Patent Number: 
Section: claims

1. A seal system for use in a nuclear reactor environment, the system comprising:a first component;a second component abutting the first component, wherein the second component includes a groove in a surface abutting the first component;a seal in the groove configured to seal against the first component in a first direction, wherein the seal includes an opening into a concavity in the seal configured to drive the seal in the first direction under relative higher pressure at the opening, wherein the groove opens only in the first direction, and wherein the first component has a continuously flat surface that directly abuts the surface of the second component and the seal in the groove so as to completely close the groove; andwherein the first and second component, when abutted, separate a downcomer having a first fluid flow from a reactor core having a second fluid flow, and wherein the first and the second fluid flows are either parallel or antiparallel to the first direction. 2. The seal system of claim 1, wherein the opening faces a second direction perpendicular to the first direction. 3. The seal system of claim 1, wherein the seal has at least one of an E-shaped and C-shaped cross-section. 4. The system of claim 1, wherein the seal is annular around an external axis in the first direction so as to extend continuously about an entire perimeter where the second component abuts the first component. 5. The system of claim 1, wherein the seal is metallic and elastic, and wherein the uncompressed seal has a height in the first direction extending out of the groove, and wherein when compressed to a height of the groove, the seal experiences elastic, and not plastic, deformation. 6. The system of claim 1, further comprising:a retainer holding the seal in the groove. 7. The system of claim 1, wherein the second component is a core shroud, and wherein the opening faces the first fluid flow. 8. A seal system for use in a nuclear reactor environment, the system comprising:a first flow divider inside a nuclear reactor;a second flow divider inside the nuclear reactor vertically above and directly joined to the first flow divider, wherein the first and second flow dividers together separate an annular downcomer containing a first coolant flow from a core area containing a second coolant flow in the nuclear reactor;a seal internally compressed between the first and second flow dividers so as to not be directly exposed to the first coolant flow or the second coolant flow; andwherein the first flow divider and the second flow divider are parts of a chimney system inside the nuclear reactor. 9. The seal system of claim 8, wherein the first flow is liquid feedwater flowing downward, and wherein the second flow is upward core flow. 10. The seal system of claim 8, wherein the first flow divider and the second flow divider directly join about a ring, and wherein the seal is an annulus compressed in the ring. 11. The seal system of claim 8, wherein the seal has at least one of a C-shaped and an E-shaped cross-section. 12. The seal system of claim 11, wherein the seal has an E-shaped cross-section with two openings facing the first flow, and wherein the first flow has a higher pressure than the second flow. 13. The seal system of claim 12, wherein the seal is annular and a flexible metallic alloy. 14. The seal system of claim 13, wherein the uncompressed seal has a height extending out of the at least one of the first and the second flow dividers, and wherein when compressed to a height of the groove, the seal experiences elastic, and not plastic, deformation. 15. The seal system of claim 8, further comprising:a bolt removably joining the first flow divider and the second flow divider; anda retainer holding the seal internal to the at least one of the first and the second flow dividers, wherein the retainer is joined to the bolt. 16. The seal system of claim 8, wherein at only one of the first and the second flow dividers includes a groove that opens only toward the other of the at least one of the first and the second flow dividers. 17. The seal system of claim 16, wherein the groove is in a surface at which the first and the second flow dividers directly abut, and wherein the seal is compressed to a height of the groove by the first and the second flow dividers directly abutting. 18. The seal system of claim 1, further comprising:a bolt removably joining the first component and the second component; anda retainer holding the seal in the groove, wherein the retainer is joined to the bolt.