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  Citation statistics : Table of Contents
   2015| July-September  | Volume 38 | Issue 3  
    Online since November 10, 2015

 
 
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ORIGINAL ARTICLES
Comparison of neutron attenuation properties of ferro boron slabs containing 5% natural boron with other high density materials
D Venakata Subramanian, Adish Haridas, Subhrojit Bagchi, D Sunil Kumar, A John Arul, RS Keshavamurthy, P Puthiyavinayagam, P Chellapandi
July-September 2015, 38(3):109-114
DOI:10.4103/0972-0464.169389  
Modeling and designing cost-effective neutron attenuation along with shield volume reduction is a challenging task in fast reactors. It involves reducing the neutron energy and absorbing them with suitable materials. A series of experiments were conducted in the South beam end of Kalpakkam Mini reactor with powders of ferro boron (FeB), ferrotungsten (FeW), boron carbide, slabs of FeB, and mild steel plates to study their neutron attenuation characteristics. In one of the experiments, FeB slab cast with 5% natural boron was used, and neutron attenuation measurements were carried out. The attenuation factors were found over a thickness of 28 cm for the measured reaction rates of 195 Pt (n, n') 195m Pt, 111 Cd (n, n') 111m Cd, 103 Rh (n, n') 103m Rh, 115 In (n, n') 115m In, 180 Hf (n, n') 180m Hf, 63 Cu (n,g) 64 Cu, 23 Na (n,g) 24 Na, 55 Mn (n,g) 56 Mn, and 197 Au (n,g) 198 Au reactions representative of fast, epithermal, and thermal neutron fluxes. A comparative analysis of the neutron attenuation behavior measured with various materials is presented. In case of attenuation of both thermal and fast fluxes, FeB is better than other high density materials such as mild steel and FeW. The outcome of the experimental study is that FeB slab cast with 5% natural boron can be utilized as cost-effective neutron shield in streaming paths in nuclear reactors.
  3 981 186
Origin of thorium deposits in Kerala beach sands
MR Iyer
July-September 2015, 38(3):98-101
DOI:10.4103/0972-0464.169381  
The origin of the thorium deposits on the West Coast of India is not well established though a number of studies on the various aspects of these deposits have been carried out for more than 50 years. The deposits are believed to be washed down from highlands through water streams. It is proposed that atom ratios of various radioactive and stable products in the uranium and thorium series as a function of time could be effectively used for the purpose. Accordingly, the various ratios have been calculated as a function of the age in the time range of 100-70,000 years. The stable products are included for the first time.Pb-208/Th-232 in Th-232 series, Pb-207/U-235, Pb-207/Pa-231, and in U-235 series and Pb-206/U-238, Pb-206/U-234, Pb-206/Th-230, and Pb206/Ra226 in U-238 series, are presented. The ratios show significant variations in the time range studied. The ratio Pb-206/Pb-207 from the two uranium series is of interest and is examined. This ratio shows a variation of up to 100 times whereas, the natural isotopic ratio is around unity. It is suggested that an extensive measurement of these ratios and their correlation in samples from the hypothesized source in highlands, in river beds, and on the beach sand might give some idea of the transport path for these minerals. Further, it is suggested to measure the ratio of all the lead isotopes from the three series with Pb-204 which is purely of primordial in origin which would also be useful to indicate the contribution from radiogenic sources. In order to undertake such a project which, of course, involves many disciplines large efforts in sampling, in modeling of possible transport paths and strategies for analysis are required.
  2 10,185 317
Acceptance testing and quality assurance of Simulix Evolution radiotherapy simulator
Ashutosh Sinha, Navin Singh, Om Prakash Gurjar, Priyusha Bagdare
July-September 2015, 38(3):102-108
DOI:10.4103/0972-0464.169386  
The success of radiotherapy depends on precise treatment simulation and proper patient positioning. The simulator is a conventional radiographic and fluoroscopic system which emulates the geometrical positions of radiotherapy treatment unit. Hence, the acceptance tests and quality assurance (QA) of the simulator are important prior to its commissioning for the safe and precise clinical use. The verification of mechanical and optical readouts, field size, isocenter, optical and radiation field congruence were performed. The X-ray beam parameters were tested for kVp , mAs and consistency of radiation output. The flat panel detector performance was checked with respect to resolution, low contrast sensitivity (LCS), automatic dose rate control (ADRC), and gray image resolution (GIR). Gantry, table, and imaging system collision possibility was checked. Radiation survey around the room was also performed. The field size test for digital readout and on graph paper, the results of isocenter checkup for rotation of gantry, collimator, and couch, and the deviations observed in auto stop for various movements were found within the tolerance limits. Optical field and radiation field was found congruent. All the lasers were found aligned with the established isocenter. Maximum deviation for set and measured kV was found to be 3% in fluoro mode. The maximum deviation observed in mAs was 1.5% in 3-point as well as in 2-point film exposed mode. The X-ray output was found consistent. The results of tests for resolution, LCS, ADRC, and GIR of the flat panel detector were within tolerance limits. All the six safety interlocks were found working. Radiation level around the room was found within the acceptable limits. All the tests carried out were found within the tolerance limits. The data which has been taken in this study will provide basic support to the routine QA of the simulator.
  1 2,015 259
Comparison of effective atomic numbers of the cancerous and normal kidney tissue
HC Manjunatha
July-September 2015, 38(3):83-91
DOI:10.4103/0972-0464.169376  
The effective atomic number (Z eff ) and electron density (N e ) of normal kidney and cancerous kidney have been computed for total and partial photon interactions by computing the molecular, atomic, and electronic cross section in the wide energy range of 1 keV-100 GeV using WinXCOM. The mean Z eff and N e of normal kidney and cancerous kidney in the various energy ranges and for total and partial photon interactions are tabulated. The variation of effective N e with energy is shown graphically for all photon interactions. In addition to this computer tomography (CT), numbers of normal kidney and cancerous kidney for photon interaction and energy absorption is also computed. The role of Z eff in the dual-energy dividing radiography is also discussed. The values of Z eff and N e for cancerous kidney are higher than normal kidney. This is due to the levels of elements K, Ca, Fe, Ni, and Se are lower and those of the elements Ti, Co, Zn, As, and Cd are higher in the cancer tissue of kidney than those observed in the normal tissue. The soft tissue and cancerous tissue are very similar, but their atomic number differs. The cancerous tissue exhibits a higher Z eff than the normal tissue. This fact helps in the dual-energy dividing radiography which enables to improve the diagnosis of the kidney cancer. Hence, the computed values may be useful in the diagnosis of the kidney cancer. CT numbers for normal kidney are higher than cancerous kidney.
  1 1,192 175
REVIEW ARTICLES
Marine environmental radioactivity measurement programme in India
SK Jha, SJ Sartandel, RM Tripathi
July-September 2015, 38(3):72-77
DOI:10.4103/0972-0464.169368  
Coastal marine Environmental Radioactivity Measurement Programme in India assume significance in view of massive expansion of nuclear power plants in the Asia Pacific region and to establish benchmark of specific radionuclides in coastal marine environment. In the present study Marine Environmental Surveillance was carried out along the east and west coast of India. Fallout out 137 Cs and naturally occurring 226 Ra, 228 Ra were assessed by in house developed in-situ pre-concentration method using copper ferrcyanide and manganese di-oxide coated filter cartridges. 137 Cs activity concentration mapped for Indian coastal region varied from 0.30 to 1.25 Bq m -3 and these were compared with 137 Cs levels of Asia Pacific Region. The marine surveillance data also indicates no input from any source including operation of nuclear power plant in east and west coast of India.
  1 1,355 303
EDITORIAL
Editorial
DD Rao
July-September 2015, 38(3):57-58
DOI:10.4103/0972-0464.169365  
  - 694 180
ORIGINAL ARTICLES
Nasal swab reference levels for plutonium based on aerosol characteristics and breathing patterns of individuals
PD Sawant, SP Prabhu, DP Rath, RK Gopalakrishnan, DD Rao
July-September 2015, 38(3):115-119
DOI:10.4103/0972-0464.169391  
In plutonium (Pu) handling facilities, there is a potential for internal exposure of radiation workers along with external exposure. Nasal swabs (NS) taken rapidly, on site, help in not only providing an early estimate of internal dose due to inhalation of Pu but also in decision making for medical intervention. However, the Committed Effective Dose (CED) computed based on the observed NS activity and that estimated from bioassay measurements of individuals may vary significantly. One of the reasons would be the use of default particle size (5 µm) for computing the CED based on the activity on NS. Other parameters like breathing pattern and levels of exercise would also influence the NS reference activity level and hence their impact needs to be assessed. This study indicated that observed NS reference levels had a direct dependence on all these parameters and use of default parameters for evaluation of internal dose based on NS activity would result in large uncertainties in the dose assessment.
  - 855 222
Comparing the impact of melatonin and captopril on early effects of radiation on the heart tissue by studying glutathione, malondialdehyde, and lactate dehydrogenase enzyme activity in rats
Alireza Shirazi, Farnaz Tabatabaie, Mahmoud Ghazi-Khansari, Hamidreza Mirzaei
July-September 2015, 38(3):92-97
DOI:10.4103/0972-0464.169379  
Prevention of secondary malignancy while the patient is receiving radiotherapy for the management of primary cancer has been an enormous challenge for biological and medical safety. The aim of the study is to compare protective effects of melatonin and captopril on early effects of radiation on the heart tissue of rats. Forty-eight adult male Wistar rats weighing 180-220 g were used. The rats were divided into six groups and the rats were exposed to 8 Gy whole body dose from cobalt-60 sources. Thirty minutes prior to irradiation, six animals received melatonin (100 mg/kg body weight), and six animals received captopril (50 mg/kg body weight). All groups were sacrificed 10 days post-irradiation, and hearts were collected. Malondialdehyde (MDA), lactate dehydrogenase (LDH), and glutathione (GSH) were measured to evaluate cellular oxidative stress-induced injury. The biochemical data are presented as mean ± standard error of the mean, and the difference between the groups was analyzed using a two-way variance analysis. Treatment with captopril resulted in a significant increase in LDH and MDA, although the level of GSH was decreased (P < 0.01). MDA and LDH levels were decreased after melatonin treatment while GSH level was increased (P < 0.001). Melatonin has protective effects following radiation, while treatment with captopril post-irradiation seems to be radiosensitizing and does not have protective effects against radiation exposure.
  - 927 163
REVIEW ARTICLES
Low-level radiation exposures: Time to revisit linear no-threshold concept
MR Iyer, Pushparaja
July-September 2015, 38(3):78-82
DOI:10.4103/0972-0464.169375  
The concepts of LNT (Linear No-Threshold) and the resulting ALARA (As Low As Reasonably Achievable) used for radiological protection have been stumbling blocks for public acceptability of nuclear power. Often, public get confused and easily get exploited by interested people. The application of this concept has perhaps resulted in a more harmful phenomenon now known as "radiophobia." Over the years, LNT has become the corner stone of radiation protection philosophy for the international organizations like ICRP, UNSCEAR etc. which is followed by all national regulators. The genesis of these theories is the cellular level findings of half a century back. Most of these are findings at high dose levels in macro systems and extrapolated to low dose. It is time that international radiation safety organizations revisit the assumptions and have a more pragmatic approach towards these abstract concepts in the light of new findings. The article reviews the evolution of LNT hypothesis and the basis for LNT, examines the possibility that there might be a threshold dose, below which there would be no radiation-related cancer risk. Evidences against LNT and the possible existence of a threshold dose are reviewed. The article concludes that this is definitely time to have a re-look of the corner stone concepts in radiation protection philosophy.
  - 1,179 229
Radiological protection against exposure to naturally occurring radioactive material
PP Haridasan, M Harikumar, PM Ravi, RM Tripathi
July-September 2015, 38(3):59-67
DOI:10.4103/0972-0464.169367  
A large effort is under way at a national and international level to assess exposure to the naturally occurring radioactive material (NORM) and to develop strategies to address existing situations that give rise to exposures. The new International Basic Safety Standards (the BSS) published by the IAEA in 2014 provides requirements reflecting the concept of planned, existing, and emergency exposure situations. This concept is yet to be incorporated in the national standards. Exposure to natural sources, in general, is subject to the requirements for existing exposure situations with some exceptions to be considered as planned exposure situations. Several radiation protection challenges exist for controlling exposures to NORM including concerns on regulatory approaches, diverse nature of the industries, and classification as either existing exposure situations or planned exposure situations, optimization using reference levels or dose constraints, and management of NORM residues and wastes. A review of the current situation on radiological protection applicable to NORM is outlined.
  - 1,263 368
Emergency exposure situations: An update
Pushparaja
July-September 2015, 38(3):68-71
DOI:10.4103/0972-0464.169372  
International Commission on Radiological Protection (ICRP) publication 103 (2007) provided the basic recommendations on radiological protection to cover all radiation exposure situations. It has provided dose limits, dose constraints, and reference levels for use in such situations. Based on these recommendations, International Atomic Energy Agency (IAEA), in its revised basic safety standards (BSS, 2014), provided generic requirements and guidance levels for use by the operators, radiation protection professionals, and the regulators. However, these are generic in nature, and national regulatory authorities are required to decide on the levels for use in their own emergency preparedness and response plans as appropriate: This article just updates the present scenario for emergency exposure situations. The information/material provided in this paper is extracted from the documents listed in the references. For detailed information required for any medical/legal purposes, the readers are expected to refer to the original documents, ICRP-103 (2007) and IAEA-BSS-2014.
  - 891 215
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