Passive Dosimeters Research Articles

Measurement of radon concentration inside houses in Tafila Province, Jordan.

The scope of this paper is to present a brief study related to the investigations we have already made at three districts of Tafila province, which is located in the south part of Jordan and where the most important hot spa and phosphate mines are located. The main concern in these investigations is to measure the indoor radon concentration levels by means of CR-39 detectors installed in randomly selected houses during winter season. The exposure time started from December 2008 and lasted for ninety days. After exposure, the detectors were etched in aKOH solution at 70°C for 8 h. The obtained average values of indoor radon concentration in the three different districts were ranged from 20.45 to 32.41 Bq/m3. It was found out that the Ayma district possesses the highest radon concentration. Meanwhile, the district of Aina Al-Badah possesses the lowest. Key words: Indoor radon, CR-39, passive dosimeter, exposure time.

Indoor 222Rn concentrations and the corresponding lung cancer risk in Celein region, west of Al Khums, Libya

222Rn concentrations were measured in 50 dwellings in Celein region, west of Al Khums city in Libya. Time-integrated passive radon dosimeters containing CR-39 detectors were used in this study. The measurements were done in living and bedrooms for each dwelling. After 3 months detectors were collected. Then, applying chemical etching to the exposed detectors, nuclear track numbers and corresponding indoor radon concentrations were determined. The arithmetic mean is 76.1 ± 49.4 Bq m−3 and the geometric mean is 63.8 Bq m−3 with a geometric standard deviation of 1.8. Data distribution is well fitted by a log-normal curve. The fractions of rooms where radon concentrations exceed the reference levels of 148 Bq m−3 is 7.8%. Risk of lung cancer ranges from 4 to 32 per thousand dwellers for nonsmokers and smokers respectively.

Study of Radon Concentration and Lung Cancer Risk in The Right Area of Shirkatt District

During the summer season, in Shirkatt District and by using time integrated passive radon dosimeters containing (CR-39) plastic radon detectors, indoor radon concentration level and lung cancer risks have been measured in 16 sites. The radon concentration ranged between 50.38 and 212.35 Bq/m3 with an average value 103.98 Bq/m3, which lies within the acceptable radon levels (50-150 Bq/m3) recommended by ICRP. Potential alpha energy concentration was varying from 5.4×10-3 to 22.9×10-3 WLM with average value 17.2×10-3 WLM which corresponds to absorption effective dose equivalent 2.4713 mSvy-1in human, It is observed that this value lies within the recommended levels (3-10 mSvy-1) reported by ICRP. The average lung cancer cases per year per 106person were found to be 44.49, there were no inductions of existence of radon problems in this survey

The experimental and simulated LET spectrum and charge spectrum from CR-39 detectors exposed to irons near CRaTER at BNL

Human will be sooner or later return to the moon and will eventually travel to the planets near Earth. Space radiation hazards are an important concern for human space flight in deep space where galactic cosmic rays (GCR) and solar energetic particles are dominated and radiation is much stronger than that in LEO (Low Earth Orbit) because in deep space there is no magnetosphere to screen charged particle and no big planet nearby to shadow the spacecraft. Research indicates that the impact of particle radiation on humans depends strongly on the particles' linear energy transfer (LET) and the radiation risk is dominated by high LET radiation. Therefore, radiation research on high LET should be emphasized and conducted systematically so as to make radiation risk as low as reasonably achievable (ALARA) for astronauts. Radiation around the moon can be measured with silicon detectors and/or CR-39 plastic nuclear track detectors (PNTDs). At present stage the silicon detectors are one of the preferred active dosimeters which are sensitive to all LET and CR-39 detectors are the preferred passive dosimeters which are sensitive to high LET (≥5 keV/μm water). CR-39 PNTDs can be used as personal dosimeters for astronauts. Both the LET spectrum and the charge spectrum for charged particles in space can be measured with silicon detectors and CR-39 detectors. Calibrations for a detector system combined with the silicon detectors CRaTER (Cosmic Rays Telescope for the Effects of Radiation) from Boston University and Massachusetts Institute of Technology, and the CR-39 PNTDs from JSC (Johnson Space Center) – SRAG (Space Radiation Analysis Group) were conducted by exposing the detector system to the accelerator generated protons and heavy ions. US space mission for the radiation measurement around the moon using CRaTER was carried out in 2009. Results obtained from the calibration exposures indicate an excellent agreement between LET spectrum and charge spectrum measured with CR-39 detectors and simulated with PHITS (Particle and Heavy Ion Transport System). This paper introduces the LET spectrum method and charge spectrum method using CR-39 PNTDs and the Monte Carlo simulation method for CR-39 detectors, presents and compares the results measured with CR-39 PNTDs and simulated for CR-39 detectors exposed to heavy irons (600 MeV/n) in BNL (Brookhaven National Laboratory) in front and behind the CRaTER.

Radiation protection measurements around a 12 MeV mobile dedicated IORT accelerator

The aim of this study is to investigate radioprotection issues that must be addressed when dedicated accelerators for intraoperative radiotherapy (IORT) are used in operating rooms. Recently, a new version of a mobile IORT accelerator (LIAC Sordina SpA, Italy) with 12 MeV electron beam has been implemented. This energy is necessary in some specific pathology treatments to allow a better coverage of thick lesions. At an electron energy of 10 MeV, leakage and scattered x-ray radiation (stray radiation) coming from the accelerator device and patient must be considered. If the energy is greater than 10 MeV, the x-ray component will increase; however, the most meaningful change should be the addition of neutron background. Therefore, radiation exposure of personnel during the IORT procedure needs to be carefully evaluated. In this study, stray x-ray radiation was measured and characterized in a series of spherical projections by means of an ion chamber survey meter. To simulate the patient during all measurements, a polymethylmethacrylate (PMMA) slab phantom with volume 30 x 30 x 15 cm3 and density 1.19 g / cm3 was used. The PMMA phantom was placed along the central axis of the beam in order to absorb the electron beams and the tenth value layer (TVL) and half value layer (HVL) of scattered radiation (at 0 degrees, 90 degrees, and 180 degrees scattering angles) were also measured at 1 m of distance from the phantom center. Neutron measurements were performed using passive bubble dosimeters and a neutron probe, specially designed to evaluate ambient dose equivalent H*(10). The x-ray equivalent dose measured at 1 m along the beam axis at 12 MeV was 260 microSv/Gy. The value measured at 1 m at 90 degrees scattering angle was 25 microSv/Gy. The HVL and TVL values were 1.1 and 3.5 cm of lead at 0 degrees, and 0.4 and 1 cm at 90 degrees, respectively. The highest equivalent dose of fast neutrons was found to be at the surface of the phantom on the central beam axis (2.9 +/- 0.6 microSv/Gy), while a lower value was observed below the phantom (1.6 +/- 0.3 microSv/Gy). The neutron dose equivalent at 90 degrees scattering angle and on the floor plane on the beam axis below the beam stopper was negligible. Our data confirm that neutron exposure levels around the new dedicated IORT accelerator are very low. Mobile shielding panels can be used to reduce x-ray levels to below regulatory levels without necessarily providing permanent shielding in the operating room.

Protecting Lunar Colonies From Space Radiation

Protecting Lunar Colonies From Space Radiation

Intercomparison of radiation protection devices in a high-energy stray neutron field. Part III: Instrument response

The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organizational framework for this project was provided by the European radiation Dosimetry Group EURADOS. Work Package 6 of CONRAD dealt with “ complex mixed radiation fields at workplaces” and in this context it organised a benchmark exercise, which included both measurements and calculations, in a stray radiation field at a high-energy particle accelerator at GSI, Germany. The aim was to intercompare the response of several types of active detectors and passive dosemeters in a well-characterised workplace field. The Monte Carlo simulations of the radiation field and the experimental determination of the neutron spectra with various Bonner Sphere Spectrometers are discussed in Rollet et al. (2008) and in Wiegel et al. (2008). This paper focuses on the intercomparison of the response of the dosemeters in terms of ambient dose equivalent. The paper describes in detail the detectors employed in the experiment, followed by a discussion of the results. A comparison is also made with the H * (10) values predicted by the Monte Carlo simulations and those measured by the BSS systems.

Radiation measured for MATROSHKA-1 experiment with passive dosimeters

The radiation field in low Earth orbit (LEO) and deep space is complicated. The radiation impact on astronauts depends strongly on the particles’ linear energy transfer (LET) and is dominated by high LET radiation. Radiation risk is a key concern for human space flight and can be estimated with radiation LET spectra measured for the different organs of an astronaut phantom. At present the best passive personal dosimeters used for astronauts are thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) for low LET and CR-39 plastic nuclear track detectors (PNTDs) for high LET. CR-39 PNTDs, TLDs and OSLDs were used for the MATROSHKA-1 experiment to measure radiation experienced by astronauts outside the international space station (ISS). LET spectra and radiation field quantities (differential and integral fluence, absorbed dose and dose equivalent) were measured for the different organs and skin locations of the MAROSHKA phantom using CR-39 PNTDs and TLDs. The spectra and results can be used to determine the radiation quantities for astronaut's extra vehicular activity (EVA) and for the further in-depth study of the radiation risk for astronauts. Sensitivity fading of CR-39 detectors was observed for the MATROSHKA experiment and a practical method was developed to correct it. This paper presents the radiation LET spectra measured with CR-39 PNTDs and the total radiation quantities combined from results measured with CR-39 PNTDs and TLDs.

Influence of temporally variable groundwater flow conditions on point measurements and contaminant mass flux estimations

Monitoring of contaminant concentrations, e.g., for the estimation of mass discharge or contaminant degradation rates, often is based on point measurements at observation wells. In addition to the problem, that point measurements may not be spatially representative, a further complication may arise due to the temporal dynamics of groundwater flow, which may cause a concentration measurement to be not temporally representative. This paper presents results from a numerical modeling study focusing on temporal variations of the groundwater flow direction. “Measurements” are obtained from point information representing observation wells installed along control planes using different well frequencies and configurations. Results of the scenario simulations show that temporally variable flow conditions can lead to significant temporal fluctuations of the concentration and thus are a substantial source of uncertainty for point measurements. Temporal variation of point concentration measurements may be as high as the average concentration determined, especially near the plume fringe, even when assuming a homogeneous distribution of the hydraulic conductivity. If a heterogeneous hydraulic conductivity field is present, the concentration variability due to a fluctuating groundwater flow direction varies significantly within the control plane and between the different realizations. Determination of contaminant mass fluxes is also influenced by the temporal variability of the concentration measurement, especially for large spacings of the observation wells. Passive dosimeter sampling is found to be appropriate for evaluating the stationarity of contaminant plumes as well as for estimating average concentrations over time when the plume has fully developed. Representative sampling has to be performed over several periods of groundwater flow fluctuation. For the determination of mass fluxes at heterogeneous sites, however, local fluxes, which may vary considerably along a control plane, have to be accounted for. Here, dosimeter sampling in combination with time integrated local water flux measurements can improve mass flux estimates under dynamic flow conditions.

Deficiencies of active electronic radiation protection dosemeters in pulsed fields

Nowadays nearly all radiation fields used for X-ray diagnostics are pulsed. These fields are characterised by a high dose rate during the pulse and a short pulse duration in the range of a few milliseconds. The use of active electronic dosimeters has increased in the past few years, but these types of dosimeters might possibly not measure reliably in pulsed radiation fields. Not only personal dosimeters but also area dosimeters that are used mainly for dose rate measurements are concerned. These cannot be substituted by using passive dosimeter types. The characteristics of active electronic dosimeters determined in a continuous radiation field cannot be transferred to those in pulsed fields. Some provisional measurements with typical electronic dosimeters in pulsed radiation fields are presented to reveal this basic problem.

Radiation measured during ISS-Expedition 13 with different dosimeters

Radiation in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). The biological impact of space radiation to astronauts depends strongly on the particles’ linear energy transfer (LET) and is dominated by high LET radiation. It is important to measure the LET spectrum for the space radiation field and to investigate the influence of radiation on astronauts. At present, the preferred active dosimeters sensitive to all LET are the tissue equivalent proportional counter (TEPC) and the silicon detectors in various configurations; the preferred passive dosimeters are CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET and thermoluminescence dosimeters (TLDs) as well as optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET. The TEPC, CR-39 PNTDs, TLDs and OSLDs were used to investigate the radiation field for the ISS mission Expedition 13 (ISS-12S) in LEO. LET spectra and radiation quantities (fluence, absorbed dose, dose equivalent and quality factor) were measured for the space mission with different dosimeters. This paper introduces the role of high LET radiation in radiobiology, the operational principles for the different dosimeters, the LET spectrum method using CR-39 detectors, the method to combine the results measured with TLDs/OSLDs and CR-39 PNTDs, and presents the LET spectra and the radiation quantities measured and combined.

L’exposition professionnelle aux rayonnements ionisants à l’Assistance publique–Hôpitaux de Paris en 2006

Summary Purpose of the study To analyse the annual level of global external, internal and skin exposure to ionizing radiation of employees in a university health care establishment (AP–HP). Method The exposure to ionizing radiation was assessed among the 6,618 subjects (7.12% of the personnel of AP–HP) occupationally exposed. Their external exposure was monitored using 43,680 passive dosimeters, every month (34.8%) for category A or three months (65.2%) for category B. Ring dosimeters were used to measure the finger doses for workers in nuclear medicine and interventional radiology. Moreover, 1,672 workers in controlled zone had electronic dosimeters. The internal exposure was determined by radiochemical and radiometric measurements. Results The annual average external effective dose was low (0.032 mSv). No internal contamination was observed. Total body doses and skin doses never exceeded the dose limit. Ring dosimeter gave a better assessment of finger doses. The upper doses were observed in radiotherapy (0.038 mSv) and nuclear medicine (0.66 mSv). Conclusion The occupational exposure of health care workers was very far from the regulatory total body dose limit (20 mSv). These measurements remain a step into the radiation protection optimization process needed by the stochastic effects of ionizing radiation, without known threshold.

Radiation measured with different dosimeters during STS-121 space mission

Radiation impact to astronauts depends on the particles’ linear energy transfer (LET) and is dominated by high LET radiation. Radiation risk experienced by astronauts can be determined with the radiation LET spectrum measured and the risk response function obtained from radiobiology. Systematical measurement of the space radiation is an important part for the research on the impact of radiation to astronauts and to make the radiation ALARA (as low as reasonably achievable). For NASA space missions at low Earth orbit (LEO), the active dosimeter used for all LET is the tissue equivalent proportional counter (TEPC) and the passive dosimeters used for the astronauts and for the monitored areas are the combination of CR-39 plastic nuclear track detectors (PNTDs) for high LET and thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeter (OSLDs) for low LET. TEPC, CR-39 PNTDs and TLDs/OSLDs were used to measure the radiation during STS-121 space mission. LET spectra and radiation quantities were obtained with active and passive dosimeters. This paper will introduce the physical principles for TEPC and CR-39 detectors, the LET spectrum method for radiation measurement using CR-39 detectors and TEPC, and will present and compare the radiation LET spectra and quantities measured with TEPC, CR-39 PNTDs and TLDs/OSLDs.

Radiation dosimetry for high LET particles in low Earth orbit

Research indicates that the impact to human tissues from radiation exposure is strongly related to the LET (linear energy transfer) of the particles and particles with high LET ( ⩾ 5 KeV / μ m water) dominate the damage. High LET radiation in LEO (low Earth orbit) is composed mainly of galactic cosmic rays (GCR), solar energetic particles, particles trapped in the SAA (South Atlantic Anomaly), and albedo neutrons and protons scattered from the Earth's atmosphere. So far the active personal dosimeters are not available and the best passive personal dosimeters currently applied to the radiation assessment for astronauts are CR-39 detectors (for the high LET part) in combination with thermoluminescence detectors (TLDs) or optically stimulated luminescence detectors) (OSLDs) (for the low LET part). LET spectra for radiation in LEO were determined with CR-39. This paper introduces the operational principles for CR-39 detectors, describes the method of LET spectrum using CR-39 and presents the results measured with CR-39 and TEPC (tissue equivalent proportional counter) for space mission ISS-Expedition 2, STS-108, STS-112, ISS-7S, STS-114 and STS-121.

Passive dosimeters for nitrogen dioxide in personal/indoor air sampling: A review

Accurate measurement of nitrogen dioxide concentrations in both outdoor and indoor environments, including personal exposures, is a fundamental step for linking atmospheric nitrogen dioxide levels to potential health and ecological effects. The measurement has been conducted generally in two ways: active (pumped) sampling and passive (diffusive) sampling. Diffusion samplers, initially developed and used for workplace air monitoring, have been found to be useful and cost-effective alternatives to conventional pumped samplers for monitoring ambient, indoor and personal exposures at the lower concentrations found in environmental settings. Since the 1970s, passive samplers have been deployed for ambient air monitoring in urban and rural sites, and to determine personal and indoor exposure to NO2. This article reviews the development of NO2 passive samplers, the sampling characteristics of passive samplers currently available, and their application in ambient and indoor air monitoring and personal exposure studies. The limitations and advantages of the various passive sampler geometries (i.e., tube, badge, and radial type) are also discussed. This review provides researchers and risk assessors with practical information about NO2 passive samplers, especially useful when designing field sampling strategies for exposure and indoor/outdoor air sampling.

Evaluation of radon gas concentration in the air of soil and dwellings of Hawar and Foara villages, using (CR-39) detectors

The present study has measured radon concentration in dwellings and soil of two villages of Hawar and Foara by using a passive dosimeter containing a solid-state nuclear track plastic detector commercially known as (CR-39). About 224 dosimeters were distributed inside houses of both villages. Additionally, 56 dosimeters were placed in the soil of each village at 50 cm depth. Soil dosimeters were retrieved after 14 days while house dosimeters were retrieved after three months. The collected dosimeters were chemically etched and then counted using an optical microscope. The study found that indoor radon concentration in Hawar village ranged from 31.6 ± 4.4 Bq m - 3 in the south area to 41.7 ± 5 Bq m - 3 in the west area, and in Foara village, varied between 39.9 ± 9 Bq m - 3 in the east area to 47.9 ± 10.8 Bq m - 3 in the south area. Moreover, the indoor radon concentration in the living rooms at Hawar village was 33.2 ± 2.2 Bq m - 3 which is almost the same as that in the guest rooms, 40.1 ± 3.3 Bq m - 3 , whereas the indoor radon concentration in living rooms at Foara was 36.6 ± 7.5 Bq m - 3 and in the guest rooms was 50.8 ± 5.4 Bq m - 3 . The study indicated also that radon concentration in soil air at Hawar village was 3.7 ± 0.2 kBq m - 3 and in Foara village was 4.3 ± 0.9 kBq m - 3 . The average indoor radon concentrations were comparable in both villages Hawar and Foara. Radon concentration in the study area is comparable to the national radon concentration.

Verification of angular dependence for track sensitivity on several types of CR-39

We verified the angular dependence of track registration sensitivity for four types of CR-39 plastic nuclear track detectors using heavy ion beams. These detectors have been launched with several types of luminescence detectors on the Russian segment of the International Space Station (ISS) to intercompare passive radiation dosimeter components from several institutions. CR-39 detectors were irradiated by several kinds of heavy ions with several hundred MeV/n. All the etched tracks were analyzed using a high-speed microscope (HSP-1000) with ellipse fitting software (PitFit). Reduction of sensitivity was observed near the region of the critical angle. Corrections were made using an empirical method based on the known structure of the galactic cosmic ray spectrum.

Assessment of well being in a crypt with microclimatic, air quality and radon exhalation investigations

We studied the microclimatic and air quality conditions inside the crypt of the cathedral of Otranto (south-east of Italy), which is under the ground level, in order to state if health and well-being conditions are satisfied for tourists and fellows. In particular, we analyzed the heat transfer mechanism and the relative humidity to state the comfort of the environment, applying the Fanger index. The presence of artificial and human pollutants was monitored, respectively, inspecting the carbon monoxide and dioxide concentration. The crypt and the cathedral showed an acceptable state, even during ceremonies when there is crowding inside the crypt. More worrying were the levels of radon concentration, steadily over 500 Bq m - 3 , which constitute a serious threat for the health of workers and visitors. A continuous control during one year was performed, using E-PERM passive electret dosimeters and taking into account troubles connected to the presence of outliers that appear sometimes when using electrets, especially in high-level humidity habitats like crypts.

Recent developments of optically stimulated luminescence materials and techniques for radiation dosimetry and clinical applications

During the last 10 years, optically stimulated luminescence (OSL) has emerged as a formidable competitor not only to thermoluminescence dosimetry (TLD) but also to several other dosimetry systems. Though a large number of materials have been synthesized and studied for OSL, Al2O3:C continues to dominate the dosimetric applications. Re-investigations of OSL in BeOindicate that this material might provide an alternative to Al2O3:C. Study of OSL of electronic components of mobile phones and ID cards appears to have opened up a feasibility of dosimetry and dose reconstruction using the electronic components of gadgets of everyday use in the events of unforeseen situations of radiological accidents, including the event of a dirty bomb by terrorist groups. Among the newly reported materials, a very recent development of NaMgF3:Eu2+ appears fascinating because of its high OSL sensitivity and tolerable tissue equivalence. In clinical dosimetry, an OSL as a passive dosimeter could do all that TLD can do, much faster with a better or at least the same efficiency; and in addition, it provides a possibility of repeated readout unlike TLD, in which all the dose information is lost in a single readout. Of late, OSL has also emerged as a practical real-time dosimeter for in vivo measurements in radiation therapy (for both external beams and brachytherapy) and in various diagnostic radiological examinations including mammography and CT dosimetry. For in vivo measurements, a probe of Al2O3:C of size of a fraction of a millimeter provides the information on both the dose rate and the total dose from the readout of radioluminescence and OSL signals respectively, from the same probe. The availability of OSL dosimeters in various sizes and shapes and their performance characteristics as compared to established dosimeters such as plastic scintillation dosimeters, diode detectors, MOSFET detectors, radiochromic films, etc., shows that OSL may soon become the first choice for point dose measurements in clinical applications. A brief review of the recent developments is presented.

Neutron field characterisation in a high-energy proton–synchrotron environment using bubble detectors

During the beam adjustment of high energy accelerator facilities, a significant number of energetic particles impinge on the internal wall of the vacuum chamber thereby causing the production of intense parasitic radiation field, resulting in a short-term radiation exposure to personnel as well as interference in the operation of accelerator instrumentation systems usually based on sophisticated microelectronics. High-energy particle accelerators operate in pulsed mode; therefore, commercially available, general purpose radiation detectors for health physics activities are unsuitable for the assessment of such radiation field due to “pulse pile-up” effects. Hence, we have used passive neutron dosimeters, i.e. temperature compensated superheated emulsion (bubble) detectors of types BDPND and BDT, to evaluate the neutron fluence at three selected locations of the 7.6 GeV proton synchrotron operated by DESY: (a) the 1.2-m thick concrete shielding roof of the experiment hall housing the proton synchrotron, (b) the 0.9-m thick shielding roof of the proton injector hut, and (c) at the lateral wall (2.5 m concrete and earth shielding) of the experiment hall, facing the proton injector delivering 7.6 GeV protons into the PETRA booster ring.