Environmental Dosimeter Research Articles

Comparison of dose measurements using environmental and personal dosimeters in real scenarios to deal with radiological and nuclear emergencies

Assessment of dose rates with environmental dosimeters typically takes much longer than with personal dosimeters. This work compares the results of two dosimetry systems with the aim of showing how to use personal dosimeters as environmental dosimeters in the case of radiological and nuclear emergencies, when the processing of a large number of dosimeters is essential. For this purpose, a long-term study has been carried out on the variability of the response of personal (CaSO4:Tm) and environmental (LiF:Mg,Cu,P) dosimeters corrected for the influence of secondary cosmic radiation (SCR). Comparison with each other provided a correlation factor between measurements made using these two passive dosimetry systems. The SCR response of the personal dosimeter was found to be 0.41 (σ = 0.03) significantly lower than 1.24 (Uk=2 = 0.12) that of the environmental dosimeter, which notably affects the comparison of dose measurements made with these two systems in free field. The correlation factor found of 0.86 (σ = 0.08) between the personal and environmental dosimeters allows preparing the personal dosimeters to be used in environmental radiation monitoring.

Dosimetric response of radiophotoluminescent glass detectors in a scanning pencil proton beam

The dose and linear energy transfer (LET) dependence of the radiophotoluminescence (RPL) response was evaluated for RPL glass detectors, taken from the environmental dosimeter type SC-1, using a clinical 100 MeV and 200 MeV scanning pencil proton beam. The measurements were performed at different positions along the Bragg curves. The fluence-averaged (LETf) and dose-averaged (LETd) LET at the positions of the detectors were calculated using two Monte Carlo codes (MCNP and PHITS). Before measurements in proton beams, the linearity of the dose response for the dose range of interest (up to 10 Gy) was checked and confirmed in a Co-60 gamma ray field, since the FGD-202 reader for SC-1 dosimeters is usually used for doses up to 1 Gy and we found no data for higher doses in the literature. For proton beams, the linear dose response was determined for the doses investigated from 0.5 Gy to 8.8 Gy. For the LET range, which corresponds to the LETd from 0.47 keV/μm to 4.70 keV/μm, a decrease in response with an increase in LET was observed.

Evaluation of Radioactivity in Patient Specimens Received in the Core Laboratory at a National Cancer Institute (NCI) Designated Cancer Center.

Biological specimens from patients who have received radiopharmaceuticals are often collected for diagnostic testing and sent to clinical laboratories. Residual radiation has long been assumed to be minimal. However, literature is sparse and may not represent the specimen volumes or spectrum of radionuclides currently seen at National Cancer Institute (NCI)-designated cancer centers. This study examined the radiopharmaceuticals associated with patient specimens received in the hospital core laboratory and assessed the potential risk of external radiation exposure to laboratory personnel. The types and amounts of radiopharmaceuticals administered in a large metropolitan hospital system were retrospectively examined over a 20-month study period. The associated biological specimens sent to the largest core laboratory in the system for testing were evaluated. In addition, manual survey meter assessment of random clinical specimens and weekly wipe tests were performed for 44 weeks, and wearable and environmental dosimeters were placed for 6 months. Over 11 000 specimens, collected within 5 physical half-lives of radiopharmaceutical administration, were processed by our laboratory. Manual survey meter assessment of random clinical specimens routinely identified radioactive specimens. If held in a closed palm for >2 min, many samples could potentially deliver a 0.02 mSv effective dose of radiation. The laboratory regularly receives radioactive patient specimens without radioactive labels. Although the vast majority of these are blood specimens associated with low-dose diagnostic radiopharmaceuticals, some samples may be capable of delivering a significant amount of radiation. Recommendations for laboratories associated with NCI cancer centers are given.

Out-of-field doses for scanning proton radiotherapy of shallowly located paediatric tumours—a comparison of range shifter and 3D printed compensator

The lowest possible energy of proton scanning beam in cyclotron proton therapy facilities is typically between 60 and 100 MeV. Treatment of superficial lesions requires a pre-absorber to deliver doses to shallower volumes. In most of the cases a range shifter (RS) is used, but as an alternative solution, a patient-specific 3D printed proton beam compensator (BC) can be applied. A BC enables further reduction of the air gap and consequently reduction of beam scattering. Such pre-absorbers are additional sources of secondary radiation. The aim of this work was the comparison of RS and BC with respect to out-of-field doses for a simulated treatment of superficial paediatric brain tumours. EURADOS WG9 performed comparative measurements of scattered radiation in the Proteus C-235 IBA facility (Cyclotron Centre Bronowice at the Institute of Nuclear Physics, CCB IFJ PAN, Kraków, Poland) using two anthropomorphic phantoms—5 and 10 yr old—for a superficial target in the brain. Both active detectors located inside the therapy room, and passive detectors placed inside the phantoms were used. Measurements were supplemented by Monte Carlo simulation of the radiation transport. For the applied 3D printed pre-absorbers, out-of-field doses from both secondary photons and neutrons were lower than for RS. Measurements with active environmental dosimeters at five positions inside the therapy room indicated that the RS/BC ratio of the out-of-field dose was also higher than one, with a maximum of 1.7. Photon dose inside phantoms leads to higher out-of-field doses for RS than BC to almost all organs with the highest RS/BC ratio 12.5 and 13.2 for breasts for 5 and 10 yr old phantoms, respectively. For organs closest to the isocentre such as the thyroid, neutron doses were lower for BC than RS due to neutrons moderation in the target volume, but for more distant organs like bladder—conversely—lower doses for RS than BC were observed. The use of 3D printed BC as the pre-absorber placed in the near vicinity of patient in the treatment of superficial tumours does not result in the increase of secondary radiation compared to the treatment with RS, placed far from the patient.

Performance of a radiophotoluminescence (RPL) system in environmental and area monitoring

The objective of this work was to perform an extensive side-by-side comparison between a radiophotoluminescence (RPL) dosimetry system and thermoluminescent dosimeters (TLDs) or EDIS-1™ Environmental Direct Ion Storage Dosimeters during environmental and area monitoring. The measurement locations include points around and within the perimeter of the Paul Scherrer Institute (PSI) and nearby facilities. These data are complemented by a study on the RPL detection limit, uncertainty and dose linearity, as well as two intercomparisons of environmental dosimeters, a Swiss intercomparison organized by PSI and an international intercomparison organized by the German National Metrology Institute (Physikalisch-Technische Bundesanstalt, PTB, Germany). The laboratory irradiations show that the detection limit of the RPL dosimeters is < 50 μSv if the time between pre-dose measurement and readout is < 200 days, and the response is linear up to at least 100 mSv with less than 15% deviation from linearity, satisfying the requirements of the Swiss dosimetry ordinance. The RPL doses were more consistent than the TLD doses over time. The RPL system shows slightly lower doses (12–14%) in comparison with EDIS-1 dosimeters. The intercomparisons for passive environmental dosimeters in terms of H*(10) showed a good agreement between the RPL dose values and the conventional true values. Altogether, the results demonstrate the equivalence between RPL and the other dosimetry systems, providing support for the RPL adoption for environmental dosimetry.

Potential Use of Environmental Biological Samples for Retrospective Electron Paramagnetic Resonance Dosimetry of Radiation Accidents

Retrospective dosimetry is one of the most important tools of accident dosimetry for environmental dose estimation when large-scale radiological incidents and nuclear mass-casualty events occur. Electron paramagnetic resonance (EPR) dosimetry is a physical method for the retrospective assessment of absorbed dose based on the measurement of stable radiation-induced radicals in materials. Different from the fast disappearance of radials in aqueous systems, the radials can persist indefinitely in some organized matrices. Therefore, environmental materials contained in creatures from sea or land can be potentially used as environmental dosimeters for a retrospective dose analysis. This study aims to assess the EPR signals of free radicals from environmental biological samples, potentially for the retrospective dose estimation. The evaluated samples involve ox bone, cyclina shell, clam shell, chitin from squid, and human tissue (enamel and fingernail). First, we dehydrate and grind these materials to the powder with different sizes. Subsequently, all materials were irradiated with different doses ranging from 5 Gy to 50 Gy using 6 MV linear accelerator, and EPR spectra of these materials were obtained from the calculation of peak-to-peak amplitudes. The dose-response curve of EPR signals versus irradiated dose for the six materials shows good linearity (R2~0.99). For the grain-size experiment, the ox bone and tooth with 0.5 mm, the chitin with 0.1 mm, and the others with 1 mm have the strongest signal. For the storage temperature experiment, the optimal temperature of storage is at −20 °C for tooth, fingernail, ox bone, and chitin, at 45 °C for clam shell and cyclina shell where the signal fading is minimal. In conclusion, the developed dose-response curves of the six materials may potentially help a fast, rough retrospective dose reconstruction under the environment when radiation accidents occur.

An Investigation of Radiation Protection Status in Radiology Centers of Kurdistan in 2014-2015

Using personal protective equipment (PPE) properly and following available rules and regulations in the field of ionizing radiation protection can significantly decrease these harms. If these equipment and facilities are not available in diagnostic radiation centers or are not used properly, radiographers’ and people’s health will be jeopardized. To date, no study has examined the protective condition against radiation in diagnostic radiation centers of Kurdistan province. The present study, therefore, was an attempt to address this gap. This cross-sectional study was conducted in 2014-2015 among 35 diagnostic radiation centers of Kurdistan. Data were collected through a checklist (which was developed based on the available radiation protection laws), a survey for patients and their caregivers, and insite observation and dosimetry. The radiation health expert of the province proceeded to each of the radiology centers personally. Upon arrival to each center, he informed health physics officials of the centers about the study and collected data through observation, interview, and the checklist. On the other hand, in order to examine radiation leakage in different modes of imaging session, dosimetry was conducted by the use of an environmental dosimeter (Fluke 451 manufactured in the United States). The collected data were analyzed through Excel. It was found that in 67.3% of the cases, there was personal protective equipment for patients and their caregivers (robes, thyroid strap, gonadal shield, glasses, and lead gloves). Furthermore, this equipment and other physical holders were used for patients and their caregivers in 75.7% of the cases. This rate was 87.6% for pregnant women. In addition, we found that around 94% of the personnel went through medical examinations every six or twelve months, a rate that was much higher than that found in Nohi’s study. When it comes to improving the indices of protection against radiation in radiation centers, it seems that adding the proposed items in this study to the present data collection form (form 110 used for urban areas) or designing a new form will change the attitude toward the concept of protection. This will highlight the importance of this topic and will result in decision makers’ more serious attempts to promote the protection condition.

On-Site Calibration Method of Dosimeter Based on X-Ray Source

The real-time monitoring of environmental radiation dose for nuclear fa-cilities is an important part of safety, in order to guarantee the accuracy of the monitoring results regular calibration is necessary. Around nuclear facilities there are so many environmental dosimeters installed dispers-edly, because of its huge quantity, widely distributed, and in real-time monitoring state; it will cost lots of manpower and finance if it were tak-en to calibrate on standard laboratory; what’s more it will make the en-vironment out of control. To solve the problem of the measurement ac-curacy of the stationary gamma radiation dosimeter, an on-site calibra-tion method is proposed. The radioactive source is X-ray spectrum, and the dose reference instrument which has been calibrated by the national standard laboratory is a high pressure ionization. On-site calibration is divided into two parts; firstly the energy response experiment of dosim-eter for high and low energy is done in the laboratory, and the energy response curve is obtained combining with Monte Carlo simulation; sec-ondly experiment is carried out in the field of the measuring dosimeter, and the substitution method to calibrate the dosimeter is used; finally the calibration coefficient is gotten through energy curve correction. In order to verify the accuracy of on-site calibration method, the calibrated dosimeter is test in the standard laboratory and the error is 3.4%. The re-sult shows that the on-site calibration method using X-ray is feasible, and it can improves the accuracy of the measurement results of the stationary γ-ray instrument; what’s more important is that it has great reference value for the radiation safety management and radiation environment evaluation.

The Thermoluminescence Response of Dy Doped Calcium Borate Glass Subjected to 6MV Photon Irradiation

This paper presents the thermoluminescence (TL) response and sensitivity of various dopant concentration of Dy into borate glass. Borates glass present absorption coefficient that closely to human bone and teeth. This fact makes borate as an ideal material for TL material either for medical or environmental dosimeter. Therefore, a series of glasses based on xCaO-(100-x)B2O3system (0 x 100) % weight has been prepared by using melt quenching method. In this research, Dy doped (0.01-0.4) mol% to 30CaO-70B2O3glass sample were studied to investigate the TL properties in terms of dose-response relationship and sensitivity. Samples were irradiated to various doses range 0.5-4.0 Gy subjected to 6 MV photon irradiation by using LINAC Primus MLC 3339. The TL intensity of various dopant concentration were studied and it was founds that the 0.3 mol% Dy has the highest TL response and has linear dose response relationship. The highest sensitivity was calculated as 58 nC.mg-1.Gy-1for 0.3 mol% Dy concentration.

Environmental monitoring using LiMgPO4:Tb, B based optically stimulated luminescence dosimeter

A new optically stimulated luminescence based environmental dosimeter (EnOSLD) was developed using LiMgPO 4 :Tb, B phosphor (LMP). The dosimeters were deployed along with the conventional thermoluminescent based environmental thermoluminescent detectors (EnTLD) for a period of six quarters in the environs of a nuclear power plant in India. The dose estimated by the EnOSLDs was compared with that of the dose estimated by EnTLDs. The mean ratio of the doses measured by thermoluminescent detector to that measured by optically stimulated luminescence dosimeters was found to be 1.04 ± 0.11. The results show that LMP based OSLDs can be used as environmental dosimeter.

An environmental BeO-OSL dosimeter for emergency response

A conceptual design is presented to use measurements of localized absorbed dose in inner cities for production of high resolution maps of the radioactive contamination following a nuclear emergency or radiological attack. The doses are derived from luminescent detectors pre-fixed at places of high importance (e.g. public squares). For such an environmental dosimeter, BeO is used, which can be read out using optically stimulated luminescence (OSL). A suitable casing of black Perspex has been developed to give a sufficiently accurate estimate of the air kerma value at the detector position. The dosimeter is characterized according to light tightness, dose response and angular photon energy dependence. A short overview of the approach for map production is also given. ► An inexpensive, environmentally stable BeO based OSL dosimeter has been developed for emergency response. ► The detector enables fast readouts and shows highly favorable dosimetric properties. ► A conceptual design is described to produce maps of radioactive contamination from localized dose measurements in urban areas.

Radioactivity in the industrial effluent disposed soil

Studies on radiation and radioactivity distribution in the soils of effluent disposed from the sugar industry in India have been conducted. The external gamma dose rates in air and natural radionuclides activities in the soils were measured using an Environmental Radiation Dosimeter and a Gamma-ray Spectrometer respectively. The soil samples were also subject to various physico-chemical analyses. This study revealed some remarkable results that are discussed in the article.

Measurement of gamma natural background radiation in Chamaraja Nagar district, Karnataka state, India

Background: All objects in nature are exposed to ionizing radiation emitted by primordial radionuclides and cosmogenic radionuclides due to cosmic rays, the influence of which on living beings is very imminent and important to study. The amount of this background radiation received by an individual depends on altitude, latitude type of building and the building construction materials. Materials and Methods: In the present study, measurements of natural background radiation were made in the schools, temples, dwellings, and hill stations etc., in Chamaraja Nagar District, Karnataka State, India by using Environmental Dosimeter technique. Results and Conclusion: The absorbed dose rate in dwellings of different villages in this region varies from 98.3 ± 7.1 to 708.2 ± 59.3 nGyh−1 with an average of 291.8 ± 23.4 nGyh−1 , whereas in temples it varies from 71.4 ± 5.2 to 589.0 ± 46.3 nGyh−1 with an average of 240.5 ± 19.2 nGyh−1 .

Investigation on natural radiation level and its hazardous nature of river sediments using γ-ray spectroscopy

The content of natural radionuclides (238U, 232Th, 40K) in sediment samples of Ponnaiyar River, taken from different depths, were determined using a γ-ray spectroscopic system with a NaI(TI) detector with an aim of evaluating the radiation hazard. The results are compared with Indian and world average values. To know the complete radiological characteristics, the radiological indices such as absorbed dose rate, annual effective dose equivalent (indoor and outdoor), radium equivalent activity, hazard index (H ex and H in), γ-index, activity utilization index, and excess lifetime cancer risk were calculated. The results obtained were discussed and compared with the recommended values. The outdoor γ-dose rates were measured at each sampling site using an environmental radiation dosimeter. The measured results were compared with literature values and correlated with the calculated absorbed dose rate. Averages of all the radiation hazard indices and concentrations of all the measured radionuclides in all the layers are lower than the recommended level. The origin of the detected radionuclides is assessed by comparing the present results with the corresponding values for the earth crust and other rock formations.

Development of new system for environmental monitoring based on [formula omitted] detectors

The thermoluminescence detectors (TLD) have been widely used for environmental radiation monitoring around nuclear facilities. In this study, a new environmental dosimeter based on Al 2 O 3 : C detectors placed in black Perspex holder with appropriate filtrations (0.2 mm Aluminium, 0.2 mm Copper and 0.4 mm Lead) has been proposed. The energy response beneath each filter was determined over a photon energy ranging from 20 keV to 1.3 MeV according to the recommendations of the International Standards Organisation (ISO). An algorithm has been elaborated in order to evaluate the ambient dose equivalent from linear combination of the TL-reading of each detector. The results obtained in terms of energy and angle responses are analysed regarding the environmental monitoring standard performance.

A retrospective dosimetry method based on luminescence measurements of food seasonings

Nowadays, due to the socio-political events of the last decade, the problem of how to administrate an emergency caused by a radiological accident or a radiation casualty event is considered of crucial importance by the international scientific community. One of the important activities which have to be accomplished immediately after the occurrence of a radiological accident or attack is the evaluation of doses absorbed by the individuals not carrying physical dosimeters, in order to carry out a triage of the population and to minimize the harmful or lethal effects of radiations. In a following phase of the management operations the environmental dose assessment has to be done in order to get a classification of the level of exposure of different areas and to obtain a confirmation, with the support of numerical calculation models, of the doses absorbed by the population. An estimation of the dose absorbed by common use objects (like bricks and tiles) and biological tissues (such as cut fingernails) collected from areas and individuals may be performed through the identification of radio-induced defects with physical techniques (EPR and stimulated luminescence). A long time experience in food irradiation detection field has shown that herbs and spices contain mineral contaminants with high luminescent sensitivity at high absorbed doses (some kGy). Moreover, different types of natural salt are known to have good luminescence properties. The high availability of these aliments makes them very good candidates to be used as “emergency” environmental dosimeters. The following aspects have been investigated: -the possibility of using photo-stimulated luminescence (PSL) on herbs, spice and salt samples as a screening technique for a qualitative identification of the occurred accidental exposure to the low doses involved in a radiological accident or attack (order of some gray); -the thermoluminescence (TL) signal properties of different kind of salt samples exposed to low doses (0.5-2 Gy); -the characterization of the dosimetric TL properties of mineral debris extracted from a particular kind of herb, the Jamaica Mexican Flower, focusing in particular on its TL signal sensitivity and stability. The performed measurements have provided encouraging results in view of the utilization of salt, herbs and spices as retrospective dosimeters. In particular, the PSL technique on some of the examined samples seems to be suitable for a qualitative low dose exposure estimation, while TL measurements allow also a quantitative estimation of the absorbed dose. A survey of the main results will be presented.

Undoped and calcium doped borate glass system for thermoluminescent dosimeter

Borate glasses present an absorption coefficient very close to that of human tissue. This fact makes some borates ideal materials to develop medical and environmental dosimeters. Glass compositions with calcium tetraborate (CaB4O7) and calcium metaborate (CaB2O4), such as the xCaB4O7−(100−x)CaB2O4 system (0⩽x⩽100wt%) were obtained by the traditional melting/quenching method. A phenomenon widely known as the ‘boron anomaly’ was observed in our thermal analysis measurements, as indicated by the increase of Tg and the appearance of a maximum value in the composition with 40wt% of CaB2O4. The Dy doped and Li co-doped 80CaB4O7–20CaB2O4 (wt%) glass samples were studied by the thermoluminescence technique. The addition of Dy improved the signal sensitivity in about three times with respect to the undoped glass sample. The addition of Li as a co-dopant in this glass caused a shift to a lower temperature of about 20°C in the main glow peak. The structural analysis of the 80CaB4O7–20CaB2O4 (wt%) undoped and doped samples were studied through infrared absorption. We have noted an increase in the coordination number of the boron atoms from 3 to 4, i.e., the conversion of the BO3 triangular structural units into BO4 tetrahedra.

A new environmental dosimeter with imaging plates for the fast neutron monitoring

We describe a dosimeter incorporating BaFBr:Eu2+ imaging plates (IPs) for fast neutron ambient dose equivalent measurements. Its configuration and some of its characteristics will be described. While IPs are far more sensitive to radiation than photographic film or track detectors, they are nevertheless subject to fading and account must be taken of this phenomenon in order to arrive at a correct dose estimation. A procedure for making the fading correction will be presented.

Natural radiation level in the environment of Tehri Garhwal, Uttaranchal

The natural radiation levels were measured in about 50 residential houses of Tehri Garhwal, Uttaranchal, using an environmental radiation dosimeter in both the indoor and the outdoor atmosphere. The total gamma ray activity was found to vary from 29.74 µR/h to 41.19 µR/h with a mean of 36.5 µR/h for the indoor environment, whereas for outdoors it varied from 28.76 µR/h to 43.46 µR/h with a mean of 30.1 µR/h. The resulting gamma ray dose at 20 traditional rural houses was also measured. The values varied from 38.91 µR/h to 77.68 µR/h with a mean of 66.6 µR/h. Measurements of the diurnal variation of the dose rates showed that they are higher in the rural traditional houses than in modern houses. The variations of dose rate with the type of building material, the mode of construction and the age of houses are also discussed.

Blind performance testing of personal and environmental dosimeters based on TLD-100 and natural CaF 2:NaCl

Blind performance testing was performed to evaluate the personal H p(10), ambient H ∗(10) and directional H′(10, α) operational quantities for penetrating radiation using dosimeters containing two TLD-100 and two natural CaF 2:NaCl thermoluminescent (TL) detectors, one of each type placed between a lead filter. Initially, the curve of the TL response dependence with the photon energy was obtained for each detector. The monitors were irradiated on a polymethil methacrylate slab water phantom to evaluate H p(10) and free in air in case of H ∗(10) and H′(10, α). The analysis was performed based on the trumpet curves derived from the recommendations of ICRP (1990 Recommendations of the International Commission on Radiological Protection. ICRP Publication 60, 1991; General Principles for the Radiation Protection of Workers. ICRP Publication 75, 1997). A combination of two CaF 2:NaCl detectors (one without and one with lead filter) and one LiF TLD-100 without filter provides values of operational quantities within 95% confidence level as recommended by the international organization. The average ratios 〈 H(10) determined/ H(10) nominal〉 (deviation) obtained for personal and ambient dose equivalents are 1.00(12) and 1.03(06), respectively, with the combination of three of the detectors above quoted.