Abstract
The in service inspection (ISI) of MONJU fast breeder reactor vessel is performed at elevated temperature (about 200℃). A horizontally polarized shear (SH) wave electromagnetic acoustic transducer (EMAT) is used to perform the volumetric inspection of the MONJU reactor vessel. In this paper, the magnetic flux density distributions of a SH wave EMAT with a so-called Halbach magnet structure is analyzed from room temperature up to 240℃. The relative reduction of the magnetic flux density is less than 15% and the thermal demagnetization is about 5%, respectively. As a result, the Halbach magnet structure can be used at elevated temperatures without large performance reduction as compared to its performance at room temperature. This new structure EMAT is suitable for MONJU reactor vessel ISI.
