DE1667095C - Process for making uranium dioxide-yttria-zirconia microspheres - Google Patents

Description

spheres are obtained, 30 to 55 percent by weight method is characterized in that micro-

Uranium dioxide, 10 to 45% yttrium oxide and 15 bis spheres with a content of three metal oxides,

Contains 55 percent by weight of zirconium dioxide. by using an aqueous solution as the starting product

2. The method according to claim 1, characterized ge 25 of soluble U ^M -, Y * ³ - and (ZrO) ^t2 salts or indicates that the microspheres are separated from the solvent before the Aquasol of uranium dioxide, yttrium oxide and zirconium on a water dioxide in such proportions that the water content dries below 50 percent by weight. Microspheres are obtained, which 30 to 55 Ge

3. Process according to claims 1 and 2, weight percent uranium dioxide, 10 to 45% ytlrium oxide characterized in that the ammonia contains from 30 and 15 to 55 percent by weight of zirconium dioxide, giving substance in an amount to the aqueous The contents of metal oxides are after Solution adds which is about 70 to 300% of the phase diagram for the uranium dioxide-yttrium oxide conversion with the salts in the solution stoichio-zirconium dioxide system in the area of mutual Lösmetrisch supplies the required amount of ammonia. opportunity. Of particular importance here is the

4. The method according to claim 1, characterized in 35 production of microspheres, which is 45 percent by weight, that the starting material is a uranium cent uranium dioxide, 35.5 percent by weight yttrium oxide dioxid-yttrium oxide-zirconium dioxide-Aquasol and contain 19.4 percent by weight of zirconium dioxide, det and this with such an amount of ammo-die as the starting material for an embodiment niak-releasing compound mixed that the MepH value that can be used in the process according to the invention des Aquasol about 1 * 0 to 0.1 units 40 talloxidaquasols are known. When using is brought below the gelling pH of the sol. Aquasolen, which are largely free of soluble metal salts a first-class microsphere product is obtained, which is also available in a wide range

rich in working conditions can be established.

45 The method according to the invention is also suitable for the production of metal oxide microspheres from metal

Dense spherical particles made from mixtures of tallow oxide aquasols, which contain substantial amounts of

Actinide metal oxides and other metal oxides contained in the dissolved U ⁴⁴ , Y ^f3 and (ZrO) ' ^a . The anions

Size range from 50 to 400 μηι are for the cookers salts can be all anions, soft water

position of fuel assemblies for high-temperature 5 ° soluble salts result. So it can for example

Nuclear reactors, such as gas-cooled reac metal chlorides, bromides, nitrates, sulfates, formates

goals important. These spherical particles are made up of and acetate, with monovalent anions being preferred

of two parts, a core, which are the invention.

according to manufactured microspheres corresponds, and a- The concentration of the metal compounds in the

a cover. The core contains the actinide oxides in 55 gangsaquasol can move within wide limits,

solid solution with other oxides. The total concentration of metal compounds in the

good spherical shape, firm and very dense. On the starting aquasol, expressed as metal oxides, can

Core will be an impermeable coating of between 1 and 500 g / l and is preferably

refractory metal oxide or pyrolytically obtained about 50 to 150 g / l. Dissolved metal salts can be in the

Carbon applied to return decomposition products containing 60 aquasols up to saturation concentration

keep. The coated microspheres will then be. An aqua that is "saturated" with soluble metal salts

Dispersed in a matrix and converted into fuel elements means that the liquid phase with the soluble

is working. Metal salts is saturated. The amounts of dissolved

Subject of the earlier German patent 1 542 179 tall salts in the Aquasol can be over 0.1 g / l. Vorist the content of dissolved metal salts is not a method for the production of compact me- ings Talloxid microspheres by dropping a metal so high that the sol particles are flocculated. A oxidaquasols or a mixture thereof in a flocculated starting material is slightly heavier in dehydrating solvent, isolation of dehydrating to bring the solvent column, however, it leaves

still process. Under metal oxide aquasols are treated. Suitable metal salts are, for example in the present description in addition to the metal chlorides, bromides, nitrates, sulfates, -for-metal oxide aquasols, which do not contain dissolved metal mates and acetates.

salts or less than those which lead to flocculation. The metal salt content of the aqueous solution

Contain quantities of dissolved metal salts, also Me- 5, calculated as MetalJoxid, between 1 g / l and the talloxidaquasole with a to flocculate the sol saturation concentration of the solution lie. Preferred particles with a sufficient content of dissolved metal salts, the concentration, expressed as oxide, is Roger that. By changing the solution concentration between about 50 and 150 g / l. By changing the tion and the pot size in the dehydrating solution, concentration of the solution and the size of the in the medium it is possible to dehydrated microspheres which is the ver io dehydrating solvent introduced drops in various sizes. it is also possible here to use dehydrated microspheres of the

Uranium dioxide is used to obtain uranium oxides with various sizes of oxygen.

held from 2.0 to 2.3 oxygen atoms per uranium - Compounds that release ammonia are used

atom understood. Excess oxygen is the same in this embodiment of the invention presumably bound mainly interstitially and 15 used as in the first embodiment. the is used in later stages of the process, for example, the ammonia-releasing substance can be sintered in the metal salt, removed from the product. solution are introduced in amounts which are about

The 70% of the stoichiometres used in the process according to the invention to precipitate the metal salts Substances emitting ammonia consist of the generally required amount of ammonia and up to mean from compounds which, when heated, provide ao 300% excess over this amount; preferred Room temperature by thermal decomposition, amounts are used which are the stoichiomessential Release quantities of ammonia, with a spatial quantity of ammonia up to 50% excess temperature are relatively stable. Deliver on reason about this. The ammonia-releasing substance Their slow reaction rate and their ability to form the meringue in solid form or dissolved in water Ammonia release at room temperature can be given 25 thawing salt solution. Preferably the give off these compounds at room temperature to the metal-metal salt solution upon addition of the ammonia oxidaquasols given without immediate stirring of the substance to local overconcentrations Induce reaction. When heating the Aua- the ammonia-releasing substance in the metal salt salt drop in the dehydrating solvent decompose solution and an associated premature precipitation to quickly prevent these compounds from being exposed to ammonia.

would exist. The ammonia reacts with the metal compounds from the mixture of ammonia-releasing compounds in the Aquasol with the formation of a metal oxide bond and metal oxide aquasol, metal oxide aquasol gel in the drop. Suitable ammonia-releasing metal salt solution or metal salt solution are the Compounds are, for example, hexamethylene tetra microspheres gemin in a hot solvent column, Acetamide, ammonium carbamate, ammonium- 35 recovered. In this system the starting solution becomes carbonate, ammonium cyanate, urea and mixed or the starting sol in drop form above in a gen same. The ammonia-releasing substance is preferably dewatered by high columns of hot countercurrent introduced shortly before the introduction of the starting material serndem solvent. The hot solution rials in the dehydrating solvent to the water medium heats the drops and causes a Zersol given, but the ammonia-releasing substance can be set for several hours beforehand, and that be added forth when the mixture until briefly released ammonia reacts with the metal before use at low temperature on oxide sol particles and / or metal cores under preservation will. precipitation and gelation of the corresponding oxides in

The ammonia-releasing compound is in one of the aqueous drops. When falling through the mixed with the starting aquasol in such an amount, 45 column, the drops are dewatered; which is on that dehydrated microfen accumulating from the metal compounds in the Soltrop foot of the column Upon contact with the dehydrating solution balls are continuously withdrawn from the solvent forms a metal oxide gel. Metal oxide aquasols, solvent-free and dried further before sintering largely free of dissolved metal salts.

are, can with as much ammonia-releasing substance 50 The above device for dewatering with hot be mixed so that the pH of the starting solvent consists of a high column with komaterials to a 1.0 to 0.1 and preferably approximately niche soil in which the microspheres are 0.8 to 0.4 pH units, below the gelling pH of the collect. The dehydrating solvent is from Sols lying value is brought. The gelling pH is introduced down into the column and up out of the same The value of an Aquasol is the pH value at which the 55 is deducted. The starting material can be used on different levels within 15 minutes of setting this dene mode with drop formation at the top of the column pH-value gels. When the starting aquasol larger ones are introduced. For example, it can be used for BiI quantities contains dissolved metal salts, the ammodification of the preferred particles is carried out through a narrow pipe niak-releasing substance added in an amount that or a needle with a clear diameter of 0.15 to 70 to 300% and preferably 100 to 150% of the 60 0.6 mm is injected into the solvent. Pre-failures Of the metal salts in the starting material, the needle is preferably a bit wider the metrically required amount of ammonia. Capillary tube surrounded by which solvent

According to a second embodiment of the invention, the suspension is introduced in the same process according to the invention, the microspheres containing oxides in said direction with this solvent stream are generally introduced into the column with countercurrent solvent by introducing an ammonia-releasing compound with Das Starting material can, however, also be mixed in a suitable solvent containing U ^HI , Y ^ ³ and (ZrO) ^{+ J} salts to form an emulsion of drops of solution and these can be further dispersed of uniform size as indicated above and the emulsion

then through a suitable insertion device ir,

SSääS

conical collecting part withdrawn. Sen The microspheres are therefore used for fixation

In this process the solvent can then be treated _with ^{ammonia for 5 J ^^ ™ ^ B}

Des.nialtans.empera.ur sor ^ u- I «P £ ^" · ate method MdIlein einfacto

mine of the settling microspheres The solution the drop precipitated "g ^ ^^

medium is about 10 cm above the pedestal emgepumpt ^ ungsmmel ex ™ _{"s0 that eventually} ßhch ziem-

and about 10 cm below the head of the column a ₅ from Jnausge ™ £ j ¹ _{haU be drawn}

The choice of solvent for this system is very rocky M ^ ^krok | _ate process received

Smaller density, so that the microbeads with special properties can settle in them, and must be heated to a temperature sinteredUUiKroKUg _fuel . Fuel assemblies

are heated, at which the ammonia-releasing 35 ^^ 'V "^", ^ of this composition are extra-material in the aqueous genes introduced into the system Trc-p-J ™ M \ krokuge η * es ^ of _{special interest} Fen Ammonia development is decomposed. JVe - ojtoü ch s ab.l un _{mU Ur}

ter.iin must be the saturation concentration of the solution areI f ui ξ ™ Autovermietung weight percent, an yttrium agent for water in a certain range, ^ oxidgeh mw, _{percent and} a Zir-Sher the setting of drying conditions ₄ "« ^ "^ J ^ _{0 §4 Ge} i _ic hts _P r _O center. The Pro enables. Good results were obtained with loose condi «Wg _{» h in the} range from 50 to 40% for water between about 1 and 30%. ^ t has em β perfect spheres Preferred solvents are, for example, hexanol 400 Mton ^ _{fewer> as} depressions ethylhexanol and Äthylbutanol. Solvent ™ ^l "*" £ ^ ™ _{n When} using as fuel a too high water dissolving capacity can with a 45 and blowing ^holes J _{ndioxidkomponente u} ngewohnhch certain water content from the distillation vessel shock ^ ^ ^e _{di From the} inventive Mizurückgeführt be, so that it has a lower effec- «Jk ^" ^^. ^ Fuel elements therefore have tive water-dissolving power. Thus, butanol, K ^r ° ^k ^ f ^ esserte structural stability in use, which is a ve bessertet _(u length _S Interten) Mikrovon has in a hot state Wasserlosevermogen about 28 weight percent, for example Near-50. J ^ ^ * _{t between} 15 and 60% and too saturated with water introduced into the column. Da- ball »« ^r £ ™ _h | _{n 2} | _{and 5O} o _{/ o det} theoretical

ZrO ,, and / b «^ g / c ^ _{inert Mlkro} has a solvency capacity of 10 to 11 percent by weight.

is generally between density when entering the column.

about 60 and 120 ⁰ C and when leaving it by 60 B e 1 s ρ 1 e 1 1 about 10 to 40 ⁰ C lower. This was Temowaturbedingungen _Hersle Settin g of microspheres of the composition are in most ammonia-releasing substances to Herste ^»u 6 _{ZxQj 1940 /} γ, ο the evolution of ammonia in the aqueous drop-down ■ J ^ ·. ^ 'of _the corresponding chlorides ideal. Ammonia-releasing substances such as urea, ^"ne ^" ^a ™ ^ _v ^g _{rial erwendet} and just before the Entstoff, higher solvent reasonable temperatures 6 ₅ ^ J ^^ f ^ examethylenletramin be displaced helically. 7i, r Herstellune of the ternary solution, / wmi The suspension drops are in the column to ^ ur production ^^ ^ _{8 g UOj each} a water content below 50% and preferably under Lhan-IV chioriaiosu _B

Liter corresponding uranium chloride content, 43.5 ml zirconyl chloride solution with a 3200 g ZrO ₂ per liter corresponding zirconyl chloride content and 80 ml yttrium chloride _{solution mixed with a yttrium chloride content corresponding to 200 g YgO 3} per liter. A solution of 45.9 g of crystalline hexamethylenetetramine in 57 ml of deionized water was added to this mixture with vigorous stirring, whereby the pH of the mixture was brought to 1.4.

The mixture was injected in the form of a drop through a hypodermic needle (0.58 mm), which was fed by an in the same Direction of hexanol flowed through 2.8 mm wide capillary was surrounded, at the top in a 2.13 m high Injected column through which hexanol was pumped in countercurrent. The conditions in the facility were as follows:

Feeding the starting mixture, ml / min 2.8

Solution milk supply, ml / min

to needle 120

to the column., 690

Solvent temperature, ° C

upon entering needle 30

upon entry into pillar 100

when leaving column 72

in the distillation vessel 108

Black perfect microspheres with smooth glossy surfaces and sizes ranging from 70 to 300 microns were withdrawn from the column. The spheres were immersed in concentrated ammonia solution for 15 minutes to fix the oxide components, and then washed with water to remove electrolytes. They were then dried on a filter and then placed in a vacuum oven, the temperature of which was gradually increased to 120 ^° C. over 7.5 hours.

The microspheres had a density determined by the mercury displacement method of 48% of the theoretical density (6.66 g / cm ³ ).

Example 1 2

To produce microspheres of the same composition as in Example 1, the starting material was however, a ternary sol is used in place of the solution.

ίο It was made into reactive uranium dioxide-zirconium dioxide sol produced by electrodialysis of a uranyl-zirconyl chloride solution. To form the ternary Sols, the uranium dioxide-zirconium dioxide sol was heated with an yttrium oxide sol in the autoclave. A share 200 nil of the ternary sol was added with vigorous stirring to 20 ml of 5 g of hexamethylenetetramine containing solution added, whereby the pH rose to 6.2 to 6.7.

The sol to which hexamethylenetetramine was added was

ao treated under the following conditions in the same device as in Example 1:

Sol feed, ml / min 4.0

Solvent feed, ml / min

to needle 85

to column 690

Solvent temperature, ° C

upon entering needle 28

upon entry into pillar 100

when leaving pillar 73

in the distillation vessel 110

Black microspheres ranging in diameter from 150 to 230 microns were found at the base of the column deducted. As in Example 1, they were immersed in concentrated ammonia solution for 15 minutes, washed and dried.

Claims (1)

ί 2nd microspheres from the emtwässernende solvent- Patentansp: üche: tel and optionally sintering, whereby the Aquasol is mixed with an ammonia-releasing agent 1. Process for the preparation of metal oxide and the mixture in a dehydrating solvent Mix containing microspheres by mixing 5, the temperature of which for extensive disintegration of an ammonia-releasing agent with settling of the ammonia-releasing agent is sufficient, an input product in the form of an Aquasol with the present invention is now a VerDioxide of the metals uranium and zirconium as well as drive for the production of uranium dioxide-yttrium oxide-yttrium oxide or an aqueous solution of SaI zirconia microspheres, in wheat the metals as well as dropping the insert pro io chen the oxides in an intimate mixture or solid solution ducts are present in a dehydrating solvent. a solvency for water of 1 to According to the invention becomes similar to the method 30 percent by weight for an ammonia-releasing agent that causes the older patent to deteriorate to a large extent exposure of the ammonia leaving agent with an input product in the form of an aquasol reaching temperature, characterized in that 15 dioxides of the metals uranium and zirconium as well as yttri that microspheres with a content of three umoxid or in the form of an aqueous solution of SaI- Metal oxides are produced by mixing the metals as starting materials and pouring them into a dehydrating product an aqueous solution of soluble U ⁺⁴ -, solvent with a solubility for water Y ^<3 - and (ZrO) ⁺² salts or an Aquasol from 1 to 30 percent by weight with a largely Uranium dioxide, yttrium oxide and zirconium dioxide in the decomposition of the ammonia-releasing agent such proportions begins that micro-sufficient temperature dripped in, whereby the