Patent Number: 039649679
Section: claims

1. In a fuel element for a nuclear reactor comprising a substantially nonmagnetic fuel tube, an end cap closing one end of said fuel tube, a multiplicity of stacked fuel pellets disposed within said tube and spaced from said end cap to form a plenum, the improvement comprising a substantially nonmagnetic sealed capsule fitting within said plenum with one end adjacent said end cap and containing an isotopic mixture of gases, said capsule having at said one end a thin, rupturable diaphragm spaced inwardly from said end cap of said fuel tube, and a ferromagnetic punch having a sharp-pointed penetrator on at least one end, freely slidably movable longitudinally within said capsule, said punch having a length much less than that of said capsule and said penetrator being on the end of said punch pointed toward said diaphragm whereby said punch can be driven against said rupturable diaphragm in response to an external magnetic field induced around said fuel tube so that said rupturable diaphragm is breached by said penetrator and said isotopic mixture of gases is released from said sealed capsule into said fuel element. 2. A device as defined in claim 1 wherein said fuel tube comprises type 316 stainless steel, said capsule comprises type 316 stainless steel and said ferromagnetic punch comprises type 410 stainless steel.