Verfahren zum Entfernen der aus rostfreiem Stahl bestehenden Umhuellungen auf Gegenstaenden, insbesondere auf Uran-Kernbrennelementen

摘要

Stainless steel is removed from a stainless steel clad body by intimately contacting the body with a gaseous stream containing oxygen and solid metal fluoride particles. In the preferred embodiment, a stainless steel clad body such as a stainless steel clad uranium bearing fuel element is immersed in a fluidized bed of which 1% by weight of the bed particles are aluminium fluoride and the remainder aluminium oxide. The bed is activated by intimately contacting and fluidizing the bed particles with fluorine at a temperature between 400 DEG C. and 450 DEG C. for a period of up to half an hour, whereupon the bed is fluidized and the element immersed therein intimately contacted with oxygen at a temperature between 675 DEG C. and 750 DEG C. until the desired degree of decladding is achieved. The steel cladding is often found to split, perforate or rupture during the decladding leaving the uranium exposed for immediate recovery. Fluorine is then passed through the bed to intimately contact the exposed uranium and convert it into uranium hexafluoride which after being passed through filters is condensed and further treated by conventional means to recover the uranium therefrom. The bed is fluidized by fluorine in this latter stage under the same conditions as in the first stage so that the bed particles are again activated and the bed is ready to receive another fuel element for decladding. In the preferred embodiment, the fluorine makes up 25% by volume of a mixture with argon, this mixture being used because of the high reactivity of fluorine, whereas the oxygen used is 100% pure.