In a process of reprocessing nuclear fuel particles by chemical dissolution to separate fission products and the disintegration products which form during reactor operation from reusable fuel materials wherein during said dissolution waste gases containing oxygen, carbon dioxide, nitrous oxides, hydrocarbons, and steam, xenon and radioactive krypton are released, the method of separating xenon and radioactive krypton from said waste gases comprising the steps of:
- adding a chemically inactive carrier gas to said fuel particles during the chemical dissolution step, withdrawing said carrier gas mixed with said waste gas mixture released in said dissolution step, removing oxygen, carbon dioxide, nitrous oxides and hydrocarbons and steam from the gaseous mixture, cooling the resultant gas mixture comprising xenon, radioactive krypton and carrier gas by means of liquid nitrogen to first precipitate xenon as a solid, thereafter increasing the pressure of the substantially xenon-free gas mixture and further cooling by means of liquid nitrogen to substantially separate krypton from said mixture in solid form.