The key goal of the European FP6 project MTR+I3 was to build a durable cooperation between Material Testing Reactor (MTR) operators and relevant laboratories that can maintain European leadership with updated capabilities and competences regarding reactor performances and irradiation technology. The MTR+I3 consortium was composed of 18 partners with a high level of expertise in irradiationrelated services for all types of nuclear plants. This project covered activities that foster integration of the MTR community involved in designing, fabricating and operating irradiation devices through information exchange, know-how cross-fertilization, exchanges of interdisciplinary personnel, structuring of key-technology suppliers and professional training. The network produced best practice guidelines for selected irradiation activities. This project allowed to launch or to improve technical studies in various domains dealing with irradiation test device technology, experimental loop designs and instrumentation. Major results are illustrated in this paper. One of the major benefits of this project is that, starting from a situation of fragmented resources in a strongly competitive sector, it has created a framework opening the way to further collaboration between the involved partners regarding the development and utilization of irradiation devices.