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thus preventing its dispersion in the downstream operations where its controlled management would be
quite difficult.
The operating conditions of fuel dissolution are selected to ensure that the iodine is brought to
and maintained in the elemental state, and to entrain it in the off-gas. The iodine is recovered in an
aqueous solution by caustic scrub of the off-gas.
This specific effluent of iodine, which is discharged into the sea today, thus contains nearly all
the iodine initially present in the irradiated fuel. Some reprocessing plants envisage the use of iodine
immobilisation by adsorption on silver impregnated zeolites.
Other long-lived fission products
As to the other long-lived fission products, it is clear that the PUREX process cannot be used
to separate caesium and strontium, since these mono- and divalent elements are unextractable by TBP.
The behaviour in the PUREX process of the other fission products which have long-lived isotopes (Pd,
Se, Sn) is not precisely known. A combined electrolytic extraction of Pd 2+ with the other platinum group
elements (RuNO 3+ , Rh 3+ −
) and TcO 4
2−
(and probably SeO 4
) seems to be promising from even higher
acidic PUREX liquors [1].
1.1.1.3 Long-lived activation products
The activation products formed in the fuel element structural metals (stainless steels, inconel
and zircaloy) mostly remain in these materials and are found in the corresponding “hulls and end pieces”
waste stream. The 14 C issue should receive increasing attention because of this isotope’s impact on the
biosphere.
1.1.1.4 Conclusions
The behaviour of the minor actinides and long-lived fission products in the PUREX process
can be divided into three categories:
• elements already partially separated by the PUREX process: neptunium, technetium and
iodine. For these elements, the R&D objective involves process extensions to achieve the
desired separation performance. This first aspect is discussed further in Section 1.1.2.
• elements separable by TBP, for which a complementary step to the present PUREX
process can be developed. This applies to zirconium.
• elements that cannot be separated by the PUREX process:
– americium and curium,
– caesium, strontium and probably the other fission products (Pd, Se, Sn).
To separate these elements, it is necessary to develop new classes of extractants, or to resort
to different separation methods. The corresponding developments are discussed in Section 1.1.3 (Am
and Cm) and Section 1.1.4 (FPs).
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