Evaluate the radioactivity along the central thimble hole of a decommissioned heavy water research reactor using TLD approach

The radioactivity along the central thimble hole of a decommissioned heavy water research reactor, TRR, was evaluated using TLD approach. The decay radionuclide was verified to be Co-60. The dose along the TRR central thimble hole was detected and revised by performing an unfolding analysis. The revised data reduced to 70–90% of the original data (for example, the maximum dose rate was reduced from 6447 to 4831 mSv/h,) and were more reliable.

► Well calibrated TLDs were applied to verify the dominant radionuclides remained in the decommissioned reactor.
► Point spread function was used to reveal the real dose distribution along the central vertical hole of reactor.
► Estimation of radioactive dose was built for the coming 10 years.