Measurements of MeV charged particles losses in the JET tokamak are reported. The technique is based on samples activation by nuclear reaction from MeV particles. Samples are used as flux monitors for leaking fusion plasma particles in the MeV energy range. Ultra low-level gamma-ray measurements were performed at three underground facilities in order to significantly enhance detection levels. Two measured radionuclides (48V, 7Be) were identified as produced predominantly from charged particle reactions. Quantitative data on charged particle fluxes to the wall were obtained for the first time as well as angular distribution with respect to the magnetic field.