ThO2 spent fuel assembly’s gamma dose rate dependency to burnup and cooling time

Document Type: Original Article


Reactor and Nuclear Safety Research School‎, ‎Nuclear Science and Technology Research Institute (NSTRI)‎, ‎Tehran‎, ‎Iran


Today thorium based fuels are being investigated as an alternative fuel technology. However, the majority of thorium fuel research studies are limited to reactor physics investigations, which leaves a gap for dose evaluation and shielding concerns of such spent fuels. The present work investigates thorium oxide fuel assemblies in Tehran research reactor. The fuel gamma dose rates are calculated at different burnups and cooling times. A comparison between the reactor routine fuel and the thorium oxide fuel is conducted to reveal the thorium-based fuel application shielding challenges. The obtained results showed that inverse to U3O8-Al routine fuel the spent ThO2 gamma dose rates are completely dependent to the burnup values. In addition, for transporting the spent ThO2 fuel with the routine transport casks there is needed to be waited for the higher cooling times than U3O8-Al transportation time or construction of thicker transport casks is needed for transportation of the thorium-based spent fuels at shorter times.


  • Thorium-based fuel gamma dose rate dependencies on burn-up values were calculated.
  • The required shield thickness was discussed for transportation of the Thorium-based spent fuel.
  • Gamma dose rate of the thorium-based and uranium-based fuels were compared in cooling times.