A simultaneous determination of lead-210 and polonium-210 in sea water

A new radiochemical procedure is described for the determination of lead-210 and polonium-210 in sea water. These nuclides are concentrated by coprecipitation with calcium carbonate from a sea water sample of large volume and then separated from calcium by formation of the hydroxides. Polonium-210 is deposited spontaneously onto a silver disc and determined by an α-counting technique. Lead-210 is also determined by counting the activity of polonium-210 produced during storage for 3 months.     

Improved technique for recovery and measurement of polonium-210 from environmental materials

Polonium-210 obtained in acidic solution by digestion of sediment or tissue samples is efficiently plated onto one side of a silver disc for measurement of α-activity. Optimum conditions for solutions obtained from environmental samples are pH 1.5–2 in the presence of citrate and ascorbic acid, with the solution at 80°C and the silver disc rotated at 100–150 radian s^?1. Observed recoveries using a polonium-208 tracer are 97.5 ± 2.5% for sediments and 99.3 ± 1.3% for tissues.     

The determination of low levels of polonium-210 in environmental materials

A method is presented for the determination of polonium-210 at very low levels in the presence of many different ions. Essentially quantitative recoveries were obtained in 60 min by deposition on to a silver plate in a special holder from 50 ml solution at 85–90° with sodium citrate present.     

An efficient quantitative technique for the simultaneous analyses of radon daughters (210)Pb, (210)Bi and (210)Po

An improved and time efficient technique has been developed for quantitative determination of the long-lived (222)Rn daughters ((210)Pb, (210)Po and (210)Bi) in atmospheric and oceanic samples. The sample is first spiked with yield tracers for polonium (208 or 209), bismuth (207), and lead (stable lead carrier). These nuclides may then be scavenged through iron hydroxide precipitation and redissolved in a dilute (pH approximately 2) nitric acid plating medium with citrate and hydroxylamine hydrochloride at 90 degrees centrigrade with constant stirring. First a silver planchet is suspended in the solution which plates polonium to high efficiency. Second, a nickel planchet is suspended in the same solution which is maintained hermetic (e.g. bubbling with helium) and bismuth is plated next with high efficiency. Third, lead is purified from the same solution using anion exchange techniques and isolated for beta counting as the sulfate. Polonium is analyzed by isotope dilution alpha spectrometry. Bismuth and lead are analyzed by anti-coincident beta counting in a low level shield. In the case of bismuth, the 207 tracer is added in quantities at least comparable to the background of the beta system such that counting before and after the decay of (210)Bi gives the bismuth yield. The unique characteristics of this technique are its speed and efficiency; all three radon daughters can be isolated for counting within 4 hr of pre-treating the sample. The remaining solution can be treated subsequently for other analyses as appropriate.     

Rapid determination of 210Po in water samples

A new rapid method for the determination of ²¹⁰Po in water samples has been developed at the Savannah River National Laboratory (SRNL) that can be used for emergency response or routine water analyses. If a radiological dispersive device event or a radiological attack associated with drinking water supplies occurs, there will be an urgent need for rapid analyses of water samples, including drinking water, ground water and other water effluents. Current analytical methods for the assay of ²¹⁰Po in water samples have typically involved spontaneous auto-deposition of ²¹⁰Po onto silver or other metal disks followed by counting by alpha spectrometry. The auto-deposition times range from 90 min to 24 h or more, at times with yields that may be less than desirable. If sample interferences are present, decreased yields and degraded alpha spectrums can occur due to unpredictable thickening in the deposited layer. Separation methods have focused on the use of Sr Resin?, often in combination with ²¹⁰Pb analysis. A new rapid method for ²¹⁰Po in water samples has been developed at the SRNL that utilizes a rapid calcium phosphate co-precipitation method, separation using DGA Resin^® (N,N,N′,N′ tetraoctyldiglycolamide extractant-coated resin, Eichrom Technologies or Triskem-International), followed by rapid microprecipitation of ²¹⁰Po using bismuth phosphate for counting by alpha spectrometry. This new method can be performed quickly with excellent removal of interferences, high chemical yields and very good alpha peak resolution, eliminating any potential problems with the alpha source preparation for emergency or routine samples. A rapid sequential separation method to separate ²¹⁰Po and actinide isotopes was also developed. This new approach, rapid separation with DGA resin plus microprecipitation for alpha source preparation, is a significant advance in radiochemistry for the rapid determination of ²¹⁰Po.     

Development of a sequential method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra,and210Pb. in environmental samples

A sequential analytical method for the determination of²³⁸U,²³⁴U,²³²Th,²³⁰Th,²²⁸Th,²²⁸Ra,²²⁶Ra and²¹⁰Pb in environmental samples was developed. Uranium and thorium isotopes are first chromatographically sepaaated using tri-n-octyl phosphine oxide (TOPO) supported on silica gel. The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane. Thorium isotopes are co-precipitated with lanthanum fluoride before counting in an alpha spectrometer. Radium isotopes and²¹⁰Pb are separated by co-precipitation/precipitation with mixed barium/lead sulphate. Radium-226 is determined by gross alpha counting of the final BaSO₄ precipitate and²²⁸Ra by gross beta counting of the same source. Lead-210 is determined through beta counting of its daughter product²¹⁰Bi.     

An example of situational radiological analysis: An incident with polonium-210

Data on the nuclear physical, chemical, and radiobiological characteristics of polonium-210 are generalized. The characteristics of the radionuclide intake by the human body, its transport, and deposition in different organs are considered. The formation of the α radiation dose has been analyzed using RBE = 3 for deterministic effects in terms of formal dosimetry of incorporated radionuclides. Radiological analysis of a case of polonium-210 poisoning in London has been performed. The activity of the radionuclide at which it is lethal upon a single peroral administration has been evaluated (0.012–0.36 GBq), and the formal possibility of detecting a carrier of polonium-210 on the basis of data on excreta and γ radiation measured using a whole-body counter (WBC).     

Isolation of radioactive strontium from natural samples: A semi-automatic procedure

A procedure for semi-automatic isolation and determination of radioactive strontium from natural samples was developed. The method was tested by the determination of⁹⁰Sr in soil samples and the results obtained were compared to those obtained by the standard procedure. The procedure consists of leaching of strontium (and other cations as well) from soil samples with a water suspension of the cation exchanger Amberlite IR-20, the separation of strontium from other cations, e.g., potassium, calcium, sodium, barium by the anion exchangers Amberlite CG-400 or Dowex Ag 1×8 with 0.25M HNO₃ in ethanol-methanol mixture as eluent in the apparatus specially constructed for this purpose. Determination of⁹⁰Sr was done on the low-level gas-flow β-counter and by Cherenkow counting on the liquid-scintillation counter few hours after the separation. It was shown that this procedure might be successfully applied for rapid determination of⁹⁰Sr in soil samples and other natural samples in a timesaving manner.     

Determination of (210)Pb, (210)Bi and (210)Po in natural waters and other materials by electrochemical separation

An improved method for determination of (210)Pb, (210)Bi and (210)Po in both natural waters and solid materials has been developed. Polonium-210 is spontaneously plated onto a silver disc from dilute hydrochloric acid medium. Bismuth-210 is then electro-deposited onto a platinum gauze cathode directly from the same solution, with a graphite rod as anode. Finally, (210)Pb is electro-deposited from a fluoroborate medium onto the same platinum gauze, used as the anode. All three nuclides are subsequently measured by standard low-level alpha and beta counting techniques. The speed of this method (approximately 6 hr per sample after pretreatment) is a distinct advantage over existing techniques, as (210)Bi must be quickly separated from (210)Pb because of its 5.02-day half-life. Another advantage of this method is that the chemical form of the sample solution is suitable for use of established separation schemes for determining other decay-series isotopes (U, Th, Pa, etc.) after the three short-lived nuclides have been processed.     

Effects of digestion,chemical separation,and deposition on Po-210 quantitative analysis

The purpose of this work was to determine polonium losses from a variety of sample types (soil, cotton fiber, and air filter) due to digestion technique, chemical separation, and deposition method for alpha energy analysis. Results demonstrated that yields from a perchloric acid wet-ash (87 ± 5 %) were similar to that from a microwave digestion (100 ± 7 %), but both were greater than the dry-ash procedure (38 ± 5 %). The polonium was separated from an SRM soil using an AG1X8 ion exchange column and deposited on a Ag disk with a recovery of 83 ± 7 % of polonium-209 (Po-209). Deposition yields without chemical separation averaged 90 ± 5 % of Po-209. The polonium-210 content was successfully measured in the three matrix types and quantitated using alpha spectroscopy.     

Radiochemical determination of lead-210 in environmental water samples using Cerenkov counting

A relatively simple method has been developed for the determination of²¹⁰Pb via its -emitting daughter,²¹⁰Bi. Lead-210 was separated from interfering elements as lead sulphate. The precipitate was dissolved in an alkaline solution of EDTA and the Cerenkov signal produced by the build-up of²¹⁰Bi was counted 30 days after storage using tritium channel of a liquid scintillation counter. Cerenkov counting efficiency was found to be approximately 20%. A lower limit of detection of 5.1 mBq/1 (based on 3 of the background with 500 minute counting time) was achieved. Chemical recoveries in the range of 70–100% were determined gravimetrically. Interference associated with currently used methods is avoided. Data from from both spiked samples and natural samples are presented.     

Simultaneous determination of lead-210, gross beta and gross alpha activities of air filters by pulse shape discrimination liquid scintillation counting

A chemical procedure for transferring deposited solid matter from a cellulose filter into the liquid scintillation cocktail has been described. The influence of chemical and color quenching on alpha and beta detection efficiency, as well as on misclassification of beta and alpha pulses was corrected by an external standard method. Under the chosen pulse shape discrimination level (PSD), the alpha and beta detection efficiencies were above 85% and spillovers of alpha and beta pulses were below 10% and 2% respectively. Determination limits for samples containing up to 200 mg of mineral matter were 0.015 mBq m^–3 for alpha, 0.055 mBq.m^–3 for²¹⁰Pb and 0.055 mBq.m^–3 for beta activity (counting time 12000 s and volume of filtered air 1000 m³). The method has been applied for routine monitoring of²¹⁰Pb as well as for gross alpha and beta activities of longer-living radionuclides (T_1/2.>11 hrs) in suspended air matter.     

Determination of polonium-210 in phosphoric acid

Polonium-210 in phosphoric acid has been recognized as a significant source of alpha contamination of processed Si-wafers for memory devices of computer. In the present work, a convenient method was developed for the determination of trace²¹⁰Po in phosphoric acid of high purity. For the determination,²⁰⁹Po was used as a yield tracer. The present method consists of (1) addition of the tracer to 5 ml aliquot of phosphoric acid sample, (2) pH adjustment (to 2) of the sample solution to make up electrolytic solution, (3) electrodeposition for the simultaneous achievement of Po separation and preparation of counting source on stainless-steel disc, and (4) alpha-ray spectrometry. By the developed method, more than 95% of Po was separated from phosphoric acid sample onto counting disc. The minimum detectable radioactivity of²¹⁰Po in 5 ml of phosphoric acid was about 0.03 mBq by counting the electrodeposited alpha-activity for 10 days under a counting efficiency of ≈30%.     

Anion exchange method for the sequential determination of uranium,thorium and lead-210 in coal and coal ash

A radiochemical procedure is presented for the sequential determination of uranium isotopes, thorium isotopes, and²¹⁰Pb in coal and coal ash. This procedure consists of dry ashing the sample, a nitric—hydrofluoric acid dissolution, removal of iron with ether extractions, and separation of the elements of interest by anion exchange chromatography. Uranium and thorium isotopes are measured by alpha spectrometry, while²¹⁰Pb is measured by beta counting its daugther activity,²¹⁰Bi. For 10 g coal samples and 1 g ash samples, the chemical yields for the radioactivities measured were 70–80%, and the relative standard deviations for replicate analyses were generally less than 9%. The deviations of the means from the reference values were within the combined errors of each and were usually less than ±5%. Minimum detectable activities were about 0.02 pCi for uranium and thorium isotopes and 0.2 pCi for²¹⁰Pb.     

Distribution of137Cs in soil in Central Slovakia and fast prediction of contamination

This paper describes the measurement of²¹⁰Bi by Cerenkov counting in a commercial liquid scintillation counter. The counting efficiency in water is 0.17 counts per second per Becquerel (17%). When the enhancers Triton X-100 (15% v/v) and sodium salicylate (1% m/v) are added to the solution the counting efficiency for²¹⁰Bi increases from 17% to 75%. The²¹⁰Po daughter of²¹⁰Bi causes interference of 0.85 counts per second per Becquerel in the presence of the enhancers but not in water. When²¹⁰Bi and²¹⁰Po are present in secular equilibrium the total counting efficiency is 160%. When²¹⁰Bi and²¹⁰Po are not in secular equilibrium the²¹⁰Po can be removed immediately before counting by plating onto silver foil. The use of the enhancers gives a substantial increase in counting efficiency compared to counting in water. Compared with solutions used in liquid scintillation counting the enhancer solution is inexpensive and can be disposed of without environmental hazard.     

A sequential radiochemical procedure for isotopic analysis of uranium and thorium in soil

A sequential radiochemical procedure for isotopic analysis of uranium and thorium in soil has been developed. Analysis involves total dissolution of the samples to allow equilibration of the natural isotopes with added tracers, followed by radiochemical separation using anion exchange chromatography (BioRad AG 1–X8). Further separation and purification is performed employing solvent extraction techniques. Finally, the U and Th fractions are co-precipitated with lanthanum and cerium fluoride, respectively, and quantified by alpha-particle spectrometry. Overall chemical yields range from 60 to 90%. Under normal operating conditions and present counting set up, the minimum detectable concentration (MDC) is approximately 2 Bq/kg for soil samples. This is based on one gram aliquot of sample, 80% chemical yield, and 1000 minute counting with a detector having about 15% counting efficiency. The procedure has been successfully tested with Standard Reference Materials. Various soil samples were analyzed with high chemical yields and fine quality of alpha-spectra. Decontamination factor studies were performed to determine the extent of the carry over of²¹⁰Po,²²⁵Ac,²²⁶Ra, and²²⁹Th into U fraction and²¹⁰Po,²²⁵Ac,²²⁶Ra, and²³²U into Th fraction.     

Determination of210Po in lead

A quantitative separation procedure for²¹⁰Po in lead has been developed by cupferron and dithizone extraction. The²¹⁰Po activity is plated on a silver foil for counting with a ZnS(Ag) scintillator, or by α-spectrometry with a surface barrier semiconductor. Different lead samples were analyzed ranging from very old lead with a negligible²¹⁰Po content to recently manufactured lead samples showing up to 9100 disintegrations per hour and per gram of lead. The reproducibility and the accuracy of the analyses are satisfactory.     

Determination of 210Po and uranium in high salinity water samples

A method for the determination of uranium and ²¹⁰Po in high salinity water samples has been elaborated. Both radionuclides are preconcentrated from 0.5 dm³ saline media by co-precipitation with hydrated manganese dioxide, followed by dissolution of the precipitate in 200 mL of 1 M HCl. Uranium isotopes ²³⁵U and ²³⁸U can be directly determined by ICP MS method with a detection limit of 0.01 ppb for ²³⁸U. Prior to a selective determination of ²¹⁰Po, the majority of other naturally occurring α-emitting radionuclides (uranium, thorium and protactinium) can be stripped from this solution by their extraction with a 50% solution of HDEHP in toluene. Finally, ²¹⁰Po is simply separated by direct transfer to an extractive scintillator containing 5% of trioctylphosphine oxide in Ultima Gold F cocktail and determined by an α/β separation liquid scintillation technique with detection limit below 0.1 mBq/dm³.     

Radiochemical determination of210Po and210Pb in water

A method for²¹⁰Po and²¹⁰Pb determination in water samples is described. The nuclides are concentrated, in presence of added²⁰⁸Po and lead carrier, by evaporation. Then the polonium is plated electroless from the acidic solution on a copper planchet and measured by alpha spectrometry.²¹⁰Pb separation from the other isotopes is based on the solutility of PbSO₄ in citrate.²¹⁰Pb content is determined by measuring the activity of its daughter²¹⁰Bi. The critical steps in the isolation of lead have been examined and discussed.     

The role of Cherenkov and liquid scintilation counting in evaluating the anion-exchange separation of210Pb−210Bi−210Po

Using as eluent a sequence of 3M HCl, 12M HCl, and 8M HNO₃, a mixture of²¹⁰Pb,²¹⁰Bi, and²¹⁰Po may be clearly separated on a column of Dowex 1×2−100 anion exchange resin. A Cherenkov count in H₂O and the variation in count rate with time confirm that the nuclides emerge in the order²¹⁰Pb→²¹⁰Bi→²¹⁰Po. If 12M HCl is replaced by 1.5M H₂SO₄/2.3 M Na₂SO₄, a clean separation also results, but recovery of²¹⁰Po becomes considerably more difficult. All three nuclides are readily detectable by liquid scintillation counting, with the efficiency for²¹⁰Pb in the 60–70% range. The Cherenkov aqueous counting efficiency for²¹⁰Bi is ∼14–15%.