Concept design of supercritical water cooled reactor core with double-row-rod assemblies

A new pressure-vessel type supercritical water cooled reactor (SCWR) core concept was proposed by combining merits of several SCWR core designs in the world. This core design employs a new type of closed assembly with double-row fuel rods in square geometry and a three-batch low-leakage refueling scheme. The assembly consists of two rows of fuel rods and a moderator rod, which causes the moderation more uniform. The three-batch low leakage refueling scheme obviously increases the cycle length and reduces the neutron fluence on the pressure vessel. Three-dimensional neutronics/thermohydraulics coupling calculation shows that the maximum cladding surface temperature (MCST) is 684°C, the cycle life is 300 effective full power days and the power distribution is flat. Then the more conservative sub-channel analysis was performed for all fuel assemblies. The MCST was evaluated to be 685.3°C, showing that the core design is feasible.