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.