Significant Reduction of Electromagnetic Interference for Fine-Motion Control Rod Drive in a Nuclear Reactor

A significant reduction of electromagnetic interference (EMI) for a fine-motion control rod drive (FMCRD) in a nuclear reactor is presented in this paper. A reactor design with the FMCRD can achieve high performance. However, the FMCRD produces electromagnetic noise, which affects the startup-range neutron monitoring (SRNM) system. Moreover, because the FMCRD and the SRNM system are arranged near each other under a reactor vessel, the SRNM unit is influenced by the FMCRD electromagnetic noise, leading to uncertain monitoring results and system alarms. Strong EMI could even result in a system trip. To alleviate the EMI, a grounded metal sheet is wrapped around the FMCRD cable, partially shielding it from radiation. To further overcome the EMI, a proposed three-dimensional (3-D) low-pass filter (LPF) structure is combined with the SRNM wire for noise reduction. To implement the 3-D LPF structure, an industrial passive electronic device (zippered cable shielding) is adopted in this paper. This approach not only achieves a remarkable noise amplitude reduction but also minimizes the radiated emissions from the FMCRD cables, yielding an improved and stabilized nuclear reactor. In addition, a real-time analytical method is utilized to capture events while the FMCRDs are active, and the captured waveforms are transferred to the frequency domain by using a fast Fourier transform to analyze the experiment data, lending more insight into the actual situation.