In-situ gamma-ray mapping of environmental radioactivity at Ithemba Labs and associated risk assessment
type: CreativeWork
description: In February and July 2005, following up on June 2004, the Environmental Radioactivity Laboratory (ERL) of /Themba LABS performed in-situ and ex-situ measurements of environmental radioactivity on the /Themba LABS (/TL) site. The ERL's Multi-Element-Detector-for-Underwater-Sediment-Activity (MEDUSA) and high-purity germanium (HPGe) detector systems were used to make in-situ and ex-situ measurements, respectively. MEDUSA consists of a CsI(Na) crystal (length 15 cm, diameter 7 cm) for y-ray detection. MEDUSA was mounted - 0.5 m above the ground on the front of a 4x4 vehicle to traverse [at ~ 2 m.s"'] the accessible portions of the /TL site. Spatial data (via a GPS receiver mounted above the crystal) were acquired every 1 s, and y-ray spectra (0-3 MeV) every 2 s. Maps of count rate were produced from the MEDUSA data to show the spatial distribution of radioactivity on the site. The lead-shielded HPGe detector is a Canberra p-type model with built-in pre-amplifier, crystal diameter 62.5 mm, and length 59.9 mm. The HPGe was used to measure the radioactivity in soil (and also in some grass) samples collected at particular spots on the /TL site. The sampled spots include six identified high activity spots ("hotspots") and two ''calibration spots". The activity concentration results that were obtained for the naturally occurring radioactive materials (NORM) [from both HPGe and MEDUSA data from off-road /TL site sections] have the ranges 7.8 - 39.0, 5.9 - 21.4? and 29.8 - 63.3 Bq.kg"1 for 238U, 2j2Th, and "^K, respectively. The absorbed and effective doses (from external gamma irradiation) that were calculated for the NORM radionuclides have the ranges 10.4 -27.2 nGy.h"1 and 12.8 - 33.4 /iSv.y"!r respectively. The average NORM activity concentration results (from February and July 2005) for the jTL road are 30.3, 29.6, and 345.0 Bq.kg1 for 238U, 232Th, and 40K, respectively- When averaging over the off-road sections of the iTL site, and excluding data from the hotspots, the a…
abstract: In February and July 2005, following up on June 2004, the Environmental Radioactivity Laboratory (ERL) of /Themba LABS performed in-situ and ex-situ measurements of environmental radioactivity on the /Themba LABS (/TL) site. The ERL's Multi-Element-Detector-for-Underwater-Sediment-Activity (MEDUSA) and high-purity germanium (HPGe) detector systems were used to make in-situ and ex-situ measurements, respectively. MEDUSA consists of a CsI(Na) crystal (length 15 cm, diameter 7 cm) for y-ray detection. MEDUSA was mounted - 0.5 m above the ground on the front of a 4x4 vehicle to traverse [at ~ 2 m.s"'] the accessible portions of the /TL site. Spatial data (via a GPS receiver mounted above the crystal) were acquired every 1 s, and y-ray spectra (0-3 MeV) every 2 s. Maps of count rate were produced from the MEDUSA data to show the spatial distribution of radioactivity on the site. The lead-shielded HPGe detector is a Canberra p-type model with built-in pre-amplifier, crystal diameter 62.5 mm, and length 59.9 mm. The HPGe was used to measure the radioactivity in soil (and also in some grass) samples collected at particular spots on the /TL site. The sampled spots include six identified high activity spots ("hotspots") and two ''calibration spots". The activity concentration results that were obtained for the naturally occurring radioactive materials (NORM) [from both HPGe and MEDUSA data from off-road /TL site sections] have the ranges 7.8 - 39.0, 5.9 - 21.4? and 29.8 - 63.3 Bq.kg"1 for 238U, 2j2Th, and "^K, respectively. The absorbed and effective doses (from external gamma irradiation) that were calculated for the NORM radionuclides have the ranges 10.4 -27.2 nGy.h"1 and 12.8 - 33.4 /iSv.y"!r respectively. The average NORM activity concentration results (from February and July 2005) for the jTL road are 30.3, 29.6, and 345.0 Bq.kg1 for 238U, 232Th, and 40K, respectively- When averaging over the off-road sections of the iTL site, and excluding data from the hotspots, the a…
author: Hlatshwayo, Israel Nkululeko
keywords: Environmental radioactivity
license: https://devspace.unizulu.ac.za/bitstreams/8d463b1c-0449-4880-b736-4fcf2dedc670/download
date published: 2007
date modified: 2026-07-24T06:17:15Z
provider: University of Zululand
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Zululand