Title: Inert Matrix Fuel
Publisher: Elsevier
Publication Year: 2012
JRC N°: JRC65450
ISBN: 978-0-08-056027-4
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC65450
Type: Articles in periodicals and books
Abstract: In a strict sense the term inert matrix fuel (IMF) refers to any nuclear fuel containing a low activation matrix as carrier for the fissile material. Since the early days of nuclear technology, this idea has been investigated, originally with the goal to improve fuel properties or to save uranium resources. However, currently, the term IMF is strongly associated with plutonium fuel that does not contain uranium to obtain the highest efficiency for destruction of excess plutonium (separated civil plutonium or plutonium from dismantled weapons) in a single irradiation campaign. This chapter focuses on this application. The term IMF is also used in the context of uranium-free fuels for transmutation of minor actinides (MA), although in many cases this is not appropriate as the fissile content is too low for fuel purposes and it is better to call this type of materials targets. Transmutation fuels and targets are described in detail in 3.05, Actinide Bearing Fuels and Transmutation Targets. A variety of materials has been proposed as inert matrix for nuclear fuel, ceramics such as MgO, ZrO2, or CeO2, refractory materials such as graphite or SiC, and metals such as stainless steel, zirconium, or molybdenum, depending on the type of application and the type of reactor foreseen. In thermal reactors, only a few matrices can be envisaged as a result of the very tight neutron economy. MgO and ZrO2 have been the focus of research during many years. This chapter principally deals with IMFs based on these materials. In this context, one can distinguish two fuel types: solid solutions (SS), such as the zirconia-based fuels ((Zr,Y,Pu)O2x), and composite fuels such as ((Zr,Y,Pu)O2x (ss)þMgO (matrix)). The composite fuels can be split into two groups: microdispersion fuels, which have usually fissile inclusions smaller than 25 mm and macrodispersed fuels, with fissile inclusions larger than 100 mm. The main difference is that in irradiated microdispersion or SS type of fuels the fission fragment damage is distributed homogeneously in the fuel matrix, while in the macrodispersed fuel the fission fragment damage is concentrated in a small volume shell around the fissile inclusions. All designs (SS, micro, or macro) have their advantages and disadvantages. Although some aspects of the composite fuels will be addressed here, the reader is referred to 3.10, Composite Fuel (cermet, cercer) for a comprehensive discussion of composite fuels.
JRC Directorate:Nuclear Safety and Security

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