In this paper we present the results of residual stress measurements in a bimetallic stainless steel –zirconium adapter, which is used in some structures of RBMK reactor channels. The stresses in this component arise due to various manufacturing processes and the thermal expansion factor mismatch between the two alloys. The residual stress distribution in stainless steel was investigated. The residual stresses on three different cross sections were measured. The experiments were carried out on High Resolution Fourier Diffractometer (HRFD) and Fourier stress Diffractometer (FSD) at the pulsed reactor IBR-2 (Dubna, Russia) and on the high-resolution neutron diffractometer at power reactor LVR 15 (NPI, Rez, Czech Republic).