Patent Number: 
Section: claims

1. A system for delivering and retrieving irradiation targets through a nuclear reactor, the system comprising:a loading/offloading system providing irradiation targets, wherein the loading/offloading system is outside of an access barrier of the nuclear reactor;a penetration pathway extending completely through the access barrier and connecting the loading/offloading system to one of a plurality of instrumentation tubes outside the nuclear reactor, wherein the penetration pathway is traversable by the irradiation targets to the instrumentation tube;a retention mechanism including a mechanical hold inside the access barrier and coupled to the penetration pathway at a flange of the instrumentation tube immediately outside the reactor, wherein the mechanical hold is configured to block access to or from the instrumentation tube to hold the irradiation targets within the instrumentation tube;a plurality of the irradiation targets, wherein the irradiation targets and the mechanical hold are sized to prevent movement of the irradiation targets out of the instrumentation tube past the mechanical hold when the penetration pathway is evacuated; anda drive positioned outside the access barrier, wherein the drive includes a plunger configured to extend through the access barrier in the penetration pathway and past the mechanical hold. 2. The system of claim 1, wherein the mechanical hold is a restriction fork having at least two prongs that extend around opposite sides of the penetration pathway. 3. The system of claim 2, wherein the prongs of the restriction fork are spaced apart less than a width of the irradiation targets, and wherein the prongs include matching and facing surface divots spaced apart greater than a width of the irradiation targets. 4. The system of claim 3, wherein the restriction fork blocks passage of the irradiation targets through the penetration pathway with the prongs, and wherein the restriction fork allows passage of the irradiation targets through the penetration pathway when moved such that the surface divots align with the penetration pathway. 5. The system of claim 3, wherein the prongs of the restriction fork are spaced apart more than a width of the plunger driving the irradiation targets. 6. The system of claim 1, wherein the retention mechanism further includes at least one motor connected to the mechanical hold, wherein the motor drives the mechanical hold to block or unblock passage area within the penetration pathway. 7. The system of claim 1, wherein the retention mechanism includes a position detector configured to detect a position of the irradiation targets in the penetration pathway. 8. The system of claim 7, wherein the position detector is at least one reed switch. 9. The system of claim 8,wherein the plunger is a magnetized plunger having a width smaller than the irradiation targets that passes through the retention mechanism. 10. The system of claim 9, wherein the magnetized plunger includes a discreet magnet detectable by the reed switch, and wherein the discreet magnet is positioned in the plunger at a location corresponding to full insertion of the irradiation targets in the instrumentation tube. 11. The system of claim 10, wherein the reed switches are positioned to trip the retention mechanism when the magnet is detected at the location, and wherein the reed switches are configured to notify the drive system based on an approach of the magnet. 12. The system of claim 9, wherein the drive system is outside the access barrier except for the plunger that is configured to extend to the instrumentation tube inside the access barrier. 13. The system of claim 1, wherein the retention assembly includes a casing directly attached to the flange of the instrumentation tube. 14. The system of claim 13, wherein the casing is configured to be sealed and allow airflow only into the penetration pathway. 15. The system of claim 1, wherein the system includes a plurality of the penetration pathways connecting the loading/offloading system to a plurality of the instrumentation tubes, and a plurality of the retention mechanisms each coupled to one of the penetration pathways. 16. The system of claim 1, wherein the nuclear reactor is a commercial nuclear reactor that generates heat that is converted to electricity during operation, wherein the access barrier is a containment building surrounding the nuclear reactor in an air-tight manner during operation, and wherein the loading/offloading system is accessible during operation. 17. The system of claim 1, wherein the penetration pathway is tubing completely sealed from an interior volume inside the access barrier such that no matter can move through the system from the interior volume outside the access barrier.