| 摘要 |
Lead with a low alpha particle emission is produced by selecting an orebody wherein lead mineral is present in a coarsely disseminated form and substantially free of impurities. The ore is selected from a host rock that is relatively low in alpha emitters, such as a carbonate rock. The ore is mined and is milled such that the lead mineral can be separated from the host rock and any other minerals. The ground ore may be screened into one or more fractions having a narrow range of particle sizes. Each fraction is formed into a fluid suspension, and each suspension is subjected to gravity separation to remove the host rock and any other minerals which substantially contain the alpha particle-emmitting substances, and to recover the lead mineral as a concentrate with a low alpha count. The lead concentrate is subjected to a suitable reduction operation that may include a conversion of the concentrate into a reducible form, without the introduction of alpha emitters, for the recovery of a low alpha lead. When the lead mineral is galena, suitable reductions include the smelting with sodium carbonate with or without an oxygen-bearing gas and electrolytic reduction in a molten bath of lead chloride. The low alpha lead recovered from these operations has an alpha count of about 0.02 alpha particle per cm<2> per hour or less, and the count does not substantially increase with time. The recovered low alpha lead may be further purified by electro-refining. |
