Vessel internals provide the structural support for the core and fuel located within the reactor vessel. It also provides for the alignment of the core with instrumentation. It serves as a shield to protect the reactor vessel from radiation damage. It is fabricated from austenitic stainless steel. It is comprised of two basic components: core support barrel assembly and upper guide structure assembly. In addition to the two assemblies, the vessel internals include a flow skirt. The flow skirt is a cylindrical structure having a large number of holes and located between the core support barrel and lower head of the reactor vessel.
The VFD drive panel takes in a fixed voltage and frequency and gives out a variable voltage and frequency to the motor. In doing so, drive gives off heat. Depending upon the drive size, the amount of heat is produced. Without proper cooling a drive shuts down on over temperature.