Simulation-Based Fault Detection and Diagnosis for Electric Servomotor Control Rod Drives in BWRX-300

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Published Oct 19, 2026
Tran C.H. Nguyen Ark Ifeanyi Daniel Dos Santos Nicholas Fullilove Abhinav Saxena Jamie Coble

Abstract

GE-Hitachi’s BWRX-300 Small Modular Reactor design adopts innovations from the Advanced Boiling Water Reactor (ABWR), including the use of servomotor-driven fine motion control rod drives (FMCRDs) instead of the hydraulically-driven locking piston control rod drives (LPCRDs) commonly used in current boiling water reactors (BWRs). The FMCRDs provides more precise power control during normal operation and functional backup to the hydraulic SCRAM system during emergency scenarios. To address the challenge of monitoring the novel servomotor-driven FMCRDs in the BWRX-300, for which no operational data exist, this paper develops and validates a simulation-based, two-stage diagnostic framework. A model of the FMRCDs was created and verified in MATLAB/Simulink to generate comprehensive datasets for healthy operation and key fault modes, including stator short circuits and mechanical load failures. From these simulations, diagnostic features were extracted from motor currents and control response signals. The proposed framework first uses Auto-Associative Kernel Regression (AAKR) and a Sequential Probability Ratio Test (SPRT) for robust anomaly detection, achieving an 85.9% true positive rate with a 2.15% false positive rate. Upon detection, a second-stage multi-channel SPRT classifier diagnoses the specific fault, successfully identifying 100% of load faults and 75% of short faults. This study validates that a simulation-driven approach can establish an effective and interpretable predictive health monitoring system for critical reactor components before they are physically deployed, enabling condition-based maintenance from the outset.

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Keywords

Fine Motion Control Rod Drive, Anomaly Detection, Diagnostics, Nuclear Power

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