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Higher specific activity: Recycled uranium fuel typically has several times the specific activity of fresh fuel, mainly due to the presence of U-232 and increased U-234.
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Higher surface dose rates: Surface dose rates from recycled fuel are 3—4 times higher than for fresh uranium fuel (Source: Radiation Protection Dosimetry, 2005, Vol. 115, No. 1—4, pp. 110—112).
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Fission product contamination: Recycled fuel will also contain very small, but radiologically significant, quantities of fission products.
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Enrichment complications: Both U-232 and U-234 are lighter than U-238, so they tend to concentrate in the enriched (rather than depleted) output during enrichment. This means reprocessed uranium that is re-enriched for fuel must be segregated from enriched fresh uranium.
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Shielding requirements: The strong gamma radiation from the Tl-208 daughter of U-232 means that shielding is necessary in enrichment and fabrication plants handling recycled uranium.
Fuel manufacture using recycled uranium therefore requires additional precautions beyond those used for fresh uranium fabrication.