[en] This report provides a summary of the events which led to the accident at the Fukushima Dai-ichi NPP and of the impact on Ireland of the resulting releases of radioactivity. It constitutes a comprehensive record and single point of reference for all of the data generated by the additional environmental monitoring which was performed in Ireland. Trace amounts of radioactive isotopes consistent with the Fukushima nuclear accident were detected in samples of air, rainwater and milk collected in Ireland during the period March to May 2011. The activities were at levels so low as to be only detectable with highly sensitive radio-analytical instrumentation. As such they were of no radiological significance in Ireland and no protective measures were required. The levels measured were consistent with those measured elsewhere in Europe. On the basis of the low levels of radioactivity detected, monitoring of other samples such as drinking water, other foods, grass and soils was not warranted. The accident proved a good test of Ireland's capacity to respond effectively to a nuclear emergency. It demonstrated that a comprehensive monitoring network capable of measuring even trace levels of radioactivity in the environment is in place. In addition, it showed the effectiveness of atmospheric dispersion models used by RPII as part of its technical assessment capability. However, it should be noted that for an accident closer to Ireland, a much larger monitoring response would almost certainly be required