Improvement of detector shield in PGNAA facility for boron concentration measurement.

A radiation shield consists of borated polyethylene (7 % wt of boron) and lead was used for the HPGe detector in Isfahan MNSR's PGNAA facility in order to remove scattered neutrons and gamma rays, respectively. Therefore, the boron peak in gamma spectroscopy is related to both resources in the sample and in the shield, and it has caused a challenge in determination of boron concentration in the samples. In this research, various methods have been investigated to remove the effect of boron in the shield of the detector. For this purpose, Monte Carlo simulations of radiation transportation have been used. The results showed that by covering the detector shield using a cadmium sheet can greatly (99.32 %) reduce the height of the boron peak in prompt gamma spectrum recorded in the detector that come from the shield. The experiments have been done to validate the results obtained from the simulations.