Neutron fluence rate measurement using prompt gamma rays.

A gamma ray spectrometer, with a 3('') Ø X 3('') NaI(Tl) detector, with a moderator sphere has been utilised to measure the neutron fluence rate, with this value the H(10) was estimated. When a neutron is captured by the hydrogen-based moderator, a 2.22 MeV prompt gamma ray is produced. In a multichannel analyser the net area under the 2.22 MeV photopeak is proportional to the total neutron fluence rate. The features of this system were determined by a Monte Carlo study that includes 3-, 5- and 10-inches diameter, water and polyethylene moderators and a (239)Pu-Be source. The prompt gamma response was extended to monoenergetic neutron sources. To verify the response, a (239)Pu-Be source in combination with a 10('') polyethylene sphere having a gamma-ray spectrometer with NaI(Tl) was utilised to estimate the neutron fluence rate and the H(10). These results were compared with neutron fluence rate and H(10) obtained using a Bonner sphere spectrometer and with the H(10) measured using a neutron remmeter.