Response of LiF:Mg,Cu,P TL detector simulated with Geant4

The Geant4 simulation code was developed to study the Hp(10) energy response of the LiF:Mg,Cu,P (TLD-100H). Initial study chose the simulation conditions similar to the work reported by Obryk et al. in year 2011, in which a TLD-100H chip without filter was used. The work went further to simulate the Hp(10) results obtained experimentally at SSDL Malaysia. The experiment used a TLD-100H chip embedded in a TLD card and the card was enclosed in a badge complete with PTFE filter. Irradiation with eleven photon energies in the range of 24-1250 keV was applied. The simulation code therefore took into accounts the details of the badge (the materials type and the dimensions of the chip, the card, the badge and the filters) and the set-up of the experiment (the source distance and the energies). In comparison with Obryk’s work, the simulation code yielded the mean deviation of 0.59%. For the experimental work, the simulated Hp(10) curves obtained were quite similar and comparable and a mean deviation of 13.96% was obtained. As both 0.59% and 13.96% deviations are within the acceptable limit of ±25%, it was concluded that a satisfactory level of accuracy has been achieved by the developed simulation code and the selection materials and physics processes that have been adapted in the code were correct. Sources of uncertainty that has contributed to this deviation are discussed

Penilaian kepekatan aktiviti radionuklid tabii 226Ra, 232Th dan 40K dalam makanan di kawasan tengah Malaysia

Tujuan kajian ini adalah untuk menilai kepekatan aktiviti radionuklid tabii (226Ra, 232Th dan 40K) dalam makanan asas, sayur-sayuran, buah-buahan dan lauk-pauk di kawasan tengah Malaysia. Kepekatan aktiviti purata (Bq/kg) diukur menggunakan spektrometer gama berketulenan tinggi (HPGe). Tiga radionuklid 226Ra, 232Th dan 40K masing-masing memberikan keputusan 0.64 ± 0.17, 1.23 ± 0.14 dan 96.61 ± 1.87 (bagi sampel makanan asas); 2.07 ± 0.31, 2.12 ± 0.24 dan 791.51 ± 3.66 (bagi sampel sayur-sayuran); 2.44 ± 0.34, 1.54 ± 0.25 dan 288.63 ± 2.83 (bagi sampel buah-buahan) dan 0.72 ± 0.25, 0.80 ± 0.25 dan 195.67 ± 2.54 (bagi sampel lauk-pauk). Keputusan kajian ini didapati berada di dalam julat keputusan kajian terdahulu sekaligus menunjukkan kepekatan aktiviti purata 226Ra, 232Th dan 40K berada pada aras yang selamat dan dapat diterima

Determination of Fano factor and pre-amplifier noise from the measurement of energy resolution of a HPGe detector

A HPGe detector and γ-ray multinuclide standard solution were used to get several data pairs of photon energy E and detector’s energy resolution FWHM. A series of graph of FWHM2 versus E was plotted to determine the detector’s Fano factor and pre-amplifier noise, which yielded the mean values of 0.123±0.003 and (7.448±0.011) × 10−1 keV, respectively. The Fano factor value agrees within 95% confident interval with the mostly quoted value of 0.13 for semiconductor detectors. The obtained preamplifier noise is in agreement with typical manufacturer’s specification

Assessment of radiation hazard indices arising from natural radionuclides content of powdered milk in Malaysia

The activity concentration of 226Ra, 232Th and 40K were determined by gamma spectrometry in twenty-six different brands of powdered milk available in Malaysia. The measured activity concentration was then used to estimate the radiation hazard indices in term of ingestion dose and cancer risk. The total ingestion dose was found to range between 35.19 and 461.72 μSv y−1 and the estimated cancer risk for adult is 1.23 × 10−4. These results were found to be below the internationally recommended level. This indicates that the powdered milk in Malaysia would not pose any significant radiological impact to the population