TEM study of alpha-damaged plutonium and americium dioxides
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Philippe Martin CEA, DEN, DEC, Centre d’études nucléaires de Cadarache, Saint Paul Lez Durance 13108, France
Rudy Konings European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe 76125, Germany (Received 10 October 2014; accepted 5 February 2015)
Actinide-based nuclear ceramics, oxides particularly, are not only used as fuel in nuclear power reactors (uranium and plutonium) but are also used/envisaged as materials for electrical power sources in space probes (plutonium or americium). These actinides are all alpha-emitters, some having rather short half-lives. As a result of their strong alpha-activity, the actinide-based materials cumulate radiation damage and radiogenic helium. The stability of such materials needs to be assessed and understood for predicting the long-term stability of not only spent fuel in storage/disposal conditions but also of electrical power sources to be used in space probes. This paper describes the specific transmission electron microscope microstructure analyses of aged 238 PuO2, 238Pu-doped UO2 (to simulate aged spent nuclear fuel), and of 241AmO2 samples (candidate electrical power source) and makes the correlation of the observed defects with other properties like helium thermal desorption and lattice parameter. It is shown that these fluorite structured materials resist to high alpha-damage levels and can accommodate large quantities of helium.
I. INTRODUCTION
Contributing Editor: William J. Weber a) Address all correspondence to this author. e-mail: [email protected] b) Present address: The University of Manchester, Oxford Rd, Manchester, M13 9PL, UK c) Present address: Commissariat à l’Energie Atomique et aux Energie Alternatives, Centre de Marcoule, B.P. 30207 Bagnols-sur-Cèze, France DOI: 10.1557/jmr.2015.37
that, if released, could build some pressure in storage containers, needs to be characterized and understood. Not only separated plutonium but also significant amounts of spent uranium dioxide nuclear fuel are accumulating worldwide from decades of commercial nuclear power production. Around 300,000 tons of spent fuel from civil power plants are currently stored in the world4 and this amount steadily grows. While nuclear fuel in reactor undergoes significant restructuring due to the radiation effects from fission and to operating high temperatures, the radiation and temperature environment for spent fuel out of reactor is substantially different. After decay of the short-lived fission products the spent fuel activity will be dominated by alpha-decays from the minor actinides and mainly from plutonium for the longer times.5 The self-radiation damage and helium accumulation at near ambient conditions will dominate for millions of years. The spent nuclear fuel available and characterized today is not representative of the structure and state of aged spent fuel after hundreds or thousands of years of storage because it has not yet experienced a significantly long accumulation of microstructural defects and of He due to a-decay.6 Rec
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