Assessment of empirical potential for MOX nuclear fuels and thermomechanical properties

Abstract

International audienceWe assess five empirical interatomic potentials in the approximation of rigid ions and pair interactions for the (U1−y,Puy)O solid solution. The assessment compares available experimental data and Fink's recommendation with simulations on: the structural, thermodynamics, and mechanical properties over the full range of plutonium composition, from pure UO2 to pure PuO2 and for temperatures ranging from 300 K to the melting point. The best results are obtained by potentials referred as Cooper and Potashnikov potentials. The first one reproduces more accurately recommendations for the thermodynamics and mechanical properties exhibiting ductile-like behaviour during crack propagation, while the second one gives brittle behaviour at low temperature

Damage characterization of (U,Pu)O2 under irradiation by molecular dynamics simulations

“…This mechanical study is carried out using two different potentials: Cooper's potentials [22,23] and MOX-07 potentials [21]. These two rigid ions potentials were selected among five from a previous assessment based on structural and mechanical properties for a full range of Pu content (0 to 100%) and temperatures up to the melting point [19]. Both give good results for structural and thermodynamics properties.…”

“…The value of σ H depends on the interatomic potentials. Based on our previous assessment of the strain-strain curves during crack propagation [19], σ H is chosen equal to 6 GPa and 8 GPa for MOX-07 and Cooper's potentials respectively. These values correspond to the maximal stress found before crack propagates.…”

“…These simulations examined the strain-stress curves during crack propagation and reported the existence of phase transitions ahead from the crack tip from fluorite to scrutinyite-type or rutile-type structure. We also obtained, in our previous assessment [19], the same behaviour in U x Pu 1−x O 2 solid solution with more or less emphases according the loading direction and the empirical potential used. However, to the best of our knowledge, the influence of radiation damage on the cracking processes has not been yet investigated.…”

“…Nonetheless, the elastic modulus evolution with temperature or in case of MOX with Pu content is not usually included into the fitting process. However, they are rather used as justification for the reliability of the potentials [19][20][21][22]. But yet, evolution with radiation damage is not reported.…”

“…This work is an attempt to fill this gap. In our previous studies [19], we have assessed 5 empirical potentials on some thermodynamics and mechanical properties (e.g. thermal expansion, specific heat capacity, elastic constants, and ultimate tensile strength) for U 1−x Pu x O 2 solid solution.…”