TRS435_web

The material is, owing to its isotopic composition and high radiation level,
not directly suitable for weapons purposes and requires further chemical
processing. This would involve longer warning times and requires a high
technological standard in order to prepare a material suitable for weapons
purposes. Consequently, a certain degree of proliferation resistance is inherent
in this scenario.
3.5.3. Safeguardability of advanced aqueous partitioning
HAR typically contains 0.09 g of americium and curium per litre, 0.10 g of
neptunium per litre and less than 0.006 g of plutonium per litre. At present, the
available measurement technology allows for plutonium assay at this level of
concentration after appropriate sample preparation. The MAs, however, also
need to be controlled. A typical reprocessing plant with an annual throughput
of 800 t of spent fuel is estimated to produce some 4000 m 3 of HAR per year.
An advanced aqueous partitioning of the required capacity of 4000 m 3 /a would
then show an annual throughput of about 25 kg of plutonium, 410 kg of
neptunium and 370 kg of americium and curium. A measurement uncertainty
of 5% relative should hence enable detection of the diversion of a quantity
equivalent to the respective critical masses of neptunium or americium
(~50 kg). Measurement techniques for neptunium and americium have been
developed [16], and more recently advanced measurement techniques for
directly determining neptunium in highly active solutions have been successfully
tested [17]. These methods can easily be applied to advanced aqueous
reprocessing and should allow a (near) quantitative verification of material
flows and inventories. Evidently, these concentration measurements need to be
complemented by tank volume measurements. Advanced aqueous reprocessing
facilities will be comparable with existing chemical processing facilities.
Consequently, containment and surveillance techniques can be applied in
analogy, complementing the aforementioned measures.
The separation of MAs from HLLW is a much more difficult task, since
the concentration of nitric acid is close to 2M and the final salt content is close
to crystallization. Although much R&D work has in the past focused on this
type of liquor, it is not suggested to pursue this route. Once concentrated from
5 m 3 /t to ~0.3 m 3 /t (concentration factor of 15) the liquor is ready for vitrification
and is not suitable for delicate chemical operations. A DIAMEX
(diamide extraction) flowsheet for the partitioning of MAs from high active
concentrate is under development within the European PARTNEW
programme (2000–2003). A successful hot test of DIAMEX high active
concentrate was carried out in the summer of 2003 at the ITU in Karlsruhe,
Germany.
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