Porous UO2 sintered pellets and method for fabricating porous UO2 sintered pellets and electrolytic reduction using same

Patent metadata

Field	Value
Publication number	US-9558853-B2
Application number	US-201213712189-A
Country	US
Kind code	B2
Filing date	Dec 12, 2012
Priority date	Dec 13, 2011
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

A method for fabricating porous UO 2 sintered pellets to be fed into the electrolytic reduction process for the purpose of metallic nuclear fuel recovery is provided, which includes forming a powder containing U 3 O 8 by oxidizing spent nuclear fuel containing uranium dioxide (UO 2 ) (step 1 ), fabricating green pellets by compacting the powder formed in step 1 (step 2 ), fabricating UO 2+x sintered pellets by sintering the porous U 3 O 8 green pellets fabricated in step 2 at 1200 to 1600° C., in an atmospheric gas (step 3 ), and forming UO 2 sintered pellets by cooling the UO 2+x sintered pellets to room temperature, and reduction the same at 1000 to 1400° C., in a reducing atmosphere (step 4 ).

First claim

The invention claimed is:

1. A method for fabricating porous UO 2 sintered pellets to be fed into an electrolytic reduction process for the purpose of metallic nuclear fuel recovery, comprising the following steps of:
forming a powder containing U 3 O 8 by oxidizing a spent nuclear fuel containing uranium dioxide (UO 2 ) (step 1 );
fabricating U 3 O 8 green pellets by compacting the powder formed in step 1 (step 2 );
fabricating UO 2+x sintered pellets by sintering the porous U 3 O 8 green pellets fabricated in step 2 at 1200 to 1600° C., in a non-reducing atmospheric gas in a sintering step (step 3 ); and
forming UO 2 sintered pellets by cooling the UO 2+x sintered pellets in step 3 to room temperature, and reducing the same at 1000 to 1400° C., in a reducing atmosphere in a reducing step (step 4 ), the reduction of UO 2+x sintered pellets being performed independently of step 3 , such that the sintering step (step 3 ) is discontinued before the reducing step (step 4 ), the temperature of reduction (step 4 ) being controlled independently of the temperature of sintering (step 3 ), such that the UO 2 sintered pellets formed at the end of the reducing step (step 4 ) have a O/U ratio of 2.00.

2. The method as set forth in claim 1 , prior to the sintering in step 3 , further includes a step of collecting the fission products through step-wise heating the green pellets in step 2 up to the sintering temperature.

3. The method as set forth in claim 1 , wherein the oxidizing in step 1 is performed at 400 to 500° C., in an oxidizing atmosphere.

4. The method as set forth in claim 1 , wherein the fabrication of the green pellets in step 2 is performed under a compacting pressure of 100 to 500 MPa.

5. The method as set forth in claim 1 , wherein the sintering in step 3 is performed in one atmosphere selected from a group consisting of air, carbon dioxide, nitrogen, and argon.

6. The method as set forth in claim 1 , wherein the sintering in step 3 is performed for 1 to 10 hours.

7. The method as set forth in claim 1 , wherein the reducing atmosphere in step 4 is a hydrogen gas-included atmosphere.

8. The method as set forth in claim 1 , wherein the reduction in step 4 is performed for 1 to 10 hours.

9. Porous UO 2 sintered pellets fabricated according to the method as set forth in claim 1 .

10. Porous UO 2 sintered pellets as set forth in claim 9 , wherein porous UO 2 sintered pellets have 45 to 85% of the theoretical density (T.D.).

11. Porous UO 2 sintered pellets as set forth in claim 9 , wherein porous UO 2 sintered pellets have 65 to 75% of the theoretical density (T.D.).

12. A method for performing an electrolytic reduction process using the porous UO 2 sintered pellets fabricated according to the method as set forth in claim 1 .

Assignees

• Korea Atomic Energy Res
• Korea Hydro & Nuclear Power Co

Inventors

• Na Sang-Ho
• Kim Ki Hong
• Song Dae-Yong
• Shin Hee-Sung
• Kim Ho-Dong

Classifications

• G21C3/044 Primary

  Fuel elements with porous or capillary structure · CPC title

• G21C19/44 Primary

  of irradiated solid fuel · CPC title

• Y02W30/882

  Cross-Sectional Technologies · mapped topic

• G21F9/28 Primary

  Treating solids · CPC title

• G21F9/30

  Processing (separating different isotopes of the same chemical element B01D59/00) · CPC title