A prototype neutron dose measuring instrument based on prompt gamma detection

Abstract.

Neutron detection and the measurement of ambient dose equivalent are essential to ensure radiation safety in the workplace neutron environment existing in neutron-generating facilities, like particle accelerators, nuclear reactors and other neutron-generating facilities. Based on the measurement of the prompt gammas emitted from elements like hydrogen, boron and carbon, consequent to neutron interactions, a prototype neutron dose measuring instrument has been fabricated using high-density polyethylene and borated high-density polyethylene. This instrument provides an optimized response that closely approximates the fluence to dose conversion coefficients recommended by the International Commission on Radiological Protection (ICRP) to estimate the ambient neutron dose equivalent. Experimental evaluation of the performance of the instrument has been done using neutrons emitted from a ²⁴¹ Am-Be source, kept inside a concrete enclosure with a square opening on one side. The present system can measure neutron dose with a match of about 5% with theoretical estimates and an existing rem-meter. The measured minimum detection level (MDL) of the instrument is 8.35 μSvh^-1 in the presence of significant gamma background and can be improved using a larger NaI(Tl) detector.