Massic Activity Research Articles

Intercomparison of 99mTc, 18F and 111In activity measurements with radionuclide calibrators in Belgian hospitals

This study presents current status of performance of radiopharmaceutical activity measurements using radionuclide calibrators in Belgium. An intercomparison exercise was performed among 15 hospitals to test the accuracy of 99mTc, 18F and 111In activity measurements by means of radionuclide calibrators. Four sessions were held in different geographical regions between December 2013 and February 2015. The data set includes measurements from 38 calibrators, yielding 36 calibrations for 99mTc and 111In, and 21 calibrations for 18F. For each radionuclide, 3 ml of stock solution was measured in two clinical geometries: a 10 ml glass vial and a 10 ml syringe. The initial activity was typically 100 MBq for 99mTc, 15 MBq for 111In and 115 MBq for 18F. The reference value for the massic activity of the radioactive solutions was determined by means of primary and secondary standardisation techniques at the radionuclide metrology laboratory of the JRC.The overall results of the intercomparison were satisfactory for 99mTc and 18F, since most radionuclide calibrators (>70%) were accurate within ±5% of the reference value. Nevertheless, some devices underestimated the activity by 10–20%. Conversely, 111In measurements were strongly affected by source geometry effects and this had a negative impact on the accuracy of the measurements, in particular for the syringe sample. Large overestimations (up to 72%) were observed, even when taking into account the corrections and uncertainties supplied by the manufacturers for container effects. The results of this exercise encourage the hospitals to perform corrective actions to improve the calibration of their devices where needed.

Natural Uranium Radioactivity Solution Standard: SRM 4321d.

A new natural uranium solution standard has been produced and will be disseminated by the National Institute of Standards and Technology (NIST) as Standard Reference Material 4321d. The standard is certified for the massic activities of 234U, 235U, and 238U in solution, and it is based on isotopic mass data for the metallic Certified Reference Material (CRM) 112-A (originally issued as SRM 960) that was obtained from THE U.S. Department of Energy, New Brunswick Laboratory. The metallic CRM was chemically cleaned, dissolved, and gravimetrically diluted to prepare a master solution, which was quantitatively dispensed into 5 mL aliquots that were contained within flame-sealed glass ampoules for each SRM unit. Homogeneity among SRM units, verifying solution homogeneity, was substantiated by photonic-emission integral counting with a NaI(Tl) well counter. Confirmatory measurements were performed by liquid scintillation counting for the total massic activity, and by isotope dilution α spectrometry for the 234U and 238U massic activities.

Estimating soil redistribution patterns with 137Cs measurements in a Mediterranean mountain catchment affected by land abandonment

AbstractIn Mediterranean mountainous environments, the removal of natural vegetation for developing agriculture increased the surface areas prone to erosion in the past centuries. In Southern Pre‐Pyrenees, the process was inverted during the middle of the 20th century. This work aims to assess how land use changes after widespread land abandonment affect soil redistribution. For this purpose, 137Cs was used in a 23 km2 catchment that was mostly cultivated at the beginning of the past century. After land abandonment, 16.5% of croplands persisted but afforestation and natural revegetation occupy 83.5% of the catchment area. 137Cs massic activity and related soil properties—stoniness, grain size, and organic matter contents—were analysed in 98 bulk core samples. Physiographic characteristics—slope, altitude, and solar radiation—at the sampling points were determined by using Geographic Information Systems. Soil erosion and deposition rates were derived from 137Cs measurements after applying conversion models and were spatially interpolated to estimate the amount of net soil loss. In cropland soils, mean erosion (62.6 Mg ha−1 yr−1) and deposition rates (55.2 Mg ha−1 yr−1) were significantly higher than in the other land uses. The lowest mean erosion rates (2.4 Mg ha−1 yr−1) were found in natural forests and the lowest mean deposition (2.6 Mg ha−1 yr−1) in pine afforestation evidencing the soil stabilization achieved in the last decades due to revegetation. A sediment budget with the interpolated rates, result in a specific sediment yield of 4.15 Mg ha−1 yr−1. These results outline the impact of land use changes on soil redistribution in fragile mountain agroecosystems.

A review of the TAEA proficiency test on natural and anthropogenic radionuclides activities in black tea

A proficiency test amongst 15 Turkish laboratories with participation of 5 non-Turkish laboratories was organized to determine the 137Cs, 40K and 90Sr massic activities in black tea powder samples. The bulk material, consisting of tea produced in 2014, was mixed with contaminated tea that was withdrawn from the market after the Chernobyl accident. Nineteen laboratories reported 41 results. The evaluation of the results was based on the accuracy and precision criteria adopted by the IAEA Proficiency Testing Group and resulted in 49% acceptable results, 19% acceptable with warning and 32% were found to be not acceptable.

Uncertainty of determination of 158Tb in the RBMK nuclear reactor waste

The activity of 158Tb was measured in waste samples from the Ignalina NPP Unit I RBMK-1500 reactor using gamma-ray spectrometry. The origin of 158Tb and the other observed gamma-ray emitters has been studied by using SCALE 6.1 modeling and comparing radionuclide ratios in the RBMK-1500 radioactive waste. The results of the calculation of the massic activity of gamma-ray emitters were used for interpretation of the total gamma-ray spectrum and the determination of 158Tb massic activity uncertainty in the waste of RBMK-1500.

New certified reference materials and proficiency test for environmental radioactivity measurements

A reliable determination of natural and anthropogenic radionuclides in environmental samples is necessary to comply with the radiation protection and environmental regulations. This paper presents the results of the characterisation of massic activities of natural and anthropogenic radionuclides in soil and water matrices produced as test items to conduct the proficiency test ERAD-PT-2013. The proficiency test ERAD-PT-2013 was designed to investigate analytical performance in analysing both natural and anthropogenic radionuclides, to assist laboratories to identify analytical problems, and to improve the quality of measurement results. The proficiency test items, their spectral interferences and the activity concentration levels of the analytes were designed in a way to enable identification of potential analytical problems. Methodologies, data evaluation approach and evaluation of proficiency test results for each radionuclide are described and discussed.

Comparison of Tritiated-Water Standards by Liquid Scintillation for Calibration of a New Standard Reference Material

A new National Institute of Standards and Technology (NIST) tritiated-water ((3)H-labeled oxidane) standard was prepared and calibrated. It is the 17th in a series of linked standards since 1954 and will be disseminated as Standard Reference Material® SRM 4927G, having a massic activity of 544.2kBqg(-1), with an expanded (k=2) relative standard uncertainty of 0.96%, at a Reference Time of 1200 EST, 1 May 2015. The calibration is based on relative liquid scintillation (LS) measurements using quench-varied efficiency tracing with two previous 1999 issues, viz., SRM 4927F and 4926E. Measurement comparisons were also made with respect to a 1994 tritiated-water French national standard and to a tritiated-water solution measured by 19 laboratories as part of an international measurement comparison organized by the Bureau International des Poids et Mesures (BIPM) in 2009. Confirmatory measurements for the massic activity of both SRM 4927F and 4927G by a triple-to-double coincidence ratio (TDCR) technique were also made.

Comparison of tritiated-water standards by liquid scintillation for calibration of a new Standard Reference Material®

A new National Institute of Standards and Technology (NIST) tritiated-water (3H-labeled oxidane) standard was prepared and calibrated. It is the 17th in a series of linked standards since 1954 and will be disseminated as Standard Reference Material® SRM 4927G, having a massic activity of 544.2kBqg−1, with an expanded (k=2) relative standard uncertainty of 0.96%, at a Reference Time of 1200 EST, 1 May 2015. The calibration is based on relative liquid scintillation (LS) measurements using quench-varied efficiency tracing with two previous 1999 issues, viz., SRM 4927F and 4926E. Measurement comparisons were also made with respect to a 1994 tritiated-water French national standard and to a tritiated-water solution measured by 19 laboratories as part of an international measurement comparison organized by the Bureau International des Poids et Mesures (BIPM) in 2009. Confirmatory measurements for the massic activity of both SRM 4927F and 4927G by a triple-to-double coincidence ratio (TDCR) technique were also made.

Ge検出器－γ線スペクトロメトリーによる玄米認証標準物質中<sup>134</sup>Cs, <sup>137</sup>Cs及び<sup>40</sup>Kの分析─第1部 放射能濃度の定量─

Ge検出器－γ線スペクトロメトリーによる玄米認証標準物質中<sup>134</sup>Cs, <sup>137</sup>Cs及び<sup>40</sup>Kの分析─第1部 放射能濃度の定量─

Low level measurement of 60Co by gamma ray spectrometry using γ–γ coincidence

This paper presents the latest development of the laboratory to measure the natural and artificial massic activities in environmental samples. The measurement method of coincident emitters by gamma–gamma coincidence using an anti-Compton device and its digital electronics is described. Results obtained with environmental samples are shown. Despite its low efficiency, this method decreases detection limits of 60Co for certain samples compared to conventional gamma-ray spectrometry due to its very low background.

Assessment of measurement result uncertainty in determination of 210Pb with the focus on matrix composition effect in gamma-ray spectrometry

Reference materials were used to assess measurement result uncertainty in determination of 210Pb by gamma-ray spectrometry, liquid scintillation counting, or indirectly by alpha-particle spectrometry, using its daughter 210Po in radioactive equilibrium. Combined standard uncertainties of 210Pb massic activities obtained by liquid scintillation counting are in the range 2–12%, depending on matrices and massic activity values. They are in the range 1–3% for the measurement of its daughter 210Po using alpha-particle spectrometry. Three approaches (direct computation of counting efficiency and efficiency transfer approaches based on the computation and, respectively, experimental determination of the efficiency transfer factors) were applied for the evaluation of 210Pb using gamma-ray spectrometry. Combined standard uncertainties of gamma-ray spectrometry results were found in the range 2–17%. The effect of matrix composition on self-attenuation was investigated and a detailed assessment of uncertainty components was performed.

Study of parameters relevant for a better prediction of the radon potential

In 2012 and 2013 measurements of parameters relevant for a better prediction of the radon potential were carried out in Austria at 100 sites. The parameters were the 222Rn activity concentration in soil gas, the soil's permeability, the ambient equivalent dose rate above the ground and the soil's massic activity by gamma spectrometry. The uncertainties of sampling and measurements are discussed as well as the correlations between these parameters.

A preliminary study for the development of reference material using oyster for determination of 137Cs, 90Sr and plutonium isotopes

A new reference material for the determination of 137Cs, 90Sr and Pu isotopes (238Pu and 239,240Pu) is being developed using dried oyster matrix by Korea Research Institute of Standards and Science (KRISS). The oyster was collected from Tongyoung harbour, southern part of Korea and the artificial radionuclides (137Cs, 90Sr, 238Pu and 239,240Pu) were spiked into the material. After pretreatment and processing, the material was tested for homogeneity and massic activities were determined by measuring 137Cs, 90Sr, 238Pu and 239,240Pu. The reference value and extended uncertainty for those isotopes will be reported later.

Spatial patterns of SOC, SON, 137Cs and soil properties as affected by redistribution processes in a Mediterranean cultivated field (Central Ebro Basin)

Mediterranean mountain agroecosystems are sensitive areas to soil degradation due to climatic conditions and anthropogenic pressure from agriculture and grazing practices. Soil redistribution processes affect the spatial variability of soil properties and nutrients, as soil organic carbon and nitrogen (SOC and SON) are linked to soil quality and soil functions. A representative cereal field of rain-fed agroecosystems in a Mediterranean mountain environment where conventional and conservation agricultural practices have been implemented was selected on the northern border of the Ebro valley (NE Spain) to gain a better understanding of the effect of soil redistribution processes on the spatial pattern of soil properties at field scale. One hundred and fifty-six bulk (30–50cm) and 156 topsoil samples (5cm) were collected on a 10×10m grid. Furthermore, 21 soil samples (40cm) were collected at a nearby undisturbed reference site. 137Cs massic activity was measured on bulk and reference soil samples, and SOC and SON were measured on all soil samples. The characterisation of SOC pools into active (ACF) and stable carbon fraction (SCF) was carried out to study SOC pool dynamics. The fallout 137Cs was used in order to identify areas of 137Cs loss and gain and that of soil within the study field. Similar spatial patterns and direct and significant correlations (p<0.01) were found between 137Cs and soil nutrients. As much as 70% of the total study field had lower values of 137Cs inventory than the reference for the area. In addition, there was a generalised loss of soil nutrients. SOC gain was found in less than 1% of the study field and there was a large loss of SON compared to the undisturbed reference site. Higher and significant (p<0.01) contents of soil nutrients were found in topsoil than in bulk samples. Furthermore, there was an enrichment of the relative contribution of ACF to total SOC in sampling points where there was a 137Cs gain in both bulk and topsoil samples as a consequence of the soil redistribution particles by tillage and runoff. Understanding patterns of soil nutrients can be useful for developing or implementing land management strategies to preserve soil quality in Mediterranean agricultural areas.

Uncertainties in 4πβ–γ coincidence counting

The 4πβ–γ coincidence counting method and its close relatives are widely used for the primary standardization of radioactivity. Both the general formalism and specific implementation of these methods have been well-documented. In particular, previous papers contain the extrapolation equations used for various decay schemes, methods for determining model parameters and, in some cases, tabulated uncertainty budgets. Two things often lacking from experimental reports are both the rationale for estimating uncertainties in a specific way and the details of exactly how a specific component of uncertainty was estimated. Furthermore, correlations among the components of uncertainty are rarely mentioned.To fill in these gaps, the present article shares the best-practices from a few practitioners of this craft. We explain and demonstrate with examples of how these approaches can be used to estimate the uncertainty of the reported massic activity. We describe uncertainties due to measurement variability, extrapolation functions, dead-time and resolving-time effects, gravimetric links, and nuclear and atomic data. Most importantly, a thorough understanding of the measurement system and its response to the decay under study can be used to derive a robust estimate of the measurement uncertainty.

Preparation of &lt;sup&gt;188&lt;/sup&gt; W from Unenriched Targets in Middle Flux Nuclear Reactors

Ways of increasing massic activity of 188W resulting from irradiation of tungsten targets in the middle flux nuclear reactor IRT-T have been analyzed. Calculation and experimental results of evaluating the influence of blocking effect on accumulation of target radionuclides are presented. The possibility to increase effective activation cross section by creating definite target shape has been experimentally proven.

Characterization of 226Ra activity in low-level slag reference standards

Within the EURAMET European Metrology Research Programme project IND04 named MetroMetal, several different reference standards have been developed for the metallurgical industry. This paper describes the characterisation of low-levels of 226Ra in samples of slag. The activity was determined through spiking with a known amount of solution containing 226Ra to a previously characterised slag material. The measurements were performed at both 225 m underground and aboveground. The total (spiked + natural) massic activity of 226Ra obtained from the gamma-ray spectrometry measurements was (126.3 ± 5.6) Bq/kg. A comparison of the different measurements and studies of the distribution of radon-daughters in the samples is presented.

Measurement of the French national tritiated-water standard by helium-3 mass spectrometry

The 3He ingrowth technique is based on the detection of the tritium radioactive daughter, 3He, by mass spectrometry. Over the last three decades it has been used extensively in oceanography and groundwater studies for measurements of very low to ultra-low levels of tritium. To compare it with the best available methods of radioactive counting, we applied this method to measure the massic activity of a tritiated-water primary standard prepared by the French Laboratoire National Henri Becquerel (LNHB). One liter of a low-level tritium solution was prepared from a small aliquot of the LNHB standard by two-step gravimetric dilution with tritium-free groundwater. Sixteen samples of this solution were analyzed at the LSCE-Saclay noble gas facility, using the 3He ingrowth method. The massic activity of the prepared solution was also measured by Liquid Scintillation Counting using the Quantulus LNHB counter and an internal calibration method with the LNHB tritiated water standard. All results agree within their standard uncertainty.

Standardization of 237Np

The standardization of 237Np was investigated. The certified massic activity for 237Np was obtained by 4παβ liquid scintillation (LS) counting with correction for the 233Pa daughter using the CIEMAT/NIST efficiency tracing method using a 3H standard. Confirmatory measurements were also performed by high-resolution HPGe gamma-ray spectrometry, and by 4παβ(LS)-γ(NaI) anticoincidence counting. All results agree within the respective method's uncertainties. It was confirmed that the 237Np/233Pa radioactive equilibrium is disturbed when making dilutions and/or removing aliquots.

Half-life measurements of lutetium-176 using underground HPGe-detectors

The half-life of 176Lu was determined by measuring the 176Lu activity in metallic lutetium foils. Three different HPGe-detectors located 225m underground were employed for the study. Measurements using the sum-peak method were performed and resulted in an average massic activity of (52.61±0.36)Bqg−1. The foils were of natural isotopic abundance so using the massic activity and the value of the natural isotopic abundance of (2.59±0.01)%, a half-life of (3.722±0.029)×1010a could be calculated.