Application of chlorine-36 technique in determining the age of modern groundwater in the Al-Zulfi province, Saudi Arabia.

The present study aims to estimate the residence time of groundwater based on bomb-produced (36)Cl. (36)Cl/Cl ratios in the water samples are determined by inductively coupled plasma mass spectrometry and liquid scintillation counting. (36)Cl/Cl ratios in the groundwater were estimated to be 1.0-2.0 × 10(-12). Estimates of residence time were obtained by comparing the measured bomb-derived (36)Cl concentrations in groundwater with the background reference. Dating based on a (36)Cl bomb pulse may be more reliable and sensitive for groundwater recharged before 1975, back as far as the mid-1950s. The above (36)Cl background concentration was deduced by determining the background-corrected Dye-3 ice core data from the frozen Arctic data, according to the estimated total (36)Cl resources. The residence time of 7.81 × 10(4) y is obtained from extrapolated groundwater flow velocity. (36)Cl concentration in groundwater does not reflect the input of bomb pulse (36)Cl, and it belongs to the era before 1950.

Analytical approach for radioactivity correlation of disc sources with HPGe detector efficiency.

The HPGe detector efficiency is measured as a function of source to detector separation using disc sources of (131)I with diameter ranging from 10 to 400mm. Detector efficiencies are characterized using single photon point-like standard sources at different distances; the calculated efficiencies for disc sources were analyzed by utilizing the double point detector model (DPDM) and the efficiency transfer method. The developed approach provided satisfactory results. The axial variation and radial dependence for disc sources efficiency determination in gamma-ray spectrometry were described with both gamma ray standard sources and measured samples as their extended sources.

Gamma-ray efficiency of a HPGe detector as a function of energy and geometry.

The concept of double points detector model approach (DPDM) is developed as a procedure to find the full energy peak efficiency of the coaxial 120 cm(3) closed hyperpure germanium (HPGe) detectors. Usually in the experimental nuclear physics work, which involves using HPGe detector for gamma-ray spectrometry, the full energy peak efficiency function must represent adequately the HPGe detector response. In the current work the gamma-ray energy in the range from 60 keV to 1332 keV and gamma-ray intensity changes by changing source to detector distance from 10mm to 800 mm. The detector was characterized using a number of point-like standard sources. The calculated efficiencies obtained by (DPDM) are in good agreement with experimental data.