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TABLE 2. SOME WATER RADIOTRACERSIsotope137m Ba113m In99m TcHalf-life 2.6 min 100 min 6.02 hours 1.5 days 8.04 days 84 daysγ Energy(keV)ObtainingPreparation82 Br662 410 140 ≈ 700 360 900 and 1100137 Cs/ 137m BaGeneratorNone113 Sn/ 113m InGeneratorEDTAcomplexation99 Mo/ 99m TcGeneratorReactoractivation131 IReactoractivationNone NH 4 Br KI or NaI46 ScReactoractivationEDTAcomplexation3.1.4. Radiotracers for solid tracingAdsorption of a radiotracer on the surface of a solid has been used as a labeling method for manytypes of particles. For massive (i.e. non porous) particles such as sand, the labeling is proportional tothe surface of the particle. This methodology is operational but we consider that it is not a convenientone. It is quite better to simulate sand by a glass containing an activable element. The activity of theparticle will be in this case proportional to its mass. Fine particles such as mud or sludge, are verysmall and form aggregates (flocks). It is in this case possible to obtain mass labeling through theadsorption technology. Tables 3 and 4 present some radiotracers for labeling different kind ofsludge’s, in particular for fine particle silt and inert particle sand.3.1.5. Radiotracers for gas tracingSome gas tracers can be produced by direct neutron activation in nuclear reactors such as 41 Arand 79 Kr (Table 5). Methyl bromide (CH 3 82 Br) is produced through chemical synthesis of radioactive82 Br.TABLE 3. SOME RADIOTRACERS FOR FINE PARTICLE SLUDGE (SILT)Isotope113m In99m Tc82 Br198 Au175-181 Hf160 TbHalf-life 100 min 6.02 hours 1.5 days 2.7 days 45 days 73 days 84 daysγ Energy(keV)ObtainingPreparation410 140 ≈ 700 410113 Sn/ 113m InGeneratorNone99 Mo/ 99m TcGeneratorReductionby SnCl 2ReactoractivationChloridesolutionReactoractivationChloridesolutionComplexspectrumReactoractivationChloridesolutionComplexspectrumReactoractivationChloridesolution46 Sc900 and1100ReactoractivationChloridesolutionTABLE 4. SOME RADIOTRACERS FOR SAND PARTICLESIsotope140 La198 Au52 Mn147 NdHalf-life 1.7 days 2.7 days 5.7 days 11 days 74 daysγ Energy(keV)Obtaining330 to 1600 410 730 to 1460ReactoractivationReactoractivationReactoractivationComplexspectrumReactoractivation192 Ir296 to 468ReactoractivationPreparation Glass powder Glass powder Glass powder Glass powder Glass powder29