Magnox cladding

Magnox fuel was originally stored in open skips in pools with no weather protection. This resulted in chloride contamination of the poolwater by chloride ions entrained in the coastal air. Under these conditions the Magnox cladding materials were susceptible to corrosion but storage was short-term and the fuel was generally reprocessed before penetration of the cladding. 

Magnox cladding, which has been removed mechanically from spent fuel rods at the start of reprocessing operations, is contaminated with small pieces of fuel and will require treatment before disposal to the environment. At present, this waste is stored under water (to eliminate any fire risk) in large concrete silos and processes are now under development for the conditioning of this waste to make it suitable for disposal. The favored processing route comprises the following operations ... 

A. Magnox-Clad Uranium Metal Fuel Elements... 

The large physical size of the later Magnox stations, such as Wylfa, led to the development of the more compact advanced gas-cooled reactor (AGR) design [31] that could utilize the standard turbine generator units available in the UK, Stainless-steel clad, enriched uranium oxide fuel can tolerate higher temperatures... 

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. 

Degradation of cladding in a water environment means that SNF from the Magnox reactors has been, and will continue to be, reprocessed at Sellafield. AGR fuel can be reprocessed or placed in long term storage. 

Irradiated Magnox and AGR fuel is stored at the power stations in open topped skips and transported to Sellafield in shielded flasks. At Sellafield, in the Fuel Handling Plant (FHP), the fuel is placed into ullaged containers which can be stacked. Based upon an extensive research programme an optimiun water chemistry of pH 13 was identified for the containers. Under these conditions storage times of at least five years without cladding penetration are achievable. 

Deuterium is in very low concentration. Lithium has an atomic weight of 6.94 and the abundance of Li is around 7% in natural Li. The main reaction product of B is Li which does not generate but there are other, minor reactions that do. Except in boron steels, the activation of Li predominates. Another source of in fission reactors is the low yield, ternary fission of fuel (-130 x 10 atoms per fission product pair). In Magnox gas-cooled reactors, from ternary fission is mainly retained in the metallic uranium fuel and its cladding but some is released into the coolant circuits, where it may possibly diffuse into structures within the primary vessel. Tritium is a low energy /5 emitting radionuclide of low radio-toxicity and with a half life of 12.3 years. 

Fuel Preparation. Magnox fuel cladding is removed and the bare uranium bars fed into a magazine this is then transferred to the reprocessing plant by rail. The fuel cladding is transferred to an... 

The Advanced Gas-cooled Reactors (AGR) are built into PCPV with internal boilers and gas circulators. The uranium-enriched oxide fuel is clad in stainless steel so that the risk of a charmel fire or fuel meltdown under fault conditions inherent in the Magnox design has been greatly reduced. 

Two visits were made to the Dungeness site. On 21 November 1986, a familiarisation visit was made to the Magnox Dungeness A station, where there were particular discussions on the procedures for monitoring of accidental releases and on the planned Magnox Dissolution Plant for handling spent fuel element cladding. 

The maximum coolant temperatures are limited by the stainless-steel cladding (and also by the coolant-moderator interaction between the CO2 and carbon), so that the steam generator surface area tends to be large, although considerably smaller than that of the magnox plant. 

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