ISO2975/II1-1976(E) 8 EXAMPLEOFCALCULATIONOFFLOWRATE 8.1 A measurement was carried out in the following way : Injection of a sodium-24 solution by a positive displacement pump driven by a synchronous motor connected to a 50 Hz electrical supply. Dilution of five samples of the injected solution with water from the conduit; determination of the dilution ratios by a - gravimetric method; analyses in a counting equipment (A) and in a counting equipment (B) for one of them (No. 3). Collection of ten samples to be analysed in a counting equipment (B). 8.2 Calculation of injection volume rate of flow .Injection rate at 50 Hz (q)2,099 cm3/s Mean frequcncy (f)49,96 Hz Density of injected solution at injection temperature (p;) 1,016g/cm3 Density of water at the conduit pressure and temperature (p)1,002 g/cm3 49,96 q = 2,099 × 50 = 2,097 cm3/s or 2,097 × 10-6 m3/s 8.3 Calculation of dilution ratios of solution samples Diluted solution No. 1 2 3 4 5 Sample of injected 0,848 5 g 1,108 5 g 0,980 7 g 0,972 2 g 0,851:0 g Sample of injected 945,5 g 901,0 g 914,5 g solution + water 923,3 g 942,7 g from first dilution Samplec after first 1,025 5 g 1,165 4g 0,883 0g 1,0235 g 0,992 4 g Sample after first 3 835,0 g 3 837,0 g 3844,5 g 3 852,0 g 3 821,0 g dilution + water Density of conduit 0,998 2 g/cm3 0,998 2 g/cm3 0,998 2 g/cm3 0,998 2 g/cm3 0,998 2 g/cm3 water Density of water 0,998 2 g/cm3 0,998 2 g/cm3 0,998 2 g/cm3 0,998 2 g/cm3 0,998 2 g/cm3 used for dilution 4,167 2,676 4,060 3,574 4,265 rate × 10-6 7 ISO2975/l11-1976(E) 8.4 Calculation of count rate from samples of diluted solution with equipment (A) Decay time from Corrected counting Time at end of datum from reference Sample counting from zero Counting period Recorded counts rate1) per minute time 173,7 min min min min Conduit water 5 16,67 7 059 Standard cobalt-60 46 16,67 414 027 86 16,67 412992 Conduit water 105 16,67 6 907 182 16,67 506 013 0 Diluted solution No. 1 30 001,0 210 16,67 495 375 28 29 999,8 mean 30 000,4 Diluted solution No. 2 259 16,67 740 489 77 46 849,1 312 16,67 709 932 130 46 846,0 mean 46 847,5 Standard cobalt-60 337 16,67 413 344 Conduit water 369 16,67 7 225 388 16,67 7 378 Diluted solution No. 3 449 16,67 424 157 267 30 814,7 473 16,67 417 882 291 30 878,9 mean 30 846,8 Diluted solution No. 4 513 16,67 458 060 331 35 006,3 539 16,67 449295 357 34 973,3 mean 34 989,9 Diluted solution No. 5 612 16,67 358 162 430 29 404,4 640 16,67 350 401 458 29 380,2 mean 29392,3 The correction includes the corrections 1) for dead time : 4,25 μs, for background count rate (Co) : 426 counts per minute, for decay time from a datum arbitrarily selected : 173,7 min. Calculation of corrected count rate for solution No. 3 on equipment (B) Recorded counts during counting period of 40 min 883,438 (see 8.6) - Decay time from datum 498 min (in minutes) 218,3 - Corrected count rate (correction of equipment B) C, = 25 712,6 counts per minute 8.5 This check may be carried out by comparing the spread of the values corresponding to the product of the count rate and dilution ratio about the mean value on the one hand and about the value estimated from counting statistics only on the other hand (F-variance ratio test). Standard 2 3 4 Diluted solution No. 5 Mean deviation s Dilution ratio 4,167 2,676 4,060 3,574 4,265 (X 10-6) Product of count rate by dilution ratio 1,250 2 1,253 6 1,252 4 1,250 5 1,253 6 1,2521 0,11 % (X 10-11) The standard deviation estimated from counting statistics only is approximately given by : 100 % 0= Nmean where Nmean is the average count number recorded for each diluted solution. In the example g = O,10 %. 8 ISO297.5/II1-1976 (E) The maximum value of the ratio S/o below which there is no significant difference between both standard'deviations at a 95 % confidence level may be derived from the distribution of the variance ratios for this confidence interval, i.e. : Number of samples 3 4 5 6 7 Maximum value of 1,41 1,40 1,38 1,36 1,34 variance ratio for a 95 % confidence