In-core thermal high-neutron fluence measurement by TLD-activation method

Thermal neutron fluence between 1014 and 1018 n/cm2 in the Health Physics Research Reactor-Core of Tehran was measured conveniently by a TLD reader using the 6Li(n,α)3H reaction in TLD-700. The primarily induced thermoluminescence (TL) by irradiation of the crystal in the reactor core was first cleared by annealing. The secondary TL of TLD-700 produced after a storage time by the absorbed energies of decayed tritons in crystal was used as a basis for assessment of prior exposure to neutrons. A thermal treatment stabilized the readings of the high-dose-irradiated dosimeters and reduced the influence of radiation damage in TLD-700. The response reduction as a consequence of high-dose radiation was corrected by Elemental Correction Coefficients (ECC) using gamma responses prior to in-core irradiation. The resulting correlation between neutron fluence and build-up TL of TLD-700 as a consequence of internal activity is presented.