System and method for annealing nuclear fission reactor materials

1. A method of treating at least a portion of at least one component of a reactor core of a nuclear fission reactor, the method comprising:

in a reactor core of a nuclear fission reactor, elevating, from an operating temperature range of the nuclear fission reactor to an annealing temperature range of at least one selected component of the reactor core, a temperature of a region that includes the at least one selected component of the reactor core for a time period sufficient to produce annealing of at least a portion of the at least one selected component without removing the at least one selected component from the reactor core by adjusting operational parameters of the nuclear fission reactor to establish operating conditions of the region of the nuclear fission reactor containing the at least one selected component within the determined annealing temperature range for a period of time selected to produce annealing of at least the portion of the at least one selected component;

stopping elevating, from the operating temperature range of the nuclear fission reactor to the annealing temperature range of the at least one selected component of the reactor core, a temperature of the region that includes the at least one selected component of the reactor core; and

post-anneal treating at least the portion of the at least one selected component by lowering temperature from the annealing temperature range to a quenching temperature range.

2. The method of claim 1 , wherein the at least one selected component includes a reactor core component chosen from a nuclear fission fuel assembly, a reactor core cooling component, and a reactor core structural member.

3. The method of claim 2 , wherein the at least one component includes at least one nuclear fission fuel assembly component chosen from cladding, a cooling component, a structural member, a thermally conductive member, and nuclear fission fuel material.

4. The method of claim 1 , wherein the at least one selected component includes a metallic component.

5. The method of claim 4 , wherein metal of the metallic component includes at least one metal chosen from steel, refractory metal, a refractory metal alloy, a non-ferrous metal, and a non-ferrous metal alloy.

6. The method of claim 1 , wherein elevating the temperature to perform annealing is performed in-place.

7. The method of claim 1 , further comprising moving the at least one selected component to a location within the reactor core after elevating the temperature to perform annealing.

8. The method of claim 7 , further comprising re-orienting a nuclear fission fuel assembly.

9. The method of claim 1 , further comprising moving the at least one selected component from an in-place location after elevating the temperature to perform annealing.

10. The method of claim 1 , wherein adjusting operational parameters includes providing heat from an external heat source.

11. The method of claim 10 , wherein the external heat source includes at least one source of residual heat.

12. The method of claim 11 , wherein the residual heat includes decay heat.

13. The method of claim 10 , wherein the external heat source includes a heating fluid.

14. The method of claim 1 , wherein adjusting operational parameters includes:

providing coolant to the reactor core at a coolant flow rate;

substantially maintaining the coolant flow rate; and

reducing an amount of heat transferred from the coolant.

15. The method of claim 1 , wherein adjusting operational parameters includes:

providing coolant to the reactor core at a coolant flow rate;

substantially maintaining the coolant flow rate; and

reducing an amount of heat transferred to the coolant.

16. The method of claim 1 , wherein adjusting operational parameters includes:

providing coolant to the reactor core at a coolant flow rate; and

lowering the coolant flow rate into the region of the nuclear fission reactor containing the at least one metallic component.

17. The method of claim 1 , wherein adjusting operational parameters includes:

providing coolant to the reactor core at a coolant flow rate; and

reversing direction of coolant flow into the region of the nuclear fission reactor containing the at least one metallic component.

18. The method of claim 1 , wherein adjusting operational parameters includes:

providing coolant to the reactor core at a coolant flow rate; and

raising temperature of coolant entering the region of the nuclear fission reactor containing the at least one selected component.

19. The method of claim 1 , wherein adjusting operational parameters includes replacing at least a portion of a first coolant having first heat transfer characteristics with second coolant having second heat transfer characteristics.

20. The method of claim 1 , wherein adjusting operational parameters includes raising pressure in the region of the nuclear fission reactor containing the at least one selected component.

21. The method of claim 1 , wherein adjusting operational parameters includes lowering pressure in the region of the nuclear fission reactor containing the at least one selected component.

22. The method of claim 1 , further comprising determining when the at least one selected component is to be annealed by testing materials that are indicative of the at least one selected component.

23. The method of claim 22 , wherein testing materials that are indicative of the at least one selected component includes testing at least a portion of the at least one selected component.

24. The method of claim 22 , wherein testing materials that are indicative of the at least one selected component includes testing for changes in material properties indicative of radiation damage.

25. The method of claim 24 , wherein the material properties indicative of radiation damage include at least one material property chosen from electrical resistivity, physical dimensions, displacement response to physical stress, response to stimulus, speed of sound within material, ductile-to-brittle transition temperature, and radiation emission.

26. The method of claim 1 , wherein the region containing the at least one selected component is less than all of a reactor core of the nuclear fission reactor.

27. The method of claim 1 , wherein the region containing the at least one selected component is substantially all of a reactor core of the nuclear fission reactor.

28. The method of claim 1 , further comprising:

during elevating the temperature, testing material properties of at least a portion of the at least one selected component; and

wherein elevating the temperature is stopped responsive to testing material properties of at least a portion of the at least one selected component.

29. The method of claim 1 , further comprising post-anneal treating at least the portion of the at least one selected component further by raising temperature from the quenching temperature range to a tempering temperature range.

30. The method of claim 1 , wherein elevating the temperature is performed after commencement of transition of reactivity condition of at least a portion of the nuclear fission reactor from a first state to a second state.

31. The method of claim 30 , wherein:

the first state includes power range operation; and

the second state includes a shut-down state.