Core Design of a Direct-Cycle, Supercritical-Pressure, Light Water Reactor with Double Tube Water Rods

Abstract

Core design of a direct-cycle, supercritical-pressure, light water reactor (SCLWR) is carried out. Double tube water rods are used for enhancing the moderation. Whole coolant flows upward in the inner tube and downward in the outer tube of the water rod, and then the fuel is cooled. The double tube water rods flatten the axial power distribution easier than the single tube water rods. Since the hot coolant from the fuel channel does not mix with the cold coolant from the water rod and keeps high temperature, the thermal efficiency is not deteriorated. Whole coolant flows through the fuel channel and the mass flow rate is high. The critical heat flux, hence, increases and the enthalpy difference between the inlet and the outlet becomes large. The core height decreases to 3.7m from the core using the single tube water rod of 5.7m. The axial power distribution was further flattened by changing the gadolinia concentration and the fuel enrichment. Clustered control rods like PWR are adopted as the primary reactivity control system. Borated water injection system is adopted as the backup system. Each system attains cold shutdown independently. The designed plant has thermal efficiency of 40.8%, gross electric power of 1,006 MW.

KEYWORDS:

• direct cycle
• supercritical pressure
• light water reactor
• reactor core design
• uranium dioxide
• water rod
• control rod
• thermal efficiency
• thermodynamics
• electric power