Short-lived Daughters Research Articles

Calibration coefficient of the SSNTD and equilibrium factor for radon

Disintegration, ventilation and deposition were considered as removal processes of the radon and its short-lived daughters in air and the respective concentration equations were applied. Calibration coefficient (KF) of the solid state nuclear track detector (SSNTD) LR-115 for radon and the equilibrium factor (F) were related to track densities of the bare detector (D) and the filtered one (Do). A useful relationship between KF, F and detector sensitivity coefficient (k) was derived. Using the calibrated value k=3.29×10−3 m, the exposed detectors gave the average values of the equilibrium factor, calibration coefficient and indoor radon concentration of a single house living room in Osijek 0.46, 142.3 m−1 and 37.8 Bq m−3, respectively.

Radon concentration levels in ground water from Toluca, Mexico

Concentration levels of 222Rn have been analysed in water samples from deep wells of the aquifers around the City of Toluca, Mexico. The 222Rn source is the decay of 226Ra within the solid matrix of the aquifer. With a half life of 1600 years the 226Ra continuously releases 222Rn to the pores, from which it diffuses into the main body of water. This paper describes the methods used for sampling and measuring solubilized and 226Ra-supported 222Rn in the water samples, in order to evaluate possible health hazards due to the presence of radon in the drinking water supplies. The relationship of 222Rn with the hydrogeologic characteristics of the zone is also described. The analytical method involves laboratory extraction of 222Rn into toluene. Alpha disintegrations of 222Rn and contributions from short-lived daughters are counted by the liquid scintillation technique. The system was calibrated using a 226Ra standard solution. Results up to 11.3 Bq/l of 222Rn were obtained in the water samples.

An Online α-Impactor for Short-Lived Radon Daughters

A low-pressure cascade impactor was developed for continuous measurements of the size distributions of aerosol-attached radon and thoron decay products under environmental conditions. The emitted α-particles of the size fractionated activities are registered during air sampling with surface barrier detectors (active area = 2000 mm2) with an energy resolution < 6% (FWHM). The impactor consists of nine stages and back-up filters and operates at a flow rate of 5.1 m3 /h. The 50% cutoff diameters range between 65 and 15,530 nm. The detection limit for the short-lived radon daughters is ∼ 2 Bq/m3 for a sampling time of 1 h and a statistical error of 10%. To minimize energy losses of the ∼-particles and blow-off effects the sampling units are rotatable.

Nuclear track detectors for radon monitoring in coal mines in the Kouzbass Siberian region (Russian confederation)

The main source of exposure to radiation for both workers and civilians in mining areas is known to be the inhalation of radon and its short-lived daughters. The actual data obtained from measured radon levels stimulated research on radiation-induced human health risks from this type of exposure.A radon survey was consequently carried out in the Kouzbass coal-mining area near Kemerovo. Radon measurements were taken in mines, schools and different dwellings, using special cells with LR115 plastic track detectors. For each building studied, radon concentration levels were measured at four different points: in the ground (outside), in the cellar, on the ground floor and in storeys. In mines, radon was measured in all of the galleries and in open air.Preliminary results will be used in mapping out radon emanation in the Kouzbass Region and in indicating the areas where protection measures are to be taken due to abnormally-high radon levels.

Radiological aspects of former mining activities in the Saxon Erzgebirge, Germany

In the Middle Ages, rich silver occurrences were exploited intensively in the Saxon Erzgebirge. The unprofitable ores, the socalled “pechblende”, were dumped as waste materials in the environment. The high uranium and radium contents of these rocks prompted later investigations by Henri Bequerel and Marie Curie. In the city of Schneeberg, most of the houses were built directly on these waste materials. Furthermore, the whole subsoil is crossed by a system of numerous pits and adits; therefore, radon gas from the soil can easily penetrate into the houses. The radon exhalation rates from the soil and also from ground floors in this region increase to values of about 1 Bq/m 2.s. In some houses in Schneeberg, 222Rn concentrations of about 50 kBq/m 3 were found in the living rooms. Maximum values in the cellars were about 200 kBq/m 3. From the inhalation of its short-lived radon daughters, an effective dose of about 1.2 Sv/y may result. Mitigation methods like insulation and subsoil ventilation are proposed, and the efficiency of the different measures are discussed.

Measurement of concentrations of radon and its daughters in indoor atmosphere using CR-39 nuclear track detector

This paper presents the results of the measurements of indoor 222Rn and daughter levels in houses of different types located in different parts of Bangladesh. The passive time-integrated method of using a solid state nuclear track detector (CR-39) was employed for measuring both the 222Rn gas concentration as well as the potential alpha energy exposure (PAEE) level from the short lived daughters of 222Rn. The 222Rn concentration from cup exposure and the PAEE from the bare exposure were obtained directly from the track density using calibration curves. A total of 275 exposures were made in the bare mode in 15 locations and 71 exposures in the cup mode in 6 locations. The geometric mean PAEE level obtained is 9.5 mWL with a geometric standard deviation of 1.9. The corresponding value for 222Rn concentration are 61.3 Bq.m-3 and 2.4. The total data was collected over a period of one and a half years. The monthly variation of the geometric mean of PAEE is also shown. The annual effective dose equivalent has been estimated for each location by using the conversion factor of 9 mSv per WLM as obtained from ICRP-50. The average PAEE level obtained from the total data is below the intervention level as suggested by US EPA. However, the individual averages for each location show that in 8 out of 15 locations intervention may be considered and in others no intervention is called for. The 222Rn concentrations at the seven locations are equal or less than the equilibrium equivalent 222Rn concentration value as suggested by EPA. Attempts have also been made to see the variation in the PAEE levels according to different type of construction material used for the houses.

Indoor Radon Concentrations in Kindergartens from Different Regions of Yugoslavia

In the winter period of 1990–1991 instantaneous radon concentrations in air were measured in around 450 kindergartens from different regions from Yugoslavia. Alpha scintillation counting was used as a screening method, and the measurements, were carried out in the rooms where the children spent the majority of their time. All of the air grab samples were taken under the same conditions which excluded ventilation of the interior 12 hours prior to sampling. In addition to indoor radon concentrations, gamma dose rate was measured using portable equipment. The indoor radon concentrations were generally low, in the range from 10 to 180 Bq.m-3 of air, with an overall average of about 100 Bq.m-3. There were a few exceptions where indoor radon levels exceeded 150 Bq.m-3, mainly in old buildings containing higher contents of natural radionuclides in the building materials, and in the cellars or basements of the buildings. In all rooms with a level exceeding 150 Bq of 222Rn per m3, solid-state nuclear track detectors were applied for long-term measurements. In order to investigate the equilibrium between radon and its short-lived daughters, mainly with respect to their contribution to the effective dose, alpha spectrometry is also being introduced in selected kindergartens with elevated radon concentrations.

The Seasonal Variation of Rainout Activity of Short-Lived Radon Daughters

The Seasonal Variation of Rainout Activity of Short-Lived Radon Daughters

The Seasonal Variation of Rainout Activity of Short-Lived Radon Daughters

The Seasonal Variation of Rainout Activity of Short-Lived Radon Daughters

Indoor Behaviour and Characteristics of Radon Progeny

First brief information about the latest state of knowledge of the formation of the radon daughter cluster and aerosols, desorption and deposition processes given. After that the values of the characteristic parameters of the airborne short-lived radon daughters, the equilibrium factor, the unattached fraction, and the activity size distribution, measured in realistic domestic environments, are summarised.

Risque radiologique dans les mines de charbon en Pologne

Les conditions d'exploitation du charbon font que les mineurs travaillent en présence d'un risque d'exposition aux rayonnements ionisants. Ce risque provient des radionucléides naturels : radium présent dans les eaux et les sédiments des mines et descendants à vie courte du radon existant dans l'air des mines. La dose collective annuelle des mineurs (540 h.Sv) est plus élevée que celle des individus travaillant dans le domaine nucléaire en Pologne (137 h.Sv). Le système du contrôle et de la prévention du risque a été introduit dans les mines de charbon en 1989.

Uranium-series dating and the origin of modern man.

Uranium-series dating is based on measurement of the radioactivity of short-lived daughter isotopes of uranium formed in samples which initially contained only the parent uranium. Materials suitable for U-series dating are found in many prehistoric archaeological sites, and include stalagmitic layers (flowstones), and spring-deposited travertines. Some marls and calcretes are also datable using isochron methods, whereas dates on molluscan shells, bones and teeth are less reliable. Ages obtained using alpha counting to determine isotope ratios have errors greater than 5%, and can range from 1 to 350 ka. Mass spectrometric methods slightly increase the range (0.1-500 ka) but greatly decrease the error to less than 1%, making this the optimal method for high-precision dating of the origin of modern man.

Age-Dependent Dose to Red Bone Marrow from Natural Radon, Thoron and 40K

The age-dependent radiation dose to the haematopoietic tissue of bone marrow has been calculated for exposure to radon, thoron and their daughter products, for the foetus, children and adults. The component of dose due to pure radon is dependent on the fat content of the marrow, since the solubility of radon in fat is about sixteen times that in tissue. The mean dose equivalent µSv to the total active marrow is estimated for a range of fat cell diameters from 25 to 200 µm, taking account of the percentage cellularity and distribution of active marrow as a function of age. Similarly the dose due to the inhalation of short-lived radon daughters was estimated, based on measurements in blood and marrow, modified to allow for the greater deposition of daughter products expected in children. An estimate of the age-dependent dose from long-lived radon daughters was made from uranium miners and natural exposure data. Dose estimates were made for the average UK indoor exposure to radon gas of 20 Bq.m-3 and an equilibrium equivalent thoron concentration of 0.3 Bq.m-3. The annual radon and thoron derived dose to the active marrow of the newborn was calculated as 30 and 40 µSv respectively. For a 10 year old child, the radon and thoron derived annual doses are 70 and 40 µSv and for the 40 year old adult 90 and 30 µSv, respectively.

Age-Dependent Dose to Red Bone Marrow from Natural Radon, Thoron and 40K

The age-dependent radiation dose to the haematopoietic tissue of bone marrow has been calculated for exposure to radon, thoron and their daughter products, for the foetus, children and adults. The component of dose due to pure radon is dependent on the fat content of the marrow, since the solubility of radon in fat is about sixteen times that in tissue. The mean dose equivalent µSv to the total active marrow is estimated for a range of fat cell diameters from 25 to 200 µm, taking account of the percentage cellularity and distribution of active marrow as a function of age. Similarly the dose due to the inhalation of short-lived radon daughters was estimated, based on measurements in blood and marrow, modified to allow for the greater deposition of daughter products expected in children. An estimate of the age-dependent dose from long-lived radon daughters was made from uranium miners and natural exposure data. Dose estimates were made for the average UK indoor exposure to radon gas of 20 Bq.m-3 and an equilibrium equivalent thoron concentration of 0.3 Bq.m-3. The annual radon and thoron derived dose to the active marrow of the newborn was calculated as 30 and 40 µSv respectively. For a 10 year old child, the radon and thoron derived annual doses are 70 and 40 µSv and for the 40 year old adult 90 and 30 µSv, respectively.

Standardisation of 125Sb and 154Eu, and measurement of absolute gamma-ray emission probabilities

A method has been devised to separate 125Sb from its short-lived daughter 125mTe. This technique was based on the repeated use of columns of anion exchange resin and supplemented by chemical procedures chosen to avoid any steps involving evaporation. which in initial trials gave severe problems due to the volatility of the antimony. Standardisation by 4πβ-γ coincidence counting was carried out within a few days of the separation, allowing for the daughter which grows in at about 0.25% per day. Beta counting efficiencies, as measured by the ratio of coincidence to gamma count rates, of up to 90% and 95% respectively were obtained for the two gamma-ray energy windows used. The ingrowth was monitored over a period of one month by gamma-ray spectrometry, using the weak 109 keV gamma-ray of 125mTe, to check the original separation.Samples of 154Eu were produced by neutron irradiation of high purity 153Eu, which was obtained by passing inactive europium through the NPL isotope separator. A solution of the 154Eu was standardised by coincidence counting, again using two gamma-ray energy windows, to give efficiencies of 96% and 98%.Absolute gamma-ray emission probabilities were measured for both nuclides using a germanium spectrometer calibrated with a range of nuclides of known activities and gamma-ray emissions. Sources were positioned 55 cm from the detector to ensure that real summing effects were negligible.

Dose to red bone marrow from natural radon and thoron exposure.

The age-dependent radiation dose to the haematopoietic tissue of bone marrow has been calculated for exposure to radon, thoron and their daughter products. The component of dose due to pure radon is dependent on the fat content of the marrow, since the solubility of radon in fat is about 16 times that in tissue. The mean dose equivalent muSv to the total active marrow is estimated for a range of fat cell diameters from 25 to 200 microns, taking account of the percentage cellularity and distribution of active marrow as a function of age. Similarly, the dose due to the inhalation of short-lived radon daughters was estimated, based on measurements in blood and marrow, modified to allow for the greater deposition of daughter products expected in children. An estimate of the age-dependent dose from long-lived radon daughters was made from uranium miner and natural exposure data. Dose estimates were made for the average UK indoor exposure to radon gas of 20 Bq/m3 and an equilibrium equivalent thoron concentration of 0.3 Bq/m3. The annual radon and thoron derived dose to the active marrow of the newborn was calculated as 30 and 40 muSv, respectively. For a 10-year-old child, the radon and thoron derived annual dose are 70 and 40 muSv, and for a 40-year-old adult 90 and 30 muSv, respectively. The above values exhibit wide range limits due principally to uncertainties in the accumulation of 210Pb in bone, and 210Po in marrow. These data indicate that at the average UK exposure, the alpha-particle dose to active marrow is dominated by that derived from inhaled radon and thoron compared with dietary intake. In infants the dose is dominated by thoron daughters. At the UK radon Action Limit of 200 Bq/m3, the radon and associated thoron derived dose is similar to that from all low LET sources. This work shows that the dose to red bone marrow from radon and thoron is significant, and that the possibility of leukaemia induced by these radiation sources warrants further investigation.

Time Series Analysis of Short-lived Radon Daughter Aerosol Activity at Four Different Sites

Time Series Analysis of Short-lived Radon Daughter Aerosol Activity at Four Different Sites

Statistical Information on Individual Dosimetry in Underground Uranium Mines from the Measurement of 218Po, 214Po and 212Po Exposures

Since the beginning of individual dosimetry in French underground uranium mines in 1983, a dynamic approach has been used according to the optimisation principle of dose limitation. In addition to the regulatory assessment of the individual monthly exposure to the short-lived radon daughters, the French alpha dosemeter made it possible to provide valuable statistical information on the radiological pattern of the uranium mines with regard to the specific parameters related to the underground characteristics and mining conditions. By modelling the time evolution of point and diffuse radon sources in a gallery, different parameters of interest were estimated from the measurements of 212Po, 214Po and 218Po exposures within several mines. The mean 222Rn monthly exposures were found to vary between about 100 and 600 kBq.h.m.-3. From the model, mean apparent radioactive ages of 222Rn sources were estimated in the range of about 1000 to 3000 s. For each dosemeter the equilibrium factor between radon and radon daughters was also calculated and gave mean values between 0.17 and 0.35 in the different mines. From the 222Rn + 220Rn flux from the gallery walls, a 222Rn to 220Rn ratio was calculated and found to vary slightly between 2.5 x 103 and 7.4 x 103. Data were finally analysed according to the function of the workers under dosimetric survey. Significant differences were obtained between the miners working underground all the time and those who were there for only a fraction of their time.

Analysis of radon-222 daughters in air

Common formula for radon-222 short-lived daughter concentration by total α-counting and spectrometric method is detailed in this paper. A computer program has been written, and two procedure errors in references are pointed out. Some coefficients have been corrected and supplemented, and the corresponding formulas in SI units are given. The thoron daughters can be dealt with in the same way.

Diurnal variation of the concentrations of radon and its short-lived daughters in the atmosphere near the ground

Abstract The continuous measurement of radon ( 222 Rn) and radon daughters (RaA( 218 Po), RaB( 214 Pb), RaC ( 214 Bi)) concentrations and meteorological parameters (temperature, wind velocity) is carried out simultaneously at different heights of the boundary layer near ground level (0.1, 1, 2 and 5 m above the ground) over a long time period with the aim of determining the change of the eddy diffusivity near ground level during a day under different weather conditions. The results show the great variation of the activity concentration of radon and radon daughters during a day (up to a factor of 20) depending on weather conditions. The temperature gradient appears to provide a good indication of which eddy diffusivity most closely represents the mixing strength in the atmosphere. The change of the equilibrium values between radon and its daughters during a day were used to calculate the diurnal variation of the eddy diffusivity.