212Pb Activity Research Articles

Primary standardization of 212Pb activity by liquid scintillation counting

An activity standard for 212Pb in equilibrium with its progeny was realized, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) counting. A Monte Carlo-based approach to estimating uncertainties due to nuclear decay data (branching ratios, beta endpoint energies, γ-ray energies, and conversion coefficients for 212Pb and 208Tl) led to combined standard uncertainties ≤ 0.20 %. Confirmatory primary measurements were made by LS efficiency tracing with tritium and 4παβ(LS)-γ(NaI(Tl)) anticoincidence counting. The standard is discussed in relation to current approaches to 212Pb activity calibration. In particular, potential biases encountered when using inappropriate radionuclide calibrator settings are discussed.

Calibration of sodium iodide detectors and reentrant ionization chambers for 212Pb activity in different geometries by HPGe activity determined samples

Lead-212 is a promising radionuclide for cancer therapy, but no primary 212Pb activity standardization has been published. A need therefore exists for accurate estimation of injected doses of 212Pb activity in equilibrium with progeny, when it comes to preclinical and clinical trials. In this study, 212Pb activity was determined using a high purity germanium (HPGe) detector, which allowed the determination of geometry-specific calibration factors for commercially available reentrant ionization chambers (ICs) and sodium iodide (NaI) detectors.

Influence of Meteorological Parameters on the Variations of Atmospheric Radionuclides Concentration in Dar es Salaam, Tanzania

Atmospheric concentrations of 7Be and 212Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06 mBq/m3, respectively. The annual mean activity concentrations of 7Be and 212Pb were 4.72 ± 1.18 mBq/m3 and 29.76 ± 13.63 mBq/m3, respectively. Distinct annual trends were depicted on 7Be and 212Pb, suggesting that the two radionuclides were affected differently with atmospheric conditions. Monthly atmospheric concentrations of 7Be showed a strong seasonal variation trend with the highest in January and February and lowest in April. 212Pb depicted the highest concentration during June and July and lowest in January and December. The regression analysis for 7Be and 212Pb activity concentrations together with number of meteorological parameters revealed that the relative humidity, rainfall, air temperature, absolute humidity and wind speed are the most significant parameters affecting radionuclides activity concentrations in the atmosphere. The sunspot numbers show 66.7% of its variability with 7Be activity concentration which further suggesting that other parameters may influence its variation. 212Pb, on the other hand, shows only 27.3% of its variability which clearly indicates that the existence of cosmic rays does not affect its activity concentration in the atmosphere.

Optimization of the thoron progeny compensation system of a thoron calibration chamber

The long-term stability and homogeneity of thoron progeny are key to the performance of a thoron calibration chamber, which is vital to quality assurance in measuring thoron progeny. It is difficult to build a stable and high level of thoron progeny because the half-life of 212Pb is long. Thus, a stable and efficient compensation system is necessary to compensate for the loss of thoron progeny caused by sampling, decay, and wall deposition. In this paper, a thoron progeny compensation system at the University of South China is optimized, and a suitable ventilation rate regulation method is developed that can effectively improve the activity level and stability of output rate for thoron progeny. The experimental results show that the 212Pb activity output rate increases by 28% and that the output rate is more stable. Under these conditions, the time for the output rate of ThB activity to reach stability is reduced by 33%, and for ThC, the time to reach stability is reduced by 40%. Furthermore, the concentration ratios of ThC and ThB range from 0 to 0.82.

Increasing the detection sensitivity of the Radionuclide Aerosol Sampler/Analyzer using a cosmic veto system

Abstract Different configurations of a cosmic veto system have been evaluated for the Radionuclide Aerosol Sampler/Analyzer (RASA). The upgrade has the potential to resolve the issue that U.S. International Monitoring System (IMS) radionuclide stations have difficulty meeting the 140Ba Minimum Detectable Concentration (MDC) certification requirement when the natural background radioactivity is high. It also aims to improve the detection sensitivity of the RASA system for other fission and activation products indicative of a nuclear explosion. This proof of principal utilizes a prototype RASA system located at Pacific Northwest National Laboratory (PNNL), and has demonstrated background reductions by up to 11.3% and improvements in the average MDC by up to 7.7%. Recommendations are made for either a 1 or 3 plate configuration, which improves the 140Ba MDC by 5.6% and 7.2% for a blank filter. Whilst elevated 212Pb activity remains problematic, the cosmic veto system provides a practical solution for sensitivity improvement with little design modification of the RASA. It also has value in improving sensitivity and preventing false-positives at remote U.S. IMS station locations where sample transfer for laboratory analysis is logistically difficult.

Assessment of temporal variations of natural radionuclides Beryllium-7 and Lead-212 in surface air in Tanay, Philippines

Detection of radionuclides in surface air allows researchers to gain further insight on the behavior of radionuclides that may affect human radiation exposure especially in the event of a nuclear emergency. In this study, activity concentrations of naturally-occurring radionuclides Beryllium-7 (7Be) and Lead-212 (212Pb) in surface air and meteorological data collected in Tanay, Philippines from January 2012 to December 2017 were evaluated to determine the impact of atmospheric conditions and processes to airborne radioactivity. Surface air concentrations of 7Be and 212Pb were found to range from 0.00779 ± 0.00188 to 11.2 ± 0.116 mBq/m3 and from 1.371 ± 0.036 to 106.6 ± 1.075 mBq/m3, respectively. 7Be and 212Pb show distinct annual trends, suggesting that atmospheric conditions affect both radionuclides differently and independently. 7Be shows two peak concentrations annually, with the first peak occurring between January to April and the second lower peak occurring between October and November. 212Pb, on the other hand, shows annual peak concentrations occurring between April and June. Ambient temperature showed strong positive correlation with 212Pb concentration in surface air and a weak negative correlation with 7Be; relative humidity and precipitation showed varying degrees of negative correlation with radionuclide concentrations in surface air. Source locations for the unusually high 212Pb activity concentrations detected on 11–13 May 2013 and 19–31 May 2015 determined using WEB-GRAPE and HYSPLIT atmospheric transport models are presented as a case study. The data and findings of this study shall serve as basis for further studies on local and regional atmospheric transport and radiological impact assessment for the implementation of an effective nuclear and radiological emergency preparedness and response system in the country.

Evaluation of mean transit time of aerosols from the area of origin to the Arctic with 210Pb/210Po daily monitoring data

In this study, the activity concentrations of 210Pb and 210Po on the 22 daily air filter samples, collected at CTBT Yellowknife station from September 2015 to April 2016, were analysed. To estimate the time scale of atmospheric long-range transport aerosol bearing 210Pb in the Arctic during winter, the mean transit time of aerosol bearing 210Pb from its origin was determined based on the activity ratios of 210Po/210Pb and the parent-progeny decay/ingrowth equation. The activity ratios of 210Po/210Pb varied between 0.06 and 0.21 with a median value of 0.11. The aerosol mean transit time based the activity ratio of 210Po/210Pb suggests longer mean transit time of 210Pb aerosols in winter (12 d) than in autumn (3.7 d) and spring (2.9 d).Four years 210Pb and 212Pb monitoring results and meteorological conditions at the Yellowknife station indicate that the 212Pb activity is mostly of local origin, and that 210Pb aerosol in wintertime are mainly from outside of the Arctic regions in common with other pollutants and sources contributing to the Arctic. The activity concentration ratios of 210Pb and 212Pb have a relatively constant value in summer with a significant peak observed in winter, centered in the month of February. Comparison of the 210Pb/212Pb activity ratios and the estimated mean 210Pb transit time, the mean aerosol transit times were real reflection of the atmosphere transport characteristics, which can be used as a radio-chronometer for the transport of air masses to the Arctic region.

Controlling 212Bi to 212Pb activity concentration ratio in thoron chambers

It is necessary to establish a reference atmosphere in a thoron chamber containing various ratios of 212Bi to 212Pb activity concentrations (C(212Bi)/C(212Pb)) to simulate typical environmental conditions (e.g., indoor or underground atmospheres). In this study, a novel method was developed for establishing and controlling C(212Bi)/C(212Pb) in a thoron chamber system based on an aging chamber and air recirculation loops which alter the ventilation rate. The effects of main factors on the C(212Bi)/C(212Pb) were explored, and a steady-state theoretical model was derived to calculate the ratio. The results show that the C(212Bi)/C(212Pb) inside the chamber is mainly dependent on ventilation rate. Ratios ranging from 0.33 to 0.83 are available under various ventilation. The stability coefficient of the ratios is better than 7%. The experimental results are close to the theoretical calculated results, which indicates that the model can serve as a guideline for the quantitative control of C(212Bi)/C(212Pb).

212Pb as tracer for PM deposition on urban vegetation

212Pb concentration in outdoor air is closely correlated with fine suspended particulate matter in the atmosphere. Thanks to this association, this isotope can be used to trace the sinking processes of particulate matter due to the vegetation, also providing accurate estimations of the deposition velocity on foliar surfaces. This approach is particularly effective in areas with high thoron fluxes and, consequently, high 212Pb fluxes from soil.The contribution of vegetation to the improvement of air quality (AQImp) in the municipality area (MA) of Rome (Latium, Italy), almost entirely located on Th-enriched volcanic soils, was estimated by studying 212Pb deposition velocity on the grasses (0.9–2.5mm·s−1) and on the most common tree classes, namely conifers (1.5–15mm·s−1), evergreen (1–4mm·s−1) and deciduous (0.2–1.5mm·s−1).212Pb activity in outdoor air was determined by gamma spectrometry after air pumping with accumulation on cellulose filters and after collection on artificial electrostatically charged surfaces (ECS). The high 212Pb activity values obtained from this analysis (0.90±0.6Bqm−3 and 0.58±0.15Bqm−3, respectively near and far from the soil) are consistent both with the average regional thoron flux from volcanic soils (2.9·104Bqm−2·h−1) and with the thoron flux measured in the volcanic soils of the study area. Thoron and 212Pb fluxes were also measured both in laboratory and in the field under different soil moisture conditions. The total AQImp for the period from September 2014 to September 2015, calculated after the classification of the MA of Rome into six classes of vegetation, provided a value of 0.20 corresponding to 2.3 Tons per day of removed PM10. The role of grasslands in the PM10 removal, the contribution of the vegetation to the improvement of AQImp and the possibility of improving the sinking efficiency of green areas by increasing conifer trees coverage were also highlighted.

Imaging, biodistribution, and toxicology evaluation of 212Pb-TCMC-trastuzumab in nonhuman primates

IntroductionThe biodistribution and toxicology of a radiotherapeutic 212Pb-trastuzumab conjugate were evaluated in nonhuman primates to meet the investigational new drug requirements prior to a phase I clinical trial in human subjects. MethodsMale cynomolgus monkeys (n=3/group) were injected intraperitoneally with the 212Pb-trastuzumab conjugate and terminated at 8h, 10d, and 90d post-injection. Quantitative imaging studies in phantoms and monkeys were conducted using a planar gamma camera and a high purity germanium (HPGe) detector out to 48h following injection. Biodistribution analyses were conducted at 8h; all tissues and time points were evaluated for macroscopic and microscopic pathology. Blood samples were taken throughout the 90d study period for assessment of hematology parameters and serum chemistry parameters. ResultsQuantitative gamma camera imaging and region-of-interest analyses of phantoms and monkeys indicated that 95.5±5.0% of the decay-corrected 212Pb activity was retained in the peritoneal region up to 48h following administration of the 212Pb-trastuzumab. Gamma-ray spectroscopy analyses confirmed that 87.6±4.5% of the decay-corrected 212Bi activity was also retained in the peritoneal cavity during this time. Serum chemistry parameters for all groups always fell within normal ranges. Gross and histopathology evaluations showed no radiation-related toxicity in any tissue at any time. ConclusionIn vivo imaging and biodistribution analyses showed that about 90% of both 212Pb and decay product 212Bi remained in the monkey peritoneal cavity. The imaging methods could also be applied to human subjects. The lack of toxicity observed in monkeys following intraperitoneal injection of the 212Pb-trastuzumab conjugate supports its clinical assessment in humans.

Estimation of the Arctic aerosols from local and long-range transport using relationships between 210Pb and 212Pb atmospheric activity concentrations

In this study, the aerosol activity concentrations of 210Pb at 28 Canadian radiological monitoring stations from 2009 to 2013 were analyzed. The results show that the ratio of 210Pb winter average concentration to summer average concentration increases with increasing latitude. This could be used to evaluate the transport of pollutants to the Arctic region such as the Arctic haze from Eurasia through long-range atmospheric transport during winter. Based on 12 years of monitoring results from the Yellowknife station that includes both 210Pb and 212Pb concentrations, the study confirms that the seasonal distribution of 210Pb to 212Pb activity concentration ratios has a significant peak in winter and a relatively low value in summer, which can be used as an indicator of the air mass flow to the Arctic. The period dominated by long-range aerosol transport and Arctic haze was estimated by fitting a Gaussian distribution function to the peak values of this ratio in winter. A peak width parameter of full width at half maximum (FWHM) allows a year by year estimate of the period of influence by long-range transport of aerosols, and this varied between 67 and 88 days in this study. The fitted Gaussian peak also shows that the season of the continental influenced air mass in Yellowknife usually starts in mid-to-late November and ends in mid-to-late April. Thus, the 210Pb to 212Pb ratio distributions may enable the determination of periods dominated by long-range aerosol transport and the scale of the Arctic haze at different latitudes.

Radionuclides from the Fukushima accident in the air over Lithuania: measurement and modelling approaches

Analyses of 131I, 137Cs and 134Cs in airborne aerosols were carried out in daily samples in Vilnius, Lithuania after the Fukushima accident during the period of March–April, 2011. The activity concentrations of 131I and 137Cs ranged from 12 μBq/m3 and 1.4 μBq/m3 to 3700 μBq/m3 and 1040 μBq/m3, respectively. The activity concentration of 239,240Pu in one aerosol sample collected from 23 March to 15 April, 2011 was found to be 44.5 nBq/m3. The two maxima found in radionuclide concentrations were related to complicated long-range air mass transport from Japan across the Pacific, the North America and the Atlantic Ocean to Central Europe as indicated by modelling. HYSPLIT backward trajectories and meteorological data were applied for interpretation of activity variations of measured radionuclides observed at the site of investigation. 7Be and 212Pb activity concentrations and their ratios were used as tracers of vertical transport of air masses. Fukushima data were compared with the data obtained during the Chernobyl accident and in the post Chernobyl period. The activity concentrations of 131I and 137Cs were found to be by 4 orders of magnitude lower as compared to the Chernobyl accident. The activity ratio of 134Cs/137Cs was around 1 with small variations only. The activity ratio of 238Pu/239,240Pu in the aerosol sample was 1.2, indicating a presence of the spent fuel of different origin than that of the Chernobyl accident.

Pre-concentration of naturally occurring radionuclides and the determination of 212Pb from fresh waters

A novel technique has been developed for determining the 212Pb activity of fresh waters. This is of interest to environmental monitoring programmes that utilise gross α-activity methods to screen for anthropogenic radionuclides. The contribution from 212Pb varies, and is difficult to experimentally measure due to its relatively short half-life ( t ½ = 10.6 h) and low environmental activity (<0.1 Bq l −1). The use of a three-stage technique that encompasses a unique form of pre-concentration, separation and analysis by liquid scintillation counting allows a lower detection limit of 0.006 Bq l −1 with a chemical yield of 92.5 ± 5.6%. The measurement can be obtained within 7 h of sample collection, and is calculated using the radioactive decay of 212Bi. Other naturally occurring radionuclides may also be extracted using the pre-concentration stage of the technique, with efficiencies above 90% at a range of pH values.

Continuous Air Monitor Algorithm Development

This paper describes an algorithm intended for use in the U.S. Navy’s next-generation air particle detector designed for measuring 60Co air contamination. The algorithm measures both alpha and beta activity from an air filter utilizing passivated implanted planar silicon detectors for spectrometry of both particle types and is designed to compensate for radon progeny to discriminate this from the beta emissions of 60Co. This is done by correlating the specific alpha emissions with their beta emission parents, or their beta emission progeny, as appropriate. In addition, the algorithm is unique in that by using region of interest (ROI) windows, it is less sensitive to spectral smearing due to dust or humidity effects on the particle depositions or more specifically to variable energy loss of alpha particles to the detector from deposited material on the filter. A weakness of this approach is that thoron B (212Pb) does not have a detectable alpha parent and the next alpha progeny must decay through an isotope (212Bi) with a half-life of 60.6 min. This causes predictions of the 212Pb activity to lag in time to some extent. Mitigation of this effect is realized by using a first-order correction utilizing appropriate mathematical equations to account for the physics of this buildup and decay. This paper concludes by demonstrating that the beta assay value is a linear superposition of the alpha ROI values from the three dominant alpha peaks. Initial estimates on the coefficients of the alpha ROI values are derived with final values recommended to be determined from operational measurements.

AN EXPERIMENTAL ANALYSIS OF THE CONTRIBUTION OF 224Ra AND 226Ra AND PROGENY TO THE GROSS ALPHA-PARTICLE ACTIVITY OF WATER SAMPLES

The gross alpha-particle activity of water samples analyzed by EPA Method 900.0 is investigated as a function of residue mass and geometry, time between sample collection and analysis, and time between sample preparation and analysis for samples containing 224Ra, 212Pb, and 226Ra. It is shown that the gross alpha-particle activity due to 224Ra and its progeny can be up to 10 times the 224Ra activity at collection time and that due to 212Pb progeny can be up to 3 times the 212Pb activity at collection time. In samples with roughly equal activities of 224Ra and 226Ra analyzed soon after collection, it is shown that the gross alpha-particle activity is approximately constant with time because the decay of 224Ra and its progeny is offset by the ingrowth of 226Ra progeny.

Temporal variation of thoron decay product concentration in the atmosphere and comparison with radon decay product concentration.

Seasonal and long-term variation of the airborne 212Pb concentration, representative of the equilibrium equivalent concentration of thoron decay products (EECRn220), was investigated from 1989 through 1996 at a semi-natural location in southern Germany. Continuous measurement yielded a long-term average concentration of 0.082 Bq m-3, while daily mean concentrations varied from < or = 0.01 to 0.34 Bq m-3. An average annual effective dose of 1.4 mSv due to outdoor thoron progeny concentration was estimated. This is about 2% of the dose due to the average short-lived radon progeny concentration (EECRn222) of 8.4 Bq m-3 measured for this location in the same period. In most years the seasonal pattern of 212Pb activity concentration in the atmosphere is characterized by two maxima: the first in May and the second one in September. Low concentrations are observed from November through February of each year. This is in contrast to the behaviour of the short-lived 222Rn progeny which exhibit enhanced concentrations exactly during these months. The most probable reason for the different temporal behaviour of 212Pb is the extremely reduced flux of thoron gas from the ground during the winter months.

Determination of lead in standard rocks by graphite furnace AAS.

This article is a supplemental report for the determination of lead which has not yet be obtained for some of the standard rocks of GSJ in the earlier report.The sample was completely decomposed by gradual heating with HF, HNO3 and HClO4, and evaporated to dryness. In this report, the decomposing conditions for such special rocks as JF-1 and JP-1 were again examined. The decomposed sample was dissolved in 0.5 M HBr, spiked with 212Pb and was passed through a column of Bio Rad AG1-X8 100200 mesh (4 mm i.d.×4cm h). Lead retained on the column was eluted with 6 M HCl after washing the column with 0.5 M HBr. The column yield of the purified lead solution was measured using 212Pb activity and then subjected to the lead concentration measurement by GFAAS. The lead values obtained for JA-2, JA-3, JB-1a, JF-1, JG-1a, JG-2, JG-3, JP-1 of GSJ standard rocks were 19.8, 6.5, 7.5, 33.1, 47.5, 27.6, 33.2, 12.4 and 0.12 ppm, respectively. These values coincided very well with the reported values.