IL25985A - Method of preparation of sintered pollucite and its application to the production of radioactive sources - Google Patents

Description

the relates to for intended a caeei a which cubic system and has composition is knows that this mineral he obtained a process consists in heating in am autoclave and a mixture of a colloidal of silica with hydroxide fey hydrolysis aluminum and hydroxide formed fey the action of caesium sulphate em a dry in heating to AX a crushed size of order 150 with caesium sulphate to approximately water to these are and d and produce crystalline pollucite cannot readily he This invention has the to provide simple and the preparation of an powder of pollucite which can readily be shaped and sintered to he into crystalline In the method according to the a mixture and aluminum stoichiometric proportions is evaporated to preferably with the residue is heated to a temperature below the s is and the compac β are sintered at a temperature ef about the and salts used are preferably the nitrates because their relatively lew decomposition evaporation to dryness the is preferably performed at a temperature about the mixture the course of the evaporation in order to the mixture nitrates begin to decompose above The heating rate in this stage should be rather about to amorphous powder produced by the heat is and then pelleted under relatively high for about The use of high pressures at this stage reduces the shrinkage in the subsequent sintering pollucite pellets are preferably at a temperature of about The sintered produet has a specific gravity of about In preferred embodiment of the the dry residue of the evaporation process is subjected to prolonged calcination at a temperature below and preferably to a par iele then the powder is treated with steam and the are sintered in two stages at different temperature levels of about and The oaloining of the powder is preferably carried a a within the range of to in until the complete decomposition of the caesium She required duration of the calcining depends on the partiele size of the powder and the thickness of the layer of the residue obtained after For the calcining takes about 40 hours in the case of a powder having an average particle diameter of mm and a residue layer thickness of 6 and about 90 hours im the case of a powder having an average partiele diameter of 1 and a residue layer thickness of 10 The amorphous product of the heat treatment is ground to an average particle 10 The grinding operation is preferably earried out in which makes for a good partiele distribution and prevents the formation of dust She of the powder with especially in the embodiment where the grinding is effected in ether and the latter has been has the advantage of activating the making it more susceptible to the shaping sintering For the steam treatment the is preferably heated for about 15 to 50 to about in an atmosphere saturated with water This operation imparts to the powder ah improved plasticity and makes it easier to the steam treatment the amorphous powder is pelleted under a pressure about 2000 pellets are sintered in two at two the first proceeding at approximately insufficientOCRQuality

Claims (1)

1. CLAIMS od for the preparation of sintered the of forming a mixture of a colloidal with ions of al salts in stoichiometric evaporating the while heating the to a compacting the powder thus sintering the at a temperature of A to Claim wherein the the is to calcination caesium and salts used are the A according to 1 or wherein the operation is earried out at a pressure of about 2500 A according to Claim wherein the calcining is effected a temperature within the range of to A method to Claim wherein the ealeined is ground average partiele size of 10 7 A method according to wherein the powder is treated with steam at a temperature of about for a period of 15 to 50 A for the preparation of sintered substantially hereinbefore A source in that it is tituted by sintered obtained in accordance with the method of any of the preceding the Applicants A insufficientOCRQuality