Dissolution of HTGR Fuel Particles in Nitric Acid Solutions

Dissolution studies of (Th,U)O$_{2}$ particles were carried out with the objective of finding a method to reduce the inconveniently long dissolution times. Of the methods Investigated the most promising is to increase the ratio of oxide mass to Thorex volume. Leaching is discontinued when 1 mole of oxide per liter has been dissolved and continued with fresh Thorex reagent after addition of new particles to the undissolved ones. If the above ratio is increased from the usual 1 to 2 or 3 mole oxide/1 Thorex the dissolution time is shortened by as much as 80 - 90 %. Preliminary corrosion experiments indicated that the stainless steels EAS2S1 and DIN Nr. 4571 and also glass may be suitable materials for construction of a dissolver unit