Short-lived Daughter Products Research Articles

Contribution of the Photonic Component to the Ionization of the Atmosphere by Earth Crust Nuclides and Radioactive Emanations

Abstract—We investigate the contribution of gamma radiation of natural radionuclides constituting the Earth crust, radioactive emanations, and their decay product in the ground to the intensity of production of ion pairs in the atmosphere against the background of ionization of the atmosphere by radioactive gases flowing to the atmosphere from the ground and propagating together with their short-lived daughter products. The density of the radon flux to the atmosphere is estimated by three methods: the reservoir method, the integration of altitude profiles of volume activity of radon, based on gamma spectroscopic observation and diffusion model. The distribution of the gamma dose rate dose from the earth radionuclides in the soil and in the atmosphere is calculated using Gleant4 software. The propagation of the radon isotopes and their decay products in the atmosphere is calculated using large eddy simulations supplemented with kinematic simulations of the subgrid transport of a passive scalar. It is shown that depending on the specific activity of nuclides in the ground and the turbulent regime of the atmosphere, the total contribution of the γ-radiation to the ion pair production rate in the atmospheric boundary layer is approximately from 1% to 20% and increases upon a decrease in the penetrability of the upper ground layer for radioactive emanations.

Hygienic assessment of personnel working conditions in underground uranium mining

The aim of the study is to assess the main radiation-hazardous factors that determine the effective dose of personnel during underground uranium mining at the Priargunsky Industrial Mining and Chemical Association, and to summarize the data of the radiation control of the enterprise for 2016-2020. The main factors that create personnel dose loads are: the volume activity of short-lived daughter products of radon decay in the air, the dose rate of external gamma radiation, and the volume activity of long-lived alpha-emitting radionuclides of the uranium-radium series in industrial dust. Information on the structure and values of individual effective doses of workers is presented. Recommendations for improving the radiation monitoring system are given.

Actinium Biokinetics and Dosimetry: What is the Impact of Ac-227 in Accelerator-Produced Ac-225?

Among the growing list of alpha-emitting isotopes now available for pharmaceutical development, Ac-225 can act as an in vivo alpha-generator radionuclide and is of great interest for new targeted alpha-therapy applications. To seek further development of Ac-225 bioconjugate therapeutics, ongoing efforts aim at addressing current limitations, including lacking supply of the radioisotope, insufficient understanding of its biodistribution and biodosimetry, poor retention of alpha-emitting daughter products at the target site, as well as inadequate chelation, one of the major drawbacks. The U.S. Department of Energy’s Isotope Program has been exploring new pathways for the production of the radioisotope Ac-225 at accelerator facilities to address a potential increased need for medical applications. However, the presence of co-produced, long-lived Ac-227 (21.8 y half-life) is observed in about 0.15-0.3 activity percent in the accelerator derived product at the end of target bombardment. Up to 0.5 activity percent values due to Ac-227 could be anticipated in a research/clinical setting. One goal of our work is to delineate the biodistribution of Ac-225, its short-lived daughter products, and potential trace contaminants such as Ac-227 that may be co-produced in new larger-scale accelerator derived processes. The biokinetics of unchelated, chelated (with classic macrocyclic structures, amino-polycarboxylic acids, or new hydroxypyridinone ligands under development), and bio-conjugated Ac-225 and Ac-227 were determined in several mouse models. The resulting biodistribution and dosimetry profiles highlight significant differences among isotope and ligand combinations that must be considered and addressed in order to ensure bioconjugated Ac-225 is safe for use in the clinic. Part of the discussed work was supported by the U.S. Department of Energy’s Isotope Program in the Office of Nuclear Physics at the Lawrence Berkeley National Laboratory under Contract DE-AC02-05CH11231.

Radiochemical characterization and decontamination of rare-earth-element concentrate recovered from uranium leach liquors

The paper deals with two rare earth elements (REE) concentrates recovered from uranium leach liquors after sorption separation of uranium. Activity of the REE concentrates was found to be 106 Bq kg−1; Ac-227 and its short-lived daughter products were the main radioactive impurities contributing more than 99% of total activity. Activity of both U-238 + Th-232 in the REE concentrates did not exceed 0.2% of total activity. Extraction by 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) ester (P-507 extractant) in Shelsol D90 diluent was suggested for REE deactivation. It was shown that thorium may be eliminated by extraction in strong acidic media (pH − 0.5 to − 1), whereas radium extraction was suppressed over the whole studied pH range. Further REE separation to heavy and light groups at pH 1 resulted in selective concentration of actinium in light REE group. The suggested separation flowsheet was tested on the real REE concentrate. It was shown that obtaining non-radioactive fraction of heavy REE is possible.

Assessment of attached and unattached progeny concentrations of 222Rn/220Rn and their contribution to dose using deposition-based progeny sensors

The exposure of radiation from natural sources to population has become an important issue in terms of radiological protection. Mostly natural radiation comes from radon (222Rn), thoron (220Rn) and their solid short-lived daughter products that are the main threat to public health risk. The results presented in this paper are from a survey carried out in 40 villages of Jammu district, Sub-Mountainous region of Jammu and Kashmir, India, to quantify progeny concentration of radon and thoron using a passive time integrating, deposition-based technique. For estimating the total (attached + unattached) progeny concentration of radon/thoron, direct radon/thoron progeny sensors (DRPS/DTPS) have been used and only attached progeny concentration of radon/thoron has been measured by using wire-mesh capped direct radon/thoron progeny sensors (WM-DRPS/WM-DTPS). The study has been conducted for a period of 1 year during winter, rainy and summer seasons in all 112 dwellings. The exposure time of the sensors was 4 months. In this survey, the variability of progeny concentration of radon and thoron based upon variation in building construction materials and seasons-wise has also been discussed and efforts have been made to provide the reason for these variations. The highest level of progeny concentration of radon/thoron was found in the mud-type dwellings compared with dwellings made of concrete, cement and marble. Indoor and outdoor gamma dose rate (µSvh−1) has also been measured and correlated indoor gamma annual effective dose (µSvy−1) with progeny annual effective dose (µSvy−1).

Mapping of indoor radon survey and dose estimations in health centres in Turkey

Radon and its short-lived daughter products, leading to lung cancer, are the most significant contribution to the exposure of man to ionizing radiation from natural sources. Therefore, the present study aimed to assess indoor radon measurements in 39 rooms of 15 health centres in Osmaniye city, Turkey using CR-39 solid-state nuclear track detectors based on radon dosimeters. Indoor radon concentrations were found to change from 8 to 108 Bq·m−3. The associated radiological parameters such as the annual effective dose and excess lifetime cancer risk were computed for staff/patient in the rooms surveyed. The mean annual effective dose and excess lifetime cancer risk values were estimated to be 0.29 mSv and 1.02 × 10−3, respectively. The annual computed effective doses are lower than the suggested action level (3–10 mSv·y−1). Also, with ordinary Kriging method, by using R programing language and quantum geographic information system, indoor radon concentration, annual effective dose, and excess lifetime cancer risk interpolated values were recorded and mapped. The findings obtained in the current study concerning radon levels and their variations will provide baseline values for future research surveys.

Radiological impact of phosphate fertilizers on the agricultural areas in Iran

It is common practice to use phosphate fertilizers in the soil to raise crop yield. Natural Radionuclides present in fertilizers are sources of external and internal radiation exposure. External radiation exposure is caused by gamma radiation originating from radionuclides in situ. Internal radiation exposure, mainly affecting the respiratory tract, is due to short-lived daughter products of radon which are exhaled from fertilizers. This paper describes the results of gamma spectrometric measurement of the concentration of the natural radionuclides namely 226 Ra, thorium-232 and potassium-40 in the soil samples from the fields using phosphate fertilizers. The radon concentration and exhalation rate have also been discussed. The values of outdoor annual effective dose are found to vary from 0.07 to 0.09 mSv/year in soil samples containing fertilizers, whereas the outdoor annual effective dose is 0.06 mSv/year in barren soil samples.

Measurements of Indoor Radon-222 Concentration inside Iraqi Kurdistan: Case Study in the Summer Season

Exposure to natural sources of radiation, especially 222 Rn and its short-lived daughter products has become an important issue throughout the world because sustained exposure of humans to indoor radon may cause lung cancer. Therefore, indoor radon concentration levels have been measured inside 8 government hospitals in three main regions (Erbil, Duhok and Sulaymaniya) in Iraqi Kurdistan region during summer season by using CR-39 nuclear track detector. The CR-39 detectors were placed in the all hospitals for three floors (ground, first and second). The highest average radon concentration value and annual effective dose was found to be in the Shaheed Dr. Aso hospital in Sulaymaniya city (52.89 ± 3.52 Bq. m-3 , 1.37 ± 0.09 mSv/y ) respectively and the lowest was found in the Erbil Teaching hospital in Erbil city (30.15 ± 2.85 Bq. m -3 , 0.81 mSv/y) respectively, This depended on the geological formation , type of building material, and the floor level. Therefore, the results showed that the average radon concentration and annual effective dose decreases gradually as the floor level increases The highest and lowest of annual effective dose was found in ground and second floor, respectively. Thus, according to the annual exposure dose data, the workers are safety in most of the hospitals.

Measurement of radon diffusion in polyethylene based on alpha detection

Radon diffusion in different materials has been measured in the past. Usually the diffusion measurements are based on a direct determination of the amount of radon that diffuses through a thin layer of material. Here we present a method based on the measurement of the radon daughter products which are deposited inside the material. Looking at the decay of 210Po allows us to directly measure the exponential diffusion profile characterized by the diffusion length. In addition we can determine the solubility of radon in PE. We also describe a second method to determine the diffusion constant based on the short-lived radon daughter products 218Po and 214Po, using the identical experimental setup. Measurements for regular polyethylene (PE) and High Molecular Weight Polyethylene (HMWPE) yielded diffusion lengths of (1.3±0.3) mm and (0.8±0.2) mm and solubilities of 0.5±0.1 and 0.7±0.2, respectively, for the first method; the diffusion lengths extracted from the second method are noticeably larger which may be caused by different experimental conditions during diffusion.

Radon exhalation rates from zircon sands and ceramic tiles in Italy

Naturally occurring radionuclides in building materials are sources of external and internal exposure in dwellings. External radiation exposure is caused by the gamma radiation originating from members of uranium and thorium decay chain and from 40 K. Internal radiation exposure, mainly affecting the respiratory tract, is due to the short-lived daughter products of radon which are exhaled from building materials into room air. The objective of this study is to measure the radon exhalation rates from zircon materials, flours and sands, used as raw materials in the porous fired tiles body and from the final products (porcelain tiles usually commercialized in Italy). The radon exhalation rates for the zircon flours and sands ranged from 0.17 to 1.9 Bq kg-1 h-1 , and from 0.090 to 0.20 Bq kg-1 h-1 ; 222 Rn exhalation rates for most of the porcelain stoneware tiles are near or below the minimum detectable limit (LLD) of 0.0004 Bq kg-1 h-1 .

Indoor radon concentration levels in several districts of the Punjab Province—Pakistan

Exposure to natural sources of radiation, especially 222Rn and its short-lived daughter products has become an important issue throughout the world because sustained exposure of humans to indoor radon may cause lung cancer. Therefore, indoor radon concentration levels have been measured in several districts of the Punjab Province. These included Gujranwala, Gujrat, Sialkot, Mandibahauddin, Hafizabad and Narowal districts. Twenty to 30 houses were carefully selected in each district. CR-39-based NRPB radon dosimeters were installed in living rooms and bedrooms of these houses and were exposed to radon for a period of three months (i.e. from September to December 2005). Radon concentration levels were found to vary from ∼ 40 ± 5 to 173 ± 4 and 38 ± 5 to 193 ± 4 ( Bq m - 3 ) in the living rooms and bedrooms, respectively. Annual effective doses were calculated. Using ICRP-65 conversion values, annual effective doses were found to range from 0.60 ± 0.08 to 3.27 ± 0.08 mSv . It ranged from 0.87 ± 0.12 to 4.75 ± 0.12 mSv when UNSEAR 2000 dose conversion values were used. Radon concentration levels and annual effective doses were found to be within recommended limits.

A rapid field extraction method for determination of radon-222 in natural waters by liquid scintillation counting

A simple and robust method for determination of 222Rn in natural waters is described. A 1.3-L water sample is collected in a plastic (PET) water bottle and shaken with 20 mL mineral oil scintillant for 4 minutes. Radon preferentially migrates to the mineral oil, and the 222Rn activity is determined by counting 222Rn and the short-lived daughter products 214Po and 218Po using an ultra-low-level LS counter via α/β separation technique. The PET method achieves a detection limit of ~3 mBq L−1, making it an ideal method for analysis of surface water and groundwater samples.

Radon Effects in Ground Gamma-ray Spectrometric Surveys

The effect of emanation radon is shown to be a significant problem for estimating uranium concentration from ground-based gamma-ray spectrometric surveys. Radon gas (a daughter product in the U238 decay series) escapes from rocks and soils near the Earth's surface into the lower atmosphere. Under early morning, still-air conditions, radon concentrates as a thin layer near the Earth's surface. If ground radiometric surveying is undertaken before this radon layer is mixed into the lower atmosphere, large errors in U concentration estimates result.This paper shows the effect of early-morning radon accumulation on a gamma-ray spectrometric survey near Boorowa, NSW. Paddocks surveyed in the early morning show much higher apparent uranium concentrations than those surveyed later in the day. We demonstrate the radon diurnal effect by monitoring the equivalent U concentration at a fixed site over several weeks. Typically, there is a build-up of radon near the Earth's surface overnight. Radon concentration reaches a maximum at about one hour after sunrise, before slowly dispersing over a period of 2-3 hours. By reporting both the Boorowa survey and the radon monitoring results in the same units of equivalent uranium concentration, we demonstrate that the anomalous effects seen in the Boorowa survey are consistent with that of a radon diurnal.The monitoring data also show the effect of rainfall on apparent U concentrations. Rain deposits radioactive daughter products of atmospheric radon onto the ground, resulting in a significant increase in apparent U concentration. These short-lived daughter products decay to insignificant concentrations within about 3 hours. Ground surveys should not be conducted during or within 3 hours of the cessation of rain, or under early-morning, still-air conditions. Also, because high moisture concentrations in soil reduces the gamma-ray fluence rate at the Earth's surface, surveys should not be conducted after prolonged or heavy rainfall where the soil profile is saturated.

The potential for developing and the possibility of attaining radiation equivalence between uranium and wastes in future nuclear power

The development of nuclear power with capacity up to 300 GW using thermal reactors and BREST fast reactors with small excess breeding (BR ∼ 1.05) and nuclear power operating potentially for up to 3750 yr using depleted uranium is examined on the basis of fuel materials balances. To examine the radiation balance, all wastes, which have accumulated by the time mentioned from reprocessing of spent fuel from thermal and fast reactors are included, taking account of the running nuclide composition. The change in the potential biological danger is calculated as a function of the holding time of the entire mass of the wastes taking account of the short-lived nuclide daughter products. The possibility of starting coextraction of thorium and radium with uranium starting in 2010 and 2030 or without coextraction is taken into account. If coextraction is implemented during the periods indicated, then radiation balance of the radiactive wastes which accumulate by 2100 or 2200 is reached within a holding period of 80–120 yr. Without coextraction, the fraction of plutonium going into the wastes will have to be decreased from 0.1 to 0.01%.

Radon-222 in Brazil: an outline of indoor and outdoor measurements

This study discusses the methodology for measuring and assessing the radon concentration in indoor and outdoor environments. A research study was developed to investigate the long-term behavior of the diurnal and seasonal fluctuations of radon 222Rn EEC (Equilibrium-Equivalent Concentration) and the influence of temperature and other climatic aspects on this behavior. The study was performed by means of both integrated and instantaneous measurements of radon and its short-lived daughter products for a period of 1 year in an indoor environment in Rio de Janeiro city, Brazil (reference environment), with continuous measurement, using a radon monitor with an alpha spectrometry detector. For a single day, a variability of about 50% could be observed in the 222Rn EEC values measured on a hourly basis, with a maximum occurring early in the morning and a minimum in the afternoon. For the long-term period, seasonality is responsible for a two order of magnitude variability, with a maximum of 50 Bq.m −3 in winter (dry season) and a minimum of 0.5 Bq.m −3 in the summer months (wet season), outdoors. A negative correlation with temperature was observed. The conclusions of this experiment led to a survey of radon gas concentration in dwellings in Rio de Janeiro city, Brazil, in urban area with nearly 7 million inhabitants, through integrated sampling methods, using a Solid State Nuclear Track Detectors Technique (SSNTD). The study was conducted in different geomorphological locations in town. The radon gas concentration in Rio de Janeiro dwellings ranged from 5 Bq.m −3 to 200 Bq.m −3. A good correlation between indoor radon gas concentration and location of dwellings was observed. The seashore areas presented the lowest levels of indoor radon concentration, whereas the highest levels were found close to the mountains.

Radiological Benchmarks for Effects on Aquatic Biota at the Oak Ridge Reservation

Radiological benchmarks for aquatic biota were developed for use at the U.S. Department of Energy's Oak Ridge Reservation as screening values to determine the spatial extent of potential ecological effects and to identify the need for additional site-specific investigation. The Point Source Dose Distribution approach was used to calculate water and sediment activities for selected radionuclides that result in a total dose rate to small and large fish of 1 Rad d−1, which is the National Council on Radiation Protection and Measurements recommended acceptable dose rate to natural populations of aquatic biota. These screening values incorporate internal and external exposures from parent isotopes and all short-lived daughter products. They also include exposures from all major alpha, beta, and gamma emissions for each isotope. Unlike exposures to chemicals, exposures to radionuclides are expressed as the dose rate received by the organism. Dose rates that account for the biological effects to the organism are additive. If the total dose rate from all radionuclides and pathways exceeds a recommended acceptable dose rate, further analysis is needed to determine the hazards posed by radionuclides. If, however, the total dose rate falls below an acceptable dose rate, radionuclides may be eliminated from further study.

A passive individual dosemeter for integrating measurements of the radon daughter product contents in air

A simple passive long-term dosemeter for area and individual dosimetry has been developed, calibrated and tested as a prototype for direct determination of the dose-relevant potential alpha energy concentration of any mixture of short-lived radon daughter products in air. The dosemeter is based on a double-chamber method. In this way, the main factor of uncertainty in exposure estimations, the assumption of mean equilibrium factors, can be eliminated. The matchbox sized dosemeters are not expensive, simple to handle and have sufficient detection sensitivity. CR 39 equivalent PATRAS material is applied as detectors. Investigations so far have shown that the dosemeters are very attractive for routine monitoring in order to assess the radon daughter product exposures of miners and selected persons during their stay in elevated and strongly varying radon/radon daughter product atmospheres. The optinum exposure time of the dosemeter is about three months.

The effect of electric fields on 222Rn daughter products in indoor air.

A fraction of the short-lived airborne daughter products of 222Rn are charged (positively) and can thus be removed from the air by means of an electric field. A theory is presented which gives the relation between the charged fraction and the total individual daughter activity at equilibrium as a function of the field applied. The theory also allows a deduction of the mobilities of the charged daughter products. Preliminary measurements were performed in a basement room with very low ventilation rate and fairly high radon concentration (5-10 pCi/l.). The electric field was established by applying a voltage to a wire mounted at a height of 1.7 m above the floor and 1 m from the walls. The radon concentration of the air as well as the concentration of the individual 222Rn daughter products were measured at various wire voltages. As an approximation the field was assumed to have a cylindrical configuration. The preliminary results indicate that, at moderate radon activities (lower than approx. 10 pCi/l.) and low condensation nucleus concentrations, the relative activities of the positively charged daughter products are about 1:4:0.8 at equilibrium in the absence of an electric field. The measurements also show that the Working Level may be lowered by a factor of 2-3 applying a voltage of a few thousands volts to the wire.

Air filtration and radon daughter levels

The authors investigate the effect of filtration and aerosol loading of the air on the level of short-lived air-borne daughter products of radon. By the use of a combination of filtration and aerosol loading, it is possible to shift the partitioning of the radon daughters in the room between the states: airborne, plated-out on the walls, and trapped by filters; the airborne fraction will shift between being attached to aerosol particles and existing as molecular-sized clusters. When the air filtered the equilibrium factor decreases with increasing filtration rate. At high aerosol concentrations the decrease can be explained solely as an effect of the filter removing the daughter products from the air passing through it. As the aerosol production and concentration is lowered, the decrease in equilibrium factor becomes larger. This is caused by an increase in the unattached fraction of the airborne activity and hence in the wall-deposited fraction of the total activity. At a given radon concentration, the dose delivered to a certain portion of the respiratory tract depends not only upon the equilibrium factor but also upon the fraction of, especially, 84 218Po in the unattached state. It is further demonstrated that, according to the dose model of Harley and Pasternak, the dose to the basal cells of the epithelium of the bronchii will in general decrease with increasing filtration rate and increase with decreasing aerosol concentration.

気中自然放射能測定における測定地点の地域代表性

The air concentration of radon short-lived daughter products (Rn-Dts) differs considerably with location and time. This fact is the reason why the estimation of radiation doses to the respiratory system due to Rn-Dts is difficult from the viewpoint of population doses. Hence, we attempted to define an equiconcentration area with a uniform air concentration of Rn-Dts. Many points at which we measured Rn-Dts concentration were selected at the inner area within a 30km radius around the reference pointof the campus. Measurements of Rn-Dts concentrations have been carried out between the reference point and a point for comparison at same time. Similar measurements have been continued successively. The values observed at every point within the 15km radius around the reference point were consistent with that observed at the reference point with an error of 20 percent of the concentration ratio of Rn-Dts and above the correlation coefficient of 0.80. The values obtained at every point, excerpt for two points on the granits zone and 100m above sea level, agreed with that observed atthe reference point within an error of 50 percent of concentration ratio of Rn-Dts and over the correlation coefficient of 0.45.