Simulations of Joint European Torus (JET) [P. H. Rebut and et al. , Nucl. Fusion 25 , 1011 (1985)] type I high-mode H-mode discharges with edge localized modes ELMs are used to study the effect of isotope mass on the height of the pedestal and the frequency of ELMs. A dynamic model for the H-mode pedestal and ELM cycles is employed in the JETTO int…