Alpha Radionuclides Research Articles

ABSORBED INTERNAL DOSE CONVERSION COEFFICIENTS FOR DOMESTIC REFERENCE ANIMALS AND PLANT

This paper describes the methodology of calculating the internal dose conversion coefficient in order to assess the radiological impact on non-human species. This paper also presents the internal dose conversion coefficients of 25 radionuclides (<TEX>$^3H,\;^7Be,\;^{14}C,\;^{40}K,\;^{51}Cr,\;^{54}Mn,\;^{59}Fe,\;^{58}Co,\;^{60}Co,\;^{65}Zn,\;^{90}Sr,\;^{95}Nb,\;^{99}Tc,\;^{106}Ru,\;^{129}I,\;^{131}I,\;^{136}Cs,\;^{137}Cs,\;^{140}Ba,\;^{140}La,\;^{144}Ce,\;^{238}U,\;^{239}Pu,\;^{240}Pu$</TEX>) for domestic seven reference animals (roe deer, rat, frog, snake, Chinese minnow, bee, and earthworm) and one reference plant (pine tree). The uniform isotropic model was applied in order to calculate the internal dose conversion coefficients. The calculated internal dose conversion coefficient (<TEX>${\mu}Gyd^{-1}$</TEX> per <TEX>$Bqkg^{-1}$</TEX>) ranged from <TEX>$10^{-6}$</TEX> to <TEX>$10^{-2}$</TEX> according to the type of radionuclides and organisms studied. It turns out that the internal does conversion coefficient was higher for alpha radionuclides, such as <TEX>$^{238}U,\;^{239}Pu$</TEX>, and <TEX>$^{240}Pu$</TEX>, and for large organisms, such as roe deer and pine tree. The internal dose conversion coefficients of <TEX>$^{239}U,\;^{240}Pu,\;^{238}U,\;^{14}C,\;^3H$</TEX>, and <TEX>$^{99}Tc$</TEX> were independent of the organism.

Soil and sediment sample analysis for the sequential determination of natural and anthropogenic radionuclides

A new sequential method for the determination of both natural (U, Th) and anthropogenic (Sr, Cs, Pu, Am) radionuclides has been developed for application to soil and sediment samples. The procedure was optimised using a reference sediment (IAEA-368) and reference soils (IAEA-375 and IAEA-326). Reference materials were first digested using acids (leaching), ‘total’ acids on hot plate, and acids in microwave in order to compare the different digestion technique. Then, the separation and purification were made by anion exchange resin and selective extraction chromatography: transuranic (TRU) and strontium (SR) resins. Natural and anthropogenic alpha radionuclides were separated by uranium and tetravalent actinide (UTEVA) resin, considering different acid elution medium. Finally, alpha and gamma semiconductor spectrometer and liquid scintillation spectrometer were used to measure radionuclide activities. The results obtained for strontium-90, cesium-137, thorium-232, uranium-238, plutonium-239+240 and americium-241 isotopes by the proposed method for the reference materials provided excellent agreement with the recommended values and good chemical recoveries. Plutonium isotopes in alpha spectrometry planchet deposits could be also analysed by ICPMS.

System for calibration of track detectors used in gaseous and solid alpha radionuclides monitoring

A laboratory system for the calibration of track detectors and charcoal detectors used in monitoring of radon and its decay products/their aerosols in air, is proposed. The system consists of three main components: (i) the alpha exposure chambers, including alpha monitoring devices and the connection with the 226Ra radioactive source. The CR-39 track detectors are mounted in the monitoring devices pre-equipped or not with paper filter; (ii) the calibrated 226Ra source. Among the three tested sources: 222 Rn, 226 Ra+ 222 Rn and 226Ra, the 226Ra source is considered the most appropriate radon source for our calibration system. It is kept into an airtight flat bottom flask, the radionuclide 226Ra being always in the radioactive equilibrium with their descendants. In the alpha exposure chambers, the source assures the radon at a constant rate; (iii) the ALFAUURASE program for the computation of radioactive accumulation of the alpha 226Ra descendants. For any initial mass of the parent, the amount and the activity of each alpha decay product and of all the decay products can be calculated by this computation program. Each component of the calibration system is described in the paper. The use of the system for the calibration of CR-39 track detectors in radon measurements is tested.

Polonium, uranium and plutonium in the southern Baltic ecosystem

This paper presents the results of the measurement of polonium, uranium and plutonium alpha radio-nuclides in seawater and biota of the southern Baltic ecosystem as well as the recognition of their accumulation processes in the trophic chain. Investigation of the polonium210Po and plutonium239+240Pu concentrations in Baltic biota revealed that these radionuclides are strongly accumulated by some species. Mean values of the bioconcentration factor (BCF) fell within the range 9·102 to 3.7·104. The Baltic Sea algae, benthic animals and fish concentrated uranium radioisotopes only to a small extent and mean BCF values for this element range from 1 to 55, which is several orders of magnitude lower than that for polonium and plutonium. Moreover, it was found that Baltic fish constitute an important source of polonium210Po for humans.

ALFIT: a code for the analysis of low statistic alpha-particle spectra from silicon semiconductor detectors

A code for the application of the most usual algorithms to the analysis of alpha spectra from semiconductor detectors has been developed. The program is designed to obtain the activity of any alpha emitter radionuclide over a wide range of deposit quality, so that no special requirements concerning the source composition and its preparation are necessary. Some interactive steps are introduced to define the system in study. Although the program is of general application, some criteria and options are considered in order to reach a valid solution, mainly alpha sources from environmental samples. Due to statistical considerations, the smallest peaks must be constrained in position and areas related to the most intensive emission for each radionuclide present in the interval analyzed. Such criteria and options constrain the solutions of the fitting processes, in agreement with the expected relationships between the different emissions of the alpha radionuclides, and enhance the accuracy of the results.

Determination of the volume activity concentration of alpha artificial radionuclides with alpha spectrometer.

This paper introduces a method to determine the volume activity concentration of alpha and/or beta artificial radionuclides in the environment and radon/thoron progeny background-compensation based on a Si surface-barrier detector. By measuring the alpha peak counts of 218Po and 214Po in two time intervals, the activity concentration of 218Po, 214Pb and 214Bi aerosol particles were determined; meanwhile, the total beta count of 214Pb and 214Bi aerosols was also calculated from their decay scheme. With the average equilibrium factor of thoron progeny in general environment, the alpha and beta counts of thoron progeny were approximately evaluated by 212Po alpha peak counts. The alpha count of transuranic aerosols was determined by subtracting the trail counts of radon/thoron progeny alpha peaks. The total count of beta artificial radionuclides was determined by subtracting the beta counts of radon/thoron progeny aerosol particles. In our preliminary experiments, if the radon progeny concentration is less than 15 Bq m(-3), the lower limit of detection of transuranics concentration is less than 0.1 Bq m(-3). Even if the radon progeny concentration is as high as 75 Bq m(-3), the lower limit of detection of total beta activity concentration of artificial nuclides aerosols is less than 1 Bq m(-3).

Nondestructive Determination of Activity

Characterization and appraisal tests include the measurement of activity in raw waste and waste packages. After conditioning, variations in density, matrix composition, and geometry make evaluation of the radionuclide activity in a package destined for storage nearly impossible without measurements and with a low uncertainty. Various nondestructive measuring techniques that use ionizing radiation are employed to characterize waste packages and raw waste. Gamma spectrometry is the most widely used technique because of its simple operation and low cost. This technique is used to quantify the beta-gamma and alpha activity of gamma-emitting radionuclides as well as to check the radioactive homogeneity of the waste packages. Numerous systems for directly measuring waste packages have been developed. Two types of methods may be distinguished, depending on whether results that come from the measurements are weighted by an experimentally determined corrective term or by calculation. Through the MARCO and CARACO measuring systems, a method is described that allows one to quantify the activity of the beta-gamma and alpha radionuclides contained in either a waste package or raw waste whose geometries and material compositions are more or less accurately known. This method is based on (a) measurement by gamma spectrometry of the beta-gamma and alphamore » activity of the gamma-emitting radionuclides contained in the waste package and (b) the application of calculated corrections; thus, the limitations imposed by reference package geometry and matrix are avoided.« less

Extraction-chromatographic method for the determination of plutonium-239,240 and plutonium-238 in soils with high natural radioactivity

A highly selective method is described for the determination of 239,240Pu and 238Pu in soils by extraction chromatography with Microthene-710/tri-n-octylamine. The method is especially suitable for volcanic soils containing high concentrations of natural alpha radionuclides (Th, Po, U, etc.). The detection limit by α-spectrometry is 2.2 mBq kg −1 for 50-g soil samples. The average chemical yield, obtained by adding 242Pu as the internal standard, is 69.5 ± 17.1%. An IAEA reference soil was analyzed, with a relative error of 6.7% for 239Pu. The concentration of 2239,240Pu in thirteen analyzed soils and sediments ranged from 26.6 to 429 mBq kg −1.

Separation and sequential determination of americium and plutonium in urine samples

Abstract Simultaneous determination of low levels of Americium and Plutonium in complex matrices has always been difficult to carry out owing to the chemical behavior differences of the two actinides. An analytical extraction and separation technique of the two actinides has been realized utilizing Dibutyl, N,N-diethyl carbamylphosphonate (DDCP) as a reagent. The possibility has been ascertained of performing a separation through partition chromatography techniques and through liquid-liquid extraction. In particular, such technique has been applied to the determination of the two actinides in urine samples from personnel exposed to the risk of internal contaminations due to emitter alpha radionuclides. In this case, the liquid-liquid extraction technique has been adopted for reasons connected with the operation rapidity and ease. This method involves: wet way sample mineralization by HNO 3 and evaporation concentration; liquid-liquid extraction of interesting actinides by DDCP from a 12 M solution in HNO 3 ; sequential stripping of Am by HNO 3 2 M and of Pu by HCl 3 M and HN 4 I 0.1 M ; electrodeposition on a steel plate and final measurement through alpha spectrometry with surface barrier detector. Average final yields obtained through this analytical method have been: 80% for Americium, 66% for Plutonium. Activity values found in ‘urine whites’ are comparable with the full-scale value. Min. detectable values at 300 min count time have been the following: Americium 1.3 × 10 -3 Bq/l (0.03 pCi/1), Plutonium 1.6 × 10 -3 Bq/l (0.04 pCi/l). At present, experiments are carried out for applying this analytical method on other matrices as well.

Separation and sequential determination of americium and plutonium in urine samples

Simultaneous determination of low levels of Americium and Plutonium in complex matrices has always been difficult to carry out owing to the chemical behavior differences of the two actinides. An analytical extraction and separation technique of the two actinides has been realized utilizing Dibutyl, N,N-diethyl carbamylphosphonate (DDCP) as a reagent. The possibility has been ascertained of performing a separation through partition chromatography techniques and through liquid-liquid extraction. In particular, such technique has been applied to the determination of the two actinides in urine samples from personnel exposed to the risk of internal contaminations due to emitter alpha radionuclides. In this case, the liquid-liquid extraction technique has been adopted for reasons connected with the operation rapidity and ease. This method involves: wet way sample mineralization by HNO 3 and evaporation concentration; liquid-liquid extraction of interesting actinides by DDCP from a 12 M solution in HNO 3; sequential stripping of Am by HNO 3 2 M and of Pu by HCl 3 M and HN 4I 0.1 M; electrodeposition on a steel plate and final measurement through alpha spectrometry with surface barrier detector. Average final yields obtained through this analytical method have been: 80% for Americium, 66% for Plutonium. Activity values found in ‘urine whites’ are comparable with the full-scale value. Min. detectable values at 300 min count time have been the following: Americium 1.3 × 10 -3 Bq/l (0.03 pCi/1), Plutonium 1.6 × 10 -3 Bq/l (0.04 pCi/l). At present, experiments are carried out for applying this analytical method on other matrices as well.