Patent Number: 054127009
Section: description

DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2, the barrier plate 1 has a plurality of penetrations 15, and each driveline penetration is sealed with an elastomer flapper seal 4. The closure head 3 is a 28 inch thick solid plate or fabricated weldment of sufficient characteristics having penetrations for the control rod 9 and shutdown drive mechanisms 10. The closure head 3 and barrier plate 1 combined to form a secondary seal boundary 6. A primary boundary 6a is formed by the barrier plate 1 and the reactor vessel 2. All of the pressure load which is applied to the barrier plate 1 from the closure head 3 is transferred through compression posts 7 at every fuel tube 11 located at the bottom of the closure head 3. The load is then carried back to the reactor vessel 2 through the closure studs 8. All of the in-core reactor instrumentation 12 and gadolinium injection piping 13 are permanently affixed to the barrier plate 1. The instrumentation cables 20 are attached to a cable rack 14 suspended from a refueling guard plate 15a that is attached to the top of the barrier plate 1. To refuel the reactor, the external structure 26 is raised by a series of screw jacks 24. The control position extension tubes are disengaged from the barrier plate 1. An elastomer bellows seal 5 exists to insure a closed envelope between the closure head 3 and the barrier plate 1. This permits containment of heavy water evaporation which feeds directly into the cleanup system without contamination of the fuel cell. The area between the barrier plate 1 and the closure head 3 is exhausted removing all contaminated gases trapped between the primary and secondary boundaries. The external structure 26 and control mechanism 10 are then removed to allow access for refueling. During refueling instrumentation plugs 16 are removed and the fuel assembly 17 is replaced. None of the instrumentation cable 20 is disturbed during refueling. When a instrumentation closure plug 16 is removed from the top of a flow tube 11, the instrumentation in that plug is automatically disconnected at the connector 23 mounted on the guard plate 22. As the fuel assembly 17 is removed a seal may be placed over the barrier plate penetration 15 preventing heavy water evaporation while allowing the replacement of the nuclear fuel. The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching.