Neutron spectrum measurements near KAMINI reactor south beam vault door using nested neutron spectrometer.

This article focuses on the characterization of the neutron flux spectrum near the south beam vault door of the KAlpakkam MINI reactor (KAMINI), a ^233U-fueled research reactor at the Indira Gandhi Centre for Atomic Research, Kalpakkam. Using a Nested Neutron Spectrometer (NNS), measurements of neutron flux, mean energy, and ambient dose-equivalent rate were conducted at 10 kW reactor power, revealing that the paraffin-lead movable shield significantly attenuates neutron flux—reducing it by a factor of 25,000 compared to the south beam end slit—and thermalizes the neutron spectrum by lowering the average neutron energy from 370 keV to 178 keV. The neutron dose rates measured by NNS closely matched health physics survey data within ±20%, and neutron reference data for this location were generated for the first time. These findings demonstrate the effectiveness of the shielding in reducing neutron and gamma radiation streaming during reactor operation.