Validation of deformation and vibration measurement techniques for nuclear fuel pins

The Belgian Nuclear Research Centre SCK•CEN plans to construct a new reactor (name MYRRHA). This reactor will be able to sustain nuclear fission reactions driven by a proton accelerator and a liquid eutectic mixture of lead and bismuth as spallation source and coolant. The flow of the coolant will produce vibrations in the reactor core containing the fuel assembly that consists of a matrix of fuel pins. Information about these vibrations is very useful to determine the lifetime of the fuel pins and the reactor core. In this paper we report on the performance evaluation of different vibration sensors considered for measuring the flow induced vibrations on a fuel pin mockup. The sensors include a SLDV, grid method, FBGs, resistive strain gages and 2 types of accelerometers. The first show that the SLDV outperforms the other sensor types. However, considering the constraints in the reactor we believe that FBGs are the best option to try to integrate in the vessel. Moreover, these sensors exhibit a quality factor up to 99.5% in the amplitude range of interest.