Patent Number: 
Section: claims

1. An in-core electronics assembly including a solid state vacuum micro-electronic device comprising:a cathode element;an anode element;a grid disposed between the cathode and the anode;an in-core instrument assembly;a means within the in-core instrument assembly for establishing a voltage bias between the grid and ground;a voltage source for establishing a voltage bias between the anode element and ground;a housing for sealably enclosing the cathode, the anode and the grid; anda heater disposed within the housing proximate or as part of the cathode for heating the cathode,wherein the heater comprises fissile material for production of thermal energy to power the vacuum micro-electronic device. 2. The in-core electronics assembly of claim 1, wherein the cathode element is wrapped around the fissile material. 3. The in-core electronics assembly of claim 1, wherein the cathode element extends through the fissile material. 4. The in-core electronics assembly of claim 1, wherein the dimensions of the fissile material is not larger than 0.1 inch in height and 0.260 inch in diameter. 5. The in-core electronics assembly of claim 1, wherein the fissile material is uranium dioxide less than 5 w/o. 6. The in-core electronics assembly of claim 1, wherein the voltage source is responsive to irradiation within a reactor core to provide the voltage. 7. The in-core electronics assembly of claim 6, wherein the voltage source is a self-powered in-core radiation detector. 8. The in-core electronics assembly of claim 7, wherein the solid state vacuum micro-electronic device powers a wireless transmitter. 9. The in-core electronics assembly of claim 1, wherein the solid state vacuum micro-electronic device is configured to attach to a top nozzle of a nuclear fuel assembly. 10. The in-core electronics assembly of claim 1, wherein the in-core electronics assembly includes one or more sensors having signal outputs which are electrically communicated to the grid. 11. A solid state vacuum micro-electronic device comprising:a cathode element;an anode element;a grid disposed between the cathode and the anode;an in-core instrument assembly;a means within the in-core instrument assembly for establishing a voltage bias between the grid and ground;a voltage source for establishing a voltage bias between the anode element and ground;a housing for sealably enclosing the cathode, the anode and the grid; anda heater disposed within the housing proximate or as part of the cathode for heating the cathode,wherein the heater comprises fissile material for production of thermal energy to power the vacuum micro-electronic device. 12. The solid state vacuum micro-electronic device of claim 11, wherein the cathode element is wrapped around the fissile material. 13. The solid state vacuum micro-electronic device of claim 11, wherein the cathode element extends through the fissile material. 14. The solid state vacuum micro-electronic device of claim 11, wherein the dimensions of the fissile material is not larger than 0.1 inch in height and 0.260 inch in diameter. 15. The solid state vacuum micro-electronic device of claim 11, wherein the fissile material is uranium dioxide less than 5 w/o. 16. A nuclear fuel assembly comprising:a top nozzle;a bottom nozzle;a plurality of elongated thimbles extending between and attached to the top nozzle and the bottom nozzle; anda plurality of elongated nuclear fuel elements laterally supported in spaced relationship between the top nozzle and the bottom nozzle;the nuclear fuel assembly further including a solid state vacuum micro-electronics device comprising:a cathode element;an anode element;a grid disposed between the cathode and the anode;an in-core instrument assembly;a means within the in-core instrument assembly for establishing a voltage bias between the grid and ground;a voltage source for establishing a voltage bias between the anode element and ground;a housing for sealably enclosing the cathode, the anode and the grid; anda heater disposed within the housing proximate or as part of the cathode for heating the cathode,wherein the heater comprises fissile material for production of thermal energy to power the vacuum micro-electronic device. 17. The nuclear fuel assembly of claim 16, wherein the cathode element is wrapped around the fissile material. 18. The nuclear fuel assembly of claim 16, wherein the cathode element extends through the fissile material. 19. The nuclear fuel assembly of claim 16, wherein the dimensions of the fissile material is not larger than 0.1 inch in height and 0.260 inch in diameter. 20. The nuclear fuel assembly of claim 16, wherein the fissile material is uranium dioxide less than 5 w/o.