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   2016| October-December  | Volume 39 | Issue 4  
    Online since February 13, 2017

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A methodology for evaluation of absorbed gamma dose-rate factors for radionuclides distribution in soil
Kh A Allam
October-December 2016, 39(4):177-182
After Fukushima accident, new approaches are found to be needed for the simulation of the absorbed dose-rate calculation due to different reasons; the large number of contaminated areas with different shapes, geometries, compositions, and densities. Furthermore, the effect of the depth profile of gamma-emitting isotopes. In this work, a new home made computer software was developed based on a simple model for dose-rate factors computation of radionuclides distribution in soil. The software used Monte Carlo simulation for model solution. The developed software was used for studying the main factors that affect the exposure dose rate; among those are the contaminated soil (source term) geometries, the shape, the composition, and the density. In addition, the effect of radioactivity depth profile was studied using the soil layers' model. The results of the dose-rate factors show that (a) the variation of shape and the density has a slight effect on the calculation. The effect of source term composition was up to 7.4% from the standard one. (b) 98% of the dose rate comes only from the first 5 m lateral distance from the source term around the studied point. (c) The most important parameter was the depth profile of gamma emitters in soil, because about 50% of the dose rate comes from the first 5 cm of soil depth, about 20% from the second 5 cm layer, about 10% from the third 5 cm layer, and only less than 2% comes from the eighth 5 cm layer. Finally, besides the model simplicity in this work, the associated software is fast, and the calculated results are compatible with the international models.
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Review of the linear nonthreshold model
Badanidiyoor S Rao
October-December 2016, 39(4):173-176
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Assessment of natural radioactivity levels and identification of minerals in Brahmaputra (Jamuna) river sand and sediment, Bangladesh
Md. Ibrahim Khalil, Ratan Kumar Majumder, Md. Zafrul Kabir, Farah Deeba, Md. Nazrul Islam Khan, Md. Idris Ali, Debasish Paul, Md. Abu Haydar, Syed Mohammad Azharul Islam
October-December 2016, 39(4):204-211
Distribution of the natural radionuclides (238 U,232 Th, and 40 K) and their specific activities in sands and sediments of the Brahmaputra (Jamuna) river of Bangladesh together with mineral characteristics has been studied to assess the radiation levels as well as to develop a baseline database for comparison in the future in case of any change in the area under study due to anthropogenic activities. The radiological parameters of natural radioactivity were assessed calculating the radium equivalent activity, hazard index, the absorbed dose rate, and annual effective dose. The average activity concentrations of 226 Ra (238 U),232 Th, and 40 K in sand and sediment were found to be 59 ± 2 & 60 ± 2 Bq/kg, 113 ± 5 & 135 ± 5 Bq/kg, and 983 ± 42 & 1002 ± 43 Bq/kg, respectively. The calculated average absorbed dose rate and annual effective dose were found to be 150 nGy/h and 0.18 mSv/year respectively. These high values are associated with mineral content of the sediment. X-ray diffraction peaks of sand and sediment samples identify quartz, feldspar, rutile, zircon, monazite, uranium fluoride, hematite, kyanite, and uranium arsenide minerals to be present in the samples.
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Radioprotective potential of Decalepis hamiltonii: A study on gamma radiation-induced oxidative stress and toxicity in Drosophila melanogaster
Muzeer Pasha, Ganesh Sanjeev, T Shivanandappa, SR Ramesh
October-December 2016, 39(4):183-189
Radiation-induced damage to normal tissues restricts the therapeutic use of radiation in clinical application for cancer treatment and thereby limits the efficacy of the treatment. The use of chemical compounds as radioprotectors is a desirable strategy to improve the therapeutic index of radiotherapy. However, most of the synthetic radioprotective compounds studied have shown to have undesirable properties of toxicity. There is a need for safer, natural radioprotective agents without compromising efficacy of the treatment. We have investigated the radioprotective potential of Decalepis hamiltonii (Dh) root extract which is rich in natural antioxidants by employing Drosophila melanogaster as a model. Irradiation of Drosophila with 100, 200, and 400 Gy of gamma radiation induced dose-dependent mortality. Elevation in the levels of thiobarbituric acid reactive substances (TBARS), the activities of catalase (CAT) and superoxide dismutase (SOD), and depletion of glutathione (GSH) content suggested radiation-induced oxidative stress. Pretreatment of flies with Dh root extract protected them from radiation-induced mortality and oxidative stress as evidenced by reduction in TBARS and restoration of the antioxidant enzymes, SOD and CAT, and GSH to control levels. This is the first report of radioprotective action of Dh root extract in D. melanogaster.
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Radiological assessment and geochemical characterization of the sediments of Awba Dam, University of Ibadan, Nigeria
Nnamdi Norbert Jibiri, Idowu Richard Akomolafe
October-December 2016, 39(4):222-232
The distribution of natural radionuclides and geochemical parameters in the sediments of Awba Dam, University of Ibadan, Nigeria has been determined. The mean absorbed dose rates obtained were 72.3 nGy/h (upstream), 53.9 nGy/h (middle stream) and 50.29 nGy/h (downstream) with the corresponding mean annual effective dose rates of 0.09, 0.07 and 0.06 mSv/year, respectively. The geochemical analysis showed that Si, Al, Fe, Mn, Mg, Ca, Na, K, and Ti were the major elements and Zn, Cu, Cr, Rb, Ni, Ba, Ga, Ce, and Sr as heavy metals in the sediments. The moderate enrichment elements were Zn, Rb, Ba and Ga, whereas elements deficient in enrichment were Cr, Sr, Ce, Cu, and Ni. The geo-accumulation index was from unpolluted to moderately polluted environment. The enrichment factors (EF) observed in the elements indicate that these metals are entirely from crustal material or natural origin while EF >1.5 observed in Zn, Rb, Ba, and Ga suggests that the sources are more likely to be anthropogenic. The values of the radiological hazard parameter indices were below the recommended safe limits; an indication that the sediments can be used safely.
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ISOGEN: Interactive isotope generation and depletion code
Kamatam Venkata Subbaiah
October-December 2016, 39(4):212-221
ISOGEN is an interactive code for solving first order coupled linear differential equations with constant coefficients for a large number of isotopes, which are produced or depleted by the processes of radioactive decay or through neutron transmutation or fission. These coupled equations can be written in a matrix notation involving radioactive decay constants and transmutation coefficients, and the eigenvalues of thus formed matrix vary widely (several tens of orders), and hence no single method of solution is suitable for obtaining precise estimate of concentrations of isotopes. Therefore, different methods of solutions are followed, namely, matrix exponential method, Bateman series method, and Gauss–Seidel iteration method, as was followed in the ORIGEN-2 code. ISOGEN code is written in a modern computer language, VB.NET version 2013 for Windows operating system version 7, which enables one to provide many interactive features between the user and the program. The output results depend on the input neutron database employed and the time step involved in the calculations. The present program can display the information about the database files, and the user has to select one which suits the current need. The program prints the “WARNING” information if the time step is too large, which is decided based on the built-in convergence criterion. Other salient interactive features provided are (i) inspection of input data that goes into calculation, (ii) viewing of radioactive decay sequence of isotopes (daughters, precursors, photons emitted) in a graphical format, (iii) solution of parent and daughter products by direct Bateman series solution method, (iv) quick input method and context sensitive prompts for guiding the novice user, (v) view of output tables for any parameter of interest, and (vi) output file can be read to generate new information and can be viewed or printed since the program stores basic nuclide concentration unlike other batch jobs. The sample problems are chosen to serve two purposes, namely to validate the results of the code against problems where the analytical solution is possible, and the other is to demonstrate the use of particular solution method adopted for solving the problem. Besides spent fuels, results are validated for many of the useful deduced parameters of practical interest such as radioactivity, thermal power, alpha activity, neutron emission rate, and photon emission spectrum. These parameters are of utmost important in handling spent fuels, in waste disposal, in fuel management, in radiation shielding and many other areas of nuclear fuel cycle facilities.
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Development of an ionization chamber-based high sensitivity detector for the measurement of radiation dose from X-ray whole body scanners
Sunil Kumar Singh, Sudesh M Tripathi, Liji Shaiju, V Sathian, Mukund S Kulkarni
October-December 2016, 39(4):190-193
Dose from X-ray-based transmission type whole-body scanner (WBS) is very small and its measurement is a regulatory requirement as recommended by ANSI/HPS N43.17-2009. Measurement of dose of the order of 25 µ R per scan (received by the person screened) requires very sensitive detector/instrument whose response is energy independent. Such systems are not commercially available. In view of this, a large volume, high sensitivity, ionization chamber (IC) was designed and developed for its use in the measurement of reference effective dose from transmission type X-ray-based WBSs. The IC has thin aluminum wall and was tested for direct X-ray beam from 120 to 180 kV. The measured sensitivity for X-ray spectrum from 120 to 180 kV was found to be 41.75 pC/µR with a standard deviation of ± 0.53%. The field uniformity at the measurement distance of 5 m was within ± 5%.
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Correlation between dose rate and physical factors of patients undergoing peptide receptor radionuclide therapy with (Lu-177)-DOTATATE
Kamaldeep , Sushma Kaisar, Pravind Maletha, Shriram Tervankar, RK Gopalakrishnan, Sandip Basu, M. G. R. Rajan
October-December 2016, 39(4):194-198
In peptide receptor radionuclide therapy (PRRNT) for the treatment of neuroendocrine tumors with (Lu-177)-DOTATATE, large variations in dose rate at 1 m from the patient's body surface administered with same amount of Lu-177 activity are observed. The aim of this prospective study was to explain the cause of the variations and see if there is correlation between the dose rate per unit activity at 1 m distance from patient's body surface in PRRNT with (Lu-177)-DOTATATE and physical factors such as height, weight, age, body surface area (BSA), body mass index (BMI), height/weight (H/W) ratio, and BSA/BMI ratio. From this study, it is observed that dose rate per unit activity at 1 m distance from patient's body surface is significantly correlated with BMI, H/W ratio, and weight of the patients. Male and female patient's data were also separately analyzed, and there was no statistically significant difference observed in these groups of patients. As BMI or weight of the patient is increases, dose rate per unit activity at 1 m distance from patient's body surface decreases and as H/W ratio increases dose rate per unit activity at 1 m distance from patient's body surface also increases. Moderate correlation was seen with BSA and BSA/BMI ratio of the patients. No correlation was seen with age and height of the patients. From this study, H/W ratio can be considered as a good parameter for correlating the dose rate and activity retained in the patient's body. H/W ratio of patient affects the external dose measurement at 1 m from body surface immediately post-Lu-177 labeled PRRNT therapy. Thus, the study is important in formulating the regulatory criterion for discharge of patients after the treatment.
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Development of chloroform: Methyl red dosimeter for blood irradiation dosimetry
Sandip Mondal, SH Shinde, MS Kulkarni, S Adhikari
October-December 2016, 39(4):199-203
The use of chloroform (CHCl3) solution containing methyl red (CMR) was investigated for the dosimetric application. This is based on the radiolytic formation of hydrochloric acid from CHCl3, which protonates a pH indicator, namely, methyl red, and leads to a visual change in color. The optimum concentration of methyl red and wavelength for absorption maxima for the dosimeter were established at 2 × 10−4 mol/dm 3 and 550 nm, respectively. The useful dose range for the dosimeter is 5–50 Gy. The reproducibility of the system is found to be within ±5%. Pre- and post-irradiation stability of the dosimeter solution was also investigated for 1 month and 24 h, respectively. The importance of a chemical dosimeter in the dose range of 5–50 Gy prominently lies in applications such as blood irradiation. Thus, dose mapping of the Blood Irradiator-2000 was carried out using CMR dosimeter. These dose values were further confirmed using a reference standard Fricke dosimeter.
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Summary of ICRP publications, meeting of members of ICRP and IARP, and new RPEJ publication award announcement
DD Rao
October-December 2016, 39(4):233-235
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