# US 5,702,676 A · Production method for obtaining pressable powder yielding high sinter density pellets without defects

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- Number: US 5,702,676 A
- Document ID: US5702676A
- Status: Granted
- Kind: A
- Application number: 08/667,795
- Filed: 1996-06-20
- Granted: 1997-12-30
- Earliest claimed: 1996-06-20
- Assignees: General Electric Company
- Inventors: Richard I. Larson; Stephen E. Selby; Michael P. Enger
- Web page: https://patentgrep.com/patent/US5702676A

## CPC

- C01G 43/025: Uranium dioxide
- C01P 2006/10: Solid density
- C01P 2006/12: Surface area
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

This invention provides an improved process of preparing UO.sub.2 powder from poor quality, partially oxidized powder containing organic and inorganic impurities. The process is illustrated in the flow chart of FIG. 1 which includes the steps of (a) oxidizing a uranium-containing scrap also containing inorganic and cationic organic impurities; (b) solubilizing, typically with nitric acid, the uranium contained in the oxidized scrap to produce uranyl nitrate; (c) solvent extracting the solubilized product of step (b) to remove cation impurities to provide a purified uranyl nitrate solution; (d) precipitating the purified uranyl nitrate with ammonia to form ammonium diuranate powder; and (e) calcining and passivating the ammonium diuranate powder to produce UO.sub.2 powder; and optionally (f) forming the UO.sub.2 powder of step (e) into pellets and sintering the formed pellets to produce sintered UO.sub.2 pellets.

## Claims

### Claim 1

A process of preparing UO.sub.2 powder comprising the steps of:
(a) oxidizing uranium-containing scrap also containing inorganic and cationic organic impurities;
(b) solubilizing the uranium contained in the oxidized scrap to produce uranyl nitrate;
(c) solvent extracting the solubilized product of step (b) to remove cation impurities to provide a purified uranyl nitrate solution;
(d) precipitating the purified uranyl nitrate with ammonia to form ammonium diuranate powder; and
(e) calcining and passivating the ammonium diuranate powder to produce UO.sub.2 powder,
wherein the solvent after use in extraction step (c) contains dibutyl phosphate and is stripped to reduce the dibutyl phosphate content to at most about 40 ppm.

### Claim 2 (depends on 1)

The process of claim 1 including the additional step of:
(f) forming the UO.sub.2 powder of step (e) into pellets and sintering the formed pellets to produce sintered UO.sub.2 pellets.

### Claim 3 (depends on 1)

The process of claim 1, wherein the uranium is solubilized in step (b) with nitric acid.

### Claim 4 (depends on 2)

The process of claim 2, wherein the formed pellets, prior to sintering, have a green density less than about 5.30 gm/cm.sup.3.

### Claim 5 (depends on 2)

The process of claim 2, wherein the sintered pellets have a sinter density of at least about 98.0% theoretical density.

### Claim 6 (depends on 1)

The process of claim 1, wherein the UO.sub.2 powder produced in step (e) has a surface area of at least about 4 m.sup.2 /gm.