Nuclear design feasibility of the soluble boron free PWR core

A nuclear design feasibility of soluble boron free (SBF) core for the medium-sized (600MWe) PWR was investigated. The result conformed that soluble boron free operation could be performed by using current PWR proven technologies. Westinghouse advanced reactor, AP-600 was chosen as a design prototype. Design modification was applied for the assembly design with burnable poison and control rod absorber material. In order to control excess reactivity, large amount of gadolinia integral burnable poison rods were used and B4C was used as a control rod absorber material. For control of bottom shift axial power shape due to high temperature feedback in SBF core, axial zoning of burnable poison was applied to the fuel assemblies design. The combination of enrichment and rod number zoning for burnable poison could make an excess reactivity swing flat within around 1 percent and these also led effective control on axial power offset and peak pin power. The safety assessment of the designed core was performed by the calculation of MTC, FTC and shutdown margin. MTC in designed SBF core was greater around 6 times than one of Ulchin unit 3 and 4. Utilization of enriched B10 (up to 50w/o) in B4C shutdown control rods provided enough shutdown margin as well as subcriticality at cold refueling condition. (author)