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 ℃

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 ℃

showing that the core design is feasible.