| 摘要 |
Burn-up absorber rods are fixed to a spider in a nuclear reactor fuel element by a partly hollow stem of the top plug in the absorber rod which is expanded into one of a line of cylindro-conical bores along each spider arm(65). To remove an absorber rod, a mandrel(70) is pushed in from the rear and extrudes the top plug(56) with the rod(57). This creates a secure fixture of each absorber rod but facilitates their removal without flame cutting or shearing and without risk of damaging the brittle rod. All rods can be extruded in one operation by a suitable multi-mandrel fixture.
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