Thermal hydraulic design of a hydride-fueled inverted PWR core

An inverted PWR core design utilizing U(45%, w/o)ZrH1.6 fuel (here referred to as U–ZrH1.6) is proposed and its thermal hydraulic performance is compared to that of a standard rod bundle core design also fueled with U–ZrH1.6. The inverted design features circular cooling channels surrounded by prisms of fuel. Hence the relative position of coolant and fuel is inverted with respect to the standard rod bundle design. Inverted core designs with and without twisted tape inserts, used to enhance critical heat flux, were analyzed. It was found that higher power and longer cycle length can be concurrently achieved by the inverted core with twisted tape relative to the optimal standard core, provided that higher core pressure drop can be accommodated. The optimal power of the inverted design with twisted tape is 6869 MWt, which is 135% of the optimally powered standard design (5080 MWt—determined herein). Uncertainties in this design regarding fuel and clad dimensions needed to accommodate mechanical loads and fuel swelling are presented. If mechanical and neutronic feasibility of these designs can be confirmed, these thermal assessments imply significant economic advantages for inverted core designs.