Page 295 - Radiochemistry and nuclear chemistry

Uses of Radioactive Tracers 279

as it proceeds. The presence of these isotopes can be monitored from time to time by
sending a capsule with a suitable detector and recorder through the pipe.

9.6.4. Chemical processing

We have describeA some areas of application of radiotracers which are useful to the
chemical industry. To be more general, radioactive tracers are used to seek information of
flow and mixing patterns for
- parameter evaluations (mass balance, flow rates, kinetics)
- fluid dynamics (trouble shooting, residence time distributions, modelling flow
phenomena)
- chemical reaction engineering (effect of flow and mixing on conversions,
modelling of reaction systems, process control algorithms).
Each application is rather case specific and described in the chemical engineering
literature.

9.7. Environmental applications

Nuclear weapons tests have releasext large amounts of radionuclides into the atmosphere,
which through their own weight or by rain have been carried to the earth's surface.
Geophysics has made use of this weapon "fallout'. By measurements on T (as HTO water),
9~ 137Cs, and other fission products it has been possible to follow the movements of
water from land via lakes and rivers into the sea, as well as to study the water streams of
the oceans and the exchange between surface and deep water. As a result the circulation
of water on earth has been mapped in quite detail. It has also been possible to analyze how
tropical hurricanes are formed by measuring the water taken into the central part (the "eye')

_••. (a) ::~-~ ~ - .... - . crane

_
.
.
.
.
.
.
.
_--_ _~,--_ _--_-- -_-
built in detector
/
~ -- wire and cables
_ _ _ - - _
~ ._ _ ~_/ detectors
, ,.." ,;. .... ,; .,.-. ;.- -,,, / .;.
....
-'~'~:.;.-.'~. ...... .~ / ...... .;~a-
:
................ .......... .~...~, /,,'""
radioactivity "" I~ravane wlth
(b) depth gauge
.l~..-,.T._,.,,.~,.,t - 7 ..-- ~-'.- "~ .'7--,~ ~ ..-7"T - - .':,:."- -'.'~'~
FIG. 9.17. Left, technique for finding leaks in pipes. Right, technique for measuring stream
lines in the strait of Oresund. (Courtesy Danish Isotope Center.)