Nuclear modular isolated reactor support system assembly and modules

A nuclear plant, comprising:

• a reactor building;
• a plurality of seismic isolators coupled to the reactor building;
• and
• a seismically isolated assembly, the seismically isolated assembly seismically isolated from the reactor building, the seismically isolated assembly including,
• a reactor enclosure system including a nuclear reactor, and
• a reactor support assembly, the reactor support assembly including,
• a cylindrical reactor support structure that is configured to structurally support the reactor enclosure system on the plurality of seismic isolators,
• a collector cylinder configured to at least partially receive the reactor enclosure system based on the reactor enclosure system being structurally supported by the cylindrical reactor support structure, such that the collector cylinder is configured to at least partially define a riser annulus between an inner cylindrical surface of the collector cylinder and an outer sidewall surface of the reactor enclosure system,
• a divider wall configured to at least partially define a downcomer annulus between an outer cylindrical surface of the divider wall and the reactor building, wherein a bottom opening of the downcomer annulus is in fluid communication with a bottom opening of the riser annulus, and
• a plurality of exhaust ducts extending through an interior of the cylindrical reactor support structure from the collector cylinder,
• wherein,
• the reactor building is configured to structurally support the reactor enclosure system on a foundation and to enclose the reactor enclosure system within an interior of the reactor building,
• an upper surface of the reactor support assembly and an upper surface of the reactor enclosure system at least partially define a floor structure of a head access area (HAA) that is enclosed above the floor structure by an upper building structure of the reactor building, the floor structure configured to move independently of the upper building structure such that the floor structure is seismically isolated in relation to the upper building structure that encloses the HAA above the floor structure, and
• the reactor support assembly further includes an HAA seal configured to establish a seal between the floor structure and the upper building structure.