Page 293 - Radiochemistry and nuclear chemistry

Uses of Radioactive Tracers 277

9.6. Industrial uses of radiotracers

Industry has applied radiotracers in a very large variety of ways. More than half of the
500 largest manufacturing concerns in the United States use radioisotopes in the production
of metals, chemicals, plastics, pharmaceuticals, paper, rubber, clay and glass products,
food, tobacco, textiles, and many other products. Radioisotopes are used to study mixing
efficiency, effect of chamber geometry, residence time in reactors, flow rates and patterns
in columns and towers for fractionation, absorption, racemization, etc. Some of the many
uses are listed in Table 9.6 and a few are described below to reflect the scope and value
of the industrial applications of radioisotopes. Quite often the radionuclide used is not
isotopic with the system studied.

9.6.1. Mixing

Mixing is an important mechanical operation in many industries. Poor mixing may give
an unsatisfactory product and low yield of the operation; unnecessary mixing is a waste of
time and energy. By adding a radionuclide to the mixing vessel, or by labeling one of the
components, the approach to mixing equilibrium can be followed either by external
measurement or taking samples at different time intervals. Among examples of this
technique are fluxing of cement, gravel, sand, and water to concrete measured by using
irradiated pebbles. The homogeneity of glass melts can be determined by adding 24NaHCO3
to the melt; organic compounds of 95Zr (/T-y tl/~ 64.02 d) have been used to follow

TABLE 9.6. Radioisotope technique studies at ICf t undertaken in a typical year

Technique Number of applications
Level and interface measurements:
Gamma-ray absorption 210
Neutron backscatter 480
Gamma-ray backscatter 71
Blockage detection and deposition:
Gamma-ray absorption 132
Neutron backscatter 129
Entrainment and voidage:
Gamma-ray absorption 86
Thickness and corrosion measurements 15
Distillation-column scans 108
Flow measurements:
Pulse velocity 483
Dilution techniques 84
Leak detection 90
Residence-time studies 21
Carryover studies (tracer) 6
The list is not fully comprehensive as less commonly used techniques have not been
included, t Imperial Chemical Industries (UK).