reprocessed uranium

{{Short description|Uranium recovered from spent nuclear fuel reprocessing}}

{{Use dmy dates|date=December 2024}}

Reprocessed uranium (RepU) is the uranium recovered from nuclear reprocessing, as done commercially in France, the UK and Japan and by nuclear weapons states' military plutonium production programs. This uranium makes up the bulk of the material separated during reprocessing.

Commercial LWR spent nuclear fuel contains on average (excluding cladding) only four percent plutonium, minor actinides and fission products by weight. Despite it often containing more fissile material than natural uranium, reuse of reprocessed uranium has not been common because of low prices in the uranium market of recent decades, and because it contains undesirable isotopes of uranium.

class="wikitable sortable" |+Isotopic composition of reprocessed uranium{{cite web|url=http://world-nuclear.org/info/inf69.html|title=Processing of Used Nuclear Fuel|access-date=16 February 2014|date=2013|publisher=World Nuclear Association|archive-date=12 February 2013|archive-url=https://web.archive.org/web/20130212224154/http://www.world-nuclear.org/info/inf69.html|url-status=dead}} !Isotope!!Proportion!!Characteristics
uranium-238	98.5%	Fertile material
uranium-237	0%	Around 0.001% at discharge, but half-life only 1 week. Produces soluble, long-lived neptunium-237 which is hard to contain in a geological repository. {{Chem|237|Np}} is the feedstock for the production of {{chem|238|Pu|link=Plutonium-238}} which is used in radioisotope thermoelectric generators
uranium-236	0.4–0.6%	Neither fissile nor fertile. Affects reactivity.
uranium-235	0.5–1.0%	Fissile material
uranium-234	>0.02%	Fertile material but can affect reactivity differently{{cite web|url=http://www.francenuc.org/en_mat/uranium4_e.htm|title=Uranium from reprocessing|url-status=dead|archive-url=https://web.archive.org/web/20071019023302/http://francenuc.org/en_mat/uranium4_e.htm|archive-date=19 October 2007}}
uranium-233	trace	Fissile material
uranium-232	trace	Fertile material, decay product thallium-208 emits strong gamma radiation making handling difficult

Given sufficiently high uranium prices, it is feasible for reprocessed uranium to be re-enriched and reused. It requires a higher enrichment level than natural uranium to compensate for its higher levels of ²³⁶U which is lighter than ²³⁸U and therefore concentrates in the enriched product.{{cite web |url=http://www.inl.gov/technicalpublications/Documents/3667084.pdf |title=Advanced Fuel Cycle Cost Basis |publisher=Idaho National Laboratory |url-status=dead |archive-url=https://swap.stanford.edu/20090124231050/http://www.inl.gov/technicalpublications/Documents/3667084.pdf |archive-date=24 January 2009 }} As enrichment concentrates lighter isotopes on the "enriched" side and heavier isotopes on the "depleted" side, {{chem|234|U}} will inevitably be enriched slightly stronger than {{chem|235|U}}, which is a negligible effect in a once-through fuel cycle due to the low (55 ppm) share of {{chem|234|U}} in natural uranium but can become relevant after successive passes through an enrichment-burnup-reprocessing-enrichment cycle, depending on enrichment and burnup characteristics. {{chem|234|U}} readily absorbs thermal neutrons and converts to fissile {{chem|235|U}}, which needs to be taken into account if it reaches significant proportions of the fuel material. If {{chem|235|U}} interacts with a fast neutron there is a chance of a (n,2n) "knockout" reaction. Depending on the characteristics of the reactor and burnup, this can be a larger source of {{chem|234|U}} in spent fuel than enrichment.

If fast breeder reactors ever come into widespread commercial use, reprocessed uranium, like depleted uranium, will be usable in their breeding blankets.

There have been some studies involving the use of reprocessed uranium in CANDU reactors. CANDU is designed to use natural uranium as fuel; the ²³⁵U content remaining in spent PWR/BWR fuel is typically greater than that found in natural uranium, which is about 0.72% ²³⁵U, allowing the re-enrichment step to be skipped. Fuel cycle tests also have included the DUPIC (Direct Use of spent PWR fuel In CANDU) fuel cycle, where used fuel from a pressurized water reactor (PWR) is packaged into a CANDU fuel bundle with only physical reprocessing (cut into pieces) but no chemical reprocessing.{{cite web |first=Jeremy J. |last=Whitlock |date=April 2000 |access-date=11 December 2024 |url=https://www.nuclearfaq.ca/brat_fuel.htm |website=DUPIC |title=The Evolution of CANDU Fuel Cycles and Their Potential Contribution to World Peace}} Opening the cladding inevitably releases volatile fission products like xenon, tritium or krypton-85. Some variations of the DUPIC fuel cycle make deliberate use of this by including a voloxidation step whereby the fuel is heated to drive off semi-volatile fission products or subjected to one or more reduction / oxidation cycles to transform nonvolatile oxides into volatile native elements and vice versa.

The direct use of recovered uranium to fuel a CANDU reactor was first demonstrated at Qinshan Nuclear Power Plant in China.{{cite web |website=wise-uranium.org |url=http://wise-uranium.org/epasi.html#QINSHANREPU |title=Use of CANDU fuel from spent light water reactor fuel at Qinshan nuclear power plant }} The first use of re-enriched uranium in a commercial LWR was in 1994 at the Cruas Nuclear Power Plant in France.{{Cite web |work=world-nuclear-news.org |url=https://www.world-nuclear-news.org/Articles/Framatome-to-supply-EDF-with-reprocessed-uranium-f |date=25 May 2018 |access-date=11 December 2024 |title=Framatome to supply EDF with reprocessed uranium fuel}}{{Cite web |archive-date=2014-04-23 |archive-url=https://archive.today/20140423050312/http://www.wise-uranium.org/epfr.html |url=http://www.wise-uranium.org/epfr.html |title=Uranium Enrichment and Fuel Fabrication - Current Issues (France)|date=23 April 2014|website=wise-uranium.org }}

In 2020, France, one of the countries with the biggest reprocessing capacity, held a stock of {{convert|40020|t}} of reprocessed uranium, up from {{convert|24100|t}} in 2010.{{Cite web|url=https://www.statista.com/statistics/463412/uranium-stocks-france-projected-evolution/ |title=Recovered & depleted uranium stocks in France 2010-2030 |work=statista.com |access-date=11 December 2024 }} Every year France processes {{convert|1100|t}} of spent fuel into {{convert|11|t}} reactor grade plutonium (for immediate further processing into MOX fuel) and {{convert|1045|t}} of reprocessed uranium which is largely stockpiled. There are provisions in place for the storage of this reprocessed uranium for up to 250 years for potential future use.{{cite web | url=https://world-nuclear.org/information-library/nuclear-fuel-cycle/fuel-recycling/processing-of-used-nuclear-fuel | title=Processing of Used Nuclear Fuel |date=23 August 2024 |access-date=11 December 2024 |work=World Nuclear Association }} Given France's domestic uranium enrichment capabilities, this stockpile constitutes a strategic reserve for the case of a major disruption of uranium supply as France does not have domestic uranium mining.