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7.6 Calculations <br /> <br />7.6.1 Calculate the alpha radioactivity by the following equation <br />Alpha (pCi/liter) = A x 1.000 <br />2.22xCxV <br />where: <br />A = net al pha count rate (gross alpha count rate minus th <br />background count rate) at the alpha voltage plateau: <br />C = alpha efficiency factor. read from the graph (Paragrap <br />7.1.3) of efficiency vs. mg of water solids per cm <br />planchet area, cpm/dpm); <br />V = volume of sample aliquot (mL): and <br />2.22 = conversion factor from dpm/pCi. <br />7.6.2 Calculate the beta radioactivity by the following equations <br />1.6.2.1 If there are no significant alpha counts when the sampl <br />is counted at the alpha voltage plateau. the beta activity can b <br />determined from the following equation. <br />Beta (pCi/liter) = B x 1.000 <br />2.22xDx <br />where: <br />B = net beta count rate (gross alpha count rate minus the <br />background count rate at the beta voltage plateau). <br />D = beta efficiency factor. read from the graph (Paragraph <br />7.1.3) of efficiency vs. mg of water solids per cm <br />planchet area. (cpm/dpm). <br />V = volume of sample aliquot (mL). <br />2.22 = conversion factor from dpm/pCi. <br />z of <br />7.6.3 When counting beta radioactivity in the presence of alph <br />radi oactivity by gas-flow proportional counting systems (at the bet <br />plateau), alpha particles are also counted. Because alpha particles ar <br />more readily absorbed by increasing sample thickness than beta particles <br />the alpha/beta count ratios vary with increasing sample thickness <br />Therefore. ~t is necessary to prepare a calibration curve by countin <br />standards contain ng americium-241 with increasing thickness of solids on <br />e <br />h <br />Z of <br />e <br />e <br />a <br />a <br />e <br />9 <br />9310 - 6 <br />CD-ROM Revision 0 <br />Date September 1986 <br />