Patent Number: 
Section: claims

1. A clamp for sealing a slip joint formed by a juncture of a diffuser and inlet mixer in a nuclear reactor, the clamp comprising:a plurality of moveable clamp arms shaped to seat on a top end of the diffuser and against an outer surface of the inlet mixer;a joint moveably connecting at least two of the clamp arms to permit movement of the two clamp arms around the inlet mixer; anda lateral drive in one of the clamp arms, wherein the lateral drive extends in a transverse direction against the inlet mixer to bias the inlet mixer against an opposite one of the clamp arms, and wherein the lateral drive is positioned in the clamp arm to directly contact and bias only the inlet mixer in the slip joint. 2. The clamp of claim 1, wherein the plurality of moveable clamp arms are two annular halves that join to form a continuous annulus around an entire upper and inner perimeter of the diffuser. 3. The clamp of claim 2, wherein the joint is a pin allowing rotation of the two annular halves with respect to each other about a single axis with no other relative movement. 4. The clamp of claim 1, further comprising:a bolt between the two clamp arms configured to prevent the movement of the two clamp arms around the inlet mixer. 5. The clamp of claim 1, further comprising:an axial mount on one of the clamp arms, wherein the axial mount is configured to secure to only an exterior of the diffuser so as to prevent relative movement between the one clamp arm and the diffuser. 6. The clamp of claim 5, wherein the axial mount is a guide ear clamp shaped to clamp against an axial bottom end of a guide ear of the diffuser. 7. The clamp of claim 6, further comprising:a plurality of the axial mounts sufficient to clamp to each guide ear of the diffuser. 8. The clamp of claim 1, wherein the lateral drive includes a leaf spring captured in the one clamp arm. 9. The clamp of claim 8, wherein the leaf spring has a length in the clamp arm so as to extend at least 12 percent of a perimeter of the inlet mixer, and wherein the leaf spring has a thickness and spring constant to provide 750 pounds-force when compressed by an inch in the transverse direction. 10. The clamp of claim 8, wherein the lateral drive further includes a bolt connected to a wedge seating against the leaf spring in the one clamp arm, and wherein axial movement of the bolt causes transverse compression of the leaf spring via the wedge. 11. A clamp for sealing a slip joint formed by a juncture of a diffuser and inlet mixer in a nuclear reactor, the clamp comprising:at least two opposite clamp arms shaped to fit inside of the diffuser and against the inlet mixer in the slip joint and fill the slip joint completely; anda spring in one of the clamp arms configured to bias the inlet mixer in a transverse direction against at least one of the clamp arms without transversely loading the diffuser, and wherein the clamp in its entirety seats around only a single slip joint. 12. The clamp of claim 11, wherein the two opposite clamp arms are semi-circular and join to create a continuous annulus that fills the slip joint, the clamp further comprising:a bolt rigidly connecting the two opposite clamp arms, wherein the bolt may be loosened to allow movement of the clamp arms relative to each other. 13. The clamp of claim 12, further comprising:a driving bolt on a top of the clamp, wherein the driving bolt biases the spring in the transverse direction when rotated. 14. The clamp of claim 11, wherein the leaf spring is positioned in the clamp arm to directly contact and bias only the inlet mixer in the slip joint. 15. A clamp for sealing a slip joint formed by a juncture of a diffuser and inlet mixer in a nuclear reactor, the clamp comprising:a plurality of moveable clamp arms shaped to seat on a top end of the diffuser and against an outer surface of the inlet mixer;a joint moveably connecting at least two of the clamp arms to permit movement of the two clamp arms around the inlet mixer; anda lateral drive in one of the clamp arms, wherein the lateral drive extends in a transverse direction against the inlet mixer to bias the inlet mixer against an opposite one of the clamp arms, and wherein the clamp in its entirety seats around only a single slip joint.