A nuclear fuel composition includes a nuclear fissile material and a neutron-absorption material that adjoins the nuclear fissile material. The nuclear fuel composition may be used in a nuclear reactor, such as a thermal reactor.
1. A nuclear fuel composition comprising:
a nuclear fissile material; and
a neutron-absorption material adjoining the nuclear fissile material, the neutron-absorption material including 25 wt %-75 wt % samarium as a partial substitute for a remainder amount of a rare earth element to limit destroying a negative temperature coefficient of reactivity of the nuclear fissile material by the rare earth element, wherein the neutron-absorption material comprises ≦0.5 wt % of a combined weight of the nuclear fissile material and the neutron-absorption material.
2. The nuclear fuel composition as recited in claim 1 , wherein the rare earth element is gadolinium.
3. The nuclear fuel composition as recited in claim 1 , wherein the neutron-absorption material includes 30 wt % -40 wt % of the samarium.
4. The nuclear fuel composition as recited in claim 1 , wherein the neutron-absorption material includes 35 wt % -38 wt % of the samarium.
5. The nuclear fuel composition as recited in claim 1 , wherein the neutron-absorption material comprises ≦0.1 wt % of the combined weight.
6. The nuclear fuel composition as recited in claim 1 , wherein the neutron-absorption material comprises ≦0.05 wt % of the combined weight.
7. The nuclear fuel composition as recited in claim 1 , wherein the neutron-absorption material is dispersed within the nuclear fissile material.
8. The nuclear fuel composition as recited in claim 1 , wherein the neutron-absorption material is a coating disposed on pellets of the nuclear fissile material.
9. The nuclear fuel composition as recited in claim 1 , wherein the nuclear fissile material comprises uranium-zirconium-hydride (UZrH x ).
10. The nuclear fuel composition as recited in claim 1 , wherein the samarium has a neutron-absorption energy peak (cross-section) that at least partially overlaps a thermal energy range of the neutrons from the nuclear fissile material.
11. A nuclear reactor comprising:
a nuclear fissile material; and
a neutron-absorption material adjoining the nuclear fissile material, the neutron-absorption material including 25 wt % -75 wt % samarium as a partial substitute for a remainder amount of a rare earth element to limit destroying a negative temperature coefficient of reactivity of the nuclear fissile material by the rare earth element, wherein the neutron-absorption material comprises ≦0.5 wt % of a combined weight of the nuclear fissile material and the neutron-absorption material.
12. The nuclear reactor as recited in claim 11 , wherein the neutron-absorption material is dispersed within the nuclear fissile material.
13. The nuclear reactor as recited in claim 11 , wherein the neutron-absorption material is a coating disposed on pellets of the nuclear fissile material.
14. The nuclear reactor as recited in claim 11 , further comprising a hollow cladding containing the nuclear fissile material, and the neutron-absorption material is a coating disposed on an inside surface of the hollow cladding.
15. The nuclear reactor as recited in 11 , wherein the rare earth element is gadolinium.
16. The nuclear reactor as recited in claim 11 , wherein the neutron-absorption material includes 30 wt % -40 wt % of the samarium.
17. A method of rendering a nuclear fuel inherently subcritical, comprising:
forming nuclear fuel from a nuclear fissile material and a neutron-absorption material adjoining the nuclear fissile material, and the neutron-absorption material includes 25 wt % -75 wt % samarium as a partial substitute for a remainder amount of a rare earth element to limit destroying a negative temperature coefficient of reactivity of the nuclear fissile material by the rare earth element, wherein the neutron-absorption material comprises ≦0.5 wt % of a combined weight of the nuclear fissile material and the neutron-absorption material, and the neutron-absorption material has a neutron absorption energy range that overlaps a thermal energy range of neutrons from the nuclear fissile material to thereby render the nuclear fuel inherently subcritical.
18. The method as recited in claim 17 , including dispersing the neutron-absorption material within the nuclear fissile material.
19. The method as recited in claim 17 , including depositing the neutron-absorption material as a coating.
20. The method as recited in claim 17 , wherein the rare earth element is gadolinium.
21. The method as recited in claim 17 , wherein the neutron-absorption material includes 30 wt % -40 wt % of the samarium.