Minimize fission power peaking factor in radial direction of water-cooled and water-moderated thermionic conversion reactor core
In this work we investigate the feasibility of minimizing the fission power peaking factor in radial direction of the thermionic conversion reactor (TCR) core. Due to the high nonuniformity of the power density the reactors electrical power reduces and the temperature of thermionic fuel elements (TFE) increases. This impacts the reactors lifetime. In the core of a TCR with intermediate spectrum of neutron, thermionic fuel elements are located on concentric circles. This provides the nonuniformity of location TFE and allows reducing the fission power peaking factor. In the core of an earth-based TCR a larger number of TFE are located on hexagonal lattice with a uniform step. Minimization of the fission power peaking factor can be achieved by using the nuclear profiling or installing additional constructions in the core. The first approach requires creating of some different types of TFE, the second might cause the degradation of reactors neutronic parameter. All this impacts the projects economic viability. In this work we propose to split the core in sections, each of them having its uniform step on the hexagonal lattice. Moreover the step of lattice increases from center to periphery resulting in reducing the fission power peaking factor to 1,06. Number of sections is determined by step of lattice, type and size of the TFE, dimensions of the reflector and reactors design constraints. The optimal lattice step for each section can be determined using a genetic algorithm based method which can find the solution while satisfying a number of given constraints. This method does not require any significant increase of the reactors dimensions, development and accounting of new types of TFE or additional constructions in the core.