This complicates its detection and liquid scintillation counting (LSC) is required for measuring it in environmental samples.
[3] Performance assessment calculations for the Belgian deep geological repository estimated 79Se may be the major contributor to activity release in terms of becquerels (decays per second), "attributable partly to the uncertainties about its migration behaviour in the Boom Clay and partly to its conversion factor in the biosphere."
[6] Due to redox-disequilibrium, selenium could be very reluctant to abiotic chemical reduction and would be released from the waste (spent fuel or vitrified waste) as selenate (SeO2–4), a soluble Se(VI) species, not sorbed onto clay minerals.
Moreover, selenium is an essential micronutrient as it is present in the catalytic centers in the glutathione peroxidase, an enzyme needed by many organisms for the protection of their cell membrane against oxidative stress damages; therefore, radioactive 79Se can be easily bioconcentrated in the food web.
In the presence of nitrate (NO–3) released in deep geological clay formations by bituminized waste issued from the spent fuel dissolution step during their reprocessing, even reduced forms of selenium could be easily oxidised and mobilised.