S.M. Azharul Islam

Experimental cross section for the 139La(n, γ)140La reaction at 0.0536 eV

Abstract The neutron capture cross section for the 139La(n, γ) 140La reaction at 0.0536 eV was measured for the first time using monochromatic neutrons coming from a Triple Axis Spectrometer at the TRIGA Mark-II reactor. The neutron beam intensity was determined by irradiating Au-monitor foil together La2O3 target. The radioactivity of the products was determined via high resolution γ-ray spectrometry. The obtained cross section value is 6.13±0.3 b, which is 1.34% and 0.21% lower than that in the ENDF/B-VII and JENDL-3.3 data library, respectively.

Elemental distribution of metals in urban river sediments near an industrial effluent source

To study the compositional trends associated with the spatial and layer wise distribution of heavy metals as well as the sediment response towards the untreated chemical wastes, we have analyzed river (Buriganga, Bangladesh) sediments by instrumental neutron activation analysis (INAA) and energy dispersive X-ray fluorescence (EDXRF). In nine sediment samples 27 elements were determined where Na, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Zn, As, Rb, Cs, La, Ce, Sm, Dy, Hf, Th and U were determined by INAA and Cu, Sr, Ba, Hg and Pb were determined by EDXRF. Pollution level and the origin of pollutants were evaluated by the aid of geo-accumulation index (Igeo), enrichment factor (EF), pollution load index (PLI) and the inter-element correlation analysis. Major elements are somehow buffered even though the pollution level is severe while the trace metals seem to be highly responsive. Among the heavy metals, Cr is the dominant pollutant, though the pollution level varies systematically with the sampling depth and the distance from the contamination source. Positive linear correlation between Cr and Zn (0.94) ensures the similar anthropogenic source(s) for these two metals, but the sediments of this study respond differently depending upon their geochemical behavior. Rare earth elements (here La, Ce, Sm and Dy), Th and U seem to have crustal origin and the Th/U ratio varies from 2.58 to 4.96.

Neutron capture cross-section measurement for the 186W(n,γ)187W reaction at 0.0536 eV energy

The thermal neutron-induced activation cross section for the (186)W(n,gamma)(187)W reaction was measured at 0.0536eV neutron energy using TRIGA Mark-II research reactor, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh. The (197)Au(n,gamma)(198)Au monitor reaction induced in a high-purity gold foil was used to determine the effective neutron beam intensity. The activities induced in sample and monitor foils were measured nondestructively by a high-resolution HPGe gamma-ray detector. The present experimental cross-section value is the first one at 0.0536eV. The obtained new cross section that amounts to 26.6+/-1.6b is 2% higher than the recently reported data in ENDF/B-VII and 5% lower than that of JENDL-3.3.

Natural Radioactivity of Feed Coal and Its by-products in Barapukuria 2×125 MW Coal Fired Thermal Power Plant, Dinajpur, Bangladesh

The detection and measurement of radionuclides in feed coal, bottom ash and fly ash samples collected from Barapukuria 2×125 MW coal-fired thermal power plant in Dinajpur district of Bangladesh, have been performed by gamma ray spectrometry technique. The average activity concentrations of 226 Ra, 232 Th and 40 K in feed coal, bottom ash and fly ash samples were 10.46±5.24, 23.50±10.88 and 232.23±131.94 Bqkg -1 ; 56.91±2.77, 69.22±4.26 and 189.79±64.65 Bqkg -1 ; and 70.91±2.90, 115.26±5.79 and 205.53±65.56 Bqkg -1 ; respectively. These measured values were compared with other literature values. The calculated absorbed dose rates were found higher than the worldwide average values for both the bottom ash and fly ash samples. Moreover, the radium equivalent activity in all the samples was less than 370 Bqkg -1 and external hazard

A study of neutron shielding properties of some multilayers containing polyethylene

Abstract Shielding properties of polyethylene (PE), heavy concrete (HC), ordinary concrete (OC), lead (Pb) and their multilayers PE + HC, PE + OC and PE + Pb have been measured. The results of this investigation reveal the effectiveness of the multilayers over their respective composites for neutron shielding.

Full Energy Peak Efficiency Calibration and Efficiency Transfer to ETNA in Gamma-ray Spectrometry

Accurate determination of the radionuclide concentration in environmental sample depends directly on the accurate efficiency calibration in gamma ray spectrometry. The detection efficiency may vary due to some factors (density, sample filling height, matrix, measurement geometry, self-absorption, detection system, etc.) for voluminous samples. Some studies has been conducted in this work and presented in here. The efficiency calibration was performed for two HPGe detectors (relative efficiency of 20% and 40%), using samples (STDMS, STDMP, STDMPF, STDMRL, STDB, STDMC, & STDMG) of various densities (0.55 to 1.59 g/cm 3 ) in cylindrical containers (V=240 cm 3 ) for the gamma ray energy range of 121 keV to 2614 keV. Secondary reference material was prepared by using the standard reference liquid source 152 Eu. From the experimental result it can be seen that efficiency value is inversely proportional to the gamma ray energy. For lower gamma energies of selected nuclide, the efficiency value comparatively higher than the high energies of that nuclide. Efficiency value also varies with filling height of sample. Computer software ETNA was used for the efficiency transfer measurements of three samples (STDMP, STDMPF, & STDMRL) for the configuration of 20% relative efficiency detector. The efficiency value obtained from ETNA was compared with analytical efficiency value. Approximately 2.2% to 15.5% variation was found within the two systems. From the result it can be said that at the initial stage this kind of technical approach is not convenient for the environmental sample measuring laboratory due to the availability of input data for running the ETNA.