The results of the irradiation experiment MARIOS on americium transmutation

Abstract

The MARIOS irradiation experiment is the latest in a series of experiments on americium transmutation, and has been carried out in the framework of EURATOM’s 7th Framework Programme (FP7) project FAIRFUELS, which started the 1st January 2009 and is still ongoing. The Post Irradiation Examination (PIE) of MARIOS samples will be performed under the PELGRIMM project. The transmutation of Minor Actinides (MA) is a fundamental step in order to be able to close the nuclear fuel cycle. One of the attractive possibilities to burn MA, is represented by the Minor Actinides Bearing Blanket (MABB) concept. In this option, MA are diluted in a UO2 matrix and irradiated for a long time (from 2000 to 4100days) in radial blankets at the periphery of the outer core of a Sodium Fast Reactor (SFR). Past experimental activities in the field of transmutation and testing of innovative nuclear fuel containing Am has proved that the release or trapping of helium as well as the studies on the swelling of such kind of fuel is a key issue for its safety design. Therefore, the main objective of the MARIOS experiment is the study of the in-pile behaviour of UO2 (with natural uranium) containing Am as minor actinide in order to gain knowledge on the role of the microstructure and of the temperature on the gas release and on fuel swelling for the MABB concept.The MARIOS irradiation experiment started on the 19th of March 2011 and finished on the 2nd of May 2012 after 11 reactor cycles (∼304 full power days) in the HFR (High Flux Reactor) in Petten (The Netherlands). The MARIOS irradiation experiment will determine the performance of the MABB fuel, the behaviour of such targets during the irradiation did not show any anomalies. It is possible to conclude that from an operational point of view, these kinds of fuel which have been developed mainly having in mind the possibility to burn MA in a blanket at the periphery of a Sodium Fast Reactor, did not show significant issues. This paper summarises the main experimental data obtained after the 11-cycle irradiation of the MARIOS experiment in the HFR.