Beta particle spectrometry

It has been shown (Holm et al., 1990) that ion implanted detectors can be used not only for alpha particle spectrometry but also for beta particle spectrometry. Their drawback, however, is the high background around 100 keV and noise below 1 keV. 

Oikari, T., Kajola, H., Nurmi, I., Kaihola, L. Simultaneous counting of low alpha-and beta-particle activities with liquid scintillation spectrometry and pulse-shape analysis. Appl. Radial Isot 38A, 875-878 (1987)... 

Preparation of purified samples for alpha-particle spectrometry is usually by either electrodeposition or micro-coprecipitation. Either technique takes at least an hour. Many beta-particle emitters are precipitated with several milligrams of carrier and weighted for determining the chemical yield prior to counting, which also takes time. In contrast, a few millilitres of solution are satisfactory for ICP-MS. If the analyte concentration should exceed the linear part of the calibration curve, a simple dilution overcomes the problem. 

Accelerator mass spectrometry (AMS) extends the capabilities of atom-counting using conventional mass spectrometry, by removing whole-mass molecular interferences without the need for a mass resolution very much better than the mass difference between the atom and its molecular isobar. This technique has been used with great success for the routine measurement of C, Be, " Al, C1 and, recently, (see Table 5.15). Analysis of " C by AMS can, for example, generate dates with a precision that is at least equal to the best conventional beta-particle-counting facility. In many cases, where small sample analysis is required, the AMS method has proved superior (Benkens, 1990). A complete description of AMS can be found in review articles (Litherland et al., 1987 Elmore and Philips, 1978) or recent conference publications. The application of AMS to measurement has been discussed in detail in Kilins et al. (1992). 

Quantities of plutonium-241, a beta-particle emitter, can be quantified from (1) assumed isotopic abundance ratios, (2) estimated in-growth of its progeny americion-241 by gamma spectrometry, or by (3) mass spectrometry (Bernhardt 1976). Americium-241 is produced from the beta decay of plutonium-241 and, therefore, can be used to indirectly measure the concentration of plutonium-241 (Metz and Waterbury 1962). Direct determination of plutonium-241 by measurement of its low energy beta-particle decay has been reported using liquid scintillation analysis (Martin 1986). 

In this study, we have extended these results to include S. In addition, we have presented methods utilizing fluorography by which proteins labeled with weak beta-particle emitters such as H, can be used to produce autoradiograms and then analyzed by liquid scintillation spectrometry. 

Uranium-233 (V, = -1.59 10 years) is formed through neutron capture by Th (mainly in thorium-fueled nuclear reactors) followed by emission of two beta particles. Alternatively, may be formed by alpha decay of Np that in turn is produced through a sequence of nuclear reactions in uranium-fueled reactors. The °Th decay product of is the relatively short-lived (t = -7880 years) so the ratio between these nuclides is linear for thousands of years after purifications. Alpha spectrometry and mass spectrometry can be used for measuring the Th/ U ratio. In special cases, this pair of nuclides cau serve as a chrouometer for nuclear proliferation, particularly if fissile is produced in reactors fueled with thorium. 

R Straub, M Linder, RD Voyksner. Determination of beta-lactam residues in milk using perfusive-particle liquid chromatography combined with ultrasonic nebulization electrospray mass spectrometry. Anal Chem 66 3651-3658, 1994. 

Particle induced desorption methods are commonly used to ionize low-volatility compounds. Cesium ion desorption (or cesium ion secondary ion mass spectrometry, SIMS) uses a primary beam of cesium ions to desorb and ionize a non-volatile sample. This technique has been used with FTMS to produce pseudomolecular ions of vitamin B12, ((812)2 + Cs - 2CN +, at m/z 2792 (24) and molecular ions of beta-cyclodextrin (m/z 1135) (92, 93). Detection limits of 10"13 mol for the peptide gramicidin S has been demonstrated using Cs+ SIMS with FTMS (25), and additional structural information was obtained using MS/MS processes. 

The activities of some isotopes, in particular °Sr- °Y, can also be detected by liquid-crystal spectrometry with the use of the Cherenkov phenomenon [10, 11]. The Cherenkov effect is used to determine beta isotopes emitting particles whose iiniax IS above 500 keV [12]. The main advantage of beta activity determination by the Cherenkov effect is the use of analytical preparation used for another chemical analysis (e.g. calculation of recovery). Moreover, the addition of low energy beta or alpha radiation does not disturb the measurement, thereby lowering the cost of analysis. The weakness of this method is the decreased recovery registration and the decline in information about the realistic appearance of the beta spectrum [13]. The determination of beta isotopes in environmental samples is very difficult and requires their chemical isolation. The type of sample and the time of chemical analysis determine the choice of analytical method. Also, the time between contamination and sample collection is important procedures used for samples recently contaminated are different to those used for old samples in which the decay of short-lived radionuclides has aheady taken place [1, 5]. 

Radiation detectors are specially designed to provide information about the type (alpha, beta, gamma, etc.), energy (radiation spectrometry), and intensity (number of particles or quanta) of the radiation. Some detectors also provide information about the spatial distribution of the radiation (nuclear imaging detectors). 

A special case was concerned with measurement of uranium aerosols generated when DU munitions penetrate armored vehicles (Parkhurst 2003). In this study, DU penetrators were fired at a tank and another armored vehicle and the aerosols were collected by different means (filter cassettes, cascade impactors, five-stage cyclone, and a moving filter). Wipe samples were also collected from surfaces and deposition trays. Analysis included particle size distribution, morphology, uranium oxide phases, and dissolution in vitro. The uranium mass was determined by different methods radioanalytical beta spectrometry for some filters and ICPMS, ICP-AES, and KPA for other samples. 

Methods for bulk analysis and particle analysis of nuclear materials for detection of undeclared activities were described in a review article (Piksaikin et al. 2006). The bulk detection methods included radiometry (alpha, beta, and gamma spectrometry) based on the natural decay of the radionuclides, including the use of 234Th/23°Th gamma activity ratio for age determination (see detailed discussion later) and ratio that should be about 21 for undisturbed ores higher in mining... 

The product in this case is the most common isotope of radon, Rn (usually just called radon and which incidentally is responsible for the largest radiation dose from a single nuclide to the general population). A fixed quantity of energy, g, equal to the difference in mass between the initial nuclide and final products, is released. This energy must be shared between the Rn and the He in a definite ratio because of the conservation of momentum. Thus, the alpha-particle is mono-energetic and alpha spectrometry becomes possible. In contrast to beta decay, there are no neutrinos to take away a variable fraction of the energy. 

All of the plutonium isotopes, with one exception, decay by alpha particle emission. The exception - " Pu beta-decays to " Am. It follows that uranium which has been reprocessed, and materials contaminated by it, may contain all of these transuranic nuclides. Because of their low gamma-ray emission probabilities, low levels of the plutonium isotopes are not easily measured by gamma spectrometry. 

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