RSDetection
User’s Manual
March 2016
S131-200-UM Rev A
Page 20
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Table 3 "F" Factors for Common Isotopes
Isotope
Energy (MeV)
F
Co-60
1.17, 1.21
0.89
Cs-137
0.667
0.91
Ra-226
Various
0.91
Kr-85
0.5
0.94
Kr-85m
0.15, 0.3
1.19
Kr-87
0.4, 0.85, 2.6
0.93
Kr-88
0.19, 2.4, 0.85, 2.2,1.55
0.92
Xe-133
0.081
1.46
Xe-133m
0.233
1.11
Xe-135
0.25, 0.6
1.07
Am-241
0.059
0.46
These values can be used to provide a correction factor if the source of the gamma field is
known. Since the detector is calibrated with respect to Ra226 this correction is the ratio of
the measured isotope to the Ra226 “F” factor. A table of these correction factors is shown
in Table 4.
Table 4 Correction Factors
Co-60
0.980
Cs-137
1.002
Ra-226
1.000
Kr-85
1.035
Kr-85m
1.314
Kr-87
1.027
Kr-88
1.013
Xe-133
1.608
Xe-133m
1.223
Xe-135
1.178
Am-241
0.507
To use these factors, assume you were measuring Co60 and a dose rate of 150uR/h was
measured. To correct this reading this value should be divided by 0.98, yielding 153 µR/h.
