In order to investigate the production and diffusion mechanisms of defects in Fe-Rh intermetallic compounds, the positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements are carried out for Fe-50at %Rh alloys irradiated with 6 MeV and 28 MeV electrons at 100 K. A long lifetime component of about 250 psec is observed in the specimen irradiated with 6 MeV electrons. The result shows that vacancy clusters including 3 or 4 vacancies are formed during electron irradiation. Furthermore, the vacancy clusters remain stable up to about 360 K. The CDB results indicate that the atomic configuration around irradiation-induced vacancies strongly depends upon the electron energy and/or total election fluence.