Fast screening of operational aqueous samples by gross alpha and beta counting with LSC systems

At nuclear installations a large number of samples is used to control operational tasks and health physics parameters. A fast screening process can be applied to provide immediate indication on possible contamination, and liquid scintillation counting (LSC) is the preferred method. Many LSC systems, which do not perform pulse shape analysis, are still in use. A screening procedure for these systems is presented based on three windows analysis. It may greatly reduce work and time, compared to using a proportional counter system, besides providing more accurate results.     

Establishment of rapid LSC method for direct alpha/beta measurements in waters

Development of rapid gross alpha/beta screening in waters has been presented. Modification of conventional ASTM method assumed direct mixing of samples with liquid scintillation cocktail, without any sample pretreatment. Optimization of method involved sample-to-cocktail ratio determination based on the achieved detection limit and quench level of sample as well as the optimal value of pulse shape analysis discriminator investigation. Results of calibration experiments and method’s validity measurements are presented. Direct alpha/beta method provides deviations <40% from reference values, but offers advantages over conventional alpha/beta measurements, it is ultra fast, simple and inexpensive test for efficient screening of water samples.     

Gross alpha determination in salt rich water samples using an extraction chromatographic resin and LSC

The application of an extraction chromatographic resin to the determination of the gross alpha activity of drinking water samples with volumes greater than 100 ml and of salt rich aqueous samples, like mineral, waste or sea waters was tested. Alpha-emitters are extracted from the water sample onto the resin, the gross alpha activity is then determined by direct measurement of the dried resin using α/β discrimination LSC. The resin shows strong affinity for actinides, as well as for radium, out of pH 2 solutions. The extraction is robust against Ca, sulphate and other potential interferents. The method was tested by analyzing reference materials, intercomparison samples and spiked real samples. Results of good precision and accuracy were obtained in counting times notably shorter than routinely used for gas proportional counting.     

Current status of gross alpha/beta activity analysis in water samples: a short overview of methods

Gross alpha/beta measurement is one of the simplest radioanalytical procedures which are applied widely as a screening technique in the field of radioecology, environmental monitoring and industrial applications as well. Due to the uncertainties of gross alpha/beta measurements this method is often the subject of discussions and debates. The aim of this work is to collect information about recently used standard and routine methods concerning gross alpha/beta activity determination in drinking waters in order to get an overview about the current situation and evaluate their possibilities. Sample preparation methods—e.g. evaporation, co-precipitation—and detection systems—e.g. gas flow proportional counting, liquid scintillation counting and scintillation counting—are compared on the ground of literature data. In the course of our work, the following parameters were analyzed and discussed: background, counting efficiency, interferences, sample capacity, minimal detectable activity, typical counting time, time demand of sample preparation.     

The development of an alpha/beta separation liquid scintillation cocktail for aqueous samples

Scintillation cocktail components were studied with regard to their impact on pulse decay discimination (PDD) and hence the separation of alpha from beta activity, using a Packard 2250 CA /. Di-isopropyl naphthalene (DIN) was found to be the most suitable solvent, both from safety considerations and also the fact that it acts in a very similar manner to naphthalene in stretching the pulses produced at the photomultiplier tube anode and hence enhancing the separation. Increasing the surfactant concentration and the use of dimethylanthracene (DMA) as secondary fluor degraded the cocktail's performance. PMT anode pulse shapes were found to be a useful indicator of PDD efficiency but could not give a quantitative guide.     

Strategy for the determination of mixtures of alpha and beta emitters in water samples with a combination of rapid methods

Journal of Radioanalytical and Nuclear Chemistry - Quantification of several alpha and beta emitters in mixtures of radionuclides arouses great interest in many fields such as surveillance around...     

Determination of 90Sr in urine samples and 89Sr/90Sr in water samples by chemical separation and Cherenkov counting with LSC system

Journal of Radioanalytical and Nuclear Chemistry - In order to determine radiostrontium with a satisfactory chemical yield, calculated by an external standard, and a low level of MDC a...     

Determination of plutonium-241 in low-level radwastes using radiochemical separation combined with LSC,alpha spectrometer and ICP-MS

Two kinds of measuring methods were described for the determination of Plutonium-241 in low level wastes in this study. Plutonium isotopes were separated and purified by highly selective UTEVA and TRU resin. LSC, alpha spectrometry, and ICP-MS were applied and compared for determination of Plutonium-241. There is a good agreement with the analytical results and also shows that the different analytical methods have high chemical recovery yields.

     

Gross alpha and gross beta radioactivity of water samples from ININ and Maquixco in the State of Mexico

The conditions to measure the gross alpha and gross beta radioactivity in water samples from the surrounding of the Nuclear Center (Instituto Nacional Investigaciones Nucleares, (ININ), and Collection, Treatment and Storage Center for Low Level Radioactive Waste (Maquixco) in the State of Mexico were established. The samples were collected from 1987 to 1996. The gross alpha and gross beta radioactivity in the samples were determined by a gas-flow proportional counter. The results indicated that the gross alpha and gross beta radioactive contamination in water samples were below the maximum contaminant level (MCL).     

Measuring salty samples without adducts with MALDI MS

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) has been used for the discovery of hundreds of novel cell to cell signaling peptides. Beyond its advantages of sensitivity and minimal sample preparation requirements, MALDI MS is attractive for biological analyses as high quality mass spectra may be obtained directly from specific locations within prepared tissue sections. However, due to the large quantity of salts present in physiological tissues, these mass spectra often contain many adducts of cationic salts such as sodium and potassium, in addition to the molecular ion [M + H]⁺. To reduce the presence of cation adducts in MALDI mass spectra obtained directly from tissues, we present a methodology that uses a slow condensation procedure to enable the formation of distinct regions of matrix/analyte crystals and cation (salt) crystals. Secondary ion mass spectrometric imaging suggests that the salts and MALDI matrix undergo a mutually exclusive crystallization process that results in the separation of the salts and matrix in the sample.     

Gross alpha and beta activities of airborne particulate samples from Wawel Royal Castle Museum in Cracow, Poland

PM-10, PM-2.5 and PM-1.0 concentrations were measured over an 8 h period at sites both inside and outside the museum of Wawel Royal Castle in Cracow, Poland. Gross alpha (α) and beta (β) activities seemed to vary across the particle size range with generally higher levels of activities in the PM-2.5 particle fraction, and higher activities in the PM-10 fraction, while both the highest and the lowest beta activities were found in PM-1.0 fraction. However, statistically there was no significant difference. The highly radioactive PM-1.0 fraction comprised mainly ²¹⁰Pb and the ²¹⁰Pb progeny, ²¹⁰Bi and ²¹⁰Po, and can be attributed to anthropogenic sourced outdoor radioactive particles brought indoors by visitors. ²¹⁰Pb is considered to be a good tracer of secondary aerosols produced by gas-to-particle conversion. Inside the Museum, the highest level of gross alpha activity was detected in the PM-10 fraction, and was mainly due to the uranium isotopes (²³⁴U, ²³⁵U and ²³⁸U) and their daughter products (²²⁶Ra, ²³²Th, ²¹⁰Po or ²²⁴Ra), and ¹³⁷Cs. The minimum and maximum total indicative doses per 8 h are caused by ¹³⁷Cs and ²³²Th, respectively.     

A new very sensitive LSC procedure for determination of Tc-99 in environmental samples

A new method for the determination of Tc-99 in different environmental samples has been developed. The sample is carefully ashed in a muffle furnace and then fused with Na₂CO₃ and K₂CO₃. The first step is an enrichment and purification of TcO ₄ ^– on an anion exchange resin. The Tc is desorbed as a cationic thiourea complex, which is held on a cation exchange resin. The complex is destroyed by oxidation to TcO ₄ ^– with (NH₄)₂S₂O₈ in sulfuric acid. From this solution TcO ₄ ^– is extracted into TBP/toluene and the organic phase is mixed with a scintillation cocktail and counted in an anticoincidence shielded LSC. Tc-99m is used as a chemical yield tracer. The decontamination factors for all important fission and activation products and naturally occurring radionuclides are in the range between > 10⁵ and > 10⁸. The detection limit is about 5 mBq per sample at a counting time of 1000 minutes. The maximum sample amount of plants is 500 g dry weight and therefore the lowest detection limit achievable is 10 mBq/kg. Ashing and dissolution of the samples takes 24 h and 4 analyses are performed by one technician in 8 hours. The chemical yield ranges from 50 to 80%.     

Low level alpha activity measurements with pulse shape discrimination--application to the determination of alpha-nuclides in environmental samples

Liquid scintillation counting of alpha rays with pulse shape discrimination was applied to the analysis of 226Ra and 239+240Pu in environmental samples and of alpha-emitters in/on a filter paper. The instrument used in this study was either a specially designed detector or a commercial liquid scintillation counter with an automatic sample changer, both of which were connected to the pulse shape discrimination circuit. The background counting rate in alpha energy region of 5-7 MeV was 0.01 or 0.04 cpm/MeV, respectively. The figure of merit indicating the resolving power for alpha- and beta-particles in time spectrum was found to be 5.7 for the commercial liquid scintillation counter.     

Analysis of dust and surface swab samples for octachlorodibenzo-p-dioxin and heptachlorodibenzo-p-dioxins by fused silica capillary GC with EC detection

A method is described for the analysis of contaminated building dust samples and surface swab samples for octachlorodibenzo-p-dioxin (OCDD) and heptachlorodibenzo-p-dioxins (HpCDDs). The samples were analyzed by fused silica capillary GC combined with electron capture detection. Analysis was preceded by a short HPLC cleanup step designed to remove polychlorinated biphenyls (PCBs) and other compounds that might interfere. The method was found to work successfully on surface swab and dust samples known to contain PCBs, OCDD, and HpCDDs. The overall recovery of the analysis procedure for OCDD was found to be approximately 80%. The detection limit for the method was sample dependent, but for one typical set of surface swab samples was 0.2 μg/m² of OCDD.     

A very sensitive LSC procedure to determine Ni-63 in environmental samples,steel and concrete

This procedure to determine Ni-63 contributes to a safe and economically resonable decommissioning of nuclear power plants. Co-60, Fe-55 and Ni-63 are the most abundant long-lived radionuclides associated with contaminated piping, hardware and concrete for a period of several decades of years after shutdown, Samples are carefully ashed, leached, or dissolved by suitable mixtures of acids. The analysis starts with the absorption of Ni²⁺ on the chelating resin CHELEX 100. The next purification steps include an anionic exchange column and a precipitation as Ni-dimethyl-glyoxime, which is extracted into chloroform. After reextraction with sulfuric acid the solution containing Ni²⁺ is mixed with a scintillation cocktail and counted in an anticoincidence shielded LSC. The decontamination factors are determined for all important artificially and naturally occurring radionuclides ranging from above 10⁴ to 10⁹. The chemical yield adopts a value of (95±5)%. up to maximum sample amounts of 0,4 g steel, 5 g concrete and about 100 g of environmental samples the detection limits are about 5 mBq per sample or 12 mBq/g steel, 1 mBq/g concrete and 0,05 mBq/g environmental sample at a counting time of 1000 minutes.     

Ashing and microwave digestion of aerosol samples with a polypropylene fibrous filter matrix

Radionuclide monitoring is one of the key techniques required by the International Monitoring System (IMS) and On-Site Inspection (OSI) in the Comprehensive Nuclear Test Ban Treaty (CTBT). There shall be a global network of 80 radionuclide monitoring stations. Atmospheric aerosols are collected generally on filters in the stations. A polypropylene (PP) fibrous filter is often used in sampling atmospheric aerosols. There might be much information to be obtained by measuring aerosol samples after digestion rather than nondestructive analysis directly by γ-spectrometry. The present work focused on pretreatment of the filter samples, which includes the influence of different ashing or microwave digestion conditions on the recoveries of analytes. The inductively coupled plasma-atomic emission spectrometric detection results indicated that the recoveries of elements in the PP fibrous filters by ashing were influenced by ashing time, temperature and the properties of the elements. High recoveries of volatile elements and consistent recovery for other elements were obtained by using a closed microwave system to digest the filters. Higher sensitivity was also obtained when the intercomparison sample was measured by a HPGe well detector after pretreatment by the recommended ashing and microwave digestion procedures.