Investigation of neutron flux by thermoluminescence dosimeters in the neutron-gamma mixed field

Abstract

Introduction: Neutrons have many applications in various fields, such as medicine. The important application of neutron in medical science is in Boron Neutron Capture Therapy (BNCT). Because of this, determination of neutron dose and flux is critical for the health maintaining of workers and patients exposed to this beam. The neutron radioisotope sources produce gamma rays in addition to the neutrons, and the neutron fields around these sources are mixed-field neutron-gamma fields. Since the separation of the dose of each radiation component in the compound field is difficult, the gamma-neutron mixed field dosimetry is a major challenge. International Commission on Radiation and Units (ICRU) recommends the use of a dosimeter pair for mixed-field dosimetry that have different responses to each component of radiation. One of the effective methods of neutron dosimetry is the use of the TLD-600/700 dosimeter pair. TLD-600 is 6Li enriched and TLD-700 is 7Li enriched. These dosimeters have the same sensitivity to gamma radiations but TLD-600 is sensitive to thermal neutrons because of high capture cross-section of 6Li, while in low fluxes, TLD-700 has no sensitivity to thermal neutrons. Materials and Methods: In this paper, in order to measure the neutron flux of the Ra-Be source in the core laboratory of the Faculty of Science of the University of Guilan. Six TLD-600/700 dosimeters were used in three intervals of 7, 14 and 20 cm from the source Results: After 24 hours of irradiation, the intensity of the thermoluminescence of TLDs was measured by TLD reader. Finally, by calculating the calibration coefficient, the measured flux values by the TLDs were determined and compared with the calculated fluxes Conclusion: Results show that the measured and calculated values are in good agreement.