Patent Number: 
Section: claims

1. An apparatus comprising:an outer sheathing of a first metal;an electron generator comprising a second metal disposed within the sheathing and forming an emitter;a positive output pin extending from the emitter through the sheathing;an electron charge collector comprising a third metal disposed between the emitter and the sheathing;a negative output pin extending from the collector through the sheathing, spaced and electrically insulated from the positive output pin;a first layer of insulating material positioned between the sheathing and the collector and a second layer of insulating material positioned between the emitter and the collector;wherein the emitter is coupled to a current source, the current source configured to provide current flow to the emitter;wherein the first metal has an atomic number lower than an atomic number of the second metal; andwherein the third metal has an atomic number lower than the atomic number of the second metal. 2. The apparatus recited in claim 1 wherein the current source is a battery. 3. The apparatus recited in claim 1 wherein the current source is a generator. 4. The apparatus recited in claim 1 wherein the current source is located external to a nuclear reactor vessel comprising the apparatus. 5. The apparatus recited in claim 1 wherein the current flow provided by the current source causes the emitter to generate heat. 6. The apparatus recited in claim 1 wherein the second metal is selected from tungsten, platinum, gold, cadmium, and lead. 7. The apparatus recited in claim 1 wherein the first metal and the third metal comprise an inconel alloy or a steel alloy. 8. The apparatus recited in claim 1 wherein the layer of insulation comprises aluminum oxide or magnesium oxide. 9. The apparatus recited in claim 1 wherein the apparatus is positioned adjacent an interior wall of a core of a nuclear reactor for housing at least fuel rods and coolant for generating heat sufficient to liquefy the coolant. 10. The apparatus recited in claim 9 wherein there are a plurality of apparatuses positioned in axial alignment along the length of the core for measuring the relative power distribution in the core. 11. The apparatus recited in claim 9 wherein there are a plurality of apparatuses positioned circumferentially around the interior of the core. 12. The apparatus recited in claim 11 wherein there are a plurality of apparatuses positioned in axial alignment along the length of the core for measuring the relative power distribution in the core. 13. The apparatus recited in claim 1 wherein the apparatus is supported on at least one wall of a fuel assembly cell of a modular fuel rack. 14. The apparatus recited in claim 13 wherein each wall of the fuel assembly cells of the modular fuel rack supports one apparatus.