KAREN NUCLEAR TIME SERIES

KAREN NUCLEAR TIME SERIES

France aims to have all its 900 MWe series of reactors running with at least one-third MOX. These reactors generally use MOX fuel as about one-third of their core, but some will accept up to 50% MOX assemblies. In Japan about ten reactors are licensed to use it and several do so. Currently about 40 reactors in Europe (Belgium, Switzerland, Germany and France) are licensed to use MOX, and over 30 are doing so. Today MOX is widely used in Europe and in Japan. In 2006 about 180 tonnes of MOX fuel was loaded into over 30 reactors (mostly PWR) in Europe. By mid-2016 over 7500 MOX fuel assemblies had been used in over 40 reactors. So far more than 2000 tonnes of MOX fuel has been fabricated and loaded into power reactors.

MOX fuel was first used in a thermal reactor in 1963, but did not come into commercial use until the 1980s. In addition, there are about 1.6 million tonnes of enrichment tails, with recoverable fissile uranium, especially where the original tails assay was about 0.25% or more. For lower tails assays, the main use for this depleted uranium is in diluting the plutonium to make MOX. Inventory of separated recyclable materials in 2007 1 It is equivalent to about three years' supply of natural uranium from world mines. Today there is a significant amount of separated uranium and plutonium which may be recycled, including from ex-military sources. A single recycle of plutonium in the form of MOX fuel increases the energy derived from the original uranium by some 12%, and if the uranium is also recycled this becomes about 22% (based on light water reactor fuel with a burn-up of 45 GWd/tU). This is well established, and two Russian proposals elaborate the basic process. The plutonium can then be used in the manufacture mixed oxide (MOX) nuclear fuel, to substitute for fresh uranium oxide fuel. The plutonium (and uranium) in used fuel can be recovered through reprocessing. Worldwide, some 70 tonnes of plutonium contained in used fuel is removed when refuelling reactors each year. Typically about one percent of the used fuel discharged from a reactor is plutonium, and some two thirds of this is fissile (c. The higher the burn-up, the less fissile plutonium remains in the used fuel. It behaves like U-235 and its fission releases a similar amount of energy.

Normally, with the fuel being changed every three years or so, about half of the Pu-239 is 'burned' in the reactor, providing about one third of the total energy. (Very small quantities of Pu-236 and Pu-238 are formed similarly from U-235.) This can become plutonium-239 and by successive neutron capture Pu-240, Pu-241 and Pu-242 as well as other transuranic isotopes (see information page on Plutonium). Most of the fuel mass in a reactor is U-238. In every nuclear reactor there is both fission of isotopes such as uranium-235, and the formation of new, heavier isotopes due to neutron capture, primarily by U-238. In each case, the fission products and minor actinides are separated as high-level waste when the used fuel is processed. This is regenerated mixture (REMIX) fuel, under development. Another way of closing the fuel cycle is to recycle all the uranium and plutonium without separating them, and topping up with some fresh uranium enriched to a higher level than usual. Very little recovered uranium is recycled at present. The current means of doing this is by separating the plutonium and recycling that, mixed with depleted uranium, as mixed oxide (MOX) fuel. A further alternative is Russia’s proposal for a dual-component power system, using two kinds of MOX fuel.Īn important and fundamental aspect of nuclear power is that, instead of just using the prepared nuclear fuel once and then dumping it as waste, most if it can be recycled, thus closing the fuel cycle.An innovative development in recycling plutonium and uranium as MOX is Russia’s REMIX fuel, not yet commercialised.MOX fuel also provides a means of burning weapons-grade plutonium (from military sources) to produce electricity.MOX fuel is manufactured from plutonium recovered from used reactor fuel, mixed with depleted uranium.Mixed oxide (MOX) fuel provides almost 5% of the new nuclear fuel used today and fuels about 10% of France's fleet.

Karen nuclear time