Radiative mantle experiments were performed on JET ELMy H-modeplasmas. The septum configuration was used where the X-point isembedded into the top of the septum. Argon radiated 50% of theinput power from the bulk plasma while Zeff rose from anintrinsic level of 1.5 to about 1.7 due to the injected argon.The total energy content and global energy confinement timedecreased 15% when the impurities were introduced. In contrast,the effective thermal diffusivity in the core confinementregion (r/a = 0.4-0.8) decreased by 30%. Usually, JET ELMyH-mode plasmas have confinement that is correlated to the edgepedestal pressure. The radiation lowered the edge pedestal andconsequently lowered the global confinement. Thus the globalconfinement was changed by a competition between the edgepedestal reduction lowering the confinement and the weaker RIeffect reducing the core transport coefficients. The ELMfrequency increased from 10 Hz type-I ELMs, to 200 Hz type-IIIELMs. The energy lost by each ELM reduced to 0.5% of the plasmaenergy content.