Patent Number: 
Section: claims

1. An assembly adapted to access a weld extending circumferentially around a core shroud of a nuclear reactor, wherein the core shroud is contained in a pressure vessel reactor, said assembly comprising:a baffle plate rail having a lower surface adapted to abut a baffle plate in a gap between the core shroud and the pressure vessel reactor;a telescoping rail slidably coupled to an upper region of the baffle plate rail, anda reciprocating rail slidably coupled to an upper region of the telescoping rail, wherein the reciprocating rail includes at least one of a weld conditioning tool, a weld inspection sensor and a weld repair device. 2. The assembly in claim 1 wherein the baffle plate rail, telescoping rail and reciprocating rail are each arched to conform to a curvature of an outer wall of the core shroud. 3. The assembly in claim 1 wherein the baffle plate rail includes at least one extendable brace having a closed position adjacent the baffle plate rail and an extended position in which the brace extends beyond the baffle plate rail. 4. The assembly in claim 3 wherein the brace is at least one panel pivotably attached to the baffle plate rail. 5. The assembly in claim 3 wherein the brace, when in the extended position, abuts a jet pump assembly when the assembly is positioned in the gap between the jet pump assembly and the core shroud. 6. The assembly in claim 3 wherein the reciprocating rail includes at least one extendable brace having a closed position adjacent the reciprocating rail and an extended position abutting an jet pump assembly. 7. The assembly in claim 1 wherein the at least one of a weld conditioning tool, a weld inspection sensor and a weld repair device, includes a brush motor and a brush rotatably driven by the brush motor, and wherein the brush movable to be aligned with the circumferential weld. 8. The assembly in claim 1 further comprising a first gear motor engaging a slidable coupling between the telescoping rail and the baffle plate rail, wherein the first gear motor drives the slidable coupling to move the telescoping rail laterally with respect to the baffle plate rail. 9. An assembly to access and work a weld extending circumferentially around a core shroud of a nuclear reactor, wherein the core shroud is contained in a pressure vessel reactor containing liquid in which the core shroud is at least partially immersed, said assembly comprising:a baffle plate rail having a lower surface adapted to abut a baffle plate in a gap between the core shroud and the pressure vessel reactor, wherein the baffle plate includes a brace having a retracted position and an extended position in which the brace abuts a jet pump assembly;a telescoping rail slidably coupled to an upper region of the baffle plate rail, wherein the telescoping rail moves across at least one half of the length of the baffle plate rail while coupled to the baffle plate rail, anda reciprocating rail slidably coupled to an upper region of the telescoping rail, wherein the reciprocating rail includes at least one of a weld conditioning tool, a weld inspection sensor and a weld repair device. 10. The assembly in claim 9 wherein the reciprocating rail moves back and forth across the telescoping rail while the brace is in the extended position. 11. The assembly in claim 9 wherein the reciprocating rail includes at least one extendable brace having a closed position adjacent the reciprocating rail and an extended position abutting the jet pump assembly while the brace of the baffle plate rail is in the retracted position. 12. The assembly in claim 9 wherein the brace of the baffle plate rail is a panel pivotably attached to the baffle plate rail. 13. The assembly in claim 9 wherein the at least one of a weld conditioning tool, a weld inspection sensor and a weld repair device, includes a brush motor and a brush rotatably driven by the brush motor, and wherein the brush is aligned with the circumferential weld. 14. The assembly in claim 9 further comprising a first gear motor engaging a slidable coupling between the telescoping rail and the baffle plate rail, wherein the first gear motor drives the slidable coupling to move the telescoping rail laterally with respect to the baffle plate rail. 15. A method to move a tool assembly around at least a portion of a core shroud of a nuclear reactor, wherein the core shroud is contained in a pressure vessel reactor, said method comprising:positioning a baffle plate rail of the tool assembly on a baffle plate in a gap between the core shroud and the pressure vessel reactor;bracing the baffle plate rail between the core shroud and a jet pump assembly;while the baffle plate rail is braced, moving a telescoping rail over a length of an upper portion of the baffle plate rail, andwhile the baffle plate rail is braced, moving a reciprocating rail over a length of an upper portion of the telescoping rail, wherein the reciprocating rail includes at least one of a weld conditioning tool, a weld inspection sensor and a weld repair device. 16. The method of claim 15 wherein the reciprocating rail moves back and forth across the upper portion of the telescoping rail while the at least one of the weld conditioning tool, the weld inspection sensor and the weld repair device are aligned with a circumferential weld on the shroud. 17. The method of claim 15 further comprising bracing the reciprocating rail between the shroud and the jet pump assembly, releasing the baffle plate rail from bracing and thereafter moving the baffle plate rail along a length of the telescoping rail. 18. The method of claim 17 further comprising bracing the baffle plate rail between another jet pump assembly and the shroud after moving the baffle plate rail along the length of the telescoping rail. 19. The method of claim 15 wherein bracing the baffle plate rail includes a plate attached to the baffle plate rail pivoting into engagement with the jet pump assembly. 20. The method of claim 15 wherein a length of the tool expands by extending the telescoping rail along the baffle plate rail, and extending the reciprocating rail along the telescoping rail.