Charcoal cartridge for i-131 monitoring

This cartridge is impregnated with radioactive material (133Ba) and is used to check and calibrate equipment that measures charcoal cartridges used for monitoring I-131.

I-131 has gamma rays at 364 keV (81.2%) and at 636, 642, and 723 keV with branching ratios of 7.27, 0.220 and 1.80%, respectively. Ba-133 has gamma rays at 356 (61.94%) and 384 keV (8.905%). The gamma rays at 356 and 384 keV from Ba-133 are used to simulate the 364 keV gamma ray of I-131 (81.2%).

To produce the same number of gamma rays as 1 uCi of I-131 (at 364 keV), the amount of Ba-133 required will be 81.2/(61.94+8.90) =1.146 μCi.

E Geometry (face-loaded type) : a radioactive disk is placed in contact with one of the inside surfaces of the housing to simulate surface contamination.

The activity of the 133Ba is homogeneously distributed over the surface of a disk 50mm in diameter which is hot-sealed between two thin plastic foils. The cartridges are made of a leak tight polycarbonate housing (volume: 44 cm3) containing the activated charcoal.

The sources are provided with an activity certificate
• Activity tolerance : +/- 30%
• Measurement uncertainty (at k=2) : 5%

Different activities and geometries can be proposed upon request.