OPTIMAL GEOMETRY FOR FUEL SOLUTION SLOSHING BASED ON THE BOUNDARY PERTURBATION-THEORY

A method which obtains an optimal goemetry maximizing k(eff) due to de formation of fuel solution sloshing has been developed. The concept of the ''boundary importance'' has been derived from the ''boundary pert urbation theory''. Optimal geometry can be achieved by letting this '' boundary importance'' be constant along the boundary. As a numerical e xample, this method is applied to a two-dimensional slab fuel solution with and without a water reflector. The neutron diffusion equation on an arbitrary geometry is solved using the boundary-fitted curvilinear coordinate transformation system. Optimal geometry and its maximum re activity are obtained as a function of the ratio of the solution heigh t (Y) to slab thickness (X). For a bare fuel solution, whose Y/X is le ss than a certain threshold value, optimal geometry does not exist exc ept for a circle. For a water-reflected fuel solution, whose Y/X is le ss than its threshold value, optimal geometry can be achieved by using asymmetric deformation.