Reprocessed uranium

Reprocessed uranium

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Reprocessed uranium is the uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

 recovered from nuclear reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...

, as done commercially in France, the UK and Japan and by nuclear weapons states' military plutonium production programs. This uranium actually makes up the bulk of the material separated during reprocessing. Commercial LWR spent nuclear fuel
Spent nuclear fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor...

 contains on average (excluding cladding) only four percent plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...

, minor actinides
Minor actinides
The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium...

 and fission products by weight.

Reuse of reprocessed uranium has not been common because of low prices in the uranium market
Uranium market
The uranium market, like all commodity markets, has a history of volatility, moving not only with the standard forces of supply and demand, but also to whims of geopolitics. It has also evolved particularities of its own in response to the unique nature and use of this material.The only significant...

 of recent decades, and because of the undesirable isotopic contaminants
  • uranium-236
    Uranium-236
    - See also :* Depleted uranium* Uranium market* Nuclear reprocessing* United States Enrichment Corporation* Nuclear fuel cycle* Nuclear power-External links:* *...

     (which absorbs neutrons without fissioning and becomes neptunium-237 which is one of the most difficult isotopes for long-term disposal in a deep geological repository
    Deep geological repository
    A deep geological repository is a nuclear waste repository excavated deep within a stable geologic environment...

    ),
  • uranium-232 (whose decay products emit strong gamma radiation making handling more difficult), and
  • uranium-234 (which is fertile material
    Fertile material
    Fertile material is a term used to describe nuclides which generally themselves do not undergo induced fission but from which fissile material is generated by neutron absorption and subsequent nuclei conversions...

     but can affect reactivity differently than uranium-238
    Uranium-238
    Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...

    ).

In the last few years uranium prices have risen again, and if the price becomes high enough, it is possible that reprocessed uranium will be re-enriched
Enriched uranium
Enriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight...

 and reused. A higher enrichment level will be required to compensate for the 236U which is lighter than 238U and therefore will concentrate in the enriched product. Also, if fast breeder reactors ever come into commercial use, reprocessed uranium, like depleted uranium
Depleted uranium
Depleted uranium is uranium with a lower content of the fissile isotope U-235 than natural uranium . Uses of DU take advantage of its very high density of 19.1 g/cm3...

, 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 U-235 content remaining in spent PWR/BWR fuel is typically greater than that found in natural uranium, 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.