Etched Track Detectors Research Articles

Computational and experimental determination of slow neutron flux by using Li-6 foil and nuclear track detector

In the present study, slow neutron flux was determined with an experimental method based on 6Li(n, t)4He reaction. 6Li coated foils were mounted on track etch detectors without any gap and they were irradiated with an Am–Be neutron source for 6 h. The track detectors were affixed on a polyethylene plate which has a thickness of 2.0 cm for neutron moderation. Following irradiation, the track detectors were etched, the tritium tracks were counted with an in-house developed track counting system, and the total number of reactions was computed. The difference in particle ranges and track diameters on the Cr-39 detector allowed for the precise distinguishing of tritium, alpha, and neutron particles. The neutron spectrum at the 6Li coated foil position was simulated with MCNP5 using Evaluated Nuclear Data File (ENDF) cross sections of 6Li(n, t)4He reaction. The total reaction numbers obtained with experimental and computational methods are compatible with each other.

Experiences with accreditation for radon measurement laboratories.

The adoption of the Council Directive 2013/59/EURATOM into Austrian national law generated new challenges for businesses, authorities and measurement services. The law defines radon priority regions in which all employers are obliged to hire an authorised radon-monitoring service to determine radon activity concentration at workplaces in basements and on ground floors. In this paper, an overview of our experiences with the process of becoming an accredited and authorised radon-monitoring body using integrating and time-resolved radon measurement equipment is given. The main challenges to overcome, such as determination of measurement uncertainty, conducting metrologically traceable calibration of the track-etch detector system, information not covered by ISO 11665-1, ISO 11665-4 and ISO 11665-5, availability of proficiency tests, etc., are described. This paper aims to be a guideline for laboratories seeking accreditation in the field of radon activity concentration measurements.

MONTE CARLO SIMULATIONS OF OUT-OF-FIELD LET SPECTRA IN WATER PHANTOM IRRADIATED BY SCANNING PENCIL PROTON BEAM.

LET spectra can be measured by track-etched detectors. However, these detectors are not able to identify the type of interacting particles. Monte Carlo simulations can provide this missing information. In this work, Monte Carlo simulations based on the EURADOS Work Group 9 experiment consisting of systematic 3D mapping of out-of-field doses and LET spectra in a prototype water phantom were performed. The simulations aimed to identify the types of particles contributing to the out-of-field LET spectra. The total absorbed dose, LET and energy spectra were calculated. The calculated dose distributions and LET spectra were compared with the ones measured by radiophotoluminiscence and track-etched detectors. The out-of-field particles and their LET values were identified. No statistically significant differences between the measured and simulated spectra were revealed in the LET range of 100-2000keVμm-1.

Out-of-Field Doses Produced by a Proton Scanning Beam Inside Pediatric Anthropomorphic Phantoms and Their Comparison With Different Photon Modalities.

Since 2010, EURADOS Working Group 9 (Radiation Dosimetry in Radiotherapy) has been involved in the investigation of secondary and scattered radiation doses in X-ray and proton therapy, especially in the case of pediatric patients. The main goal of this paper is to analyze and compare out-of-field neutron and non-neutron organ doses inside 5- and 10-year-old pediatric anthropomorphic phantoms for the treatment of a 5-cm-diameter brain tumor. Proton irradiations were carried out at the Cyclotron Centre Bronowice in IFJ PAN Krakow Poland using a pencil beam scanning technique (PBS) at a gantry with a dedicated scanning nozzle (IBA Proton Therapy System, Proteus 235). Thermoluminescent and radiophotoluminescent dosimeters were used for non-neutron dose measurements while secondary neutrons were measured with track-etched detectors. Out-of-field doses measured using intensity-modulated proton therapy (IMPT) were compared with previous measurements performed within a WG9 for three different photon radiotherapy techniques: 1) intensity-modulated radiation therapy (IMRT), 2) three-dimensional conformal radiation therapy (3D CDRT) performed on a Varian Clinac 2300 linear accelerator (LINAC) in the Centre of Oncology, Krakow, Poland, and 3) Gamma Knife surgery performed on the Leksell Gamma Knife (GK) at the University Hospital Centre Zagreb, Croatia. Phantoms and detectors used in experiments as well as the target location were the same for both photon and proton modalities. The total organ dose equivalent expressed as the sum of neutron and non-neutron components in IMPT was found to be significantly lower (two to three orders of magnitude) in comparison with the different photon radiotherapy techniques for the same delivered tumor dose. For IMPT, neutron doses are lower than non-neutron doses close to the target but become larger than non-neutron doses further away from the target. Results of WG9 studies have provided out-of-field dose levels required for an extensive set of radiotherapy techniques, including proton therapy, and involving a complete description of organ doses of pediatric patients. Such studies are needed for validating mathematical models and Monte Carlo simulation tools for out-of-field dosimetry which is essential for dedicated epidemiological studies which evaluate the risk of second cancers and other late effects for pediatric patients treated with radiotherapy.

Follow-up study on indoor radon levels in Irish schools after a National School Survey and remediation programme

Background: A National Survey of Radon in Irish Schools was carried out by the Department of Education and the Environmental Protection Agency (EPA) (formerly the Radiological Protection Institute of Ireland) between 1998 and 2004. Then, a remediation programme was developed and implemented in the schools with elevated radon levels.
 Objectives: To determine the durability of the remediation systems 10–17 years post-installation and to study the effect of radon awareness on follow-up programmes, radon retests were performed in 16 schools that had some form of remediation implemented.
 Design: The schools were chosen based on the data of the National Survey for Irish Schools and the post-remediation survey. A total of 276 rooms were tested for radon using CR-39 etched track detectors supplied by the EPA. Short questionnaires were given to the school principals to gather information about the level of radon awareness, remediation maintenance and retesting policies.
 Results: An increasing trend in the radon concentration with time was found in some schools. Potential factors contributing to this rise are lack of maintenance, lack of follow-up testing programmes and knowledge lost due to staff turnover. The results showed that 26% of the rooms which had remediation installed had risen to above the Department of Education’s reference level for schools of 200 Bq/m3 again and 10% to above 400 Bq/m3. Through case studies and questionnaires, radon awareness in schools was observed to be correlated with an ability to maintain radon concentrations below the reference level. Although the National Survey of Radon in Irish Schools is to be commended for its exhaustive completeness, many schools in this project were unaware of the remediation system installed. Only 15% of the schools in this study remember or have records of regularly checking or servicing their remediation systems.
 Conclusions: Retesting for radon is crucial in indicating where remediation methods are less effective or have failed. A follow-up programme to retest for radon and to ensure maintenance of remediation systems should be implemented.

Exposure Due to Indoor Radon in Bulgarian Schools

Indoor radon exposure is the largest contributor to population dose from natural sources. Radon as a natural radioactive gas could accumulate to harmful levels in buildings, such as homes and buildings with public access. In order to assess the exposure due to radon in school the results of indoor radon measurements in 55 state school buildings in 7 municipalities located in one district in southern Bulgaria are considered in this paper. The survey was carried out with passive CR-39 etched track detectors. Radon concentrations ranged from 17 to 868 Bq m-3, with a geometric mean of 117 Bq m-3 and a geometric standard deviation of 1.78. The findings revealed that in 30% of the measured buildings the radon concentration was higher than the national reference level of 300 Bq m-3. The statistically significant difference in indoor radon concentrations between municipalities (KW, р < 0.001) was obtained. The research was also focused on parameters affecting radon concentration levels such as type of room and floor location. The estimated annual effective dose of 0.39 to 1.07 mSv y-1, applying the ICRP and UNSCEAR methodology, was calculated for students. The results of the measurements were provided to the administrative authorities and measures were proposed to improve the air in school buildings with high radon levels.

IMPROVING THE ASSESSMENT OF OCCUPATIONAL EXPOSURE TO RADON IN ABOVE-GROUND WORKPLACES

Representative sampling of radon in indoor air is difficult because the concentration often exhibits unpredictable spatial and temporal variation. In workplaces, temporal variation may be rapid, and the minimum and maximum concentration can differ by a factor of 100. In this paper, we compare methods for assessing the radon concentration in workplaces utilising the results of an initial investigation with a track-etch detector and the results of an additional continuous measurement. The recommended method is as follows: the mean radon concentration during the working hours of 1 week, as well as the weekly mean, is calculated from the continuous measurement. The ratio between these mean concentrations is multiplied by the result from the track-etch detector. The coefficient of variation of this method is assessed as 19%. If the result of 1 week of continuous measurement is used alone, the coefficient of variation is assessed as 32%.

Methodological and Conceptual Progresses in Studies on the Latent Tracks in PADC.

Modified structure along latent tracks and track formation process have been investigated in poly (allyl diglycol carbonate), PADC, which is well recognized as a sensitive etched track detector. This knowledge is essential to develop novel detectors with improved track registration property. The track structures of protons and heavy ions (He, C, Ne, Ar, Fe, Kr and Xe) have been examined by means of FT-IR spectrometry, covering the stopping power region between 1.2 to 12,000 eV/nm. Through a set of experiments on low-LET radiations—such as gamma ray-, multi-step damage process by electron hits was confirmed in the radiation-sensitive parts of the PADC repeat-unit. From this result, we unveiled for the first-time the layered structure in tracks, in relation with the number of secondary electrons. We also proved that the etch pit was formed when at least two repeat-units were destroyed along the track radial direction. To evaluate the number of secondary electrons around the tracks, a series of numerical simulations were performed with Geant4-DNA. Therefore, we are proposing new physical criterions to describe the detection thresholds. Furthermore, we propose a present issue of the definition of detection threshold for semi-relativistic C ions. Additionally, as a possible chemical criterion, formation density of hydroxyl group is suggested to express the response of PADC.

Etched track detector methods for the identification of target nuclear fragments in cosmic radiation and accelerator proton beams

In this article, two etched track detector methods for measuring short-range particles are presented and compared. The primary method employs observations of the evolution of the track geometry in intermittent etching, with the use of the appropriate track scanning procedures. The alternative method requires one-step etching and a specific analysis of the track parameters. Both methods proved to be effective in identifying target nuclear fragments amongst a high background from primary cosmic radiation. Additionally, the linear energy transfer (LET) spectrum of the target nuclear fragments, obtained onboard the International Space Station, was found to be consistent with the results from high-energy proton beams in ground-based experiments.

Assessment of uranium concentration in blood of Iraqi females diagnosed with breast cancer.

Cancer is a widespread significant health problem in Iraq and contributes 11% to total deaths. Throughout the Gulf Wars of 1991 and 2003, about 1200 tons of ammunition were dropped around Iraq. After the wars, cancer incidence in Iraq is about 7,000 to 8,000 cancers cases per year, and the overall incidence of lymphoma, leukemia, breast cancer, and lung cancer has increased twofold and even tripled, as compared to the time before the wars. This increase could result from environmental pollution with radioactive materials including uranium, as cancer can be caused by ionizing radiation. To investigate this hypothesis, uranium concentration in the blood of 64 Iraqi females has been measured by means of CR-39 track etch detectors (42 blood samples collected from females diagnosed with breast cancer and 22 blood samples from females without breast cancer). The results show that the uranium concentrations ranged from 19.1 ± 0.3 to 238.4 ± 0.4 with an average value of 94.9 ± 5.0ng L-1 in the blood of women with breast cancer and from 5.2 ± 0.2 to 18.7 ± 0.04 with an average value of 10.5 ± 0.1ng L-1 in the blood of women without breast cancer. In comparison with the literature data, elevated levels of uranium concentration were recorded in both groups, and significantly higher average uranium concentrations were found in the blood of women with breast cancer as compared to those in the blood samples of women without breast cancer. It is concluded that there is a correlation between the incidence of breast cancer in Iraqi women and elevated levels of uranium concentrations in their blood. Whether this is a casual relationship is unclear, because cancer can be caused by various carcinogens, including environmental pollution in the region.

Radon variability due to floor level in two typical residential buildings in Serbia

Abstract It is well known that one of the factors that influence the indoor radon variability is the floor level of the buildings. Considering the fact that the main source of indoor radon is radon in soil gas, it is expected that the radon concentration decreases at higher floors. Thus at higher floors the dominant source of radon is originating from building materials, and in some cases there may be deviations from the generally established regularity. In such sense, we chose one freestanding single-family house with loft and other 16-floor high-rise residential building for this study. The indoor radon measurements were performed by two methods: passive and active. We used passive devices based on track-etched detectors: Radtrak2 Radonova. For the short-term indoor radon measurements, we used two active devices: SN1029 and SN1030 (manufactured by Sun Nuclear Corporation). The first device was fixed in the living room at the ground level and the second was moved through the floors of the residential building. Every measuring cycle at the specified floor lasted seven days with the sampling time of 2 h. The results show two different indoor radon behaviours regarding radon variability due to floor level. In the single-family house with loft we registered intense difference between radon concentration in the ground level and loft, while in the high-rise residential building the radon level was almost the same at all floors, and hence we may conclude that radon originated mainly from building materials.

Results of the first national indoor radon survey performed in Serbia

The first step in every systematic approach to investigating population exposure to radon on a national level is to perform a comprehensive indoor radon survey. Based on general knowledge of the radon levels in Serbia and corresponding doses, the results obtained from a national indoor radon survey would allow policymakers to decide whether it is necessary to establish a national radon programme. For this reason, Serbia initiated work on a national radon action plan (RAP) in 2014 when it was decided to carry out the first national indoor radon survey. The responsibility for establishing the RAP in Serbia is that of the national regulatory body in the field of radiation protection—the Serbian Radiation and Nuclear Safety and Security Directorate (SRBATOM), formerly known as the Serbian Radiation Protection and Nuclear Safety Agency. The first national indoor radon survey was supported by the International Atomic Energy Agency (IAEA) through a Technical Cooperation Programme. Thanks to the IAEA, we received 6000 passive radon devices based on track-etched detectors. In addition, in order to ensure technical support for the project, SRBATOM formed a task force made up of expert radon representatives from national research institutions. This paper presents a thorough description of the sampling design of the first Serbian indoor radon survey. It also presents the results of the national indoor radon survey, including descriptive statistics and testing of the distribution of the obtained results for log-normality. Based on GPS coordinates, indoor radon data were projected onto a map of 10 km × 10 km grid cells. Two values were calculated for each cell to create two distinct maps. One map shows the arithmetic mean value of indoor radon concentration per grid cell, and the other map shows the number of radon detectors per grid cell used for the calculation of mean values.

ANGULAR DEPENDENCE OF TRACK-ETCH DETECTOR HARZLAS TD-1.

Track-etched detectors are commonly used also for radiation monitoring onboard International Space Station. To be registered in track-etched detectors, the particle needs to meet several criteria-it must have linear energy transfer above the detection threshold and strike the detector's surface under an angle higher than the so-called critical angle. Linear energy transfer is then estimated from calibration curve from the etch rate ratio V that is calculated from parameters of individual tracks appearing on the detector's surface after chemical etching. It has been observed that V can depend on the incident angle and this dependence can vary for different detector materials, etching and evaluating conditions. To investigate angular dependence, detectors (Harzlas TD-1) were irradiated at HIMAC by several ions under angles from 0° to 90°. The correction accounting not only for critical angle but also for dependence of V on the incident angle is introduced and applied to spectra measured onboard International Space Station.

Measurement of Truebeam® Head-Leakage by Optically Stimulated Uminescence/Track-Etch Passive Detectors

This work was performed in order to measure the photon and neutron head-leakage values of the TrueBeam® (TB) accelerator. Measurements are compared with the data provided by the manufacturer for TB as well as Clinac.Four higher photon energies (10MV, 10MV FFF, 18MV and 20MV) and electron energy (22MeV) are considered in this study. The electron energy used in this study was the maximum available in this machine. Optically Stimulated Luminescence (OSL) Dosimeters are used for photon head-leakage measurements. Neutron component of the head-leakage was measured using track-etch (CR-39) detectors. Both photon and neutron head-leakage values for TB machine was measured using OSL and track-etch, respectively. These results were compared with the standard values provided by the manufacturer for both TB and Clinac. The study indicates that the higher neutron head-leakage once moved towards the 20MV range of photon energy. Also, the lower head-leakage values were recorded for flattening filter free beam (10MV FFF). It was observed that the photon head leakage value for Clinac was higher, and the neutron head-leakage value was found to be slightly less than the TB values.

Determination of number and diameter of superheated droplets in bubble detectors (BD) of Type T-12 by irradiation with high energy heavy ions 56Fe, 84Kr and 132Xe at accelerator

The number (n) and diameter (d) of superheated droplets in bubble detectors of Type T-12 have been determined with high-energy heavy ions 56Fe, 84Kr and 132Xe at HIMAC accelerator in the National Institute of Radiological Sciences (NIRS), Chiba Japan. The approach to determining the number and diameter of superheated droplets is based on determination of (1) the average gap distance (g) between two neighboring bubbles in a track of high-energy heavy ion and (2) the volume ratio (VL/V) of superheated droplets to the whole volume of the detector. The volume ratio is known from preparation process of bubble detectors. The average gap distance can be obtained from the mean of gap distances measured between two neighboring bubbles in a track of heavy ion. From g and VL/V one can obtain the two basic parameters n and d of the bubble detector, which are unknown due to invisibility of superheated droplets in bubble detector. Four batches of bubble detectors of Type T-12 were calibrated by this approach. It shows that the average gap distance of bubbles in the detectors is ∼1 mm, the volume density (number n) of superheated droplets in the detectors is ∼106 cm−3 and the diameter of superheated droplets is in the range from ∼30 to 50 μm. It also shows that the two parameters n and d are different from batch to batch of the detectors when VL/V is the same. Therefore, one should make a calibration of bubble detectors at accelerator with heavy ions before using the detectors. This property is similar to that of etch track detectors (SSNTD).

Passive etched track detectors application in outdoor radon monitoring

Summary Over 18 months long measurements of outdoor radon in three areas (a total of 69 locations) in England were conducted between years 2015 and 2017 using PADC based passive nuclear track detectors. Special measurement equipment and protocols to counteract unfavourable weather conditions have been designed, developed and optimised for the low level radon concentration.

3.2.3 Modified Structure Around Ion Tracks in Polymeric Etched Track Detectors

高分子系エッチング型飛跡検出器中に形成されるイオントラックの構造と形成機構を理解するために分析的研究とシミュレーション研究を展開している。照射後の官能基密度変化を，トラックの単位長さ当たりの損傷数（損傷密度）や，損傷の径方向サイズ（実効的トラックコア半径），放射線化学収率について，1.0から12,000 eV/nmの広い阻止能域で評価している。エッチピットを生む損傷形成に果たす多段階の低エネルギー電子のヒットの役割を明らかにしている。

Impact of constructional energy‐saving measures on radon levels indoors

Energy-efficient building refurbishment has the aim of saving energy and thus reducing CO2 emissions. Increased energy efficiency of a building often implies reduced air exchange. Together with other indoor air quality problems, this may lead to an increase in indoor radon concentration (Rn-222). In order to investigate the extent of this problem, measurements of radon concentration in energy-efficient refurbished and low-energy houses (passive houses) were carried out. Track etch detectors were exposed in each type of building over a period of 1year. A reference sample of non-refurbished non-passive buildings was drawn from the National Radon Database for comparison. Buildings were selected that have the same radon relevant properties and were built on comparable geological subsoil like those investigated. The reference sample was compiled in such a way that the measured values from the rooms on the ground floor of the refurbished and passive houses were each assigned a measured value from the database. The statistical analysis shows that the houses refurbished for energy efficiency have a wider distribution of radon concentrations indoors than the non-refurbished ones. Both the mean value and the median of the radon concentration have nearly doubled in buildings refurbished for energy efficiency. The difference is statistically significant. On the other hand, there is no significant difference between the distributions of passive houses and houses not refurbished for energy efficiency.

Analysis of distributions of indoor radon concentrations in the regions of the Russian Federation

During 2001–2017 more than 800 thousand records containing the results of measurements of radon concentration taken in 78 regions of Russia were accumulated in the Federal databank of radiation doses to the population of the Russian Federation. The paper presents the procedure and results of the first data analysis carried out to check the conformity of radon concentrations in the regions of Russia with the lognormal distribution and to calculate the parameters of these distributions. The procedure included verification and validation of data, plotting the frequency distribution histograms and Q-Q plots (normal probability plots) and the use of some methods of elimination of plateaus on the Q-Q plots and the distribution recovery. As a result, in 74 of 78 analyzed regions radon concentrations conform quite well or almost perfect to a lognormal distribution up to a certain level (this level ranged from 55 to 4915 Bq/m3). For all 78 regions geometric means with 95% confidence intervals, geometric standard deviations and arithmetic means were calculated. It should be noted that due to the fact that the Federal databank is a database containing results of measurements taken with different techniques (instant measurements, charcoal canisters, radon monitors and etched track detectors), the lognormal distributions for most regions are in fact contaminated distributions, and currently it is impossible to calculate the parameters of separate distributions that form the mixture. The results show that dose assessment based on arithmetic means could lead to an overestimation of the doses from radon up to 2.1 times compared to that based on geometric means. The calculated medians can also be used for risk assessment purposes.

An update of radial dose distribution theory for the detection threshold of Kapton as a nuclear track detector irradiated with 345 MeV/u U and other heavy ions

We aim to determine the detection threshold of Kapton as an Etched Track Detector irradiated with 345 MeV/u U ion, as well as other several heavy ions of Al, Si, Ar, Kr and Xe. The heavier ions are found to have higher detection threshold in the stopping power. At the same stopping power, the track registration sensitivity decreases with increasing the nuclear charge of ions. U ion has the lowest sensitivity as S = 0.04 at the detection threshold of 3400 keV/μm. We have updated the conventional radial dose distribution theory using a relatively new experimentally supported formula for the effective charge up to U ion. The local doses at a track radius of 0.8 nm, which is half of the length of a repeat unit of Kapton, is useful to understand the relation between the sensitivity of heavy ions and the stopping power at each detection threshold.