Patent Number: 
Section: claims

1. A nuclear-fuel sintered pellet based on oxide manufactured using an oxide to which at least one of a group including uranium (U), plutonium (Pu), gadolinium (Gd), and thorium (Th) is added, the nuclear-fuel sintered pellet comprising:a precipitate material generated due to a sintering additive during a sintering process in a microstructure of nuclear-fuel sintered pellet thereof,wherein the precipitate material is uniformly dispersed in a circumferential direction, and wherein the precipitate material forms a donut-shaped two-dimensional precipitate cluster. 2. The nuclear-fuel sintered pellet of claim 1, wherein the precipitate material is disposed along a crystal grain boundary. 3. The nuclear-fuel sintered pellet of claim 1, wherein the precipitate material has a length of 3 to 30 μm and a thickness of 1 to 10 μm. 4. The nuclear-fuel sintered pellet of claim 1, wherein an addition amount of the sintering additive is 0.5 to 10.0 wt % based on the oxide for the nuclear-fuel sintered pellet. 5. The nuclear-fuel sintered pellet of claim 1, wherein the sintering additive includes at least one of a group including copper (I) oxide (CuO), copper (II) oxide (Cu2O), chromium carbide (Cr23C6), molybdenum dioxide (MoO2), molybdenum trioxide (MoO3), molybdenum carbide (Mo2C), and molybdenum disilicide (MoSi2). 6. The nuclear-fuel sintered pellet of claim 5, wherein the sintering additive further includes titanium dioxide (TiO2). 7. The nuclear-fuel sintered pellet of claim 6, wherein a content of the titanium dioxide (TiO2) is 0.05 to 0.70 wt % based on an oxide for the nuclear-fuel sintered pellet. 8. The nuclear-fuel sintered pellet of claim 5, further comprising:a metal aluminum (Al) powder. 9. The nuclear-fuel sintered pellet of claim 8, wherein a content of the metal aluminum powder is 0.01 to 0.10 wt % based on an oxide for the nuclear-fuel sintered pellet. 10. A method of manufacturing an oxide nuclear-fuel sintered pellet in which a plate-type fine precipitate material is dispersed in a circumferential direction, the method comprising:mixing an oxide powder, including at least one of a group including uranium (U), plutonium (Pu), gadolinium (Gd), and thorium (Th), with a sintering additive powder, thus manufacturing a mixed powder (first step);manufacturing a granulated powder using a sieve after pre-compaction and crushing the mixed powder (second step);uniaxially compressing the granulated powder at 300 to 500 MPa, thus manufacturing a nuclear-fuel green pellet (third step);performing primary sintering of the manufactured nuclear-fuel green pellet in a hydrogen-containing reducing gas atmosphere at a sintering temperature of about 700 to 1100° C. (fourth step); andperforming secondary sintering in a hydrogen-containing reducing gas atmosphere at a sintering temperature of 1700 to 1800° C. successively after the primary sintering is completed,wherein the nuclear-fuel sintered pellet comprises:a precipitate material generated due to a sintering additive during a sintering process in a microstructure of nuclear-fuel sintered pellet thereof,wherein the precipitate material is uniformly dispersed in a circumferential direction, and wherein the precipitate material forms a donut-shaped two-dimensional precipitate cluster. 11. The method of claim 10, wherein, in the secondary sintering, after completion of the primary sintering, sintering is performed at a condition of 1700 to 1800° C. for 60 to 240 minutes at a heating rate of 1 to 10° C./min without cooling so that a sintering additive in a liquid state is precipitated into a plate-type fine precipitate material and is then disposed homogeneously in a circumferential direction while crystal grains of a nuclear-fuel sintered pellet based on oxide grow. 12. The method of claim 10, wherein a hydrogen-containing reducing gas contains at least one of a group including carbon dioxide, nitrogen, argon, and helium gases. 13. The method of claim 10, wherein a hydrogen-containing reducing gas contains only a hydrogen gas. 14. The method of claim 10, wherein the sintering additive powder includes at least one of a group including copper (I) oxide (CuO), copper (II) oxide (Cu2O), chromium carbide (Cr23C6), molybdenum dioxide (MoO2), molybdenum trioxide (MoO3), molybdenum carbide (Mo2C), and molybdenum disilicide (MoSi2). 15. The method of claim 14, wherein a sintering additive further includes titanium dioxide (TiO2). 16. The method of claim 15, wherein a content of the titanium dioxide (TiO2) that is added is 0.05 to 0.70 wt % based on an oxide for a nuclear-fuel sintered pellet. 17. The method of claim 15, wherein a metal aluminum (Al) powder is further added. 18. The method of claim 10, wherein in the primary sintering, heating is performed at a heating rate of 1 to 10° C./min so that sintering is performed at a condition of 300 to 1100° C. for 30 to 120 minutes, thereby maintaining a sintering additive in a liquid state. 19. The method of claim 18, wherein, when a sintering additive powder is copper (I) oxide (CuO) or copper (II) oxide (Cu2O), in the primary sintering (fourth step), a sintering temperature is 300 to 500° C. and a sintering time is 30 to 120 minutes.