Advanced first core fuel assembly configuration and method of implementing the same

A method of implementing an economical first core for a pressurized water nuclear reactor, said method comprising:

• providing energy output and discharge burn-up data for substantially all of a plurality of regions that make up a target equilibrium reload cycle core, each of said regions comprising a plurality of equilibrium reload cycle core fuel assemblies;
• providing a plurality of new fuel assemblies which when configured in a first core of a pressurized water reactor emulate the energy output and discharge burn-up of the corresponding regions that make up the target equilibrium reload cycle core, each of said new fuel assemblies having a vertical length and having not been previously irradiated in a reactor core, a majority of said new fuel assemblies having a different elemental make up than a corresponding one of the equilibrium reload cycle core fuel assemblies, said new fuel assemblies having different average enrichments of uranium 235 including high enrichment fuel assemblies and low enrichment fuel assemblies;
• and
• arranging said plurality of new fuel assemblies in a first core configuration of a pressurized water reactor based upon said data, in order to emulate said target equilibrium reload cycle core in terms of spatial reactivity distribution, said first core including an interior and a periphery,
• wherein said first core is entirely made up of said new fuel assemblies,
• wherein substantially all of said high enrichment fuel assemblies are loaded toward the interior of said first core, and
• wherein an advanced lattice design and associated structure are provided for at least some of said plurality of new high enrichment fuel assemblies of said first core in which there is no extended barrier which would prohibit cross flow of a coolant over the vertical length of said fuel assemblies, in order that lateral circulation of said coolant across said fuel assemblies is provided as said coolant moves vertically, with the advanced lattice having a peripheral row of fuel rods extending around the sides of the fuel assembly and a number of interior rows of fuel rods wherein most of the fuel rods in the peripheral row have a lower enrichment than most of the fuel rods in the interior rows.