A procedure for monostandard INAA of 21 elements (Hg, As, Br, Cr, Sb, Se, Ba, Zn, Ca, Ce, Co, Cs, Eu, Fe, Hf, K, La, Rb, Sc, Sr, Ta) in Chinese Biological Standard Reference Material (peach leaves) is described. The accuracy of the procedure was checked by analyzing the U.S. NBS Standard Reference Materials SRM-1571 and SRM-1632a.
A homogeneity test of 14 elements (Al, Cl, Mn, K, Ca, Ce, Th, Hf, Cs, Sc, Fe, Zn, Co and Eu) was made in Chinese Biological Standard Reference Material (peach leaves) by means of INAA. The procedures are described and the results are presented and discussed.
Authors:K. De Neve, K. Strijckmans, K. Vandeputte, and R. Dams
In the14C-dating by accelerator mass spectrometry (AMS) iron and copper oxide are used during sample preparation. In an investigation on the origin of the14C-blank, which in practice determines the dating limit of AMS, the carbon contamination was measured in both reagents by deuteron activation analysis via the12C(d,n)13N reaction. A first batch of iron was analysed radiochemically and a carbon concentration of 37.6 g/g was found with a standard deviation of 2.7 g/g (3 analyses). In a second batch of iron concentrations between 66 and 150 g/g were found for 6 instrumental analyses, suggesting an inhomogeneous distribution of carbon. The carbon content in copper oxide was 17.8 (3.5) g/g for 3 instrumental analyses, but preference should be given to a radiochemical analysis. These figures indicate that the carbon impurities found in iron and copper oxide are possible causes of the14C-blank. However, a final conclusion can only be drawn if the14C concentration of the contaminating carbon and the amount of carbon released during sample preparation are known.
Authors:F. de Corte, K. Masumoto, A. De Wispelaere, and F. Bellemans
A dedicated NAA calibration method was developed for the determination of the neutron spectrum monitor elements Co, Au and Lu in alloyed wires and foils, with an accuracy of better than 1%. The method does not require quantitative micropipetting for preparing the standards, and leads to vanishing errors caused by flux inhomogeneities and by differences in counting geometry and gamma attenuation. Its performance was tested by analysing various NIST, IRMM and RX aluminium-based materials with certified or specified Co, Au or Lu content.
Rock samples from seven different locations in northwestern Nigeria were analyzed by reactor instrumental neutron activation analysis and Ge(Li) gamma-ray spectrometry. Concentration values were obtained for 18 elements (As, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Sc, Sm, Sr, Ta, Tb, Th, U, Yb). The geochemical implications of the results are discussed.
Authors:K. Strijckmans, N. De Brucker, and C. Vandecasteele
A method for the determination of sulphur in fly ash by instrumental proton activation analysis using the34S/p,n/34mCl reaction was developed. The 2128.5 keV and 3305.0 keV -rays of34mCl /t=32.0 min/ were measured on a Ge/Li/ -spectrometer, shielded with a lead absorber to attenuate low energy -rays. Irradiation and measuring conditions were optimized. The detection limit for instrumental analysis is 0.3 to 1 mg g–1 and the standard deviation is cca. 4% for a typical sample.
The evolution of trace concentrations (sub ng·g–1) of uranium in aqueous reference solutions was followed over time by isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). Blank levels and detection limits needed to be determined prior to the actual investigations. Accuracy and precision of the method were determined on the basis of results obtained for uranium reference materials under similar experimental conditions. Reference solutions, certified for uranium concentration were prepared on gravimetrical basis. Analyses were performed over a period of 2 years. Taking into account the accuracy and the precision achieved, no significant change of the concentration is observed with time. Therefore, the mid and long term stability of the concentration of such reference materials was successfully demonstrated.
Authors:S. Pfanstiel, K. Hofstetter, and T. De Vol
The performance of four types of - and X-ray radiation detectors for environmental applications was evaluated in the 10–450 keV energy range. Two cadmium zinc telluride (CdZnTe) room temperature semiconductor detectors were evaluated along with a cryogenically cooled semiconductor detector and two different types of scintillation detectors. The energy resolution, absolute peak detection efficiency and peak-to-background ratio of each of the detectors were calculated and intercompared. The advantages and disadvantages of environmental applications of each detector, along with their performance results, are summarized.
Finland has the operational capability to take airborne gamma-ray measurements in emergency situations. The original purpose of airborne radiation mapping in Finland was to identify hazardous areas containing radioactive fall-out after a nuclear accident or use of nuclear weapons. Regular exercises are held annually to keep the operational functionality at a high level. The achieved capability has been well demonstrated in international INEX-2-FIN 1997 and Barents Rescue 2001 exercises. The knowledge and competence achieved can easily be applied in international radiation monitoring campaigns designed to expose undeclared nuclear materials or other clandestine nuclear activities. The essential improvements in the detection system are linked to the ability to locate point-like radiation sources rather than large areas of fall-out. This paper describes the aerial gamma-ray measurement method and its usability for the detection of nuclear material production chains and trails of fission or activation products. The ability of airborne detection systems in revealing the use of undeclared nuclear materials has been tested. Various scenarios for exposing clandestine nuclear material production, enrichment and nuclear waste trails have been considered. Based on detection capability calculations and testing in practice, it was found that the detection of one un-shielded significant quantity of natural uranium (10 tons of yellow cake in storage barrels) is possible through the daughter products, using one single 6"'4" NaI detector on the airplane. The developed fixed wing gamma measurement technique is now able to detect significant amounts of nuclear material conveniently and cost-effectively. Large areas can be screened to identify suspicious sub-areas for more detailed ground-based inspection.
A routine procedure for monostandard INAA using short-lived radionuclides with half-lives from 2 min to 15 hrs is described. Ten elements (Al, Mg, Ti, V, Mn, Cl, Na, K. Br and Cu) are determined in Chinese Biological Standard Reference Material (peach leaves). The quality of analysis was checked by analyzing the U. S. NBS Standard Reference Materials SRM-1571 and SRM-1648.