THE THERMOX PROCESS
The Thermox process is a process developed for the decladding and dissolution of irradiated Zircaloy-2-clad uranium dioxide fuel elements and consists of the following stages: 1. Decladding by means of thermal oxidation of the Zircaloy-2 with oxygen and water vapor at 825 deg C using nitrogen as a catalyst. 2. Oxidation of the uranium dioxide pellets with air and oxygen to U/ sub 3/O/sub 8/ at a temperature of 450 to 650 deg C. Dissolving and leaching the uranium oxides with dilute nitric acid leaving the insoluble zirconium oxide as a residue. 4. Filtering the solution and washing the residues of the cladding. The work has included the following parts: the laboratory scale investigation of the conditions for the oxidation of Zircaloy-2 in various gas mixtures and of the conditions for oxidizing and dissolving sintered UO/sub 2/ pellets: the development on a pilot plant scale of suitable apparatus and process techniques for the safe and reproducible treatment of half length inactive fuel elements; and studies of some special operation and handling problems, which have to be solved before the method can be applied in full scale. Five half length fuel elements have been treated, and the results have been satisfactory. The pilot plant experiments have proved that inactive fuel elements can be decanned, oxidized, and dissolved by means of the Thermox process. Solutions and canning residues are easy to filter, separate, and handle and are free from corroding agents. The uranium losses can be kept very low. The zirconium dioxide is obtained in a form suitable for permanent disposal. (auth)
- Research Organization:
- Aktiebolaget Atomenergi, Stockholm
- NSA Number:
- NSA-17-040918
- OSTI ID:
- 4632734
- Report Number(s):
- AE-120
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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