Patent Number: 047972475
Section: claims

1. A nuclear reactor including a vessel having a body and a removable head, a thermal insulating shield for said head, said sheild including a generally vertical frame of thermal insulation encircling said head, a plurality of panels of thermal insulation extending from said frame, and means, connected to said frame and to each said panel, for connecting each said panel pivotally near the top of said frame so that each said panel is pivotal on said frame between a closed position in which said panels extend over said head and a retracted position, the adjacent edges of said panels mating when said panels are in said closed position whereby in said closed position said panels provide substantially closed thermal insulation at least over a portion of said head and prevent removal or replacement of said head and when said panels are in said retracted position said panels are separated, and permit removal or replacement of said head, and remotely-actuable means, connected to said panels, cooperative with said pivotally-supporting means, for moving said panels between said closed position and said retracted position whereby access for removal of said head is obtainable without exposure of personnel to radioactivity. 2. The nuclear reactor of claim 1 wherein the frame is of generally polygonal transverse cross section and having a plurality of sides, a panel of the plurality of panels being connected by the pivotably-connecting means to said each side. 3. The nuclear reactor of claim 1 wherein the panel moving means includes a plurality of moving mechanisms, each mechanism being mounted between a pair of adjacent panels and being capable when actuated of moving both said panels. 4. The nuclear reactor of claim 1 wherein the moving means includes means, cooperative with the frame, for moving the frame between a lower position in which said frame shields the head thermally and an upper position in which said frame is removed from said head. 5. The nuclear reactor of claim 1 wherein the panels are generally horizontal in the closed position. 6. A nuclear reactor including a vessel having a body and a removable head, a thermal insulating shield for said head, said shield including a generally vertical frame of thermal insulation encircling said head, a plurality of panels of thermal insulation extending from said frame, and means connected to said frame and to each said panel for connecting each said panel pivotally, near the top of said frame so that each said panel is pivotal on said frame between a closed position and a retracted position, said panels mating over said head when said panels are in said closed position, whereby in said closed position, said panels provide substantially closed thermal insulation at least over a portion of said head and preclude access for removal or replacement of said head, and when said panels are in retracted position said panels are separated and afford access for removal or replacement of said head, a rod adjacent said frame, means, to be connected to said rod, for moving said rod relative to said frame between a first position and a second position, guide means connected to said frame for guiding said rod as it is moved between said first position and said second position, means, connected to said rod engageable with at least one of said panels, for moving said one panel between its closed position and its retracted position as said rod is moved between said first position and said secdon position, and means, connected to said one panel, engageable with said panel-moving means, for returning said one panel from said retracted position to said closed position when said rod is moveable from said second position to said first position. 7. The apparatus of claim 6 wherein the rod engages the frame at its lower end and extends at an angle to the frame and the guide means includes a plurality of U-shaped members extending from the frame and spaced vertically along the frame, said rod being guided by its engagement with the U-shaped members which function as cam surfaces. 8. The apparatus of claim 7 wherein the rod includes a finger at its lower end, said finger engaging the lower most U-shaped member as a stop when the rod is in the second position. 9. The apparatus of claim 6 wherein the rod at its upper end extends beyond the one panel and the panel-moving means includes a cross rod connected to the first-named rod just below the one panel and the panel-returning means includes cam means suspended from the one panel engageable by the cross rod for returning the one panel from the second position to the first position. 10. A nuclear reactor including a vessel having a body and a removable head, a thermal insulating shield for said head, said shield including a generally vertical frame of thermal insulation encircling said head, a plurality of panels of thermal insulation extending from said frame, and means connected to said frame and to each said panel for connecting each said panel pivotally, near the top of said frame so that each said panel is pivotal on said frame between a closed position and a retracted position, said panels mating over said head when said panels are in said closed position, whereby in said closed position, said panels provide substantially closed thermal insulation at least over a portion of said head and preclude access for removal or replacement of said head, and when said panels are in retracted position said panels are separated and afford access for replacement of said head, and means for moving each said panel between said closed position and said retracted position, the said moving means including an elongated member, movable generally vertically, upwardly and downwardly, extending from a point below said each panel to a point above said each panel in the closed position of said each panel, cam means, connected to said frame, cooperative with said elongated member for guiding said elongaated member in its generally vertical movement, means, connected to said elongated member, engageable with said each panel, for moving said each panel from its closed position to its retracted position on the upward generally vertical movement of said elongated member, cam means, connected to said each panel, cooperative with said panel-moving means, for returning said each panel from said retracted position to said closed position on the downward generally vertical movement of said elongated member, and remotely actuable means, to be connected to said elongated member, for moving said member generally vertically upwardly and generally vertically downwardly. 11. A nuclear reactor including a vessel having a body and a removable head, a one piece thermal insulating shield for said head, said shield including a one piece frame and a plurality of panels, each panel being connected to said frame by hinge means and being pivotal on the hinge means, between a closed position in which said panels make blocking access for removing or replacing said head and a retracted position affording access for removing or replacing said head, and means, connected to said frame, actuable to move said panels from said closed position to said retracted position. 12. The reactor of claim 11 including remotely operable means to be connected to the actuable means both, for actuating the actuable means to move said panels from the closed position to the retracted position and to raise the shield above the head. 13. The nuclear reactor of claim 11 wherein the panels are generally horizontal in the closed position.