The present study explores the potential of fission gas (Kr and Xe short life radioisotopes) released from a molten salt reactor, the separation of these noble gases using specific absorbents under well fixed conditions and the utilisation of these radioisotopes for radio-diagnostics. During operation, a molten salt reactor produces noble gas radioisotopes that bubble out from the liquid fuel and that can be sampled and treated for radiopharmaceutical applications including as tools for diagnostics using γ radioisotopes and/or potentially in radiotherapy for specific viral diseases using β− emitters. Among them 133Xe is currently used for lung diagnostics thanks to its 132.9 keV γ. The use of 85Kr for diagnostics is also examined. Its 514 keV γ could be used for scintigraphy. However 133Xe utilisation imply also its β− (Emean ≈ 100 keV) whose mean free pathway of 100 nm in biological tissue or in water is much smaller than the mean pathway of the 95Kr β−. Emphasis is placed on 133Xe because of its potential dual ability of imaging and as a suggested therapeutic tool of viral lung diseases.