Abstract: A head assembly for a reactor pressure vessel includes a removable closure head, an array of control rod drive mechanisms, a seismic support platform, a missile shield assembly and a cooling system for drawing atmospheric air across electromagnetic coil stack assemblies. The cooling system includes: a lower shroud surrounding the coil stack assemblies with an end open to the atmosphere around the CRDMs; a plurality of extending internal ducts disposed within the array of CRDMs upwardly to an upper plenum disposed above the seismic support platform and a plurality of fan assemblies disposed on the upper plenum. The missile shield is disposed within the upper plenum. The cooling system effectively cools the coil stack assemblies during fuel cycles and does not hinder access to the CRDMs during an outage. The head assembly has lift legs for transporting either the entire head assembly as an integral unit or the structure above the seismic support platform a subassembly.

Abstract: A head assembly of a reactor pressure vessel in an ice condenser plant is retrofitted to permit the assembly to be removed during a later refueling operation in reduced time and with reduced exposure to radiation by operating personnel. The portions of the ductwork ventilation system that originally provided cooling air to CRDMs are removed below the seismic support platform. The original CRDM cooling shroud that surrounds the lower portion of the CRDM assemblies is extended to the seismic support platform. A plenum is mounted on the seismic support platform and in air flow communication with interior portion of the extended CRDM cooling shroud. The plenum fits under the missile shield. Spool pieces are connected between the plenum and the portion of the ductwork adjacent to the seismic support platform.

Abstract: A head assembly of a reactor pressure vessel in an ice condenser plant is retrofitted to permit the assembly to be removed during a later refueling operation in reduced time and with reduced exposure to radiation by operating personnel. The portions of the ductwork ventilation system that originally provided cooling air to CRDMs are removed below the seismic support platform. The original CRDM cooling shroud that surrounds the lower portion of the CRDM assemblies is extended to the seismic support platform. A plenum is mounted on the seismic support platform and in air flow communication with interior portion of the extended CRDM cooling shroud. The plenum fits under the missile shield. Spool pieces are connected between the plenum and the portion of the ductwork adjacent to the seismic support platform.