AP1000 fuel assembly reactivity flattening using a novel candidate composite burnable absorber

Abstract

To increase fuel utilization and decrease the total cost of a nuclear reactor, it is ideal to prolong the core lifetime of a nuclear reactor as high as possible. Burnable poisons (with large neutron absorption cross sections) play a great role in this process. Burnable poisons' material, amount, concentration, and location inside the fuel assembly, as well as inside the reactor core, are the variable parameters that the designer of a pressurized water reactor can employ to attain a desirable core lifetime. In this paper, a new pattern and combination of two well-known poisons are proposed and applied for a standard AP1000 fuel assembly as our case study. The new suggested combinatorial of erbium and gadolinium bearing rods resulted in an excellent performance in less reactivity swing and negative Moderator Temperature Coefficient. The less reactivity swing can, in turn, provide the stability of the infinity multiplication factor. The stability and flattening of the reactivity will lower the cost of conserving the criticality state of the fuel.