An integrated framework for the prediction of axial offset anomaly in pressurized water reactors

During the operation of pressurized water reactors, erosion products can be deposited on the surfaces of the fuel rods, and these deposits lead to enrichment of boric acid, which influences the power distribution along the axial direction and results in axial offset anomaly (AOA)/Chalk River unidentified deposit (CRUD)-induced power shift (CIPS). In this paper, a fully integrated CIPS risk prediction framework is proposed. The framework comprises three coupled modules: CRUD deposition prediction, boron concentration calculation, and neutron flux calculation. These modules are dynamically coupled through CRUD deposition distribution and boric acid concentration data, ensuring comprehensive and up-to-date predictions. To demonstrate the framework’s capabilities, we provide a case study involving a 500-day reactor operation. Our results indicate a maximum CRUD thickness approaching 40 μm, primarily located in the upper half of the fuel rod. This deposition corresponds to a maximum boric acid concentration ratio exceeding 300, which significantly reduces heat flux in the affected region and precipitates a severe AOA/CIPS incident.