| 摘要 |
1,246,046. Coating particles. U N I T E D KINGDOM ATOMIC ENERGY AUTHORITY. 24 March, 1970 [27 March, 1969], No. 16245/69. Headings B2E and B2L. [Also in Division G6] Particles, such as microspheres of nuclear fuel material, are coated by a process comprising a number of similar coating treatment stages to which the articles are subjected in succession, undersized articles being detected by a grading operation and passed back for further treatment to the second stage and oversized articles restored to their uncoated condition and recycled through both treatment stages. The coated may be carried out by tumbling microspheres of a nuclear fuel material in a revolving drum into which a coating power is fed, transferring the microspheres between the drum of one stage and the drum of the next, preferably by fluidisation techniques, grading the particles so that undersized particles are returned to the second stage and the coating is removed from oversized particles and returned to the first stage. In the apparatus shown untreated particles are fed into the rotating drum 1 wherein a coating of graphite powder is applied by tumbling. When the coating process is only partially completed the particles are transferred to the second drum 2 where coating is continued to completion. Oversized particles are returned to the first stage drum 1 by way of a washer 4. Undersized particles from the second stage are returned to the second stage drum 2 for the application of further coating material. The particles which may have previously received a coating of a fission product retaining layer by a previous operation, e.g. in a fluidised bed coater, are coated with phenol formaldehyde resin and a spray of methylated spirits directed occasionally into the drum to soften the resin so that it adheres to the tumbling particles. |
