Dose rate measurements of neutrons using solid state detector in primary coolant systems of a research reactor

An effort has been made to evaluate the neutron dose rate in the primary coolant system of research reactor using solid state nuclear track detector. Dhruva is a 100 MW (thermal) natural uranium fuelled research reactor with heavy water as coolant, moderator and reflector. High energy photons, (>2.2 MeV) emitted from various fission and activation products produce neutrons on interaction with heavy water. Heavy water system equipment's room/areas are inaccessible due to presence of high gamma radiation field during the reactor operation. To estimate the neutron dose rate during reactor operation Solid State Nuclear Track Detector based (CR-39) detectors were installed inside coolant heat exchanger rooms during plan ned shutdown of the reactor. The detectors were removed after exposure of 20 days of continuous reactor operation. The observed neutron dose rates in the area were in the range of 210-310 μSv hr-1. The present studies discusses the sources of photo-neutrons in the coolant loops, CR-39 based neutron dosimetry and the obtained preliminary results. (author)