LR-115 Film Research Articles

Time-efficient etching of LR-115 SSNTD film for indoor radon, thoron quantification.

LR-115 Solid State Nuclear Track Detector (SSNTD) is commonly utilized for quantifying indoor radon-thoron levels, by tallying the tracks formed in the films by exposure to these gases. Conventionally, sodium hydroxide (NaOH) is used to etch LR-115 films for 90 min at 60°C. However, this study suggests a time-efficient alternative approach utilizing potassium hydroxide (KOH) as the etchant. In an initial investigation, the bulk etch rates of KOH were examined at different normalities and temperatures, revealing that KOH exhibited nearly double the bulk etch rates compared to NaOH. Subsequently, a specially designed controlled experiment was conducted to assess the efficacy of the technique by enumerating the tracks generated in the films. Both etchants demonstrated very similar track counts for identical controlled exposures, indicating the reliability of the method. A consistent behavior was observed in the real-case scenario of LR-115 films exposed indoors to alpha particles from radon and its decay products. In both experiments, the etching with KOH for 45 min gave track densities comparable to standard NaOH etching for 90 min, highlighting the time efficiency of this method. Investigations were carried out into track shape and size features, aspects crucial to the measurement technique, using microscopic imaging of samples treated with both etchants. Strikingly similar track shapes and sizes were observed, affirming the consistency in the track measurement technique. Collectively, these findings suggest that KOH etchant reduces the etching time, presenting itself as a time-efficient method for quantifying radon and thoron track density.

Evaluation of outdoor radon levels and its dependence on the radium content in soil in the environs of Belagavi India

The paper presents the seasonal variation of outdoor radon levels and the measured lung dose to the population of the Belagavi region of India. The outdoor radon levels were measured in different seasons using LR-115 (type II) films fixed in a pin-hole cup detector. The outdoor radon levels in this work were found to be high in summer with values ranging from 11.8 to 27.3 Bq m−3 with a mean value of 20.0 Bq m−3. Lower radon levels were observed in monsoon season and the values range from 3.8 to 15.8 Bq m−3, with a mean value of 10.0 Bq m−3. The potential alpha energy concentration was maximum in summer with a mean value of 3.3 mWLM. The mean annual exposure was found to be 1.4 mWLM and the mean annual inhalation dose was 0.2 mSv y−1. The activity of 226Ra in soils was measured using a NaI (Tl) detector based on gamma ray spectrometer. The 226Ra activity of the study area was in the range of 16.5 to 70.4 Bq kg−1 with a mean value of 32.4 Bq kg−1. The correlation coefficient between the radium content in soil and outdoor radon levels was studied. The present study shows a significant correlation of 0.7, between outdoor radon levels and the radium content in the soil.

Track detector based discriminative thoron measurement – An optimization study through experiments and modelling

The wide difference in the diffusion lengths of 222Rn and 220Rn in air can be exploited to selectively measure the two isotopes using the solid state nuclear track detector (SSNTD) based passive technique. For selective thoron measurement, LR-115 films are mounted at two different distances. The farther film records tracks only due to radon and its progenies and this can be subtracted from the tracks on the nearer film to obtain the thoron contributed tracks. This scheme has been explored in a previous study reported in literature. Based on this, an optimization exercise has been taken up in the present study for selectively measuring the thoron exhaled from soil samples. The optimum distance at which the LR films have to be mounted for recording maximum tracks, is experimentally deduced and this exercise has been supported with simple Monte Carlo modelling inclusive of the alpha particle range-energy relation. The optimum source-detector distance (distance at which track density is maximum) predicted by the model agreed with the experimental result.

Improved semi automatic approach to count the tracks on LR-115 film for monitoring of radioactive elements

An improved semi automatic technique for counting the tracks formed on LR-115 films with the advantages of simplicity and speed is reported. In this technique, a microscope with a Dino-Eye eyepiece camera is coupled to a PC equipped with a python compiler. After etching of the LR-115 film, 16 track images were taken to find the track density. The images generated were binarized before application of a Python algorithm. This process does not disfigure the original track and increase the spatial resolution. The batch process option in Jasc Paint Shop Pro was used to binarize the 16 images simultanously. The Python program automatically counts the total number of tracks formed on the 16 track images. This method was compared with manual counting and counting with the software program-Scion image to verify it. The results showed that the proposed method is reasonably good at counting the tracks. It is a faster and less time-consuming method, and will facilitate measurements of etched tracks in a variety of applications.

INFLUENCE OF BUILDING FEATURES ON RADON ACCUMULATION IN KINDERGARTENS OF THE SVERDLOVSK REGION

Objective: To study the levels of radon accumulation in kindergartens in Sverdlovsk Region and to deter­mine the relationship between radon concentration, and building characteristics. To perform a detailed anal­ysis of radon entry and accumulation in the kindergarten, in which radon concentration exceeds the safety standards. Materials and methods : Track detectors REI-4 on the base of LR-115 film were used. Detectors were installed in playrooms and bedrooms for day nap. In each kindergarten, at least 3 rooms were examined. The measurements were carried out twice a year, during the warm and cold seasons. The duration of exposure of the detectors was 2–3 months in each season. The AlphaGUARD radon monitor was installed in the kinder­garten with a high level of radon concentration. Results: It is shown that the distribution of radon concentration in the kindergartens of the Sverdlovsk region can be described by a lognormal distribution with an average value of 60 Bq/m 3 , a geometric mean of 44 Bq/m 3 and a standard geometric deviation of 2.23. A statistically significant differ­ence was found between the mean values of radon concentration in subgroups of buildings constructed at different periods. For the kindergartens constructed in 1950–1969, the average radon concentration was 85 Bq/m 3 , for buildings built in 1970–1989 – 54 Bq/m 3 . When comparing subgroups of rooms with different types of windows (all buildings, ground floors) it was found that in rooms with PVC windows, radon concentration is almost twice as high then in rooms with wooden windows. For the kindergarten, in which the annual radon concentration in the playroom was 620 Bq/m 3 , it was shown, that if the proper ventilation regime of this room is observed, the average radon concentration during the presence of children does not exceed 120 Bq/m 3 . Conclusions . Factors affecting the indoor radon accumulation in the kindergartens are the type of building materials associated with different periods of building construction and the type of windows. When radon concentration measured in kindergartens reach sanitary standards, it is advisable to conduct an additional study of the daily radon variations, since during the active operation of the premises (working hours) radon levels may be significantly lower

Risk assessment due to inhalation of radon in Coorg district, Karnataka

The paper deals with study of seasonal variation of outdoor and indoor radon in Somwarpet taluk, Coorg district using pin-hole dosimeter cups and LR-115(type II) films. The LR-115 films, placed in dosimeter cups with pin-holes, were exposed to radon in different seasons of the year. The annual inhalation dose due to outdoor and indoor radon ranges from 0.036 to 0.068 mSv year−1 and 0.53 to 0.75 mSv year−1 respectively. The radon levels are low, due to blocking of radon atoms in porespaces of porous soil, due to rainfall in all seasons.

SOIL GAS RADON MEASUREMENT AROUND FAULT LINES ON THE WESTERN SECTION OF THE NORTH ANATOLIAN FAULT ZONE IN TURKEY.

Soil gas radon activity measurements were made around the western section of the North Anatolian Fault Zone. In the study, the variation of radon concentration at 12 different locations along the fault line was monitored by using LR-115 (solid-state nuclear track detectors) detectors for 12-monthly periods. Twelve radon stations were determined in the study region, and in each station, LR-115 films were installed in the borehole of ∼50 cm. The recorded radon concentration varies from 29 to 7059 Bqm-3 with an average value of 1930 Bqm-3. The influence of meteorological parameters such as temperature, pressure, total rainfall and humidity on soil radon concentrations in the study area was also investigated. The positive and poor correlation was observed between average value of 222Rn concentration and temperature. There is a reverse proportion between radon level with other meteorological factors (humidity, pressure and rainfall). The results show that the measured soil gas radon activity concentration shows seasonal variation in a highly permeable sandy-gravelly soil with definite seasons without obvious long transitional periods. The summer (from June 2013 to September 2013) is characterised by 1.8 times higher average soil gas radon activity concentration (median is 2.372 kBqm-3) than the winter (from December 2012 to March 2013) (median is 1.298 kBqm-3).

Measurement of Natural Radioactivity and Radon Exhalation Rate in Coal Ash Samples from a Thermal Power Plant

Coal is the main energy source for electricity generation in the world. In Morocco, 37% of electricity generation comes from combustion coal in thermal power plants. This combustion process generates large amounts of fly and bottom ashes. In recent years, these ashes became a great topic of interest because of their different uses and especially in construction materials. In this work, we assess radiation risks due to natural radioactivity in samples of fly and bottom ashes collected from JLEC (Jorf Lasfar Energy Company) thermal power plant, and different analyses are performed through two nuclear techniques such as gamma spectrometry and alpha dosimetry based on the use of LR115 films detectors. Our analysis shows that 226 Ra activities and 232 Th in both ash samples are well above the permissible activity. The values of the external risk index (Hex) and internal one (Hin) for these ashes are below unity, with the exception of 1.28 in fly ash for Hin. The obtained values for the equivalent radium Raeq and annual effective doses Ė in fly and bottom ashes are 324 Bq/kg and 210 Bq/kg, and 0.18 mSv/y and 0.11 mSv/y, respectively. The surface radon exhalation rates for the samples of fly and bottom ashes are 276 mBq • m −2 • h −1 and 381 mBq • m −2 • h −1 , respectively. Based on these results, we have shown that fly ash and bottom one from thermal power plant JLEC didn't have, in any case, a health risk to the public so it can be effectively used in various construction activities.

THE REPUBLIC OF BELARUS RADON DANGER MAP

Radon is the major contributor to the background exposure of the population. In the world practice, the radon risk or radon potential mapping are used for the radon dose assessment. The aim of this work was a radon danger mapping of the Republic of Belarus to assess the radiation situation and determine the radon hazard critical areas. Materials and methods: The mapping is based on measured values of radon volume activity in the living rooms of different buildings on the territory of the six regions of the Republic of Belarus. We have performed more than 4000 measurements. Integral track radon radiometers based on the polymer Kodak LR-115 film were used to evaluate radon volume activity. Exposure time ranged from 90 to 120 days. The cartogram was built with using the MAPINFO software package. Results: The low levels of radon concentrations were determined in the Brest and Gomel regions, as well as in the southern districts of Minsk and south-western districts of the Mogilev region. The high levels radon concentrations were determined in some districts of the Vitebsk and Grodno regions, as well as in the north-eastern districts of the Mogilev region. About 2–5 times nonuniformity of radon distribution in settlements of the Republic was observed. The radon hazard critical areas with radon concentrations in the range of 200–400 Bq/m3 were found in some districts of the Vitebsk, Grodno and Mogilev regions. Conclusions: The radon risk map of the Republic of Belarus gives the possibility to estimate the existing radiation risk. Taking into account the low efficiency of countermeasures long after the Chernobyl accident, it is necessary to increase the level of radiation protection through the radon mitigation activities or to change the radon normative documents.

Soil gas radon–thoron monitoring in Dharamsala area of north-west Himalayas, India using solid state nuclear track detectors

The study described here is based on the measurements of soil gas radon–thoron concentrations performed at Dharamsala region of north-west (NW) Himalayas, India. The study area is tectonically and environmentally significant and shows the features of ductile shear zone due to the presence of distinct thrust planes. Solid state nuclear track detectors (LR-115 films) have been used for the soil gas radon–thoron monitoring. Twenty five radon–thoron discriminators with LR-115 films were installed in the borehole of about 50 cm in the study areas. The recorded radon concentration varies from 1593 to 13570 Bq/m3 with an average value of 5292 Bq/m3. The recorded thoron concentration varies from 223 to 2920 Bq/m3 with an average value of 901 Bq/m3. The anomalous value of radon–thoron has been observed near to the faults like main boundary thrust (MBT and MBT2) as well as neotectonic lineaments in the region.

Radon-thoron monitoring in Tatun volcanic areas of northern Taiwan using LR-115 alpha track detector technique: Pre-calibration and installation

In the present study, experiments have been carried out to calibrate LR-115 alpha detector films in bare and cup-mode exposure for the measurement of radon and thoron concentrations in soil gas. Results showed non-uniformity in track formation on the films in bare-mode exposure. However, in cup-mode exposure the non-uniformity was reduced to a greater extent. The calibration factors obtained for radon in bare- and cup-mode exposures are 0.049 and 0.034 tr. cm−2 per Bq m−3 d, respectively. An attempt has been made to calibrate the radon-thoron discriminative cup with LR-115 films for simultaneous measurements of radon and thoron. This paper also presents the preliminary results of radonthoron monitoring in Tatun volcanic areas of northern Taiwan for the first time using radon-thoron discriminators with LR-115 films. The results show that the safe temperature to install the LR-115 films in volcanic areas is ≤ 65°C and thoron concentration in the study area is low.

9151 Treatment of patients with advanced non-small-cell lung cancer (NSCLC) with erlotinib: results from clinical practice

Bare cellulose nitrate LR-115 films are being used by us as detectors in the survey of radon in dwellings in Algiers. These detectors have been calibrated in a 12-litre air-tight glass bell-jar, and also in an unmodified room atmosphere. In the first experiment, four track films, alongside a semiconductor detector (SCD), were fixed on a stand well away from a radon source. Alpha activity was allowed to grow for fifteen days, with daily measurements recorded with the SCD, until equilibrium between radon production and decay had been reached. The active volume of air producing the alpha counts in LR-115 was estimated. In the second calibration experiment, a set of ten LR-115 dosemeters was exposed in an unmodified room atmosphere in an occupied house for a period of two months. The radon-daughter concentration was monitored daily, using active devices. From these two experiments a calibration factor to be used in the measurement of activity from radon in dwellings, in terms of track densities observed on LR-115 films, was deduced.

Factors affecting the registration and counting of alpha tracks in solid state nuclear track detectors

In view of the fact that the radon progeny contribute the highest to the natural radiation dose to general populations, large scale and long-term measurements of radon and its progeny in the houses have been receiving considerable attention. Solid State Nuclear Track Detector (SSNTD) based systems, being the best suited for large scale passive monitoring, have been widely used for the radon gas (using a cup closed with a semi-permeable membrane) and to a limited extent, for the measurement of radon progeny (using bare mode in conjunction with the cup). These have been employed for radon mapping and indoor radon epidemiological studies with good results. In this technique, alpha tracks recorded on SSNTD films are converted to radon/thoron concentrations using corresponding conversion factors obtained from calibration experiments carried out in controlled environments.The detector response to alpha particles depends mainly on the registration efficiency of the alpha tracks on the detector films and the subsequent counting efficiency. While the former depends on the exposure design, the latter depends on the protocols followed for developing and counting of the tracks. The paper discusses on parameters like etchant temperature, stirring of the etchant and duration of etching and their influence on the etching rates on LR-115 films. Concept of break down thickness of the SSNTD film in spark counting technique is discussed with experimental results. Error estimates on measurement results as a function of background tracks of the films are also discussed in the paper.

INVESTIGATION OF RADON CONCENTRATIONS COMING FROM NATURAL GAS IN SOME BUILDINGS IN BURSA REGION

In this study, the contributions coming from natural gas in indoor environments of Bursa Distinct were investigated. Using the solid state nuclear track etching LR-115 film detectors, the radon concentrations of the closed buildings (houses) where natural gas is used and not used were determined. The obtained mean values were compared to each other. It was found that the mean radon concentrations in closed atmospheres using natural gas varied from 111.51 Bq m-3 to 236.98 Bq m-3. In the buildings where natural gas is not used the mean radon concentrations were found between 67.63 Bq m-3, 69.68 Bq m-3. It is clearly seen that the radon values of the houses where natural gas is used is higher than the houses not using natural gas.

DETERMINATION OF ALPHA TRACKS IN THE SOLID STATE NUCLEAR TRACK DETECTORS USING MATLAB ENVIRONMENT

There are many applications of solid state nuclear track detectors in various areas. If tracers of charged particles increase in these film detectors, it is hard to count each particle incident on the film. The Accuracy of the counting depends on the sensitivity of the measurement. Aim of this study is to determine and improve an appropriate and reliable measurement of tracking techniques to identify and development of all. LR115 films used in the experimental study exposed to Am 241 alpha source within different time intervals. The damages caused by alpha particles on the film have been counted with a programme written in Matlab environment.

Radon measurements in the residential colony of Nuclear Power Station at Kalpakkam using track detectors

It is an obvious fact that more than 55% of natural radiation exposure is due to isotopes of radon, a gaseous daughter product in both uranium and thorium series and is considered to be one of the causative factors for the increase in lung cancer cases. It was decided to create a baseline data of Radon levels in the dwellings situated in and around residential colony at Kalpakkam. Towards this, radon measurements were carried out in the new residential colony of Nuclear Power Station at Kalpakkam where large number of houses (independent bungalows, multi storied buildings) have been constructed. Solid State Nuclear Track Detector LR-115 films were exposed for one year covering the four seasons and processed using Spark Counter. The radon concentration level is even below the threshold action level of 200 Bq m - 3 as stipulated by ICRP ( 200 – 600 Bq m - 3 ) .

Radon exhalation rate in building materials using plastic track detectors

The radon flux emitted from building material samples and from the surface of building materials could be determined using a simple and reliable method. This method was based on the use of cellulose nitrate films (LR-115 II). The samples and the detectors were placed in a closed can of known dimensions. Tracks due to alpha-particles of radon that migrate from the building material into the air space in the chamber were registered on the LR-115 film. The detectors were chemically etched in 2.5N NaOH solution at 60±1 °C for 115 minutes. Exhalation rates of various building material samples and of building surfaces of various building components were determined. The results obtained by this technique could be used to establish a database for average radon exhalation rates for all available building materials and walls or floors.

Three Decades of Track Detectors in Polish Metal-Ore Mines

The assessment of exposure caused by radon (222Rn) and its short-lived daughters (RnDP) in the air of Polish underground mines is reported. The first measurements were carried out in 1966; the active methods (Lucas cells) were used at that time. The results of the measurements pointed to a high probability of exposure at the level of 35 mJ.h.m-3 (10 WLM). In the early 1970s routine investigations were undertaken in Polish underground metal-ore mines. As a measuring device the passive, open-type dosemeter with Kodak LR-115 film was used. The first measurements were performed as environmental assessments but this changed in 1977 when individual dosimetry was introduced. The results here presented indicate that the average annual exposure to RnDP in Polish metal-ore mines has stabilised since the 1980s and equals approximately 1.4 mJ.h.m-3 (0.4 WLM).

Single charged-particle damage to living cells: a new method based on track-etch detectors

Biological effects of ionizing radiation are usually expressed as a function of the absorbed dose. Low doses of high-LET radiation correspond to one or few particle traversals through the cell. In order to study the biological effectiveness of single charged particles, we have developed a new method based on solid state nuclear track detectors. Cells are seeded on mylar and a LR-115 film is stuck below the mylar base. After irradiation, the LR-115 film is etched and cells observed at a phase contrast microscope connected to a video camera and an image analyzer. In this way, it is possible to measure the number of traversals through the cell nucleus or cytoplasm. Coordinates of each cell on the microscope bench are saved. After incubation for about one week, cells are fixed and stained and the colonies observed at the microscope. The fate of each irradiated cell is therefore correlated to the number of traversals. We have tested this method with two different rodent embryo fibroblast cell lines, C3H 10T1/2 and V79, exposed to 3.2 MeV accelerated α-particles (LET=124 keV/ μm). The studied endpoint was cell killing. Preliminary biological results suggest that few α-particle tracks in V79 hamster cells are sufficient to reduce surviving fraction.

Alpha particle radiography of ants using a 244Cm alpha source

Abstract Alpha particles emitted from a radioisotope 244Cm were used fir the radiography of ants. Cellulose nitrate films, LR-115 from Kodak Pathe, were used as solid state nuclear track detectors to make the radiographs. Alpha particles of energies from 3.5 to 5.5 MeV were obtained by varying the air spacing between the 244Cm and the sample with stainless steel spacers of thickness from 2.4 to 0.5 cm to slow the 5.81 MeV alpha particles from the 244Cm by air. The resulting radiographs of the ants put on the LR-115 films and irradiated by alpha particles of different energies show that only the profiles of the ants were obtained when the ants were exposed to alpha particles of energies lower than 3.5 MeV, and almost all parts of the ant except a portion in the head were penetrated by alpha particles of energies higher than 5.0 MeV to register high density alpha tracks on the LR-115. The details of the internal organs of the ant can be shown clearly by radiography with alpha particles of energies between 4.0 and 5.0 MeV.