Process for manufacturing a pellet of at least one metal oxide

Patent metadata

Field	Value
Publication number	US-9966156-B2
Application number	US-201515535071-A
Country	US
Kind code	B2
Filing date	Dec 17, 2015
Priority date	Dec 18, 2014
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

The present invention relates to a process for sintering a compacted powder of at least one oxide of a metal selected from an actinide and a lanthanide, this process comprising the following successive steps, carried out in a furnace and under an atmosphere comprising an inert gas, dihydrogen and water:
(a) a temperature increase from an initial temperature T I up to a hold temperature T P , (b) maintaining the temperature at the hold temperature T P , and (c) a temperature decrease from the hold temperature T P down to a final temperature T F , in which the P(H 2 )/P(H 2 O) ratio is such that:
500<P(H 2 )/P(H 2 O)≤50 000, during step (a), from T I until a first intermediate temperature T i1 between 1000° C. and T P is reached, and P(H 2 )/P(H 2 O)≤500, at least during step (c), from a second intermediate temperature T i2 between T P and 1000° C., until T F is reached.

First claim

The invention claimed is:

1. A process for sintering a compacted powder of at least one oxide of a metal M 1 selected from an actinide and a lanthanide, this process comprising the following successive steps (a) to (c), carried out in a furnace and under an atmosphere comprising an inert gas, dihydrogen and water, of:
(a) increasing the temperature from an initial temperature T I to a hold temperature T P , T P being between 1 400° C. and 1 800° C.,
(b) maintaining the temperature at the hold temperature T P for a duration between 1 h and 10 h, and
(c) decreasing the temperature from the hold temperature T P to a final temperature T F ,

wherein the ratio of the partial pressures P(H 2 )/P(H 2 O) in said atmosphere is such that:
500<P(H 2 )/P(H 2 O)≤50 000, during step (a), from T I until a first intermediate temperature T i1 between 1 000° C. and T P is reached, and
P(H 2 )/P(H 2 O)≤500, at least during step (c), from a second intermediate temperature T i2 between T P and 1 000° C., until T F is reached.

2. The process according to claim 1 , wherein the first intermediate temperature T i1 is between 1 300° C. and T P .

3. The process according to claim 1 , wherein the second intermediate temperature T i2 is between T P and 1 300° C.

4. The process according to claim 1 , wherein the ratio P(H 2 )/P(H 2 O)≤500 is implemented as soon as the first intermediate temperature T i1 is reached and maintained until T F is reached.

5. The process according to claim 1 , which further comprises, between steps (a) and (b), the following successive steps (a 1 ) to (a 3 ) of:
(a 1 ) maintaining, for a duration between 1 h and 10 h, the temperature at the hold temperature T P ,
(a 2 ) decreasing the temperature from the hold temperature T P to a third intermediate temperature T i3 ,
(a 3 ) increasing the temperature from the third intermediate temperature T i3 to the hold temperature T P ,

and wherein the ratio P(H 2 )/P(H 2 O) in said atmosphere is such that:
500<P(H 2 )/P(H 2 O)≤50 000, during steps (a), (a 1 ) and (a 2 ), and
P(H 2 )/P(H 2 O)<500, during steps (a 3 ), (b) and (c).

6. The process according to claim 5 , wherein the third intermediate temperature T i3 is between 20° C. and 500° C.

7. The process according to claim 1 , wherein T P is 1 700° C.

8. The process according to claim 1 , wherein at least one from T I and T F is room temperature.

9. The process according to claim 1 , wherein increasing the temperature in step (a) is performed at a rate between 30° C./h and 400° C./h.

10. The process according to claim 1 , wherein decreasing the temperature in step (c) is performed at a rate between 100° C./h and 900° C./h.

11. The process according to claim 1 , further comprising, after step (c), an oxidation heat treatment.

12. The process according to claim 1 , wherein the inert gas is chosen from the group consisting of argon, helium and nitrogen.

13. The process according to claim 1 , wherein the volume ratio between the inert gas and dihydrogen is between 90/10 and 98/2.

14. The process according claim 1 , wherein M 1 is an actinide.

15. The process according to claim 1 , wherein M 1 is a lanthanide.

16. The process according to claim 1 , wherein the compacted powder further comprises at least one oxide of a metal M 2 selected from Sc, Y, an actinide and a lanthanide, M 2 being different from M 1 , whereby, at the end of step (c), a mixed oxide comprising M 1 and M 2 is obtained.

17. The process according to claim 16 , wherein M 2 is an actinide.

18. A process for manufacturing a pellet of at least one oxide of a metal M 1 chosen from an actinide and a lanthanide, said process comprising the following successive steps of:
preparing a powder of said at least one oxide of metal M 1 ,
compacting the powder prepared as a pellet, and
heat treating the pellet of compacted powder by the sintering process according to claim 1 .

19. The process according to claim 14 , wherein M 1 is selected from the group consisting of U, Pu and Th.

20. The process according to claim 15 , wherein M 1 is Ce.

21. The process according to claim 17 , wherein M 2 is selected from the group consisting of U, Pu and Th.

22. The process according to claim 18 , wherein the pellet is a nuclear fuel pellet.

Assignees

• Commissariat Energie Atomique
• Areva Nc
• Orano Cycle

Inventors

• Vaudez Stéphane

Classifications

• C04B35/64

  Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F}) · CPC title

• G21C3/623

  Oxide fuels · CPC title

• C04B35/50 Primary

  based on rare-earth compounds {(non-oxide rare earth compounds C04B35/5156)} · CPC title

• C04B35/51

  based on compounds of actinides ({non-oxide actinide compounds C04B35/5158;} nuclear fuel materials G21C3/62) · CPC title

• C04B2235/6582

  Hydrogen containing atmosphere · CPC title