Liquid metal vapor-eliminating device

Various devices proposed for eliminating a liquid metal vapor in a cover gas exhibit various defects. In case of the packed bed type, a packed bed need be often exchanged. The baffle plate type is low in elimination efficiency. The bubble column type is disadvantageous in that the re-use of the eliminated liquid metal is impossible, and 24Na is emitted when employed as a metal vapor-eliminating device in a failed element detector. This invention provides a liquid metal vapor-eliminating device which is free from such defects. According to this device, the cover gas from a reactor is fed into a first packed column or bubble column which contains under the molten state the same metal as the metal vapor to be eliminated and which is kept at a first temperature. By passing through the molten metal, a large percentage of the metal vapor is trapped. The resultant cover gas is fed into a second packed column or bubble column which is similar to the first column in construction, connected in cascade to the first column and kept at a second temperature lower than the first temperature. Here, major portion of the remaining metal vapor is trapped. The cover gas delivered from the second column is introduced to, for example, a measuring system. In some cases, a liquid metal vapor-eliminator of the filter type may be disposed between the second column and the measuring system so as to trap a very small amount of remaining metal vapor. (S. Takasuka)