Patent Number: 054426685
Section: claims

1. A fuel channel for a nuclear reactor comprising: a solid fuel matrix having a plurality of coolant holes extending longitudinally therethrough and receptive of light water coolant, a pressure tube surrounding the fuel matrix and a calandria tube surrounding the pressure tube and forming a gap therebetween. 2. The fuel channel according to claim 1, further comprising a thermal switch in the gap between the pressure tube and the calandria tube. 3. The fuel channel according to claim 2, wherein the thermal switch comprises axial fins alternately attached to an inner surface of the calandria tube and an outer surface of the pressure tube. 4. The fuel channel according to claim 2, further comprising a moderator tube surrounding the calandria tube and forming a moderator channel therebetween receptive of moderator fluid. 5. The fuel channel according to claim 1, wherein the fuel matrix has coated particle fuel dispersed therein and wherein the coolant holes have a protective coating on the walls thereof. 6. In a nuclear reactor having a containment vessel and means forming a calandria space having a plurality of fuel channels therein, the improvement comprising means forming a gas-filled chamber surrounding the calandria space and a solid reflector in the chamber surrounding the calandria space. 7. The nuclear reactor defined in claim 6 further comprising a light water pool arranged outside the chamber in readiness for flooding the calandria space as an emergency coolant. 8. The nuclear reactor defined in claim 7, wherein the light water pool surrounds the chamber. 9. The nuclear reactor according to claim 7, further comprising means forming a gas lock in the calandria space to prevent the light water from entering the calandria space. 10. The nuclear reactor according to claim 9, wherein the means forming the gas lock comprises self-actuating means for releasing the gas pressure in the gas lock to flood the calandria space. 11. The nuclear reactor according to claim 10, wherein the self-activating means comprises a valve responsive to a drop or an increase in system pressure. 12. The nuclear reactor according to claim 6, wherein each fuel channel comprises a solid fuel matrix having a plurality of coolant holes extending longitudinally therethrough and receptive of light water, a pressure tube surrounding the fuel matrix and a calandria tube surrounding the pressure and forming a gap therebetween. 13. The nuclear reactor according to claim 12, further comprising a thermal switch in the gap between the pressure tube and the calandria tube. 14. The nuclear reactor according to claim 13, wherein the thermal switch comprises axial fins alternately attached to an inner surface of the calandria tube and an outer surface of the pressure tube. 15. The nuclear reactor according to claim 13, further comprising a moderator tube surrounding the calandria tube and forming a moderator channel therebetween receptive of light water. 16. A fuel channel for a nuclear reactor according to claim 9, wherein a solid fuel matrix having a plurality of coolant holes extending longitudinally therethrough and receptive of light water coolant, a pressure tube surrounding the fuel matrix and a calandria tube surrounding the pressure tube and forming a gap therebetween. 17. The nuclear reactor according to claim 16, wherein the fuel matrix has coated particle fuel dispersed therein and wherein the coolant holes have a protective coating on the walls thereof.