CIPS Index Predictions for Fixed Incore Detection Systems

Crud-Induced Power Shift (CIPS) poses a significant challenge to the efficient operation of pressurized water reactors (PWRs). Traditional methods for calculating the CIPS Index, used to predict flux suppression due to crud buildup, rely on high-resolution data from movable in-core detectors. However, many reactors are equipped with fixed in-core detection systems, which provide limited axial measurements. This paper presents a novel approach for calculating the CIPS Index in fixed in-core systems, using high-fidelity simulations from the Virtual Environment for Reactor Applications (VERA). By leveraging MPACT for reactor physics, CTF for thermal-hydraulics, and MAMBA for crud chemistry, this method compensates for the reduced axial resolution of fixed detectors. The CIPS Index is computed by comparing measured neutron flux values with high-fidelity simulations, capturing localized flux suppression caused by crud, even with limited data points. Results demonstrate that the method achieves accurate CIPS Index predictions with less than 5% uncertainty, enabling early detection of crud-related power shifts with minimal conservatism. This methodology offers a valuable tool for reactor operators to mitigate CIPS risk and optimize core design, leading to cost savings and improved operational efficiency. The approach represents a step forward in applying high-fidelity simulations to fixed detector systems, ensuring that reactors can continue to operate safely and efficiently despite crud buildup.