The IAEA Nuclear Data Section (IAEA NDS) has emphasized the importance of archiving experimental nuclear data with detailed description of the uncertainties to provide reasonable evaluated ...(recommended) data sets with their uncertainties to end-usersof nuclear data. In order to achieve this goal, the IAEA NDS is transferring relevant knowledge to experimentalists by instructing uncertainty propagation for their specific experiments. This article discusses uncertainty propagation based on detailed description of uncertainties in neutron- and charged-particle-induced activation cross sections measured in our studies.
•Uncertainty propagation was performed for the data reduction equations of experimental activation cross sections.•Covariance matrices of parameters characterizing detection efficiency curve and group-wise standard cross sections were propagated to neutron activation cross sections.•Uncertainties in γ-intensities determined by the ENSDF evaluators were propagated to charged-particle activation cross sections.•Deviation from the quadratic sum formula of uncertainty propagation was studied for charged-particle activation cross section determination involving several γ-lines.
Study has been made of the thermoluminescence (TL) response of silica-based Ge-doped cylindrical, flat and photonic crystal fibres (referred to herein as PCF-collapsed) to electron (6, 12 and 20 MeV) ...and photon (6, 10 MV) irradiation and 1.25 MeV γ-rays, for doses from 0.1 Gy to 100 Gy. The electron and photon irradiations were delivered through use of a Varian Model 2100C linear accelerator located at the University of Malaya Medical Centre and γ-rays delivered from a 60Co irradiator located at the Secondary Standard Dosimetry Laboratory (SSDL), Malaysian Nuclear Agency. Tailor-made to be of various dimensions and dopant concentrations (6-10% Ge), the fibres were observed to provide TL yield linear with radiation dose, reproducibility being within 1-5%, with insensitivity to energy and angular variation. The sensitivity dependency of both detectors with respect to field size follows the dependency of the output factors. For flat fibres exposed to 6 MV X-rays, the 6% Ge-doped fibre provided the greatest TL yield while PCF-collapsed showed a response 2.4 times greater than that of the 6% Ge-doped flat fibres. The response of cylindrical fibres increased with core size. The fibres offer uniform response, high spatial resolution and sensitivity, providing the basis of promising TL systems for radiotherapy applications.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Study has been made of the thermoluminescence yield of various novel tailor-made silica fibres, 6 and 8 mol % Ge-doped, with four differing outer dimensions, comprised of flat and cylindrical shapes, ...subjected to electron irradiation. Main thermoluminescence dosimetric characteristics have been investigated, including the glow curve, dose response, energy dependence, minimum detectable dose, effective atomic number, linearity of index and sensitivity of the fibres. The studies have also established the uncertainties involved as well as the stability of response in terms of fading effect, reproducibility and annealing. In addition, dose-rate dependence was accounted for as this has the potential to be a significant factor in radiotherapy applications. The 6 and 8 mol % fibres have been found to provide highly linear dose response within the range 1 to 4 Gy, the smallest size flat fibre, 6 mol% Ge-doped, showing the greatest response by a factor of 1.1 with respect to the highly popular LiF phosphor-based medium TLD100. All of the fibres also showed excellent reproducibility with a standard deviation of < 2% and < 4% for 6 and 8 mol % Ge-doped fibres respectively. For fading evaluation, the smallest 6 mol% Ge-doped dimension flat fibre, i.e., 85 × 270 μm displayed the lowest signal loss within 120 days post-irradiation, at around 26.9% also showing a response superior to that of all of the other fibres. Moreover, all the fibres and TLD-100 chips showed independence with respect to electron irradiation energy and dose-rate. Compared with the 8 mol% Ge-doped optical fibres, the 6 mol% Ge-doped flat optical fibres have been demonstrated to possess more desirable performance features for passive dosimetry, serving as a suitable alternative to TLD-100 for medical irradiation treatment applications.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The environment of the Straits of Malacca receives pollution as a result of various industrial and anthropogenic sources, making systematic studies crucial in determining the prevailing water ...quality. Present study concerns concentrations of natural radionuclides and heavy metals in marine fish (Rastrelliger kanagurta) collected from the Straits of Malacca, since aquatic stock form an important source of the daily diet of the surrounding populace. Assessment was made of the concentrations of key indicator radionuclides (226Ra, 232Th, 40K) and heavy metals (As, Mn, Fe, Cr, Ni, Zn, Cu, Co, Sr, Al, Hg and Pb) together with various radiation indices linked to the consumption of seafish. The annual effective dose for all detected radionuclides for all study locations has been found to be within UNSCEAR acceptable limits as has the associated life-time cancer risk. The overall contamination of the sampled fish from heavy metals was also found to be within limits of tolerance.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Small fields (few cm and below) are being applied in therapy independently or as mm/sub-cm segments of larger fields. Included are intensity modulated radiotherapy (IMRT)/volumetric modulated arc ...therapy (VMAT), proton beam therapy, stereotactic radiosurgery (SRS)/stereotactic radiotherapy (SRT) and stereotactic body radiotherapy (SBRT). With an ability to more closely conform to the target volume, small field applications are nevertheless a challenge to accurate dose evaluation and treatment planning. The influencing factors include finite source size, steep dose gradients, charged particle disequilibrium, detector size and associated volume averaging effects, and changes in energy spectrum and associated dosimetric parameters. Accordingly, small-field dosimetric problems attract interest, not least in consideration of new generation small-volume detectors that promise to reduce energy and dose/dose-rate dependence, also perturbation effects. These include developments made prior to the IAEA-AAPM TRS-483 report on the dosimetry of small static fields in external beam radiotherapy. In present review, the small-field problem is revisited, attention being given to output factor determination using contemporary detectors (Gafchromic film, microDiamond-, diode- and plastic scintillation detectors), also optical fibre dosimeters developed by a University of Surrey/Malaysian Consortium, measurements being made in flattening (FF) and flattening filter-free (FFF) beams. Also included are the effects on output factors in using the daisy-chaining approach associated with the small-field detectors. A survey of small-size dosimeter research shows insignificant difference in small-field output values obtained via direct normalisation or daisy-chaining approach. For fields down to 1 × 1 cm2, microDiamond detector, stereotactic field diode (SFD) and EBT3 film show minor differences (< 3.4%) in the dose response ratio between flattened and non-flattened beams. Present review emphasizes the use of at least two dosimeters to address the variations in small-field dose response using the active micro-dosimeters or passive dosimeters discussed herein.
•Review of small-field output factor measurements using various recent detectors.•Insignificant difference between direct normalisation and daisy-chaining approach.•Difference in non-flattened:flattened beams ratio insignificant down to 1 × 1 cm2 field.•Minimum of two dosimeters needed to tackle variations in small-field dose response.
With numbers of efforts being made towards harnessing the thermoluminescence yield of doped glass media for dosimetric applications, predominantly in the radiotherapeutic regime, review is provided ...of the background to this, tracing developments leading to the present day. Included are an examination of the relative strengths of the various TLD currently on offer and that of glass fabrications, commercial Ge-doped optical fibre as well as novel fibres fabricated from Ge-doped glass. The demands that modern radiotherapeutic dose delivery systems are placing upon these passive forms of dosimetry are reviewed together with the various responses arising from current efforts. Also reviewed are the basis of the luminescence yield, citing the defect types occurring in silica, even in the absence of extrinsic dopants.
•Review of thermoluminescence yield of doped glass media for dosimetric applications.•Focuses on radiotherapeutic regime, addressing the various challenges of modern practices in radiation dosimetry.•Origin of the underpinning defects emphasised.
•We determine the uptake of naturally occurring radionuclides by rice from soil.•Transfer factor, effective dose and excess lifetime cancer risk have been assessed.•Evaluate the radiological impact ...on human body due to the radioactivity in rice.•The transfer factors for 226Ra and 232Th were found far beyond to IAEA default value.
Paddy is the third most widely planted crop in Malaysia and most of the Malaysian people consume rice as their staple food. Hence, studies on the uptake of naturally occurring radionuclides by rice from soil of widely rice cultivated areas in Malaysia have been performed under normal field environments in order to evaluate various radiation hazards via rice consumption. The soil-to-rice grain transfer factors and the annual effective dose have been assessed for the natural radionuclides 226Ra, 232Th and 40K. The estimated transfer factors for 226Ra and 232Th were found far beyond compared to the IAEA reported value for rice. Among the detected radionuclides, 40K shows the highest transfer factor in all study locations but close to the IAEA reported range. The total effective dose obtained due to an ingestion of radionuclides via rice consumption was within the range of world average value (290μSvy−1) compiled by the UNSCEAR (2000) in all study areas. On an average, the excess life time cancer risk (ELCR) values via rice consumption were found below the acceptable limit of 10−3 for radiological risk.
This work builds upon a prior study, examining the dosimetric utility of pencil lead and thin graphitic sheets, focusing upon the measurement of skin doses within the mammographic regime. In ...recognizing the near soft-tissue equivalence of graphite and the earlier-observed favourable thermoluminescence yield of thin sheets of graphite, this has led to present study of 50 μm thick graphite for parameters typical of external beam fractionated radiotherapy and skin dose evaluations. The graphite layers were annealed and then stacked to form an assembly of 0.5 mm nominal thickness. Using a 6 MV photon beam and delivering doses from 2- to 60 Gy, irradiations were conducted, the assembly first forming a superficial layer to a solid water phantom and subsequently underlying a 1.5 cm bolus, seeking to circumvent the build-up to electronic equilibrium for skin treatments. Investigations were made of several dosimetric properties arising from the thermoluminescence yield of the 50 μm thick graphite slabs, in particular proportionality and sensitivity to dose. The results show excellent sensitivity within the dose range of interest, the thermoluminescence response varying with increasing depth through the stacked graphite layers, obtaining a coefficient of determination of 90%. Acknowledging there to be considerable challenge in accurately matching skin thickness with dose, the graphite sheets have nevertheless shown considerable promise as dosimeters of skin, sensitive in determination of dose from the surface of the graphite through to sub-dermal depth thicknesses.
•Graphite foils as TL skin dosimeters.•Dermal and epithelial doses evaluated.•Support provided via the TOPAS Monte Carlo code.•Stacked graphite layers applied in evaluating skin dose down to a depth of 150 μm.
Concentrations of primordial radionuclides in common construction materials collected from the south-west coastal region of India were determined using a high-purity germanium gamma-ray spectrometer. ...Average specific activities (Bq kg(-1)) for (238)U((226)Ra) in cement, brick, soil and stone samples were obtained as 54 ± 13, 21 ± 4, 50 ± 12 and 46 ± 8, respectively. Respective values of (232)Th were obtained as 65 ± 10, 21 ± 3, 58 ± 10 and 57 ± 12. Concentrations of (40)K radionuclide in cement, brick, soil and stone samples were found to be 440 ± 91, 290 ± 20, 380 ± 61 and 432 ± 64, respectively. To evaluate the radiological hazards, radium equivalent activity, various hazard indices, absorbed dose rate and annual effective dose have been calculated, and compared with the literature values. Obtained data could be used as reference information to assess any radiological contamination due to construction materials in future.
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