Alpha counting

Alpha counting is done with an internal proportional counter or a scintiUation counter. Beta counting is carried out with an internal or external proportional gas-flow chamber or an end-window Geiger-MueUer tube. The operating principles and descriptions of various counting instmments are available, as are techniques for determining various radioelements in aqueous solution (20,44). A laboratory manual of radiochemical procedures has been compiled for analysis of specific radionucHdes in drinking water (45). Detector efficiency should be deterrnined with commercially available sources of known activity. 

Concerns that diagenetic alteration could affect measured °Th ages of corals have existed since the early applications using alpha-counting methods. Thurber et al. (1965) offered the following list for reliable coral °Th ages a) no evidence of recrystallization, b) uranium concentration of 3 ppm, c) p°Th/ Th] of > 20, d) of 1.15 ... 

The data are presented in decreasing order of U flux. Analytical precision are 2 a for samples measured by TIMS (references 1 and 13), and 1 o for those obtained by alpha counting. 

Dazhu Y, Yongjun Z, Mobius S. 1991. Rapid method for alpha counting with extractive scintillator and pulse shape analysis. J Radioanal Nucl Chem 147(1) 177-189. 

In Fig. 3 all measured data of fj = cjf/cj and f are presented as function of the attachment rate. The absolute errors of fj and fp are in the order of 0.02 and 0.01, respectively. These errors were calculated from the errors due to the alpha counting and due to the mathematical procedure of the filter activity evaluation. 

Gross alpha and gross beta activity can be determined by various radioactive counters, such as internal proportional, alpha scintillation, and Geiger counters. Radium in water can be measured by co-precipitating with barium sulfate followed by counting alpha particles. Radium-226 can be measured from alpha counting of radon-222. Various methods are well documented (APHA, AWWA, and WEF 1998. Standard Methods for the Examination of Water and Wastewater, 20 ed. Washington DC American Public Health Association). 

Electrodeposition of Pa metal has been performed from both aqueous and nonaqueous solutions. An isopropanol solution of 10-20 p,gmL Pa from 8M HCl/0.01 M HE/Pa stock was employed for quantitative electrodeposition [41]. The cell consisted of a gold-plated A1 cathode and a Pt wire anode. During deposition the current was maintained at 1 mA, which produced a potential of 400-600 V during the 90-min electrolysis. The progress of the electrolysis was externally monitored by alpha-counting of the electrolysis solution before and during the electrodeposition. Deposition studies of metal from aqueous solutions are more common. Pa was electrodeposited on platinum in 95% yield at tracer concentrations from an electrolyte of [NH4]C1/HC1 [42]. Electrochemical and chemical conditions of the plating process were described for Pu solutions, which served as a model for the other actinide elements studied. Another tracer... 

The rather variable results of half-life determinations made by direct alpha-counting of samples mounted on metallic supports may be due to... 

The counting techniques described in this paper are also readily applicable to studies of "hot radioactive waste (z.e.j radioactive waste from reprocessed nuclear fuel). With this type of material, the cesium can be analyzed as 30-y (662-keV y), the RE as 13-y Eu (964-keV and 1408-keV y), strontium as 28-y Sr (after chemical separation and beta counting), and the actinides by group separation and alpha counting. 

Leach rates for elements other than those listed in Table II can also be determined by this method. In fact, any element in the periodic table that is solid at room temperature and has an activation product with a half-life sufficiently long to allow leach testing can be studied with this technique. This method can also be applied to the study of the leach rates of alpha emitting actinides present in waste. In this case, standard carrier-free radiochemical procedures, coupled with low background alpha counting, would be invoked. 

The calculated adsorption coefficients (K) are presented in Table VII. K (alpha) refers to results from alpha counting the wafers and solutions, while K (gamma) refers to results from gamma counting. K (filter) refers to results from the alpha counting of wafers and filtered solutions. 

Except for Np, alpha counting showed that wafer surfaces facing upward consistently had higher counting rates than surfaces facing downward. The up/down ratios are also presented in Table VII. This behavior suggests that a process such as settling may be involved. 

The distribution coefficients calculated from the alpha counting data are given in Table VIII. The gamma counting of the solutions is still in progress. The symbols are the same as used previously. For K (alpha), the counting precision is + 10 percent for the U, Am and Cm samples and + 20-30 percent for the Np and Pu samples. For K (filter), the counting precision is + 10 percent for U, + 10-20 percent for Np, Am and Cm and +30-40 percent for the Pu samples. 

The plutonium solution concentration was determined by alpha counting 0.5-ml. aliquots evaporated to dryness on planchets. Gas flow internal proportional counting was used with 90% argon-10 % methane gas and Nuclear Measurement Corp. counters. 

Water Precipitate with barium sulfate, Alpha counting 0.1 D3 pCi 97.1 - APHA 1985b... 

Precipitate with barium sulfate Alpha count- 1 pCi/L No data ASTM 1988c... 

Centrifugation alone is not sufficient to separate Np solid material from the solution (j) ). Thus, the Np solution concentrations and oxidation state analyses were determined from aliquots filtered through approximately 1.8 nm pore-size Centriflo membrane cones (Amicon Corp., Lexington, MA). Each filter cone was pretreated with an initial aliquot of the suspension to be filtered. Tests using successive filtration confirmed that no significant amounts of Np were being sorbed by the filter cones. The solutions were alpha counted by liquid scintillation techniques. Major cations in the solutions were determined by inductively coupled plasma spectrometry (ICP) analyses. 

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