Temporal variations of 7Be, 210Pb and 137Cs in moss samples over 14 month period

Concentrations of ²¹⁰Pb, ⁷Be and ¹³⁷Cs in moss samples were continuously measured, using low-background HPGe spectrometer at Novi Sad, Serbia (45°14′45″N, 19°51′35″E). Weekly data collected over 14 month period from January 2007 to March 2008 are presented and discussed. Measured values of ⁷Be activity concentrations in dry moss samples are ranged from 201 to 920 Bq/kg showing prominent increase in summer and autumn season. Data for ²¹⁰Pb, ranged from 347 to 885 Bq/kg do not show such trend. The average concentration of ¹³⁷Cs is 8.9 Bq/kg. It is shown that yield of ⁷Be can be estimated using average values of activity concentrations. Precipitation amount and duration of precipitation are measured and their possible influence on activity concentrations measured in moss samples was considered.     

Distribution of radionuclides in soil samples from a petrified wood forest in El-Qattamia,Cairo, Egypt

The concentrations and distribution of radionuclides in a petrified wood forest in El-Qattamia have been determined using high-resolution gamma spectrometry to evaluate the environmental radioactivity. The mean activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were 65.26±12.99, 23.66±0.95 and 146.33±1.50 Bq kg⁻¹, respectively.Data of the soil samples show evidence of possible deposition and accumulation of ¹³⁷Cs. The mean activity concentration of ¹³⁷Cs in the soil samples was 4.37±0.16 Bq kg⁻¹ with a range of 0.00–35.70 Bq kg⁻¹. The measured activity concentration range of ¹³⁷Cs was compared with reported ranges in the literature from some of the other locations in the world. The radium-equivalent, dose rate in air and annual effective dose rate were evaluated. The mean activity concentrations of the γ-ray emissions from radionuclides in El-Qattamia petrified wood forest region were relatively low.     

Spatial distributions of 137Cs and 239+240Pu in surface seawater within the Exclusive Economic Zone of East Coast Peninsular Malaysia

The studies of ¹³⁷Cs and ^239+240Pu distributions in surface seawater at South China Sea within the Exclusive Economic Zone (EEZ) of Peninsular Malaysia were carried out in June 2008. The analysis results will serve as additional information to the expanded baseline data for Malaysia’s marine environment. Thirty locations from extended study area were identified in the EEZ from which large volumes of surface seawater samples were collected. Different co-precipitation techniques were employed to concentrate cesium and plutonium separately. A known amount of ¹³⁴Cs and ²⁴²Pu tracers were used as yield determinant. The precipitate slurry was collected and oven dried at 60 ^oC for 1–2 days. Cesium precipitate was fine-ground and counted using gamma-ray spectrometry system at 661.62 keV, while plutonium was separated from other radionuclides using anion exchange, electrodeposited and counted using alpha spectrometry. The activity concentrations of ¹³⁷Cs and ^239+240Pu were in the range of 3.40–5.89 Bq/m³ and 2.3–7.9 mBq/m³, respectively. The ^239+240Pu/¹³⁷Cs ratios indicate that there are no new inputs of these radionuclides into the area.     

Enrichment and vertical profiles of 210Po and 210Pb in monazite areas of coastal Karnataka

A study on radiation level and radionuclide distribution in the environment of coastal Karnataka has revealed the presence of low-level monazite deposit in the Ullal beach area. The paper presents systematic studies on the distribution, enrichment and vertical profiles of ²¹⁰Po and ²¹⁰Pb, important daughter products of ²³⁸U, in Ombattu Kere, Summer Sand and the Bhagavathi Temple region of the Ullal beach area of coastal Karnataka. Sand samples collected at different depths from these locations were analyzed for ²¹⁰Po and ²¹⁰Pb activities to understand the distribution, enrichment and vertical profiles of these radionuclides in monazite area. The activity of ²¹⁰Po in the Ullal region is found to vary from 1.7 to 43.2 Bq kg^?1 with a mean value of 11.2 Bq kg^?1 and that of ²¹⁰Pb varies from 1.0 to 66.7 Bq kg^?1 with a mean value of 19.1 Bq kg^?1. The mean ²¹⁰Po/²¹⁰Pb ratio was observed to be 0.6. The absorbed gamma dose rate in the region varies in the range 39–460 nGy h^?1 with a mean value of 193 nGy h^?1.     

Fukushima radionuclides in Vilnius/Lithuania aerosols: Modelling of aerosol transport

Measurements of activity concentrations of ¹³¹I; ^129mTe, ¹³²Te, ¹³⁴Cs and; ¹³⁶Cs, ¹³⁷Cs in aerosol were carried out in daily samples after the Fukushima accident during the period of March–April, 2011 in Vilnius. The maximum activity concentrations of ¹³¹I and ¹³⁷Cs were found to be 3700 μBq m⁻³ and 1040 μBq m⁻³, respectively. Variations in activity ratios of ¹³²Te/^129mTe and ¹³⁷Cs/¹³⁶Cs observed after the accident were explained by the decay of the short-lived isotopes, while those in ¹³⁴Cs/¹³⁷Cs by the dilution effect of the Chernobyl-derived ¹³⁷Cs. It was found that different behaviours of highly volatile ¹³¹I and ¹³⁷Cs resulted in enrichment of ground level aerosol particles by ¹³¹I with respect to ¹³⁷Cs. Simulated activity concentrations of ¹³⁷Cs attached to aerosol particles for the Vilnius site reasonably agreed with measured activities in aerosol samples during the Fukushima accident.     

A UK comparison for measurements of low levels of gamma-emitters in waste drums

Much of the work of the UK nuclear industry is now concerned with decommissioning many of the existing power stations and other facilities. An important aspect of this work is the accurate measurement of low levels of radioactivity in waste forms such as building materials in order that these materials can be assigned to the correct waste streams. This has led to a call for suitable standards and reference materials, and the specific needs of UK users were identified at an NPL workshop in 2005. One of the highest priorities was for ‘soft waste’ spiked with γ-emitters in a 200 L drum format, with an activity concentration of just under 0.4 Bq g⁻¹. In response, NPL prepared a single reference drum meeting this specification. The low density was achieved by loading the drum with plastic bottles, each partially loaded with ion-exchange resin. The resin in each bottle had been previously spiked with a mixture of ²⁴¹Am, ¹³⁷Cs and ⁶⁰Co, all traceable to national standards. The drum would be used primarily as the basis of a comparison exercise, but feedback on its usefulness as a calibration standard would also be sought.The drum was measured by 17 radioassay groups at 15 UK sites. The monitors used were mostly commercial γ-spectrometry systems designed to accommodate waste drums. Some groups measured the drum on more than one monitor and some used more than one efficiency calibration. Many of the groups used mathematical modelling to derive their efficiencies. The results of the exercise were discussed at a second NPL workshop (2007), after which the participants were allowed to submit supplementary or replacement results (with reasons for any changes clearly stated). In total, 88 results were submitted. A total of 51 results were in agreement with the NPL values; of the remaining results, 24 were explained by the participants concerned (or were revised to provide supplementary values), but the other 13 results were either clearly discrepant or questionable. The exercise demonstrated differences between laboratories who had used the same modelling software for their efficiency calibrations, and indeed facilitated an exchange of models between these laboratories. The importance of an accurate knowledge of the form and structure of the sample in efficiency modelling was clearly demonstrated. Uncertainty budgets were of variable quality. Some participants quoted MDA values for one or more of the radionuclides. A follow-up comparison was requested and this is now being planned.     

Influence of 210Pb on the continuous background of gamma-ray spectrometers

The contribution of the ²¹⁰Pb activity in gamma-ray spectrometer's lead shields to the spectrometer background was determined on the basis of the time dependence of the count rate in the background continuum. The time dependence, reflecting the decay of ²¹⁰Pb, was measured over a time interval of about 10 years. It is shown that the maximum contribution to the spectrometer background due to ²¹⁰Pb is around 200 keV, and that the largest fractional contribution to the total background is in the energy interval from 100 to 300 keV.     

Results of an international comparison of 57Co

As part of a Cooperative Research Project (CRP) aimed at improving the state of radioactivity measurement in nuclear medicine, the International Atomic Energy Agency (IAEA) organized a comparison of ⁵⁷Co solutions among the participants of the project. The comparison solutions were prepared from a single master stock solution and distributed to the participating laboratories, who measured the activity concentration of the solution using either the laboratory's radionuclide activity calibrator or primary standardization methods. A total of 9 sets of results were received, with 5 laboratories reporting results of primary measurements, one reporting results of secondary measurements calibrated against primary standards, and three laboratories reporting values based on measurements in commercial re-entrant ionization chambers using manufacturer-recommended calibration figures. Most of the laboratories reporting primary standardizations also provided results from secondary standardizations. The Comparison Reference Value was calculated from the mean of the five primary standardizations and was found to be 35.54 MBq g^?1, with a standard deviation of the mean of 0.17 MBq g^?1. Degrees of equivalence were calculated for each reporting laboratory and demonstrated that equivalence to within about 4% could be achieved, even in the case of those laboratories that used instruments calibrated by third parties.     

Applicability study of using in-situ gamma-ray spectrometry technique for 137Cs and 210Pbex inventories measurement in grassland environments

In-situ measurement of fallout radionuclides ¹³⁷Cs and ²¹⁰Pb_ex has the potential to assess soil erosion and sedimentation rapidly. In this study, inventories of ¹³⁷Cs and ²¹⁰Pb_ex in the soil of Inner Mongolia grassland were measured using an In-situ Object Counting System (ISOCS). The results from the field study indicate that in-situ gamma-ray spectrometry has the following advantages over traditional laboratory measurements: no extra time is required for sample collection, no reference inventories are required, more economic, prompt availability of the results, the ability to average radionuclide inventory over a large area, and high precision.     

137Cs tracing dynamics of soil erosion,organic carbon and nitrogen in sloping farmland converted from original grassland in Tibetan plateau

There is a shortage of research concerning the relationships between land-use change, soil erosion, and soil organic carbon (SOC) and nitrogen (N) dynamics in alpine environments such as those found in the Tibetan plateau. In this paper, typical sloping farmlands converted from grassland 50 years ago in eastern Tibet were selected to determine dynamics of soil erosion, SOC, and total N associated with land-use change. Soil samples were collected from sloping farmland and control fields (grassland). The ¹³⁷Cs, SOC, total N contents, and soil particle size fractions were analyzed in these samples. As compared with the control fields, ¹³⁷Cs, SOC, and total N inventories in the sloping farmlands decreased by 30%, 27%, and 33%, respectively. Meanwhile variations in the three parameters were enhanced in the sloping farmlands, with coefficients of variation (CVs) of 38%, 23%, and 20%, respectively, for ³⁷Cs, SOC, and total N. In addition, SOC and total N inventories significantly decreased with increasing soil erosion in the sloping farmland. In a sloping farmland with a steep 24° gradient, the ¹³⁷Cs inventory gradually increased along a downslope transect with its lowest value at 0 Bq m^?2 in the top-slope position (0 m). The soil clay (<0.002 mm) content in such an area increased with decreasing elevation (r=?0.95, p=0.001). Significant correlations between ¹³⁷Cs and clay (r=0.92, p=0.003), SOC (r=0.96, p=0.001), or total N (r=0.95, p=0.001) were also found in the farmland. These results showed that converting alpine grassland to sloping farmland accelerates soil erosion, losses in SOC and N, and increases the soil’s spatial variability. The combined impacts of tillage and water erosion contributed a significant decrease in the soil’s organic carbon and N storages. Particularly in steep sloping farmlands, tillage erosion contributed for severe soil loss, but the soil redistribution pattern was dominated by water erosion, not tillage erosion, due to the lack of boundaries across the field patches. It was also found that ¹³⁷Cs, SOC, and total N moved along the same pathway within these sloping farmlands, resulting in net C and N losses during soil redistribution. The negative influences of land-use conversion from grassland to farmland in sloping areas in the Tibetan plateau should be addressed.     

Activity size distributions for long-lived radon decay products in aerosols collected in Barcelona (Spain)

The activity median aerodynamic diameters (AMADs) of long-lived radon decay product (²¹⁰Pb, ²¹⁰Po) in aerosols collected in the Barcelona area (Northeast Spain) during the period from April 2006 to February 2008 are presented. The ²¹⁰Po mean AMAD was 420 nm, while the ²¹⁰Pb mean AMAD was 500 nm. The temporal evolution of ²¹⁰Pb and ²¹⁰Po AMADs shows maxima in autumn and winter and minima in spring and summer. ²¹⁰Pb AMAD are being used to estimate the mean-residence time of atmospheric aerosols.     

Atmospheric input of 137Cs and 239,240Pu isotopes in Korea after the Fukushima nuclear power plant accident

Caesium isotopes (¹³⁴Cs and ¹³⁷Cs) and ^239,240Pu in rainwater and dry deposition have been analyzed by Korea Research Institute of Standards and Science (KRISS) since the Fukushima nuclear power plant (NPP) accident in March 2011. The concentrations of ^239,240Pu and ¹³⁷Cs in the rainwater are 2.6±1.0 to 15±3 µBq/kg and 0.01 to 0.36 mBq/kg, respectively. The concentrations are concordant to those observed before the Fukushima NPP accident, on the other hand, the monthly depositional flux of ^239,240Pu and ¹³⁷Cs are much lower than the amounts observed after Fukushima NPP accident and in Monaco in 1998–2001. This confirms that the Fukushima NPP accident caused no significant impact in Korea.     

The calibration and evaluation of a radioactive waste drum counting system

The drum counting system was calibrated in this study. For ¹³⁷Cs, the counting efficiencies were around 14–1% when the density of the waste of the drum was changed from 0.15 to 2.3 g cm⁻³. The effects of the background, hot spot, system linearity, sample density and weighing were also evaluated in this work. The combined standard uncertainty of the drum counting system for the ¹³⁷Cs in the density of 1 g cm⁻³ was around 12%. To verify the counting system, the drums containing radioactive solution were prepared by the NMI as the blind samples. A discrepancy below 15% was shown between the counting results and the reference values of the NMI.     

238U, 235U, 137Cs and 133Xe in soils from two campuses in University of Douala—Cameroon

An evaluation of ²³⁸U, ²³⁵U, ¹³⁷Cs and ¹³³Xe in soils from two campuses in University of Douala—Cameroon using gamma spectroscopy based Broad Energy Germanium Detector (BEGe6530) has been performed. The mean activities in soils from Campuse 1 were 40.16±8.98 Bq/kg for ²³⁸U, 3.39±0.33 Bq/kg for ²³⁵U, 0.46±0.33 Bq/kg for ¹³⁷Cs and 0.14±0.16 Bq/kg for ¹³³Xe. In Campus 2, the mean activities in soils were 31.45±12.24 Bq/kg, 3.02±1.00 Bq/kg, 0.30±0.26 Bq/kg and 0.35±0.24 Bq/kg for ²³⁸U, ²³⁵U, ¹³⁷Cs and ¹³³Xe, respectively. Using the in situ survey meter, the mean values of the absorbed dose rate measured was 71.43 nGy/h for Campus 1 and 62.72 nGy/h for Campus 2. The evaluated average outdoor effective dose for Campus 1 and 2 were 87.60 µSv/yr and 76.93 µSv/yr, respectively. The overall results obtained in this work were generally low compared to that of UNSCEAR.     

Certified reference material for radionuclides in fish flesh sample IAEA-414 (mixed fish from the Irish Sea and North Sea).

A certified reference material (CRM) for radionuclides in fish sample IAEA-414 (mixed fish from the Irish Sea and North Seas) is described and the results of the certification process are presented. Nine radionuclides (40K, 137Cs, 232Th, 234U, 235U, 238U, 238Pu, 239+240Pu and 241Am) were certified for this material. Information on massic activities with 95% confidence intervals is given for six other radionuclides (90Sr, 210Pb(210Po), 226Ra, 239Pu, 240Pu 241Pu). Less frequently reported radionuclides (99Tc, 129I, 228Th, 230Th and 237Np) and information on some activity and mass ratios are also included. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in fish sample, for the development and validation of analytical methods and for training purposes. The material is available from IAEA, Vienna, in 100 g units.     

Radiation surveillance using an unmanned aerial vehicle

Radiation surveillance equipment was mounted in a small unmanned aerial vehicle. The equipment consists of a commercial CsI detector for count rate measurement and a specially designed sampling unit for airborne radioactive particles. Field and flight tests were performed for the CsI detector in the area where ¹³⁷Cs fallout from the Chernobyl accident is 23–45 kBq m⁻². A 3-GBq ¹³⁷Cs point source could be detected at the altitude of 50 m using a flight speed of 70 km h⁻¹ and data acquisition interval of 1 s. Respective response for ¹⁹²Ir point source is 1 GBq. During the flight, the detector reacts fast to ambient external dose rate rise of 0.1 μSv h⁻¹, which gives for the activity concentration of ¹³¹I less than 1 kBq m⁻³. Operation of the sampler equipped with different type of filters was investigated using wind-tunnel experiments and field tests with the aid of radon progeny. Air flow rate through the sampler is 0.2–0.7 m³ h⁻¹ at a flight speed of 70 km h⁻¹ depending on the filter type in question. The tests showed that the sampler is able to collect airborne radioactive particles. Minimum detectable concentration for transuranium nuclides, such as ²³⁹Pu, is of the order of 0.2 Bq m⁻³ or less when alpha spectrometry with no radiochemical sample processing is used for activity determination immediately after the flight. When a gamma-ray spectrometer is used, minimum detectable concentrations for several fission products such as ¹³⁷Cs and ¹³¹I are of the order of 1 Bq m⁻³.     

A long-term performance evaluation of the gamma-ray activity measurement laboratory in CPST,Lithuania

The quality control procedures used for two HPGe detectors (a well-type and a GAMMA-X coaxial) are described. Since 2001, check sources containing ¹³⁷Cs have been measured weekly for 7200s each, and the gamma-ray spectrometry system background was determined once per month for an acquisition time of 100,000 s. The laboratory participated in the international comparisons at environmental radioactivity level organized by the IAEA, Risø National Laboratory and NPL.     

Evaluation of the chromium contamination at Ribeirão dos Bagres,Franca (SP), Brazil,by the 210Pb method

This paper presents a chronological study focusing the use of ²¹⁰Pb in four sediment cores collected at Ribeirão dos Bagres in the region of Franca, São Paulo State, Brazil. When evaluating the sedimentation rate by using the ²¹⁰Pb method, it was possible to monitor historical changes occurring in the concentrations of chromium present in the sediments. In order to do so, several specific parameters were determined in sediments, as chromium concentration, major oxides, organic matter, grain size, and chemical and physical–chemical parameters of waters. The sediments possessed a Cr concentration range of 0.83–26.25 mg/kg that is below the world's average of shales. The sedimentation rates obtained from the ²¹⁰Pb analysis were between 0.07 and 0.77 g cm⁻² year⁻¹, while the linear sedimentation rate was from 0.6 to 3.2 cm/year. The adoption of the CIC (Constant Initial Concentration) ²¹⁰Pb model allowed characterize older sediments, aged 177 years, and younger sediments, aged 4 years. The organic matter in the sediments was more abundant in the first few centimeters of practically all profiles, and the analysis of oxides showed that silica is the major constituent of the sediments, in which there is predominance of sand and silt. In addition, the analysis of the physical and chemical parameters of waters indicated that they are suitable for navigation and natural harmony landscape.     

EC comparison on the determination of 226Ra, 228Ra, 234U and 238U in water among European monitoring laboratories

In anticipation of new European requirements for monitoring radioactivity concentration in drinking water, IRMM organized an interlaboratory comparison on the determination of low levels of activity concentrations (about 10–100 mBq L^?1) of the naturally occurring radionuclides ²²⁶Ra, ²²⁸Ra, ²³⁴U and ²³⁸U in three commercially available mineral waters. Using two or three different methods with traceability to the International System of Reference (SIR), the reference values of the water samples were determined prior to the proficiency test within combined standard uncertainties of the order of 3%–10%. An overview of radiochemical separation and measurement methods used by the 45 participating laboratories are given. The results of the participants are evaluated versus the reference values. Several of the participants’ results deviate by more than a factor of two from the reference values, in particular for the radium isotopes. Such erroneous analysis results may lead to a crucial omission of remedial actions on drinking water supplies or to economic loss by an unjustified action.     

中日γ能谱分析土壤样品中放射性核素的比对

目的 通过开展γ能谱测量分析比对活动,检验比对样品的采集、制备、测量和分析全过程,以促进放射性核素γ能谱测量分析技术的发展。方法 由中国疾病预防控制中心辐射防护与核安全医学所采集和制备环境土壤样品,比对各方分别对两个土壤样品中的²¹⁴Pb、²¹⁴Bi、²⁰⁸Tl、²²⁸Ac、⁴⁰K和¹³⁷Cs 6个核素进行测量和分析。根据3个实验室约定测量结果的评定标准,利用各实验室上报的活度浓度和总不确定度数据计算测量结果评价变量(En)值。结果 每两个实验室间计算的En值均小于1,3个实验室的结果均为可接受的结果。结论 各比对方的测量结果在一定范围内是一致的。本次比对既检验了比对方实验室的核素分析水平,又促进了本实验室样品制备中均匀性检验能力的提高。