Iron-based composition for fuel element

Patent metadata

Field	Value
Publication number	US-9303295-B2
Application number	US-201313794589-A
Country	US
Kind code	B2
Filing date	Mar 11, 2013
Priority date	Dec 28, 2012
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

Disclosed embodiments include fuel assemblies, fuel element, cladding material, methods of making a fuel element, and methods of using same.

First claim

What is claimed:

1. A method of making a composition, the method comprising:
heat treating a material including an iron-based composition at a first temperature under a first condition in which at least some of the iron-based composition is transformed into an austenite phase;
cooling the material to a second temperature at a cooling rate under a second condition in which at least some of the iron-based composition is transformed into a martensite phase; and
heat treating the material at a third temperature under a third condition in which carbides are precipitated.

2. The method of claim 1 , wherein the material is at least one of cold rolled, cold drawn, and pilgered before the heat treating at the first temperature.

3. The method of claim 1 , wherein the iron-based composition includes a steel.

4. The method of claim 1 , wherein the iron-based composition includes at least one of Cr, C, Mo, Ni, Mn, V, W, Si, N, S, and P.

5. The method of claim 1 , wherein heat treating at the first temperature includes dissolving at least substantially all of carbides, if any, present in the iron-based composition.

6. The method of claim 1 , wherein the first temperature is between about 1025° C. and about 1100° C.

7. The method of claim 1 , wherein heat treating at the first temperature includes heating the material to the first temperature.

8. The method of claim 1 , wherein heat treating at the first temperature is carried out for at least 5 minutes.

9. The method of claim 1 , wherein heat treating at the first temperature is carried out for between about 5 minutes and about 120 minutes.

10. The method of claim 1 , wherein substantially all of the iron-based composition in heat treating at the first temperature is transformed into an austenite phase.

11. The method of claim 1 , wherein the second temperature is about 20° C.

12. The method of claim 1 , wherein the cooling includes cooling by at least one of air and liquid.

13. The method of claim 1 , wherein substantially all of the iron-based composition in the cooling is transformed into a martensite phase.

14. The method of claim 1 , wherein the iron-based composition at the end of cooling is substantially free of at least one of a ferrite phase and an austenite phase.

15. The method of claim 1 , wherein the third temperature is between about 650° C. and about 780° C.

16. The method of claim 1 , wherein heat treating at the third temperature includes heating the material to the third temperature.

17. The method of claim 1 , wherein heat treating at the third temperature is carried out for between about 0.5 hours to about 3 hours.

18. The method of claim 1 , wherein the third condition mitigates formation of a ferrite phase of the iron-based composition.

19. The method of claim 1 , further including cooling the material from the third temperature to a fourth temperature lower than the third temperature.

20. The method of claim 1 , wherein heat treating at the third temperature is carried out in a vertical furnace.

21. The method of claim 1 , wherein at least some of the carbides are thermally stable at a temperature of greater than or equal to about 650° C.

22. The method of claim 1 , wherein at least some of the carbides have a size of less than or equal to about 1 micron.

23. The method of claim 1 , wherein at least some of the carbides are homogeneously distributed within the martensite phase.

24. The method of claim 1 , wherein the third temperature is lower than the first temperature.

25. A method of making a composition, the method comprising:
subjecting a material to at least one of cold drawing, cold rolling, and pilgering;
heat treating the material including an iron-based composition at a first temperature under a first condition in which at least some of the iron-based composition is transformed into an austenite phase;
cooling the material to a second temperature at a cooling rate under a second condition in which at least some of the iron-based composition is transformed into a martensite phase; and
heat treating the material at a third temperature under a third condition, in which carbides are precipitated.

26. The method of claim 25 , further including extruding an ingot including the iron-based composition.

27. The method of claim 25 , where subjecting includes intermediate annealing the material.

28. The method of claim 25 , where subjecting includes intermediate annealing the material at a temperature below a transformation temperature from a ferrite phase to an austenite phase.

29. The method of claim 25 , further including forming an ingot including the iron-based composition before the subjecting, wherein the forming includes at least one process chosen from cold cathode induction melting, vacuum induction melting, vacuum arc re-melting, and electro-slag remelting.

30. The method of claim 25 , further including forming an ingot including the iron-based composition and purifying the ingot before subjecting.

31. The method of claim 25 , wherein subjecting further includes reducing a thickness of the material by at least 15%.

32. The method of claim 25 , wherein the first condition mitigates formation of a delta-ferrite phase of the iron-based composition.

33. The method of claim 25 , further including cooling the material from the third temperature to a fourth temperature lower than the third temperature.

34. The method of claim 25 , further including cooling the material from the third temperature to a fourth temperature that is about 20° C.

35. The method of claim 25 , wherein the composition is a part of a fuel element, and the third temperatures is at about 700° C.

36. The method of claim 25 , wherein the composition is a part of a fuel duct, and the third temperatures is at about 650° C.

37. The method of claim 25 , wherein the third temperature is lower than the first temperature.

38. The method of claim 25 , wherein the second temperature is about 20° C.

39. The method of claim 25 , wherein the iron-based composition includes a steel.

40. The method of claim 25 , wherein the iron-based composition includes at least one of Cr, C, Mo, Ni, Mn, V, W, Si, N, S, and P.

41. The method of claim 1 , further comprising controlling the weight percent of N in the iron-based composition to mitigate formation of delta-ferrite phase of the iron-based composition.

42. The method of claim 41 , further comprising introducing and controlling the weight percent of N in the iron-based composition to be between about 0.01 weight percent and about 0.04 weight percent.

43. The method of claim 42 , wherein the iron-based composition comprises:
(Fe) a (Cr) b (M) c ;
wherein
a, b, and c are each a number greater than zero representing a weight percentage;
M is at least one transition metal element;
b is between 11 and 12;
c is between about 0.25 and about 0.9; and
the composition further includes at least N at between about 0.01 weight percent and about 0.04 weight percent.

44. The method of claim 43 , wherein the iron-based composition further comprises:
Cr at between about 10

Assignees

• Hackett Micah
• Klueh Ronald
• Terrapower Llc

Inventors

• Hackett Micah
• Klueh Ronald

Classifications

• Y02E30/30

  Nuclear fission reactors · CPC title

• C21D6/02 Primary

  Hardening by precipitation · CPC title

• C22C38/18

  containing chromium · CPC title

• C22C38/46

  with vanadium · CPC title

• C21D9/14

  wear-resistant or pressure-resistant pipes · CPC title