The feasibility of photon activation analysis (PAA) for river sediment has been demonstrated using a powerful linear electron accelerator at Rensselaer Polytechnic Institute. The sample was a standard sediment material (SRM 1646a Estuarine sediment) from NIST. Electron energy at 50 MeV and a tantalum target are used. Gamma-spectroscopy was performed with an HPGe detector. Sensitivities for Ca, Ti, As, Pb, Ce, Ni and Rb were obtained. The sensitivities were 14.7 µg for Ca, 21.5 µg for Ti, 0.9 µg for As, 3.9 µg for Pb, 1.1 µg for Ce, 1.6 µg for Ni and 3.5 µg for Rb. A large amount of Zr was found in SRM 1646a although it is not listed by NIST.
Sixteen minor and trace element contents of diet samples collected from the Pratas islanders were determined using instrumental neutron activation analysis. Samples were prepared by the duplicate portion technique, collecting during a 3-day period in winter. Dry weight elemental concentrations and daily dietary intake by islanders are compared with those taken by urban population living in Taiwan, resulting in higher intake of most elements. In addition, concentration of natural radionuclides and artificial fallout in daily diet were determined by means of -spectroscopy; the annual intake of radioactivity was evaluated and compared with those in population of neighboring Taiwan and South China. Features of the elemental concentration and radioactive concentration in the diet are discussed.
Authors:G. English, R. Firestone, D. Perry, J. Reijonen, Ka-Ngo Leung, G. Garabedian, G. Molnár, and Zs. Révay
Without quality historical records that provide the composition of legacy materials, the elemental and/or chemical characterization
of such materials requires a manual analytical strategy that may expose the analyst to unknown toxicological hazards. In addition,
much of the existing legacy inventory also incorporates radioactivity, and, although radiological composition may be determined
by various nuclear-analytical methods, most importantly, gamma-spectroscopy, current methods of chemical characterization
still require direct sample manipulation, thereby presenting special problems with broad implications for both the analyst
and the environment. Alternately, prompt gamma activation analysis (PGAA) provides a ‘single-shot’ in-situ, non-destructive
method that provides a complete assay of all major entrained elemental constituents.1–3 Additionally, neutron activation analysis (NAA) using short-lived activation products complements PGAA and is especially
useful when NAA activation surpasses the PGAA in elemental sensitivity.
Authors:J. M. Navarrete, J. Campos, T. Martínez, and L. Cabrera
After the Chernobyl accident in April 1986, Mexico imported from one European country a shipment of 28,000 tons of milk powder contaminated with the fission product 137Cs. Since then, the local authorities of Public Health have established as a compulsory condition to obtain through gamma-spectroscopy a certificate of no radioactive contamination either to imported or exported foodstuffs. But at the same time, the absence of long-lived, gamma-emitters fission products is certified, it is also possible to find the concentration of the important trace element K in foodstuffs, by the peak of 1461 keV from 40K, invariably present in the gamma-spectra. Taking advantage of the fact that it does not require any previous manipulation of the sample, this paper describes the general procedure in milk powder or any other foodstuff.
Authors:S. Ismail, G. Wiesinger, R. Pavlovec, and F. Grass
Different reference materials of environmental and geological origin, such as NBS 1633a (Coal Fly Ash, CFA), NBS 1645 (River Sediment, RS), GXR-2, and IAEA Soil-5, were investigated by short time activation analysis. The samples were analyzed in 5 replicates each between 100 to 150 mg, at neutron flux of 1.3 E 12 cm–2 s–1, using a high rate — high resolution gamma spectroscopy with a Loss Free Counting (LFC) System to correct the dead time and pile up to 500,000 cps. The results of the measurements indicate that the precision in determination of28Al,46mSc, and52V is between 1 to 6%. Different evaluation programs (i.e. ALCHEM, AKTAN, and ND-PEAK) were used to calculate the peak areas. The results indicate that, at lower counts, the statistical error of peak area calculation becomes more significant. Finally, Mössbauer spectroscopy was used to investigate the main Fe compounds present in some reference materials.
57Co and 109Cd simultaneous production was studied, using composite targets of natNi and natAg. The targets were irradiated at the CV-28 Cyclotron, with proton beams of 24 MeV. The average production yields of 57Co and 109Cd were 1179.93 kBq/A·h, produced by direct and indirect reactions (11.31 days after the EOB) and 71.41 kBq/A·h (EOB), respectively. The chemical separation procedure was developed in order to obtain a mixed calibration source of 57Co and 109Cd, with a separation yield higher than 80%. The gamma spectroscopy technique was used for the radioactive analysis, using a HPGe detector. The stable elements were identified by atomic absorption spectrophotometry.
Authors:H. Matsuda, B. de Araujo, and J. de Araujo
Celeste-1 is a lab-scale hot cell intended for R&D work in reprocessing of low burn-up spent fuel elements. The studies are concerned with head-end, first separation cycle by Purex Process using mini mixer-settlers and development of analytical techniques. The analytical monitoring for process control purposes is based on several off-line techniques, such as X-ray fluorescence spectrometry, potentiometric titration, -and -spectroscopy, spectrophotometry, fluorimetry, density measurement and gas chromatography. The analytical treatment takes place in a shielded working place analytical hot cell, glove boxes and hoods and some final measurements are made in the associated analytical laboratory. A pneumatic system is used for transporting analytical samples. All analytical procedures are ready and in operation.
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.
Mercury levels in the urine of Mexican dentists were determined by instrumental neutron activation analysis. A control group with no suspicion of contamination by mercury was also studied. Acid digestion was used for samples treatment and the presence of 203Hg was determined by gamma spectroscopy. The ranges of mercury concentration found in urine were: for the dentists group from 0.19 to 11.56 mg Hg/l, with a mean value of 3.16 mg Hg/l and standard deviation of 2.74 mg Hg/l, and for the control group from 0.03 to 0.05 mg Hg/l with a mean value of 0.04 mg Hg/l and standard deviation of 0.01 mg Hg/l. The mercury levels found in urine of dentists are associated with several exposure factors which appear to be positively correlated to its concentration, such as years of dental practice, amalgamation techniques, etc.
In experiments performed to simulate the interaction of cosmic radiation with matter, a great variety of high purity elemental foils and simple compounds were exposed to energetic charged and uncharged particles. In order to determine production rates of long-lived radionuclidesi such as10Be (1.6 My),22Na (2.602 y),26Al (0.72 My),41Ca (0.1 My),44Ti (47.3 y),53Mn (3.8 My), and59Ni (0.07 My), by means of -spectroscopy, --coincidence measurements, neutron activation techniques, as well as the recently developed method of accelerator mass spectrometry, radiochemical separations with high decontamination factors were carried out, lowering isotopic ratios of interfering short-lived radioisotopes and stable isobars to levels of up to 10–13. The separation methods applied include ion exchange, solvent extraction and the use of selective ion retention media as well as classical precipitation methods.