Uranium weapons-grade

The amount of HEU that becomes avadable for civdian use through the 1990s and into the twenty-first century depends on the number of warheads removed from nuclear arsenals and the amount of HEU in the weapons complex that is already outside of the warheads, ie, materials stockpdes and spent naval reactor fuels. An illustrative example of the potential amounts of weapons-grade materials released from dismanded nuclear weapons is presented in Table 7 (36). Using the data in Table 7, a reduction in the number of warheads in nuclear arsenals of the United States and Russia to 5000 warheads for each country results in a surplus of 1140 t of HEU. This inventory of HEU is equivalent to 205,200 t of natural uranium metal, or approximately 3.5 times the 1993 annual demand for natural uranium equivalent. 

A = weapon-grade uranium that would be released from warheads after reducing to warhead number in left-hand column B = value in column A plus weapon-grade uranium already held outside warheads. 

The recycle weapons fuel cycle rehes on the reservoir of SWUs and yellow cake equivalents represented by the fissile materials in decommissioned nuclear weapons. This variation impacts the prereactor portion of the fuel cycle. The post-reactor portion can be either classical or throwaway. Because the avadabihty of weapons-grade fissile material for use as an energy source is a relatively recent phenomenon, it has not been fully implemented. As of early 1995 the United States had purchased highly enriched uranium from Russia, and France had initiated a modification and expansion of the breeder program to use plutonium as the primary fuel (3). AH U.S. reactor manufacturers were working on designs to use weapons-grade plutonium as fuel. 

Weapons-grade fissionable material (U-233) is harder to retrieve safely and clandestinely from the thorium reactor than plutonium is from the uranium breeder reactor. 

Current U production is primarily from Canada (32% of world supply) and Australia (19%), as shown in Table 1 with data of the Uranium Information Centre (UIC 2003). Other U supplies are obtained through initiatives designed to reduce stockpiles of materials suitable for use in weapons. This includes the down-blending of weapons-grade uranium in the USA and Russia (UIC 2002). Uranium is... 

Natural uranium consists of different isotopes of uranium. Natural uranium is 0.7% U-235 and 99.3% U-238. Uranium-238 is nonfissionable, and therefore naturally occurring uranium must be enriched to a concentration of approximately 4% to be used as fuel for nuclear reactors or 90% for weapons-grade uranium. Yellow cake is shipped to conversion plants... 

The plutonium fuel in a breeder reactor behaves differently than does uranium. Fast neutrons are required to split plutonium. For this reason water cannot be used in breeder reactors, as it moderates the neutrons. Liquid sodium is typically used in breeder reactors, and the term liquid metal fast breeder reactor (LMFBR) is used to describe it. One of the controversies associated with the breeder reactor is the production of weapon-grade plutonium and nuclear arms proliferation. 

Nuclear weapon— A bomb or other explosive that derives it explosive force from the release of nuclear energy. PlutoniumA heavy, rare natural element that undergoes fission in a nuclear bomb. It is produced artificially by bombarding uranium-238 with neutrons. The addition of one neutron to the nucleus of uranium-238 changes it into plutonium-239 which is called "weapons grade plutonium," the most efficient form for making weapons. 

The primary use for plutonium (Pu) is in nuclear power reactors, nuclear weapons, and radioisotopic thermoelectric generators (RTGs). Pu is formed as a by-product in nuclear reactors when uranium nuclei absorb neutrons. Most of this Pu is burned (fissioned) in place, but a significant fraction remains in the spent nuclear fuel. The primary plutonium isotope formed in reactors is the fissile Pu-239, which has a half-life of 24 400 years. In some nuclear programs (in Europe and Japan), Pu is recovered and blended with uranium (U) for reuse as a nuclear fuel. Since Pu and U are in oxide form, this blend is called mixed oxide or MOX fuel. Plutonium used in nuclear weapons ( weapons-grade ) is metallic in form and made up primarily (>92%) of fissile Pu-239. The alpha decay of Pu-238 (half-life = 86 years) provides a heat source in RTGs, which are long-lived batteries used in some spacecraft, cardiac pacemakers, and other applications. 

Pu by neutron capture of the U in natural uranium. Chemical separation of Pu from the uranium and fission products would be easier than separating the isotopes of natural uranium to produce weapons grade... 

In 1995 (Operation Sapphire) the United States purchased 600 kilograms of weapons-grade uranium... 

BFS-1 critical facility was used to continue studies on the characteristics of fast reactor cores designed for the weapons grade plutonium utilization and minor actinides burning, for instance, the effect of neptunium introduction into fuel. The first stage of these studies made on the insert of the BN-800-Superphenix reactor fuel with up to 14% of depleted uranium dioxide replaced by neptunium dioxide was accomplished in 1995 (BFS-67 critical assemblies set). 

The initial core (BFS-67-1) represented a central zone with mixed fuel simulation with a weapon-grade plutonium content of 19 %. The plutonium core volume was 300 1. The latter was surrounded by the driver uranium zone of 740 1 volume with a specially selected... 

Option of nuclear power level of 40 GWe maintained after 2010 uses all uranium stocks together with the released weapons grade uranium. 

Absence of uranium blankets, replaced by lead reflector with a better albedo, which improves the power distribution, provides for negative void and density effects of reactivity, and rules out production of weapons-grade plutonium. 

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