Nondestructive determination of lead-210 and radium-226 in sediments by direct photon analysis

A method is described for the non-destructive determination of²¹⁰Pb and²²⁶Ra in sediments. The procedure is based on the direct counting of the 46.5-keV -ray of²¹⁰Pb and the 351.9-keV -emission of²¹⁴Pb. The self-absorption of the 46.5-KeV -ray is corrected using a technique involving direct gamma transmission measurements on sample and efficiency calibration standard. Several reference materials when assayed by the described method yielded results in general agreement with the certified values. The application of the method is illustrated through the analysis of the excess²¹⁰Pb profile of a Lake Ontario sediment core.     

A comparison of methods for the determination of the dating-nuclides210Pb and226Ra

Lead-210 is often used to date recent (100 y) environmental samples. Three different methods for its determination are compared:²¹⁰Pb -counting with a low level proportional counter,²¹⁰Pb -spectroscopy and²¹⁰Po -spectroscopy. Agreement within analytical errors was found for the three methods in two sediment cores from Lake Zurich, Switzerland and in IAEA SD-A-1 deep sea reference material. For²¹⁰Po -spectroscopy, the detection and determination limit is an order of magnitude lower than these for the other methods. Methods for the determination of²²⁶Ra are also discussed. Measurements on low level proportional counters are difficult to interpret and not suitable for routine work. A better way to measure²²⁶Ra is -spectroscopy of colloidal Ba(Ra)SO₄.     

Natural radiactivity of fresh waters in Serbia

Statistical tests were performed on the -spectrometry measurement data obtained during the last decade for the natural radionuclides⁴⁰K,²²⁶Ra and²³²Th, in water samples collected from the Danube River, the Sava River and its tributaries, ground waters and artificial lakes. The lognormal radiopotassium distribution indicates a single statistical population. The presence of break points in the frequency distribution plots indicates that data for²²⁶Ra and²³²Th do not come from a single statistical population. The annual iongestion of⁴⁰K,²²⁶Ra and²³²Th was calculated and expressed in Bq y^–1.     

The use of radium-226 in calibrating HpGe detectors

A technique is described for the production of sealed²²⁶Ra sources for use in efficiency and energy calibration of hyperfine germanium -radiation detectors.     

Measurement of the radioactivity of238U,232Th,226Ra,137Cs and40K in soil using direct Ge(Li) γ-ray spectrometry

Radioactivity of the nuclides²³⁸U(²³⁵U),²³²Th,²²⁶Ra,¹³⁷Cs and⁴⁰K was measured in soil by direct -ray spectrometry using Ge(Li) detector. Relative laboratory method was used. Soil was dired, powdered, sieved and put into hemetically sealed container. CCRMP certified reference materials and compounds of the above nuclides mixed with fine quartz sand were used as references. Five and four -lines were used for the determination of²³²Th and²²⁶Ra, respectively, to obtain more accurate results. The most significant interferences, caused by the limited energy resolution of the detector, were resolved. In the case of ordinary soils, using one day duration of measurement and 1 kg mass of soil,²³²Th,²²⁶Ra and⁴⁰K can be determined with less than 10% relative random error. Elevated concentrations of²³⁸U(²³⁵U) and²²⁶Ra were observed in soil samples collected around a coal-fired power plant in Ajka town, Hungary.     

Distribution of137Cs,40K,238U and232Th in soils from Northern Venezuela

More than one hundred undisturbed soil samples from Northern Venezuela and the islands of Margarita and Los Roques have been analyzed for¹³⁷Cs,⁴⁰K,²³⁸U and²³²Th by -ray spectroscopy. The specimens were taken from between 5–10 cm below the earth's surface. Thus, they are valid not only for the¹³⁷Cs deposition studies but also for the estimation of the natural -ray dose from primordial radionuclides that form the terrestrial component. The concentration of⁴⁰K was directly determined from its 1461 keV -ray, while those of¹³⁷Cs,²³⁸U and²³²Th were performed using a -ray from one of their daughter radionuclides: the 661 keV -ray of^137mBa for¹³⁷Cs, the 1760 keV -ray of²¹⁴Bi for²³⁸U and the 2620 keV -ray of²⁰⁸Tl for²³²Th. Finally, the concentration values were compared with those of global estimates.     

226Ra, 228Ra and 210Pb Isotopes in Some Water Samples of Mines

A method for the determination of ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb in water samples of mining regions by measuring the and intensities with the help of a liquid scintillation counter is presented. The high-energy part of the -particle spectrum emitted by ²¹⁰Bi is used for the determination of ²¹⁰Pb content in the samples. An attempt is also given to explain the radioactive disequilibrium between ²²⁶Ra and ²¹⁰Pb in the samples investigated.     

Natural radionuclides and cesium-137 content in Arabian Gulf bottom sediments

The activity concentration of natural radionuclides and¹³⁷Cs in the bottom sediment samples from the coastal area of Kuwait on the Arabian Gulf have been determined by -ray spectrometry with REGe detector. The data for the samples are very similar to those obtained for surface soil samples in Kuwait.¹ Two parent-progeny ratios for:^23$Th–²²⁶Ra and²²⁸Ac–²⁰⁸Tl to evaluate the geochemical behavior of the radionuclides have been estimated. The existence of a serious disequilibrium between²³⁴Th and²²⁶Ra for samples taken from the vicinity of Kuwait islands and the Ras Al-Zoor area was found. The strait between the coast of Kuwait and Bubiyan island is proposed for the future sedimentation rate determinations on the basis of²¹⁰Pb measurements. No serious contamination by technogenic radionuclides for this region of Arabian Gulf was observed.     

Distribution of137Cs and228Ra in the sediments of Aswan High Dam lake

Sediment samples of the High Dam lake were investigated for their¹³⁷Cs,²²⁶Ra,²²⁸Th, and⁴⁰K content, using low-level -spectroscopy. The results show that at the begining of the lake (500 km from the High Dam), where sediments consist mostly of sand, the level of¹³⁷Cs is very low (0.1 Bq kg^–1). The maximum value (22.3 Bq kg^–1) was found 40 km from the wall of the High Dam, where the composition of the sediments is nearly 50% clays. The distribution of the natural nuclides²²⁶Ra,²²⁸Th, and⁴⁰K shows a different trend.     

Natural radioactivity in Zambian building materials collected from Lusaka

Samples of natural and manufactures building materials collected around Lusaka have been analyzed for natural radionuclides using -spectrometry. A simple comparison of the specific radioactivities of primordial radionuclides in these materials to the world averages for soil (25 Bq kg^{–1 238}U, 25 Bg kg^{–1 232}Th, 370 Bq kg^{–1 40}K and 89 Bq kg^–1 Ra_eq) shows that, of the nine types of samples analyzed, only burnt clay bricks (for²³⁸U,²³²Th and⁴⁰K), cement roofing tiles (for²³⁸U), building and river sands (for²³²Th and⁴⁰K) have greater activities than does soil. Radiological evaluation of specific radioactivities in these materials indicates that all materials meet the external -ray dose limitation of 1.5 mSv y^–1, that is, all samples have a radium equivalent activity of less than 370 Bq kg^–1.     

Evaluation of the uranium concentration in rocks at the μg/g level by a low-background Geiger-Müller counter

A low-background -counter and a simple direct method, based on total -counting, have been developed in order to estimate the concentration of uranium at the g/g level in ordinary rock samples. The method is a relative one; international standards have been used for calibration. Only 3 g of rock powder is needed. Combining this method with -spectrometry, direct determination of²³⁸U (independently of²²⁶Ra) becomes possible near the above concentration level.     

Measurement and preliminary behavioral model of radioactive “geoaerosols”

Greater than anticipated activity from the á - and â -emittingradionuclides ²³⁰Th+²²⁶Ra, ²¹⁰Po, and ²¹⁰Pb was observed in solution during modification of an air sampler1 to improve the sensitivity of measuring airborne radioactivity. Typicalactivities ranged from several mBq to ¹⁵Bq. We use the term geoaerosols2to describe the particles' unique transport and propose a distinct quantumphenomenon mechanism to explain the radiation accumulation. If confirmed bysubsequent experiments, the technique has potential for many practical applicationssuch as locating faults or fractures, earthquake prediction, mineral and energyresource exploration, verification of underground nuclear testing, and refiningrisk estimates from environmental exposure to particles.     

Low-background Germanium spectrometry the bottom line three years later

Three years ago, state-of-the-art low-background germanium spectrometry was discussed, and speculations were advanced as to the origin of the remaining background. Some of those speculations have been shown to the incorrect. Contemporary lead shielding contains 100 Bq/kg of²¹⁰Pb. Our 450-year-old lead was shown to contain <100 mBq/kg A high purity electroformed copper Marinelli shield was placed around the detector with no efffect on the background, which implied that the source is other than the 450-year-old shield. A new limit on the²¹⁰Pb in this old lead shield is <9 mBq/kg. Electroformed copper components were found to contain²²⁶Ra and²²⁸Th contaminations at levels of 3500 and 110 Bq/kg, respectively. High purity H₂SO₄, recrystallized CuSO₄, and a BaSO₄ scavenge in the electroforming bath have reduced these contaminations to <25 and 9 Bq/kg, respectively. In copper, cosmic ray induced nuclear reactions are now the dominant source of raioactivity. For example,⁵⁸Co can be readily measured after only a 24-hour exposure at sea level. A new germanium spectrometer containing 2150 grams of 87.44% enriched⁷⁶Ge has been fabricated to mitigate the effect of cosmogenic⁶⁸Ge in the background. Current background spectra are presented, and potential sources identified.     

A new improved expression for gamma-ray detection efficiency of Ge(Li) detectors

In the present paper, a new improved expression for -ray detection efficiency of Ge(Li) detectors, ⁰ , is given. It is represented as a continuous function of x (viz. E ^–1) with a maximum and decreases very rapidly to a small positive value as -ray energy, E, drops to 40 keV or lower, but slowly as E rises to 1.7 MeV or higher. Since it can well represent the whole physical process of the -ray detection, this expression may be one of the simplest and most precise representations, for ⁰ at the present time.     

Gamma ray emission intensities of226Ra in equilibrium with its daughter products

A²²⁶ Ra source of known disintegration rate has been measured to determine the absolute -ray emission intensities of members of its decay chain in radioactive equilibrium. The results are compared with other values from the literature.     

Gas chromatography ofγ-valerolactam andγ-valerolactone from reductive amination of butyl levulinate

Summary The-valerolactam and-valerolactone in the reductive amination products of butyl levulinate in water or alcoholic medium, after removing most of the light fractions, ammonia, and water or alcohol, have been determined by isothermal gas chromatography using phenylether or isoamyl salicylate as the internal standard. With the thermal conductivity detector, a column of 6 mm I. D., 2 m long copper tubing packed with 25% glycol adipate/chromosorb-W was used, with hydrogen as the carrier gas. The accuracy was ± 0.4% for-valerolactone and ± 0.5% for-valerolactam. Using the hydrogen flame ionization detector, a column of 3 mm I. D., 2 m long stainless steel tubing packed with 10% glycol adipate/chromosorb-W was used, with nitrogen as the carrier gas; the accuracies for-valerolactone and-valerolactam were ± 0.5% and ± 0.8% respectively.

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Zusammenfassung Unterwirft man Butyllävulinat in wäßrigem oder alkoholischem Milieu der reduktiven Aminierung, so entstehen unter anderem-Valerolactam und-Valerolacton. Diese wurden nach weitgehender Entfernung der flüchtigen Anteile (Ammoniak, Wasser oder Alkohol) durch isotherme Gaschromatographie unter Verwendung von Phenyläther oder Isoamylsalicylat als interne Standards bestimmt. Mit einem Wärmeleitfähigkeitsdetektor wurde eine 2 m lange Säule mit 6 mm i. D. aus Kupferrohr mit einer Füllung aus 25% Glykoladipat und Chromosorb W verwendet, mit Wasserstoff als Trägergas. Die Genauigkeit betrug ± 0,4% für-Valerolacton und ± 0,5% für-Valerolactam. Wurde hingegen ein Ionisierungsdetektor mit Wasserstoff-Flamme verwendet, so diente eine 2 m lange Säule mit 3 mm i. D. aus rostfreiem Stahl mit einer Füllung aus 10% Glykoladipat und Chromosorb W und Stickstoff als Trägergas. Die Genauigkeit betrug dann ± 0,5 bzw. ± 1,8%.

     

Further study on parametric standardization in reactor NAA

A post-K_o study of parametric reactor NAA is described including the determination and applications of working K_oS for non-1/V reactions¹⁵¹Eu(n,)¹⁵²Eu and¹⁷⁶Lu(n,)¹⁷⁷Lu; parametric corrections for²³⁵U fission, threshold reaction and -spectral interferences; and parametric normalizations for different counting geometries. The analytical significance, the principles, the experimental confirmations, and the application examples of these methods are briefly introduced.     

Critical evaluation and experimental determination of the nuclear activation and decay parameters for the reactions:6 4Zn(n, γ)6 5Zn,1 1 2Sn(n, γ)1 1 3 (m)Sn (E. C.)1 1 3mIn,1 7 4Yb(n, γ)1 7 5(m)Yb

A best choice from literature was made of the isotopic abundance values for⁶⁴zn,¹¹²Sn and¹⁷⁴Yb, and of the absolute gamma-intensities for⁶⁵Zn,^113mIn and¹⁷⁵Yb. From these data and from activation method experiments, the following 2200 m·s^–1 cross sections were determined:⁶⁵Zn(n, )⁶⁵Zn; ₀=(0.726±0.0007) barn [cf. literature 0.76–0.78 barn];¹¹²Sn(n,)¹¹³(m)Sn; ₀(0.91 m⁺g)=(0.539±0.011) barn [cf. literature 1 barn];¹⁷⁴Yb(n,)¹⁷⁵(m)Yb; ₀(m⁺g)=(130+4) barn [cf. literature 65 barn].     

Determination of137Cs and134Cs in air samples collected near Belgrade /Yugoslavia/ following the Chernobyl accident

This paper presents the results of measurements of¹³⁷Cs and¹³⁴Cs content in air sampled during May 1986. Maximum concentrations:¹³⁷Cs 2.94±0.01 Bq m^–3 and¹³⁴Cs 1.38±0.01 Bq m^–3 were registered on May 3. Several other long lived radionuclides having -energies in the region 33 keV to 1365 keV were registered in the same samples two years later. The results of measurements of the total -activity in air for the same period are also presented.     

Aluminum-26: A nuclide for all seasons

The long-lived²⁶Al was discovered in a search for a tracer isotope of the last element for which at least one was available, but it has tumed out to have a number of other scientific applications in addition. Discussed will be: discovery and properties of²⁶Al;²⁶Al as a -ray standard; cosmic-ray-induced²⁶Al in meteorites, lunar matter, and terrestrial materials; extinct natural radioactivity of²⁶Al in meteorites and live²⁶Al in the early Solar System; 1.81-MeV -radiation from²⁶Al in interstellar space; and²⁶Al as a tracer isotope, especially in biology and medicine. Some of these applications are possible because of non-destructive low-level -ray spectrometry, and some because of accelerator mass spectrometry of extremely small amounts of the nuclide.