Hydrolysis of uranium-lanthanide mixtures by thermal decomposition of urea

Almost all of the long-term radiotoxicity in spent nuclear fuel is caused by only a few elements (mainly Pu, Np, Am, Cm, and some fission products). They can be separated (partitioning) and fissioned (transmutation) to form short-lived radioisotopes, the so-called P&T strategy. An interesting way to convert these elements into fresh fuel for transmutation is via sol-gel techniques. As opposed to classical fuel production methods (such as pellet pressing), solgel techniques do not cause the formation of highly radiotoxic dust. This makes them more efficient at avoiding contamination and easier to set up for remote handling in a hot cell. An example of a sol-gel technique is internal gelation. This method offers the opportunity to produce nuclear fuel by the conversion of an aqueous solution (for example uranyl nitrate) into gelled spherical particles. The solidification is a hydrolysis reaction triggered by ammonia. This ammonia is generated internally (in solution) via thermal decomposition of hexamethylenetetramine and/or urea. The resulting spherical gel particles could undergo thermal treatment and be used right away as spherical fuel particles. This method could be very advantageous, and therefore, it is beneficial to investigate this mechanism of hydrolysis via thermal decomposition of urea.