg and tion will become apparent from the specification and sealed to make a vacuum system. The system was main- claims. tained at 950°C for 30 min.; then the nitrogen gas 3,976,750 formed in the system was removed and the system was Since the scope of the present invention has been cooled. stated broadly in the foregoing description that is by no Single-phase uranium trifluoride was obtained in a means restrictive but merely illustrative, it should be 98.5% yeild. liberally interpreted so as to obtain the benefit of all its equivalents to which I believe this invention is justly EXAMPLE 2 entitled. Uranium tetrafluoride (UF.,) and uranium sesquini- What is claimed is: 1. A process for the production of uranium trifluo- tride (U2N:1) containing 8.61 percent nitrogen by weight were mixed together, the proportions of UF., to ride, comprising heating a mixture of uranium tetraflu- 10 oride and uranium nitride selected from the group U N being 3.61:1 by weight, and molded into pellets. 2 :! consisting of uranium mononitride and uranium ses- The thus formed pellets were then placed in a quartz quinitride, at a temperature in the range of 700°C to boat lined with a nickel plate, which was subsequently 1000°C, in a stream of inert gas or under vacuum. heated to 900°C and held then for 60 min. in a quartz 2. A process according to claim 1 wherein the mix- reaction tube in a stream of argon gas of high purity. 15 ture is heated at temperature in the range of 900°C to A single-phase uranium trifluoride was obtained in a 950°C. 97.0% yield.