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   2011| October-December  | Volume 34 | Issue 4  
    Online since January 17, 2013

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Analysis of neutron streaming through the trenches at linac based neutron generator facility, IGCAR
Usha Pujala, L Thilagam, TS Selvakumaran, DK Mohapatra, E Alagu Raja, KV Subbaiah, R Baskaran
October-December 2011, 34(4):262-266
Shielded LINAC hall has been built to accommodate a radio frequency quadrupole (RFQ) linear accelerator (LINAC) based pulsed neutron generator at RSD, IGCAR. The concrete neutron shield wall thickness for the LINAC hall is finalized by adopting NCRP-51 methodology. The dimensions of the trenches and labyrinth are decided based on the neutron generator installation requirements. As per the AERB safety criteria, the radiation dose levels in the occupancy area should be less than 1μSv/h. However, the refined dose estimate with the inclusion of actual trench and labyrinth dimensions indicates an increased dose rate of ~3.10 μSv/h in LINAC control room. Hence, the control room is declared as controlled area. Additional shielding has been proposed for the trenches and labyrinth to make the control room as full occupancy area. For designing the additional shielding, experimental and theoretical analyses are needed to estimate the radiation streaming through the trenches and labyrinth. To start with, the neutron streaming through trenches have been studied using 185 GBq (5Ci) 241 Am-Be neutron source for qualifying the trenches. The 241 Am-Be source position is selected at the trench entrance such that it contributes the same neutron flux as that of neutron generator. Neutron dose rate and spectral measurements have been carried out at five locations along the trench from the entrance (LINAC hall side) to the exit (Control room side) of the trench.The experimental results are validated with the theoretical calculations using Monte Carlo N particle (MCNP) code. The analysis shows that the trenches are having a dose reduction factor better than 800 with respect to that of entrance dose. The observed dose rate at the trench exit is found to be less than 450nSv/h. In this paper, both the theoretical and experimental neutron streaming analyses through the trenches of LINAC hall are presented.
  5 3,634 434
Radiation levels and radionuclide distributions in soils of the gogi region, a proposed uranium mining region in north Karnataka
I Yashodhara, N Karunakara, K Sudeep Kumar, Rudra Murthy, RM Tripathi
October-December 2011, 34(4):267-269
This paper reports the results of systematic studies aimed at generating a baseline database on the radiation levels and radionuclide distribution in the Gogi region, which has been identified as a prospective uranium mining region. A total of 39 villages in a 0-30 km radius zone of the Gogi region were covered under this study. The ambient gamma absorbed dose rates were measured using portable gamma dosimeters. The activity concentrations of 226 Ra, 232 Th, and 40 K in the soil samples were measured by the HPGe gamma spectrometry method. The ambient gamma absorbed dose rate varied in the range of 126-428 nGy h -1 , with a median value of 143 nGy h -1 . The activities of 226 Ra, 232 Th, and 40 K in the soil varied in the range of 5-176 Bq kg -1 , 9-687 Bq kg -1 , and 81-1493 Bq kg -1 , with the corresponding median values of 36 Bq kg -1 , 85 Bq kg -1 , and 859 Bq kg -1 , respectively. The study showed a highly non-uniform distribution of primordial radionuclides in the soil, with activity concentrations varying significantly within a small area. The results observed in the present study were compared with the literature values reported for other parts of India and the worldwide average values, and discussed.
  4 1,186 282
Study of radon exhalation rate from soil, Bangalore, South India
GV Ashok, N Nagaiah, NG Shiva Prasad, MR Ambika
October-December 2011, 34(4):235-239
The 222 Rn exhalation rate measurements are useful in identifying the locations of high radon exposure. On the other hand, atmospheric 222 Rn concentrations have been observed as an effective tracer for terrestrial air mass movements and atmospheric mixing mass movements. In view of this, year-long measurements of 222 Rn and its exhalation rates were carried out at J B Campus of Bangalore city, and the diurnal and seasonal variations have also been studied. Diurnally, exhalation rate was found to be high during night and early morning hours and low during afternoon hours. The diurnal variability of temperature difference between the lower and upper layers of the soil was found to be responsible for the observed diurnal variations. The monthly average of 222 Rn exhalation rate ranges from 10.63 ± 1.75 to 4.95 ± 0.65 mBq m -2 s -1 . The annual mean value of radon exhalation rate was found to be 8.27 ± 1.83 mBq m -2 s -1 .
  4 1,852 290
Assessment of electron and gamma-induced dna damage in human peripheral blood by alkaline comet assay
Praveen Joseph, Narayana Yerol, Rajesha Nairy, Ganesh Sanjeev, NN Bhat
October-December 2011, 34(4):221-224
In the present study, the effect of electron and gamma irradiation on the induction of DNA damage in human peripheral blood cells was investigated using comet assay. Blood samples were irradiated with an 8 MeV pulsed electron beam at a dose rate of 100 Gy min -1 . Gamma irradiation was carried out at a dose rate of 2 Gy min -1 using 60 Co gamma source. The total dose delivered to the samples was varied from 0 to 4 Gy. Samples were maintained at 0° C before irradiation, and the comet assay was carried out immediately after irradiation. Electrophoresis was performed at a field strength of 0.74 V cm -1 for 25 min at 4°C. A dose-dependent increase in DNA damage was observed. From the observed DNA damage, the relative biological effectiveness (RBE) for electron radiation with reference to gamma radiation on induction of DNA damage has been calculated.
  2 1,839 1,734
A study of gamma radiation induced changes in electrical properties of Aℓ/TeO 2 /n-Si/Aℓ mos capacitor for dosimetric applications
G Chourasiya, TK Maity, SL Sharma, J Sarkar, JC Vyas
October-December 2011, 34(4):249-252
The study of the effects of ionizing radiation on MOS devices has been an active area of research due to their wide range applications. Some attempts have recently been made to investigate the influence of ionizing radiation on properties of the MOS capacitor prepared by replacing SiO 2 layer by any metal oxide layer of large band gap and then to understand its response. The effect of gamma radiation on electrical properties of the Aℓ/TeO 2 /n-Si/Aℓ MOS capacitor has been studied in detail for the first time in the present work in order to understand its applicability in the post-exposure gamma radiation dosimetry. The effect of gamma radiation on the real and imaginary parts of the permittivity, dielectric loss, series resistance, ac conductivity and surface state density has been determined. These properties have been obtained by analyzing C-V and G/ω-V characteristics, recorded at a frequency 1.0 MHz of the small ac signal, for the MOS structure exposed to different levels of the gamma radiation dose. The linear variation of the dielectric constant with the gamma radiation dose over a wide range of doses, observed corresponding to the accumulation region of the MOS capacitor, possesses high potential for its application as the post-exposure gamma radiation dosimeter.
  2 1,549 301
Thoron interference test of different continuous passive radon monitors
CG Sumesh, A Vinod Kumar, RM Tripathi, VD Puranik
October-December 2011, 34(4):257-261
The instruments measuring radon concentration without energy discrimination may have some sensitivity towards thoron concentration. In the present paper, thoron interference tests of a pulse - ionization - chamber - type instrument - Alpha Guard and a semi - conductor - based instrument - Radon Scout Plus (RSP) have been studied in detail. The instruments are compared with a standard active radon - thoron discriminating monitor - RAD7. As a result 9% interference in measured radon concentration for the Alpha Guard monitor and 4% interference for the RSP monitor were observed. The results obtained indicate that the interference of thoron in radon monitors depends on the area of diffusion of gas, volume of detection and sensitivity factor of the monitor.
  1 1,881 276
Measurements of the natural radioactivity in building materials (raw and manufactured), other than granites in Kingdom of Saudi Arabia
A Aydarous, S Zeghib, M Eldaghmah
October-December 2011, 34(4):229-234
In this work, we have measured the natural radioactivity contents of the building materials (raw and manufactured) using HPGe detector. The intensities of γ-ray emitted by radioactive nuclides present in the samples were determined. Efficiencies of the detector at different energies were determined using standard sources, so that radioactivity content of the samples can be estimated. Samples from different areas in Kingdom of Saudi Arabia were collected. These samples were prepared in the form of fine powder suitable to be used by Marinelli beakers. Software equipped with the detector electronic system had been used to analyze the data; hence the results were recorded. The highest measured activity concentrations in the samples are: 48, 42, and 971 Bq/kg for 232 Th, 226 Ra, and 40 K, respectively, which are in the range of the corresponding typical worldwide values. The absorbed dose rates, effective dose rates, radium equivalent activities as well as the radiation hazard indices were estimated. The maximum radium equivalent activity (Ra eq ) was 186 Bq/kg, which is lower than the limit of 370 Bq/kg set by the Organisation for Economic Cooperation and Development.
  1 1,711 306
Study on airborne radioactivity levels in dwellings of Tumkur district, Karnataka state, India
A Jayasheelan, J Sannappa, K Umeshareddy, C Ningappa, S Manjunatha
October-December 2011, 34(4):225-228
Radon is a radioactive gas produced by the decay of 226 Ra present in the soil, rock, water and in atmosphere. Radon, thoron and their progeny are present in indoor and outdoor atmosphere. The concentration of these gases in indoor atmosphere is higher than that of outdoor. In the present study, the concentrations of radon, thoron and their progenies in some taluks of Tumkur district were estimated and the doses due them were calculated. Twin cup dosimeters with alpha sensitive films, LR- 115 type-2, were used for the measurement of concentrations of radionuclides. The mean indoor gamma radiation dose was found to be 0.64 mSvy−1 with highest of 0.75 mSvy−1 in Kunigal taluk. The concentrations of radon in good ventilated dwellings with granite floorings varied from 20.66 Bqm−3 in Tumkur city to 27.61 Bqm−3 in Kunigal. In poor ventilated dwellings, the concentrations of radon varied from 35.56 Bqm−3 in Tumkur to 44.87 Bqm−3 in Turuvekere. The dwellings with granite flooring showed higher concentration of radioactive gases than with marble as flooring and other floorings. The dwelling situated near the granite rocks showed higher concentrations.
  - 1,419 831
Estimation of atmospheric dilution factors for trombay site using the air pollution model
R Shrivastava, SP Indumati, MB Pote, RB Oza, VD Puranik
October-December 2011, 34(4):240-241
This paper presents the application of The Air Pollution Model (TAPM) in estimation of atmospheric dilution factors for Trombay site for unit release rate in different wind sectors. The values obtained from the model are compared with those obtained from routinely collected meteorological data at 10 m height. The measurement carried out at 10 m height is extrapolated to the release height using power laws with stability-dependent coefficient. The maximum value of dilution factor at 1.6 km, computed using model data is 0.1039E-06 s/m 3 while that obtained using measured data is 0.1238E-06 s/m 3 ; however, the two are occurring in different sectors. Thus, model-generated dilution factors can be used in case if only the maximum impact of the releases need to be studied and no measured data are available. In general, it was found that except few sectors, model-generated dilution factors remain within a factor of two as compared to that generated using measured data. The main application of this study is for upcoming sites where representative measured meteorological data may not be available; however, computation of atmospheric dilution factors is required for environmental impact assessment.
  - 1,421 204
Radiation exposure control by estimation of multiplication factors for online remote radiation monitoring systems at vitrification plant
Umesh V Deokar, VV Kulkarni, AR Khot, P Mathew, Kamlesh , RG Purohit, PK Sarkar
October-December 2011, 34(4):242-245
Vitrification Plant is commissioned for vitrification of high-level liquid waste generated in Nuclear Fuel Cycle operations by using Joule Heated Ceramic Melter first time in India. Exposure control is a major concern in operating plant. Therefore, in addition to installed monitors, we have developed online remote radiation monitoring system to minimize number of entries in amber areas and to reduce the exposure to the surveyor and operator. This also helped in volume reduction of secondary waste. The reliability and accuracy of the online monitoring system is confirmed with actual measurements and by theoretical shielding calculations. The multiplication factors were estimated for remote online monitoring of Melter off Gas (MOG) filter, Hood filter, three exhaust filter banks, and overpack monitoring. This paper summarizes how the online remote monitoring system had helped in saving of 128.52 Person-mSv collective dose (14.28% of budgeted dose) and also there was 2.6 m 3 reduction in generation of Cat-I waste.
  - 1,363 156
Radiological safety study of clad failed fuel handling during fifty years of operation of cirus
TR Meena, RK Yadav, SK Prasad, SS Deolekar, KS Babu, N Ramesh, Rakesh Ranjan
October-December 2011, 34(4):246-248
CIRUS reactor, the nucleus of nuclear programme of India is a 40MW research reactor commissioned in July 1960. The reactor was operated efficiently for nearly five decades before it was shutdown permanently on 31 st December 2010. During the reactor operation, incidences of Clad Failed Fuel (CFF) were considered as Safety Related Unusual Occurrences (SRUOs). Incidences of CFF could sometimes lead to severe contamination of system resulting in personnel exposure and generation of large amount of liquid and solid radioactive wastes. CFF detection system used earlier was Gaseous Fission Product Radiation Alarm (GFPRA), which was replaced with new gamma based Failed Fuel Detection (FFD) system during refurbishing of Cirus during 1997-2002. CFF rods handling during nearly five decades of CIRUS reactor operation were studied in detail. Important radiological data related to identification and removal of CFF rod were also analyzed. Collective dose consumption and waste generated both solid and liquid for each CFF was also studied in detail. The use of the new gamma-based FFD system resulted in lowering of collective dose from 110 to 12 Person-mSv per incidence and also reduction in spread of contamination.
  - 1,296 170
Performance of LaCl 3 detector for environmental radioactivity measurements
K Narayani, S Anilkumar, AK Rekha, D. A. R. Babu
October-December 2011, 34(4):253-256
Assessment of natural radioactivity in the environment using gamma spectrometry is common method. NaI (Tl) detectors and HPGe detectors are used for gamma spectrometry in general. The recent arrival of Lanthanum Halide detectors have better resolution compared to NaI (Tl) detectors. In the present work, the performance of Lanthanum Chloride (LaCl 3 ) detector for the natural radioactivity estimation is studied and compared with NaI (Tl) and HPGe detectors.
  - 1,834 239
Measurement of natural activities of 238 U, 232 th and 40 k in tin ore
Nassif A Mansour
October-December 2011, 34(4):270-274
Tin ore is widely used in many industrial purposes. Such as tin ore contain natural radioactive nuclides at various concentrations. If this ore contain high concentrations of natural radioactive nuclides, workers handling them might be exposed to significant levels of radiation. Therefore it is important to determine the radioactive nuclides in this ore. The natural radionuclides ( 238 U, 232 Th and 40 K) and their daughter products contents of tin ore have been estimated in gamma-ray spectrometry and their levels using 70% Hyper-Pure` Germanium (HPGe) detector. The mean activities due to the three radionuclides ( 238 U, 232 Th and 40 K) were found to be 40 ± 3, 19 ± 2.2 and 97 ± 19 Bqkg−1 , respectively. The radium equivalent activity varied from 77.87 ± 11-12.03 ± .27 Bqkg−1 . The representative external hazard index values for the corresponding Tin Ore are also estimated. The results of this assessment obtained by the gamma-ray spectroscopic analysis, have indicated that the levels of natural radioactivity were lower than the international recommended limits.
  - 2,683 351
Natural radioactivity in the volcanic field north of Sana'a, Yemen
EE Saleh, AI El-Mageed, AH El-Kamel, A Abbady, S Harb
October-December 2011, 34(4):275-281
The level of natural radioactivity in rocks and soil of 32 samples collected from locations at North Sana'a in Yemen was measured. Concentrations of radionuclides in rocks and soils samples were determined by gamma-ray spectrometer using HPGe detector with specially designed shield. The average radioactivity concentrations of 226 Ra, 232 Th and 40 K were determined and expressed in Bq kg−1 . The results showed that these radionuclides were present in concentrations of 21.79 ± 3.1, 19.5 ± 2.6 and 399.3 ± 16 Bq kg−1 , respectively, for rocks. For soil, the corresponding values were 48.2 ± 4.4, 41.7 ± 4.5 and 939.1 ± 36 Bq kg−1 . Also, the radiological hazard of the natural radionuclides content, radium equivalent activity, total dose rates, external hazard index and gamma activity concentration index of the (rocks/soils) samples in the area under consideration were calculated. The data were discussed and compared with those given in the literature.
  - 1,366 211
Radiological protection aspects of natural radioactivity of building materials
October-December 2011, 34(4):220-220
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