The study of materials plays a key role in the development of a fusion reactor. These studies are also important for other sectors, such as fission reactors, nuclear waste, etc. In particular, the microstructure of the materials and its changes under neutron irradiation, especially in the presence of gas production due to nuclear reactions, are key factors in order to control material development and, correspondingly, to optimise the design of components and systems. The studies in this field have the common requirement that the investigation techniques and the laboratories have to be adapted to the handling of highly radioactive samples. Due to the recent progress in the development of instrumentation and computers and in the use of synchrotron light, X-ray tomography has become particularly attractive, since it is in principle the only non-destructive technique, which enables a full 3D characterization and the related quantitative analysis of the material microstructure features, which are needed for the development and validation of models. This technique was already presented in EFDA Newsletter (issue December 2003).

The first Technical Meeting on X-Ray Tomography of Nuclear Materials was organised by the Association-EURATOM-FZK (Germany) on January 22nd-23rd, 2004, in collaboration with the JRC and the ESRF. The aim of the workshop was to put together all experts in this new field, with the aim of presenting the first pioneering studies and of discussing technical and safety requirements for future works. Scientist from 7 European countries, 9 research centres (FZK und JRC, Germany; SCK-CEN Belgium; NRG Petten, the Netherlands; ESRF Grenoble, CEA Cadarache and SOLEIL Paris, France; NILPRP, Association EURATOM-MEC Bucharest, Romania; UMIST Manchester, UK) and 2 companies (British Nuclear Fuel Limited Berkeley, UK, and Applied Research Solutions Grenoble, France) participated in the meeting.

To introduce the meeting Mr. G. Lander (JRC-ITU) spoke about the historical development of the tomography. In the first session fusion-relevant results of the application of tomography in the experimental characterization of helium and tritium release from neutronirradiated beryllium and of the structure of non irradiated beryllium pebble beds were presented. Beryllium pebbles are proposed as a neutron multiplier for the blanket of fusion reactors. In the second session the technical feasibility of further studies with active samples and the related safety requirements were discussed. In the third session the technical possibilities and needed developments at the synchrotron light sources ESRF, ANKA in FZK and SOLEIL and at the conventional X-ray source in NILPRP were presented. The main conclusion of the meeting was to start a coordination action among the involved experts, in order to put together common requirements and, as a consequence, to reduce development costs.


ANKA: Angströmquelle Karlsruhe GmbH

CEA: Commissariat à l’Energie Atomique

ESRF: European Synchrotron Radiation Facility

FZK: Forschungszentrum Karlsruhe

JRC: Joint Research Centre

NILPRP: National Institute for Lasers, Plasma and Radiation Physics

NRG: Nuclear Research & consultancy Group

SCK-CEN: Studiecentrum voor Kernenergie – Centre d’étude de l’Energie Nucléaire

UMIST: University of Manchester Institute of Science and Technology

Beryllium pebbles (spheres of 1 mm diameter) are foreseen as a neutron multiplier in the Helium Cooled Pebble Bed blanket. A reliable prediction of the retention of helium and tritium generated in beryllium under neutron irradiation is needed for a fusion reactor. The ANFIBE computer code is being developed in the frame of an EFDA-Technology Task in order to meet such a need. Gas release is driven by percolation through 3D interconnected porosities at grain boundaries. Microtomography has recently enabled the imaging of the 3D structure of such porosities and to analyse them quantitatively, in order to provide the data needed for the validation of the percolation models in the ANFIBE code.

The Scientific Advisory Committee of the meeting:
J. Baruchel (ESRF),
C. Ferrero (ESRF)
G. Janeschitz (FZK),
E. Rabaglino (FZK)
G. H. Lander, T. Wiss (JRC)

Chairmen of the meeting:
C.Ronchi (JRC), G. Janeschitz (FZK), C. Ferrero (ESRF)