Based on regulatory guidance regarding the prevention of electromagnetic (EM) problems, we evaluate the EM interference of an axially ruptured coaxial cable used in a nuclear power plant. We investigate regulatory guidance on EM interference and susceptibility (EMI/EMS) to safely operate a nuclear power plant. We analyze the ruptured coaxial cable rigorously using a mode-matching method in an electrostatic domain, based on Laplace's equation and the superposition principle. We perform potential formulation, enforcement of boundary conditions, and examination of the convergence of the resulting series solution. We then extract the distributions of the potential and electric field and the normalized capacitance while the geometric and material parameters of the axially ruptured coaxial cable change. Consequently, we evaluate the EMI of the axially ruptured coaxial cable by interpreting the derived results. We conclude that the evaluation results provide us with the insightful information to mitigate EMI-related problems.