Characterising legacy spent nuclear fuel pond materials using microfocus X-ray absorption spectroscopy

Abstract

Analysis of a radioactive, coated concrete core from the decommissioned, spent nuclear fuel cooling pond at the Hunterston-A nuclear site (UK) has provided a unique opportunity to study radionuclides within a real-world system. The core, obtained from a dividing wall and sampled at the fill level of the pond, exhibited radioactivity (dominantly (137)Cs and (90)Sr) heterogeneously distributed across both painted faces. Chemical analysis of the core was undertaken using microfocus spectroscopy at Diamond Light Source, UK. Mapping of Sr across the surface coatings using microfocus X-ray fluorescence (μXRF) combined with X-ray absorption spectroscopy showed that Sr was bound to TiO2 particles in the paint layers, suggesting an association between TiO2 and radiostrontium. Stable Sr and Cs sorption experiments using concrete coupons were also undertaken to assess their interactions with the bulk concrete in case of a breach in the coating layers. μXRF and scanning electron microscopy showed that Sr was immobilized by the cement phases, whilst at the elevated experimental concentrations, Cs was associated with clay minerals in the aggregates. This study provides a crucial insight into poorly understood infrastructural contamination in complex systems and is directly applicable to the UK's nuclear decommissioning efforts.

Geochemical evidence for the application of nanoparticulate colloidal silica gel forin situcontainment of legacy nuclear wastes

“…17,20 Sr complexes strongly with metal oxides (e.g. TiO2, FeOOH, Fe3O4) [21][22][23][24][25] through surface complexation reactions, and with clay minerals (e.g., talc, 17 illite, illite-smectite mixed layered phases, [25][26][27] bentonite, 28 and kaolinite 24,29 ) through both surface complexation and cation exchange reactions. 17,28,30 Cs interacts strongly with clay minerals through cation exchange reactions 17,26,31,32 and through surface complexation on the basal surface of clay minerals.…”

Uranium Contamination of Stainless Steel in Nuclear Processing Plants

“…It has previously been shown that radioactive material can be deposited on the surfaces of nuclear facility infrastructure leading to regions of contamination. − The presence of radioactive contamination on steel surfaces has numerous repercussions for the nuclear industry as a significant amount of stainless steel is used across the nuclear estate. In the UK alone, there is approximately 32 000 tonnes of contaminated stainless steel that is classified as intermediate level waste (ILW) .…”

Emerging investigator series: a holistic approach to multicomponent EXAFS: Sr and Cs complexation in clayey soils

“…24,26 Sr has been identified to complex with titanium dioxide (common as an accessory mineral in clayey soils 3,4 ) through forming inner-sphere surface complexes with anatase and rutile. 27,28 Cs complexes strongly with clay minerals such as illite and smecitite; 29,30 however, identifying Cs complexation mechanisms with clay minerals is more challenging compared to Sr due to the limitations with respect to Cs X-ray absorption spectroscopy. 19,31 Various studies have proposed the formation of outer-sphere surface complexes with clay minerals 24,[32][33][34] at relatively high concentrations.…”