The MEGAwatt Pilot Experiment (MEGAP1E) project was started in 2000 to design, build and operate a liquid Lead-Bismuth Eutectic (LBE) spallation neutron target at the power level of 1 MW. Gas measurements by y spectroscopy performed at the beginning of irradiation in August 2006 has led to the determination of main radioactive isotopes released by the LBE. Comparison with calculations performed with several validated codes supplies important volatile elements release fraction estimation in a spallation target. In addition, calculations with MCNPX2.5.0, FLUKA and SNT codes coupled with evolution programs have been performed in order to study the activation of the target. It provides important information on structural materials (such as container, window and bypass tube) and LBE activation just following the end of irradiation and at different cooling times. The induced database is relevant for safety and radioprotection during operation, for the post-irradiation experiments and for target dismantlement.