This paper demonstrates the reliability and accessibility functions of fiber Bragg grating (FBG) sensors in a radiation structural health monitoring and safety evaluation application. FBG sensors, dial gages and conventional resistance strain gages (RSGs) were attached to the temporary H-beam frame, and distributed below the path of the rail tracks for online safety measurements during the process of moving the structure of the research reactor. The results showed the high level of performance of the FBG sensors for an online structural health monitoring system. The measurement data from the FBG monitoring system were comparable to the theoretical calculation results and the FEM simulations as the movement progressed. The result of this investigation also clearly demonstrates that FBG sensors can overcome the harsh environments of electric and magnetic interference, while conventional RSG sensors are subject to serious fluctuations providing useless feedback.