Helium and fission gas behaviour in magnesium aluminate spinel and zirconia for actinide transmutation

Helium and fission gas behaviour in magnesium aluminate spinel and zirconia for actinide transmutation

Damen, P.M.G.

Van Veen, A. (promotor)

Interfaculty Reactor Institute

2003-12-09

In order to reduce the long-term radiotoxicity of spent nuclear fuel, many studies are performed on partitioning and transmutation of actinides. In such a scenario, the long-lived radio-isotopes (mostly actinides) are partitioned from the nuclear waste, and subsequently transmuted or fissioned in a neutron flux in shorter-lived or stable isotopes. In order to place the actinides in a neutron flux, they must be embedded material that behaves inert under neutron irradiation, a so-called inert matrix material. As most actinides decay by emitting a a-particle, large quantities of helium will be build up in the inert matrix material, before, during and after neutron irradiation. The behaviour of the helium in the material gives information whether or not a material could be used as an inert matrix. In the thesis, the behaviour of helium in two candidate inert matrix materials has been studied: magnesium aluminate spinel (MgAl2O4) and zirconia (ZrO2) fully stabilised with yttria (Y2O3). In most cases, a known quantity of helium has been implanted in the material and various investigation techniques were applied to see at which temperatures helium is released from the specimen and how the damage, introduced by the ion-implantation recovers. Investigations have also been performed on the behaviour of helium and fission gases in a spinel matrix irradiated with neutrons in a reactor. This inert matrix had an initial weight fraction of 241Am of 11.2%, of which after irradiation 96% had been transmuted or fissioned. The work described in the thesis has been supported with a Marie Curie fellowship. The major part of the work has been performed in the laboratories of the Institute for Transuranium Elements of the European Commission at Karlsruhe, together with the department of Defects in Materials of the Interfaculty Reactor Institute at Delft.

actinide transmutation
fission gases
helium

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Delft University Press

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doctoral thesis

(c) 2003 P.M.G. Damen