Radiator water level, construction

The HCR s as a group have several drawbacks. The materials from which they are made require cooling to prevent melting by the heat generated as the control material captures neutrons. A reliable water supply is required, and the reactor must be shut down if the cooling supply to any rod fails. The aluminum used in the rod tips must be relatively pure to reduce the residual activity of the rods for maintenance. Materials suitable for use at higher temperatures could be used in rod construction to improve corrosion resistance but these would make rod maintenance and replacement more difficult because of the higher radiation levels involved. 

A 2-ft-thick water-cooled heavy aggregate thermal shield is placed around the reactor vessel to reduce the radiation level to approximately that of the remainder of the primary. system. The primary coolant pump access pit, located inside the containment ves.scl, is constructed of 3 ft of barytes aggregate concrete to permit pump removal after the primary cell has been filled with water and the system drained and partially decontaminated. During periods of normal operation, the temperature of the... 

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