New insights into phosphate based materials for the immobilisation of actinides

Abstract

This paper focuses on major phosphate-based ceramic materials relevant for the immobilisation of Pu, minor actinides, fission and activation products. Key points addressed include the recent progress regarding synthesis methods, the formation of solid solutions by structural incorporation of actinides or their non-radioactive surrogates and waste form fabrication by advanced sintering techniques. Particular attention is paid to the properties that govern the long-term stability of the waste forms under conditions relevant to geological disposal. The paper highlights the benefits gained from synergies of state-of-the-art experimental approaches and advanced atomistic modeling tools for addressing properties and stability of f-element-bearing phosphate materials. In conclusion, this article provides a perspective on the recent advancements in the understanding of phosphate based ceramics and their properties with respect to their application as nuclear waste forms.

Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

“…Crystalline rare‐earth phosphates are widely used in high‐tech industrial applications such as for optical materials, heat‐resistant ceramics, ion‐exchange materials, luminophores and as radioactive waste sorbents . Cerium phosphates are of particular interest since they can contain cerium ions in both +3 and +4 oxidation states.…”

Local Structural Effects of Eu3+ Incorporation into Xenotime‐type Solid Solutions with Different Host Cations

“…Their crystal structures are based on phosphate tetrahedra, which are separated by interspersed rare‐earth polyhedra . Each Ln 3+ in xenotime is coordinated by eight oxygen atoms, forming a regular LnO 8 coordination geometry with two unique Ln−O bond lengths, whereas a significantly distorted LnO 9 polyhedron with nine different Ln−O bond lengths is observed in monazite . Consequently, the Ln 3+ lattice site has a much higher symmetry in xenotime ( D 2 d ) than in monazite ( C 1 ) …”

High-Pressure Elastic, Vibrational and Structural Study of Monazite-Type GdPO4 from Ab Initio Simulations

“…Additionally, since orthophosphates incorporate rare earth elements, they can also be used to determine the distribution of rare earth elements in our Planet [9]. Another interesting application of these compounds is related to their use as potential matrix for nuclear waste disposal [5,[10][11][12]. GdPO 4 and other orthophosphates have been suggested as inclusion compounds to made nuclear fuel canisters due to their high neutron absorption [13].…”