Accommodation of helium in PuO_2±x and the role of americium

Abstract

The high alpha-activity of plutonium dioxide (PuO2) results in significant ingrowth of radiogenic helium (He) in the aged material. To safely store/dispose PuO2 or use in applications such as space...

Atomistic simulation of helium diffusion and clustering in plutonium dioxide

“…The most stable site for He in defect-free PuO 2 was determined to be the Octahedral Interstitial Site (OIS), in agreement with available literature. 18,22,43 The incorporation energy for He at an OIS was 1.7 eV which is within the range of values (0.4 18 –2.73 16 eV) calculated via DFT studies available within the literature. From here on, when interstitial He is referred to, it is at an OIS.…”

“…Next, helium incorporation at defect sites were investigated. It was found that helium is most stable in V Pu sites with an incorporation energy of 0.19 eV, which is in good agreement with the 0.16 eV DFT calculated value from Neilson et al 22 . Favourable helium incorporation in actinide vacancies has also been found in UO 2 44 and ThO 2 .…”

“…45 However, PuFPs are unstable in PuO 2 . 22 So whilst V Pu sites are the most energetically favourable for He to occupy, they may not represent the majority site available to He.…”

“…Understanding the behaviour of He in PuO 2 is an area of growing interest. A recent DFT study by Neilson et al 22 investigated the accommodation of He in PuO 2 , finding the most stable He location to be interstitial sites. However, studies of helium diffusion and clustering in PuO 2 remain scarce.…”

Synthesis and multi-scale properties of PuO2 nanoparticles: recent advances and open questions

“…The fluorite configuration further allows the formation of vacant octahedral interstitial sites located at the center and middle of the edge of the cubic system thus accommodating a relatively open crystal structure. 154 This property particularly provides a strong resistance of the ceramic to radiation damage and good stability in the nuclear reactor, without deformation of the structure and surrounding cladding that could lead to migration of matter in the exchangers.…”