Atomistic simulation studies of storage and ageing behaviour of plutonium dioxide and mixed oxide fuel

Palmer, Nathan Alan (2019). Atomistic simulation studies of storage and ageing behaviour of plutonium dioxide and mixed oxide fuel. University of Birmingham. Ph.D.

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Abstract

Many of the fundamental aspects of the ageing of plutonium (Pu) in storage conditions are of theoretical interest and practical importance. The UK has a large Pu stockpile in interim storage at Sellafield, Cumbria. The aim of this research project was to employ atomistic simulations to study the properties and ageing behaviour of plutonium dioxide (PuO\(_2\)).

A range of properties of PuO\(_2\) were predicted using bulk static lattice, surface and molecular dynamics simulations. These revealed that the oxygen terminated (111) is the most stable surface and that oxygen Frenkel pairs and Schottky defects are energetically favoured. Modelling of helium incorporation showed that helium trapping is effective in octahedral interstitial sites and Schottky defects, in particular on the (111) surface, with helium segregation predicted.

In addition, molecular dynamics predicted thermal properties and 1 keV cascades in PuO\(_2\) varying the temperature, showing it be a thermally and radiation resilient material. Given its technological importance, mixed oxide (MOX) fuel was also modelled; with bulk lattice properties predicted varying the Pu content, showing it obeys Vegard’s law. Intrinsic defects and helium incorporation was modelled in 9% Pu doped MOX fuel, of relevance to nuclear reactors.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):