Abstract
This study reviews the performance analysis of a 137Cs irradiation system that has recently been installed in the laboratory of Uzbek National Institute of Metrology. The laboratory is ...responsible for calibrating calibration facilities and for calibrating most protection level radiation monitoring instruments used in medical, nuclear, industrial and academic settings in Uzbekistan. This system employs the most advanced radiation safety standards, along with 21st century source automation methods. In this work, we review the system’s performance according to ISO 4037 and present measurement uncertainty budget. Our analysis shows excellent results in terms of scattered radiation, beam uniformity and field size, change in source position, test for source impurities, chamber stability and source calibration, and all these parameters fully comply with the requirements of ISO 4037.
Abstract
The paper analyses the possibility of commercial neon indicator lamp at low pressure application as a gamma radiation detector. The diode is most often used as an indicator in electrical ...switchers. The analysis was performed on the basis of experimental electrical breakdown time delay data as a function of relaxation time, applied voltage and gamma ray air kerma rate. It has been shown that the indicator can be used as a detector for relaxation time greater than 70 ms. During this time period, a complete recombination/de-excitation of the particles formed during previous breakdown and subsequent self-sustaining discharge, which can further initiate next breakdown, takes place. It was also shown that gamma radiation leads to a significant reduction in electrical breakdown time delay for applied voltages close to indicator breakdown voltage. Based on the behavior of the dependence of the mean value of the electrical breakdown time delay on the gamma ray air kerma rate, it was shown that the indicator can be used very efficiently as a detector up to air kerma rate of $\textsf{2.3}\cdot \textsf{10}^{-\textsf{5}}$ Gy/h, when the electrical breakdown time delay is measured for applied voltage 10% higher than the breakdown voltage.
Abstract
This paper presents experimental results of dynamic breakdown voltage and delay response as functions of gamma ray air kerma rate for xenon-filled tube at 2.7 mbar pressure. Gamma ray air ...kerma rate range was considered from 123 nGy h–1 up to 12.3 mGy h–1 in order to investigate the possibility of the application of this tube in gamma radiation dosimetry. It was shown that the variations of the above-mentioned parameters are considerable up to the dose rate of 1.23 μGy h–1, which points to the possibility for application in small dose rate gamma ray dosimetry. Physical processes that make dominant impact to dynamic breakdown voltage and delay response during xenon-filled tube irradiation are also discussed in the paper.
Advancements in area monitoring caused by development of environmental monitoring networks which utilise active electronic dosimeters have led to widespread use of active area dosimeters. Currently, ...there are various sets of requirements for area dosimeters available in IEC standards. A clear distinction is not always made between requirements for area dosimeters used for workplace monitoring and that used for environmental monitoring. Performance testing methods related to the radiation characteristics were examined in a number of standards. Out of this, criteria in terms of relative response limits of variation have been derived for photon energy, angle of incidence and dose rate non-linearity for both dosimeter use cases. Testing of several active area dosimeters which are used for environmental monitoring has been performed in a wide range of photon energy, angle of incidence and dose rate. The collected requirements for environmental and workplace area dosimetry imply that some harmonization of IEC standards for area dosimeters is needed.
•Active area dosimeters are frequently used for environmental monitoring.•Analysis of existing IEC standards related to area monitoring was performed.•Harmonized influence quantity ranges and response limits of variation were proposed.•Area dosimeter performance for environmental monitoring was examined.
Quality control and assurance of mammography X-ray generators include the use of solid-state detectors and/or ionization chambers calibrated in standard reference radiation fields. The IEC 61267:2005 ...standard defines reference mammography radiation fields for Mo/Mo anode/filtration, while various anode/filtration combinations are encountered in clinical mammography X-ray units. Not all Secondary Standard Dosimetry Laboratories have an X-ray generator with Mo/Mo radiation setup. Thus, traceability can be established only for the available anode/filter combinations, commonly limited to W/Al. In this study, W/Al radiation fields were established under laboratory conditions by performing half-value layer measurements. Then, four solid-state detectors were characterized. X-ray multimeter performance was evaluated in terms of energy response in the W/Al radiation fields. In the laboratory conditions, the energy response of the dosimeters had a large deviation from unity for dosimeters without appropriate anode/filter combination selected in the software settings, even though most of the dosimeters had a uniform relative response. The discrepancy in the response was further investigated by examining its variation induced by available detector software settings, and it was determined that the dosimeter response can vary up to 20 %. In a clinical setup, the half-value layer was determined, and detector performance was examined. Dosimeters were tested in clinical fields with Mo/Mo, Mo/Rh, W/Rh, W/Ag anode/filter combinations in the X-ray tube voltage range from 25 kV to 35 kV. For most clinical radiation fields, multi-element detectors had energy response deviation within ±5 %. The single-element detector had one software setting available and exhibited strong energy dependence. Extensive testing of detector response, such as presented in this paper. allows for correction factor interpolation based on the half-value layer.
•IEC standard defines mammography reference radiation fields only for Mo/Mo.•Clinical mammography spectra differ due to various anode/filtration materials used.•Non-standard W/Al qualities for laboratory calibration purposes were developed.•Software induced changes in X-ray multimeter response for W/Al fields were examined.•Performance of X-ray multimeters in clinical mammography beams was evaluated.
Qualitative overview of indoor radon surveys in Europe Pantelić, Gordana; Čeliković, Igor; Živanović, Miloš ...
Journal of environmental radioactivity,
August 2019, 2019-Aug, 2019-08-00, 20190801, Letnik:
204
Journal Article
Recenzirano
Odprti dostop
The revised European Directive from 2013 regarding basic safety standard oblige EU Member States to establish a national action plan regarding the exposure to radon. At the same time, International ...Atomic Energy Agency started technical projects in order to assist countries to establish and implement national radon action. As a consequence, in recent years, in numerous countries national radon surveys were conducted and action plans established, which were not performed before. In this paper, a qualitative overview of radon surveys performed in Europe is given with a special attention to the qualitative and conceptual description of surveys, representativeness and QA/QC (quality assurance/quality control).
•Literature overview of indoor radon surveys performed in Europe.•Analysis of survey design and representativeness of indoor radon surveys.•Analysis of measurement techniques used in indoor radon surveys.•Analysis of sampling procedure, sampling number and type of locations in indoor radon surveys.•Analysis of quality assurance and quality control in indoor radon surveys.
Growing concern for radiological and nuclear safety and growing use of radiation protection instruments by both professionals and lay persons increase the need for low cost and reliable ...instrumentation. The aim of this work was to develop a radiation protection instrument that will be both affordable to the widest radiation protection community, including the citizen networks and provide metrologically sound data. The instrument was based on a Geiger-Muller tube, which was tested before and after the energy compensation by lead foils. Instrument energy, angular and dose rate dependence was determined for different tube compensations and the optimum compensation allowing full compliance with relevant standards was identified.
•A low cost Geiger-Müller based radiation protection instrument was developed.•Conformance to relevant standards was achieved by performing energy compensation.•Optimum compensation was achieved by introducing slits in lead foils.•Developed instrument is suitable for citizen networks and early warning networks.
Radon flux measurements provide information about how much radon rises from the ground toward the atmosphere, thus, they could serve as good predictors of indoor radon concentrations. Although there ...are many different mapping methods with many different input data, radon flux data are generally missing and are not included for the delineation of radon priority areas (RPA). The aim of this literature review is to investigate to what extent radon flux was used, or could be used, for the delineation of RPAs. Numerous factors influencing radon flux were identified, but quantifying their contribution to radon flux measurement still remains a challenge. Different methods and measuring devices were used for the determination of radon flux, thus it is necessary to identify possible inconsistencies in order to harmonise different radon flux measurements. Due to the complexity of radon flux measurements, only two countries were identified to have performed national surveys on outdoor radon, which were of much smaller scale compared to those on indoor radon. A positive correlation between radon flux and radon quantities, such as radon in soil gas and indoor radon, indicates that radon flux could be used as an input parameter for the estimation of RPA. By reviewing radon flux models, it was concluded that up-to-date modelled radon flux maps have reached excellent spatial resolution and will be further improved, hence, they could serve as an input for the estimation and delineation of RPA.
Individual monitoring service at the Department for Radiation and Environmental Protection of Vinca Institute of Nuclear Sciences performs individual whole-body and extremities monitoring of exposed ...workers, using thermoluminescent dosimetry (TLD) method. The dosemeters for eye-lens personal dose equivalent measurements, Hp(3), are not regularly used at the workplaces in Serbia, even though the individual monitoring method is accredited and available at the dosimetry service. Type testing of Hp(3) dosemeters based on LiF: Mg,Ti, placed in modified ring holders was done following the changes in ISO 4037:2019 and IEC 62387:2020. The type testing was done by varying radiation-based influence quantities: photon energies ranging from 33.3 keV up to 1.25 MeV, angle of incidence values of 0°, 45°, 60°, 75°, dose range from 0.05 mSv to 10 Sv. The results show that the passive dosimetry monitoring system satisfies IEC 62387:2020 requirements in the mandatory range of influence quantities, except for the lowest tested energy of 33 keV, when incident radiation angle is ±60° and higher.
•Recent changes in ISO 4037 and IEC 62387 prompted new type testing of TLD system.•Introduction of 20 mSv annual limit brought focus to the eye lens dose monitoring.•TLD system that measures Hp(3) due to photon radiation was tested.•Values of CoV limit the use of the system in the dose range from 0.3 mSv to 1 Sv.•System showed unsatisfactory overresponse for more than 60° incident angle.
Interventional procedures in radiology and cardiology are associated with high dose to the patient. Accurate dosimetry is essential and calibration of the equipment is a means to provide the ...necessary accuracy of dose assessment.
The objective of this work is to investigate the performance of dosimeters used in interventional procedures in different standard and non-standard X-ray radiation qualities, and to investigate potential uncertainties related to dose measurements, thus improving accuracy of patient dosimetry in interventional procedures.
Four new reference radiation qualities dedicated to interventional cardiology applications have been established, allowing calibration of dosimeters used in clinical conditions with appropriate traceability to primary standards. Testing of solid-state semiconductor detectors and thermoluminescent dosimeter properties, e.g. influence of photon energy, angle of incidence and dose rate, was performed in the standard and non-standard radiation qualities.
Both dosimeter types showed good performance in the non-standard beams during all performance tests. Solid-state dosimeters displayed weak dependence on energy, angle of incidence and dose rate, in the range defined by the manufacturer and requirements of the international standard. Thermoluminescent dosimeters displayed excellent linearity and angular dependence. The influence of energy dependence on measurement uncertainty can be reduced if appropriate radiation quality is selected for calibration.
•Interventional procedures in diagnostic radiology are not covered by standard radiation qualities.•Non-standard radiation qualities were established related to clinical conditions.•Behaviour of solid-state semiconductor and thermoluminescent dosimeters was tested.•Measurement uncertainty in dosimetry in interventional procedures was improved.
PDF
