| 摘要 |
In a brain irradiating system a large number of Cobalt 60 radiation sources are carried in ports in a heavy primary shield. After the normal ten year useful life of such radiation sources, they are often difficult to remove because due to corrosion, etc, the aluminum source holders become fused in their ports. The apparatus herein includes a hollow collet which grasps the head of the source holder surrounded by and, preferably, splined to a mechanical puller which securely holds the collet around the source holder cap. Liquid nitrogen is caused to flow into the hollow collet and against the cap of the source holder, causing the aluminum source holder to shrink more than the surrounding steel of the primary shield. The source holder and the Cobalt 60 source may then be either pulled out or, if threadedly engaged with the primary shield, turned out of its port. A second embodiment used where the above system fails to remove the source, involves members grasping the cap of the source holder, holding it centered, and using a hollow core drill, drilling the source holder out and away from its port while securely capturing the cobalt 60 source capsule within the hollow core drill bit. Following either of the above procedures, the source holder and the cobalt 60 capsule are deposited in a suitable shielded container.
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