Uranium material fuel equivalent

RU is one of the products of conventional chemical reprocessing of spent uranium oxide fuel. In this context, RU is simply a subset of SEU, acquired on the open market, as is SEU or natural uranium, and its use is not linked to the reprocessing of the spent fuel of the utility acquiring the material. It is considered simply as an alternate source of enrichment (anticipated to be much cheaper) compared with SEU from enriching fresh uranium and can be substituted by SEU of equivalent enrichment. The enrichment level is around 0.9%, with the actual U content and composition depending on the initial enrichment and burnup of the spent fuel from whence it was obtained. In general, reactor physics and fuel performance will be comparable with that for 0.9% SEU. 

The reactor core is located in the lower part of the vessel-vault and is composed of 91 hexagonal fuel assemblies with fuel rods of the WER-440 type containing uranium dioxide fuel in a zirconium cladding. The structural material of the fuel assemblies is zirconium alloy. Fuel assemblies are placed in a triangular lattice with the pitch of 147 mm and form a regular and symmetrical system. The reactor core height is 1400 mm the equivalent diameter of the core is 1420 mm. 

Before discussing the sustainability of Gen-IV systems, a reminder about natural uranium and the composition of spent nuclear fuel (SNF) is necessaryNatural uranium is composed of 0.005% U, 0.720% U%, and 99.275% U. The fuel used in a standard LWR relies on the fissile isotope U, which is typically enriched to U concentrations in the range of 4%. However, it should be noted that some 40% of the energy produced in the course of a nuclear fuel cycle in an LWR comes from Pu, which is thus an excellent fissile fuel material. Moreover, ceramic-mixed oxide fuel (MOX, which is UO2 + PUO2), consisting of about 7—10% Pu mixed with depleted uranium ( U), is equivalent to UO2 fuel enriched to approximately 4.5% U, assuming that the Pu contains approximately two-thirds fissile isotopes. 

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. 

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. 

Decisions about what to do about surplus plutonium and highly enriched uranium fi om weapons have not been reached. If they were to be vitrified, then a whole new set of scenarios would have to be investigated, from a safeguards and criticality points of view. In any case more consideration would have to be given to the question of nuclear materials diversion to non-peaceful uses. Recently, the NAS/NRC has suggested that the minimum safeguards control should be at least equivalent to that accorded spent nuclear fuel [16]. 

The fuel is amazingly energy dense. One kilogram of uranium has the energy equivalent of 17,000 tons of coal. Stockpiling the fuel or the raw material from which it is made is easy and takes up minimum space. 

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