Design and construction of a thermal neutron beam for BNCT at Tehran Research Reactor

Abstract An irradiation facility has been designed and constructed at Tehran Research Reactor (TRR) for the treatment of shallow tumors using Boron Neutron Capture Therapy (BNCT). TRR has a thermal column which is about 3 m in length with a wide square cross section of 1.2×1.2 m 2 . This facility is filled with removable graphite blocks. The aim of this work is to perform the necessary modifications in the thermal column structure to meet thermal BNCT beam criteria recommended by International Atomic Energy Agency. The main modifications consist of rearranging graphite blocks and reducing the gamma dose rate at the beam exit. Activation foils and TLD700 dosimeter have been used to measure in-air characteristics of the neutron beam. According to the measurements, a thermal flux is 5.6×10 8 (n cm −2  s −1 ), a cadmium ratio is 186 for gold foils and a gamma dose rate is 0.57 Gy h −1 .