Magnox fuel used

AGR fuel is transported to Sellafield in skips which are placed inside lidded containers using a dry inlet facility shared with Magnox fuel in the FHP. The container provides criticality control by segregation so boron addition to the water is unnecessary. The design of the lid allows containers to be triple stacked. After a minimum of 180 days cooling the elements are dismantled. 

Fully active laboratory scale experiments were started using firstly a Windscale HAW solution (5000 l/t) generated by the reprocessing of Magnox fuel elements with a burn-up value of 3500 MWd/t. The overall decay time was about 10 months and as the composition was not known, only relative activity measurements were performed. Other fully active HAW solutions were subsequently prepared in Ispra hot cells by dissolving U02 samples irradiated at 26 — 36,000 MWd/t and cooled for about 4 years. Successive TBP batch-extraction steps were carried out under the 1st extraction cycle conditions of the Purex process to remove the bulk of U and Pu. 

British Nuclear Fuels pic (BNFL) provide a complete nuclear fuel cycle service with its sites at Springfields (AGR/Magnox Fuel Fabrication) near Preston and Sellafield (MOX Fuel Fabrication and Reprocessing) in Cumbria. BNFL also generates electricity using Magnox Reactors at Sellafield (Calder Hall) and Chaplecross in Scotland. This paper provides an overview of the Windscale Vitrification Plant (WVP) and reviews the major safety issues associated with vitrification operations. The practicalities of vitrification of Pu using the current WVP process are briefly discussed. 

A variety of fuel elanents are used for different types of reactors, but there are some common features. In most conunercial nnclear power plants (BWR [boiling water reactors] and PWR [pressurized water reactors] that are called in Russian VVER), the pellets are inserted into rods or tubes (usually zirconium alloys) that provide a barrier to prevent escape of fission products, the tubes or rods are arranged in bundles that are loaded into the reactor core. Usually a number of short rods are inserted into the sealed tube and held in place by a spring as described earlier. In some cases, like advanced gas cooled reactors (AGR), peUets are inserted into short narrow steel pins. Magnox reactors use magnesium alloys (usually with aluminum) rather the zirconium alloys. The fuel in some advanced reactors (TRISO) is in the form of microfuel particles with a UO2 (or UC (uranium carbide)) core surrounded by layers of pyrolytic carbon and... 

Fabrication costs are three or four times greater with steel pin bundles than for Magnox fuel. Has the use of extruded Zr finned fuel cans, together with larger diameter pins, been considered ... 

Cladding. The Magnox reactors get their name from the magnesium-aluminium alloy used to clad the fuel elements, and stainless steels are used in other gas-cooled reactors. In water reactors zirconium alloys are the favoured cladding materials. 

Plutonium-242 and Americium-243 Pu-242 and Am-243 are produced in fuel by multiple nuclear reactions. They therefore appear in items contaminated by fuel. They were found to exceed the GQ limit in HNA and HPA MCI and HPA SPF waste (high uncertainty). In addition in IX resins at HPA and HNA, Am-243 was above the GQ. Neither of these radionuclides are currently analysed in Magnox wastes because they are used as yield tracers in other analyses. To measure these two radionuclides, it is possible to simply repeat the current analyses for Pu and Am with and without tracers. No development work should be required. It has been possible to use these isotopes as tracers because the amount present (in terms of activity) is very low. FISPIN predicts the following radioisotope ratios in fresh waste Am-241 to Am-234 of 111 to 1 and Pu-239/-240 to Pu-242 of 2,500 to 1. At these activity levels, it may be more accurate to estimate the activities rather than measure them. 

The most important fuel for currently operated nuclear power stations (mainly light-water reactors) is - U-enriched uranium(IV) oxide. Also of importance are metallic uranium for the Magnox reactors and a few research reactors and uranium-plutonium mixed oxides for light-water reactors. Fuel production comprises extraction and dressing of uranium ores to uranium concentrates, conversion into UF, the uranium compound used for enrichment of the BSy.jjjotope, enrichment of and production of fuel from enriched UF5 (reconversion). 

The loss of neutrons to non-fissile absorption represents a significant problem for the reactor designer, particularly near the end of the reactor run, when the fuel is starting to become used up. While very careful attention to neutron economy may allow a reactor to be designed to run on natural uranium (e.g. the UK s Magnox and Canada s CANDU reactors), most commercial reactors use enriched uranium as the fuel. 

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