Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 29 December 2011 C. Srinivasa Sarma, K. Rama Reddy The effects of high Frequency (HF) progressive ultrasonic wave on the F-centers in KCl single crystals are discussed in this paper. Ultrasonics of 3MHz and 9MHz are used in the present investigation to produce strain wave perturbation on the F-centers. The thermoluminescence (TL) glow curves obtained from X-irradiated normal and strain wave exposed KCl single crystals show two peaks. In the TL glow curves recorded from X-irradiation followed by the ultrasonic wave exposure of KCl single crystals result in the shift of these peaks to higher temperature side with an increase in their separation and a change in relative areas. However, no additional peaks were seen. Apart from this the strain wave perturbation was also found to effect trapping parameters.

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 28 December 2011 Danielle K. Silletti, Sarah A. Brokus, Elly B. Earlywine, Joshua D. Borycz, Graham F. Peaslee, ... At ambient temperatures, a permanent change due to neutron irradiation has been identified in the luminescent properties of the common mineral calcite. Calcite is one of many ubiquitous minerals that are known to exhibit luminescence under electron bombardment, a process known as cathodoluminescence (CL). The UV-Visible spectra of individual calcite grains were measured with CL spectroscopy before and after neutron irradiation. Exposure to neutrons causes additional crystal lattice defects (beyond those naturally occurring) that leave a permanent, readily-measurable CL signature in the 515 nm region of the spectrum. Dose-response results following irradiation have been measured and a spectroscopic signature is described that increases proportionately to neutron dose. The CL measurements are complicated by a dependence on the orientation relative to direction of excitation. When taken into account, the total dose to the crystal can be estimated, and possibly even the direction of the neutron source can be determined. This signature could potentially be developed into a nuclear forensics tool to help identify locations where special nuclear materials have been stored. Highlights ► Calcite grains produced CL spectra with consistent spectroscopic peak centroids. ► Upon neutron irradiation, the CL spectra exhibit a dose-dependent shoulder peak. ► The peak also depends on the orientation of the calcite crystal to the CL beam. ► This irradiation signature is permanent under ambient conditions.

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 28 December 2011 K. Tang, H. Cui, H. Zhu, Z. Liu, H. Fan The preparation method and some dosimetric properties of the new LiF:Mg,Cu,Si discs are presented. The effect of heat treatments on LiF:Mg,Cu,Si was investigated. The shape of the glow curve for LiF:Mg,Cu,Si is similar to that for standard LiF:Mg,Cu,P (GR-200A), and shows minimal differences when annealed in the range from 260oC to 290oC for 10 min. The TL sensitivity for LiF:Mg,Cu,Si is much lower than that for GR-200A, but is 35 times larger than that for TLD-100 and is slightly higher than that for HMCP. The height of the high-temperature peaks for LiF:Mg,Cu,Si is not only lower than that for GR-200A, but also lower than that for HMCP. The glow curve shape of LiF:Mg,Cu,Si annealed at 260oC for different times shows minimal differences and TL response remains stable. These results indicate that the new LiF:Mg,Cu,Si disc has a good stability to thermal treatments and a lower residual TL signal. Highlights ► The TL sensitivity for LiF:Mg,Cu,Si is 35 times larger than that for TLD-100. ► Glow curve shows minimal differences in the range from 260C to 290C. ► The temperature between 260C and 290C can be used to treat LiF:Mg,Cu,Si. ► LiF:Mg,Cu,Si has a good stability to thermal treatments and a lower residual TL signal.

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 29 December 2011 Grzegorz Adamiec, Aleksandra Heer, Andrzej Bluszcz We present investigations of counting statistics for five different luminescence-measuring systems. The dark current background and the counts obtained for a PM tube under constant illumination at various light intensities were measured. Where no divider is present in the counting system, the standard deviation of the number of counts exceeds the value predicted by a Poisson distribution but by different amounts in the different systems. This has implications for analysis of the uncertainties in the estimated equivalent doses and other quantitative analyses of luminescence measurements. We suggest how to account for the observed overdispersion of count numbers in uncertainty estimation. Highlights ► We investigate the scatter of count numbers registered by PM tube systems. ► The scatter exceeds the one of Poisson distribution. ► Uncertainties of count numbers should be multiplied by a correcting factor. ► The correcting factor must be determined for each system individually

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 24 December 2011 A. Timar-Gabor, Ş. Vasiliniuc, D.A.G. Vandenberghe, C. Cosma, A.G. Wintle Fast component dominated quartz single aliquot regenerative dose optically stimulated luminescence (SAR-OSL) dose response curves that display continuing growth at high doses are increasingly reported in literature. This behavior would result in higher equivalent doses being obtained. Here we document the characteristics of OSL signals from fine (4-11 μm) and coarse (63-90 μm) quartz extracted from Romanian loess that display such behavior. For very high doses (〉1 kGy up to 5-15 kGy) the data could be closely fitted to a double saturating exponential regression model. Nonetheless, the saturation charcteristics of these fine and coarse quartz grains are very different, with average saturation chracteristic doses of D01≈ 175 Gy and D02≈ 1800 Gy in the case of the fine material, while in the case of the coarse material values of D01≈ 55 Gy and D02≈ 600 Gy have been obtained. Our results imply a hitherto unexplained mechanism in OSL production at high doses and question the reliability of obtaining SAR-OSL equivalent doses in the high dose region when a second function is needed to describe the dose response. Highlights ► We document dose response of SAR OSL signals of fine and coarse sedimentary quartz. ► For high doses (〉 1kGy) data was fitted to a double saturating exponential model. ► The saturation characteristics of fine and coarse quartz grains are very different. ► The natural signal of an infinitely old sample was found not to be in saturation. ► We question the reliability of obtaining equivalent doses in the high dose region.

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 23 December 2011 J. Domienik, M. Brodecki, D. Rusicka The dose distributions at the region of eye lens and extremities of staff working in interventional cardiology were analyzed. The doses to physicians and nurses from three hospitals in Poland were measured with TL dosimeters (MCP-N) located on various places near eyebrows, on both fingers, wrists, knees and on the ankle. The procedures under investigation were coronary angiography (CA) and percutaneous coronary intervention (PCI), peacemaker and defibrillator implantations (PM/ICDs), cardiac resynchronization therapy with or without defibrillator implantations (CRT-D or CRT) and radiofrequency ablations (RFA). The study aimed at analyzing the distribution of radiation in selected anatomic regions, determining the typical locations of highest doses and estimating the dose ranges for selected types of procedures.The maximum registered doses per procedure to eye lens and ankle were 1.21mSv and 1.46 mSv for CA PCI procedures, 0.02 mSv and 0.05 mSv for RFA and 0.13 mSv and 0.51 mSv for PM/ICDs, respectively. The maximum doses to fingers, wrists and knees were, accordingly, 2.11 mSv, 1.07 mSv and 0.77 mSv for CA PCI procedures, 0.38 mSv, 0.20 mSv and 0.04 mSv for RFA ones, 0.50 mSv, 0.25 mSv and 0.01 mSv for PM/ICDs procedures and 2.25 mSv, 1,12 mSv and 0.58 mSv for CRT and CRT-D ones. The factors which might influence the dose like utilized radiation, availability of additional protective equipment and position of the staff with respect to X-ray source were also analyzed.The annual doses for eye lens and extremities were estimated on the basis of individual annual workloads of the physicians participating in the study. The highest annual doses were revealed for physicians performing CA PCI procedures. Annual eye lens doses range up to 247 mSv indicating that the occupational limit for eye lens 150 mSv has been surpassed. In case of extremities the maximal estimated annual doses were 355 mSv, 136 mSv, 55 mSv and 328 mSv, for fingers, wrists, knees and for ankle, respectively. Moreover, in the light of ICRP new Statement on Tissue Reactions raising the possibility of lowering the annual limit for the lens of the eye the annual doses estimated in our paper indicate that for some procedures the monitoring of eye lens doses should be considered. On the other hand, it is important to note that most of high occupational doses can be easily avoided if radiation protection tools are used and, moreover, used properly.The present survey is a part of ORAMED project concerning the determination of doses to extremities (fingers, wrists and knees) and eye lens during interventional procedures and includes the detailed analyses of results of Polish partner. They are, however, presented in wider context. The study is additionally extended by the investigation of the dose distribution at the eyebrows and ankle level. Highlights ► The occupational doses in interventional cardiology were analyzed. ► The dose distributions at the region of eye lens and extremities were investigated. ► Large variations in doses were observed depending on some parameters. ► It was estimated that the occupational limit for the eye lens might be exceeded. ► The best position for the eye lens dosimeter for CA PCI procedures was found.

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 3 December 2011 Kaixuan Tan, Zehua Liu, Liangshu Xia, Junwen Lv, Hanqiao Hu Tailings produced during mining and milling of uranium ores represent potentially large volumes of low level radioactive materials. A typical environmental problem associated with mill tailings is radon emanation. Covering tailings is widely applied to reduce radon exhalation rate. In this paper, the fractal theories and field covering tests are used to study the fractal characters of size distribution of six types of covering materials, including waste rock, sand, laterite，kaolin, mixture of sand and laterite,and mixture of waste rock and laterite, and their influences on radon exhalation. The size distributions of uranium tailings and the six aforementioned covering materials all exhibit a good fractal structure. The contents of fine grain increase with the increasing value of fractal dimension. The results of field radon measurement show that the radon emanation rate of tailings without covers is 14.7-18.6 Bq/m•s. Covering tests were carried out of the six abovementioned covering materials with thickness of 0.4m, 0.8m, 1.2m, 1.6m and 2.0 m. The results indicate that the application of these materials for cover layers can decrease the radon exhalation rate markedly. The effectiveness of a cover layer in reducing radon exhalation is related to its fractal texture of size distribution. Under the same thickness conditions, the attenuation coefficient of radon exhalation rate increases with the increasing fractal dimension of size distribution of covers. The empirical expressions of the attenuation coefficients in relation to fractal dimension D of size distribution and thickness x of covers is obtained for evaluating the effectiveness of final covers for uranium tailings impoundments. Highlights ► In this study, the fractal theories and field covering experiments were used to study the fractal characters of size distribution of uranium tailings and six types of covering materials, including waste rock, sand, laterite, kaolin, mixture of sand and laterite, and mixture of waste rock and laterite, and their influences on the radon exhalation. The empirical expressions of the attenuation coefficients in relation to fractal dimension D of size distribution and thickness x of covers is obtained for evaluating the effectiveness of final covers for uranium tailings impoundments.

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Volume 46, Issue 12, December 2011, Pages 1335 Anatoly Rosenfeld, Tomas Kron, Francesco d’Errico

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 25 November 2011 D.M. Bonotto, I. Karmann, M.M. Baskaran The Santana Cave is located at the Upper Ribeira Touristic State Park (PETAR-Parque Estadual Turístico do Alto Ribeira) in southern São Paulo State, Brazil. This paper describesPb activity concentration data in soda straw stalactites samples collected at Salão das Flores in Santana Cave that is a fossil tributary of the cave river. Non-expensive alpha counting following some analytical steps for extracting and depositingPo were used for providing thePb data. In the analyzed samples,Pb values of increasingly older samples fitted an exponential curve, thus suggesting that the production ofPb has been constant with time. Also, the near-ideal fit indicated that the growth was uniform and there was no break in the continuous growth. The soda straw growth rates were determined from the best fit to the exponential curve through thePb activity concentration. The results of the measurements allowed estimate a longitudinal rate corresponding to 1.3 mm/yr and a lateral rate of 0.01 mm/yr, which permitted calculate times of 70 years and 317-498 years for their formation, respectively. The lateral growth rate is compatible with values from studies of chemical weathering rates held under laboratory and natural conditions.

Beschreibung: Publication year: 2011 Source: Radiation Measurements, Available online 25 November 2011 Rosabianca Trevisi, Claudia Orlando, Paolo Orlando, Mario Amici, Carla Simeoni In Italy an extensive survey has been carried out with the aim to evaluate annual average radon concentration in underground workplaces.The survey covered 933 underground rooms located in 311 bank workplaces spread throughout in all Italian regions; at this scope the sampling was stratified random in order to be representative on national scale. The annual radon concentration was estimated by using passive radon dosemeters (NRPB/SSI type holder and CR-39 as detector): the devices were exposed for a period of about 3 months and 4 cycles were performed to cover a solar year. The radon levels in underground workplaces ranged from 27 to 4851 Bq/m3 with an overall mean value of 153 Bq/m3. As expected, radon distribution is not uniform throughout Italy: in several regions high radon annual averages have been found, confirming previous surveys.The analysis of data shows a high variability among regions and intra-region but low spread among rooms belonging to the same workplace.About 5% of underground workplaces displayed radon concentration exceeding 400 Bq/m3, and the 4.4 % exceeds 500 Bq/m3, the national action level for the exposure to natural radioactivity in workplaces. Highlights ► an extensive survey has been carried out to evaluate annual average radon concentration in Italian underground workplaces. ► The survey covered 933 underground workplaces located in 311 bank branches. ► The average annual radon concentration, estimated by using NRPB/SSI passive devices is 153 Bq/m. ► Radon distribution is not uniform among Italian regions and within each region