Abstract:
This study deals with a method nuclear technique method utilizing Gamma Ray Spectroscopy
for the assessment of material bulk densities, specially soil density. The spectroscopy system
consists of; 3" X 3" inch scintillation NaI(Tl) detector connected to multichannel analyzer
Inspector 2000 from Canberra instruments and a laptop computer,
137Cs radiation source and four
different bulk materials with known densities. To calibrate the spectrometric system, detector
and radiation source were placed in direct contact with the surface of the bulk materials located
in wood boxes manufacture for this purpose. The distance between the radiation source and the
detector varies from 10 cm to 30 cm. The Radiation source was shielded so that the emitted
photons from the source travel in direction perpendicular to the top surface of the bulk material,
and therefore the detector will register photons interacting with the material and scattered
towards it. A relation was established between the density of the materials used for calibration
and the count rate in different parts of the gamma ray spectrum, the full energy peak, the region
of expected backscattering peak (from 50 Kev to 250 Kev), and the region containing Compton's
continuum and the full energy peak as well. Actual field measurements on Terra Rosa soils
showed that, the best results of bulk density evaluation were obtained when the detector and the
radiation source are separated by 20 cm distance. Based on which parts of the spectrum are used
for data analysis, the differences in bulk densities measured in the field and real values varies
between 0.5% and 6%. |
