GB1168853A - Improvements relating to Servicing Tools for Nuclear Reactors - Google Patents

Abstract

1,168,853. Bending; breaking. FAIREY ENG. Ltd. 24 July, 1968 [25 April, 1967], No. 19094/67. Heading B3E. A parting tool for breaking a rod by repeatedly-reversed bending, for example the tie rods of fuel stringers in a nuclear reactor, comprises a pair of clasp members adapted to grip adjacent lengths of the rod, and means for angularly oscillating one clasp member relatively to the other about an axis passing transversely to the length of the rod and between the clasp members. The tool is mounted on a base 10 slidable on a fixed bed 12 located above a disposal vault for active waste the entry port 13 of which is closed by a shield plug 14. The tool frame 15 carries a front guide tube 17, a seal plug retraction cylinder 18 and a two-part articulated clasp sleeve assembly 19. The clasp assembly comprises an upper non-pivoting sleeve 21 and a lower pivoting sleeve 24 each provided with clamping jaws 31 actuated hydraulically or pneumatically by rams 32 and 33 respectively. A tie rod to be broken passes through the aligned sleeves and clamps and rests on a retractible rod stop 50 positioned over the entry port 13. The lower sleeve is oscillated by a hydraulic or pneumatic cylinder 42 mounted on a lead screw 45. In the event of failure of the cylinder 42 the sleeve may be brought to a vertical position manually or by a motor through a transmission 47. A leadscrew mechanism 60 is provided for moving the tool along the bed 12 and a manual transmission 64 is provided for emergency use. In operation, the retraction cylinder 18 is energized to withdraw the shield plug 14 into a guide sleeve 75. The tool is moved horizontally by the leadscrew 60 until the clasp sleeve assembly 19 is located above the entry port 13. With the clamps open a tie rod is lowered by a hoist (not shown) until its end rests on the stop 50. The clamps are closed and the cylinder 42 actuated to oscillate the lower clasp sleeve. On breakage of the tie rod the oscillation is stopped, the stop 50 is retracted and the lower clamp 30 opened to allow the parted lower part of the tie rod to fall into the vault. The stop 50 is advanced to cover the entry port and the upper clamp 30 is opened to allow the remainder of the tie rod to be lowered on to the stop in readiness for a further cycle of operations. The tie rod may be released from the lower clamp by a latch 80 in the event of seizure of the lower clamp cylinder 33. The front guide tube 17 is used as a bypass for a fuel tie rod on failure of the breaking tool or in an emergency. The tool is provided with limit switches connected to an indicator circuit which indicates the positions and operation of the various parts of the tool.