Improved single pass core design for high temperature Super LWR

摘要

Core design of a supercritical-pressure light water cooled and moderated reactor (Super LWR) with single flow pass is carried out for achieving high outlet coolant temperature 500 ℃ and simplifying upper core structure. Both the coolant in water rod and fuel channel flows up and is mixed at the upper plenum. The structure inside pressure vessel is simplified as a PWR by eliminating upper core moderator distribution/guide tubes applied in previous two pass core. The fuel assemblies loaded at peripheral core region are divided into four flow zones by using separation plates to adjust flow to the power for increasing average outlet temperature. The shuffling scheme is carried out separately for inner and peripheral core assemblies. Axial fuel enrichment is split into four segments to control the axial power peaking due to relatively large axial water density variation. Five fuel batches are adopted to increase the discharge burn-up. The equilibrium core is analyzed by employing neutronic/thermal-hydraulic coupled calculation. The numerical results show that all the design criteria are fulfilled by the maximum cladding surface temperature of 656 ℃ with 500 ℃ average core outlet temperature, maximum linear heat generation rate of 37.4 kW/m and positive water density as well as shutdown margin of 1.45%dk/k.