Fusion Science and Technology / Volume 48 / Number 1 / July 2005 / Pages 194-199
Technical Paper / Tritium Science and Technology - Decontamination and Waste
Due to its high diffusivity and different trapping phenomena, tritium is present in materials, such as steels which are in use in different parts of a nuclear power reactor or even in graphite which is present in fusion reactor.
From waste management point of view, it is necessary to know as accurately as possible the tritium inventory in such materials before disposal. Moreover the knowledge of tritium species (HTO or HT. . .) is also a significant information in case of detritiation prior to storage, since countries regulation already limit tritium contents and releases. There are three different strategies for tritiated waste management. The first one consists in a storage with confinement packages the second one is waiting for radioactive decay. The third one consists in the application of detritiation processes.
Studies have been performed to determine different processes that could be used for tritium removal. The aim of this paper was, to study, at laboratory scale, different procedures which may be used for stainless steels and carbon materials detritiation.
Thermal detritiation kinetics till 1300 K has been studied under various atmospheres; full chemical dissolution of samples has also been performed both for steel and graphite, this to perfectly know the tritium content in such matrices. Finally a study of tritium content in steel layers has also been made, to learn about the tritium behaviour. All results are given, allowing the possibility to take a decision either for detritiation procedure or storage conditions.
The main result is that thermal out-gassing enables higher than 95 % tritium extraction from the bulk at temperature in the range of 600K, without any material destruction under Hytec gas (Ar + 5% volume H2).