Abstract: A seismic load suppressing system for a nuclear reactor that reduces the seismic input to the reactor and the internal components of the reactor including the fuel is described. The seismic load suppressing system includes, in one embodiment, a plurality of seismic isolators positioned circumferentially between the reactor pedestal and a lower pedestal and a plurality of displacement limiters coupled to a lower pedestal skirt and positioned adjacent the reactor pedestal. The seismic isolators include a plurality of alternating layers of a resilient material and steel plates bonded together. Each displacement limiter includes a cantilever beam. The beam includes a beam core and two steel plates laminated on opposing outer surfaces of the beam core. The steel plates are fabricated from carbon steel having a lower yield strength than the beam core.

Abstract: A corium protection assembly includes a perforated base grid disposed below a pressure vessel containing a nuclear reactor core and spaced vertically above a containment vessel floor to define a sump therebetween. A plurality of layers of protective blocks are disposed on the grid for protecting the containment vessel floor from the corium.

Abstract: A reactor building for enclosing a nuclear reactor includes a containment vessel having a wetwell disposed therein. The wetwell includes inner and outer walls, a floor, and a roof defining a wetwell pool and a suppression chamber disposed thereabove. The wetwell and containment vessel define a drywell surrounding the reactor. A plurality of vents are disposed in the wetwell pool in flow communication with the drywell for channeling into the wetwell pool steam released in the drywell from the reactor during a LOCA for example, for condensing the steam. A shell is disposed inside the wetwell and extends into the wetwell pool to define a dry gap devoid of wetwell water and disposed in flow communication with the suppression chamber. In a preferred embodiment, the wetwell roof is in the form of a slab disposed on spaced apart support beams which define therebetween an auxiliary chamber.

Abstract: A nuclear fuel bundle fuel transfer system includes a transfer pool containing water at a level above a reactor core. A fuel transfer machine therein includes a carriage disposed in the transfer pool and under the water for transporting fuel bundles. The carriage is selectively movable through the water in the transfer pool and individual fuel bundles are carried vertically in the carriage. In a preferred embodiment, a first movable bridge is disposed over an upper pool containing the reactor core, and a second movable bridge is disposed over a fuel storage pool, with the transfer pool being disposed therebetween. A fuel bundle may be moved by the first bridge from the reactor core and loaded into the carriage which transports the fuel bundle to the second bridge which picks up the fuel bundle and carries it to the fuel storage pool.

Abstract: A nuclear reactor system pressure vessel comprises a steel inner liner part, an intermediate insulative layer part and an outer pre-stressed concrete part encasing these parts. Use of the pre-stressed construction allows for construction of pressure vessels of larger size than heretofore, and this coupled with utilization of squatter reactor cores allows natural convective circulation in the reactor vessel of the heated water pool in the higher capacity systems currently being introduced. The reactor pressure vessel because of its suitability allows enhanced natural steam separation in the vessel and eliminates need for use of centrifugal steam separators. The outer vessel part can be a cast single piece structure or it can be an integrated concrete segment assembled structure embodying pre-stressing tendons arranged in various orientations to effect pre-stressing.

Abstract: A gravity driven cooling system pool is disposed at an elevated location with respect to the locations of nuclear fuel rods in a pressure vessel. In the event of a loss of coolant in the pressure vessel, steam pressure is initially reduced by venting the steam into the containment or a closed suppression pool containing a quantity of water under a large air space. The suppression pool condenses sufficient steam to lower the steam pressure in the pressure vessel so that water can flow by gravity from gravity driven cooling system pool to flood the fuel rods in the pressure vessel. An isolation condenser is submerged in a large supply of water elevated with respect to pressure vessel. Steam is admitted to the isolation condenser, or heat exchanger, where it is cooled by boiling the water surrounding it. This steam is vented to the atmosphere. A depressurization valve vents steam fro the pressure vessel into the containment to aid pressure reduction, and thus to aid the gravity flow of coolant.