Secondary supplies today account for the equivalent of about 17 000 tU per year. This will drop sharply in 2014 when the supply of blended-down Russian high — enriched uranium to USA ceases, but in most scenarios will recover to at least 16 000 tU/yr by 2020.

The most obvious secondary source of uranium is civil stockpiles held by utilities and governments. The amount held here is difficult to quantify, due to commercial confidentiality. As at January 2011 some 120 000 tU total inventory was estimated for utilities, 10 000 tU for producers and perhaps 20 000 tU for fuel cycle participants, making a total of 150 000 tU (WNA Market Report 2011). These reserves are expected not to diminish, but to be replaced as they are drawn down and perhaps show a steady net increase to provide energy security for utilities and governments, especially in China.

Recycled uranium and plutonium another source, and currently save are 1500-2000 tU per year of primary supply, depending on whether just the plutonium or also the uranium is considered. In fact, plutonium is quickly recycled as MOX fuel, whereas the reprocessed uranium (RepU) is mostly stockpiled. Some 100 000 tonnes of used fuel has been reprocessed so far in the civil sector.

Used fuel is about 96% uranium (burned down to around 1% U-235), about 1% plutonium (with about one third non-fissile isotopes) and 3% fission products and actinides, which are wastes. Reprocessing the fuel separates these so that the plutonium is promptly recycled into mixed oxide (MOX) fuel and the uranium is either recycled via a conversion plant or stockpiled as strategic reserve. It is more expensive to convert and enrich than fresh uranium from the mine, due to two new uranium isotopes.

Recycling the plutonium is simply continuing and expediting something which occurs already: some of the uranium-238 comprising most of the fuel is progressively turned into plutonium, and the fissile part of this burns along with the uranium-235. Consequently about one third of the energy from any power reactor comes from burning plutonium. If MOX fuel is used, of course much more does.

Re-enrichment of depleted uranium (DU, enrichment tails) is another secondary source. There is about 1.5 million tonnes of depleted uranium available, from both military and civil enrichment activity since the 1940s, most at tails assay of 0.25­0.35% U-235. Non-nuclear uses of DU are very minor relative to annual arisings of over 35 000 tU per year. This leaves most DU available for mixing with recycled plutonium on MOX fuel or as a future fuel resource for fast neutron reactors. However, some DU that has relatively high assay can be fed through under­utilised enrichment plants to produce a natural uranium equivalent, or even enriched uranium ready for fuel fabrication. Russian enrichment plants have treated 10 000-15 000 tonnes per year of DU assaying over 0.3% U-235, stripping it down to 0.1% and producing a few thousand tonnes per year of natural uranium equivalent. This Russian program treating Western tails has now finished, but a new US one is expected to start when surplus capacity is available, treating about 140 000 tonnes of old DU assaying 0.4% U-235.

The world’s nuclear weapons stockpiles provide an important source of nuclear fuel. Since 1987 the United States and countries of the former USSR have signed a series of disarmament treaties to reduce the nuclear arsenals of the signatory countries by approximately 80%.

The weapons contained a great deal of uranium enriched to over 90% U-235 (i. e. up to 25 times the proportion in reactor fuel). Some weapons have plutonium-239, which can be used in mixed-oxide (MOX) fuel for civil reactors. From 2000 the dilution of 30 tonnes of military high-enriched uranium has been displacing about 10 600 tonnes of uranium oxide per year from mines, which represents about 15% of the world’s reactor requirements. Over 2000 to 2013 this Russian ex-weapons material is supplying almost half US power generation requirements, hence accounting for about 10% of US electricity, but that supply terminates in 2013. Under this program, by August 2011, 425 tonnes of high-enriched uranium (HEU) had been downblended into some 12 250 tonnes of low-enriched uranium (LEU) for reactor fuel, representing 75 million SWU of enrichment and about 17 000 warheads, at a cost of $7.2 billion (paid by electricity consumers).

On the US side, 174 tonnes of military high-enriched uranium has been declared to be surplus and available for civil power generation. A start has been made on downblending this and the first fuel fabricated from it has been shipped to Tennessee Valley Authority (TVA) power plants. The US Department of Energy’s (DOE’s) National Nuclear Security Administration (NNSA) has awarded contracts to downblend 17.4 tonnes of HEU from dismantled warheads to yield about 290 tonnes of LEU, 230 tonnes of which will be part of a new American Assured Fuel Supply (AFS) program. In June 2009, the NNSA awarded a further contract for downblending 12.1 tonnes of HEU, which will yield some 220 tonnes of LEU by 2012.