frequently required to produce recog- 
nizable darkening. 
APPLICATIONS 
The usefulness of tritium as a tracer 
comes from the presence of hydrogen 
in most organic substances and the 
existence of tritium and tritium-labled 
compounds as gases. Four of the 
symposium speakers discussed practical 
tracer uses of tritium. 
Biology and Drugs 
The manufacturer of pharmaceuti- 
cals uses tracers primarily to study new 
drugs. The things he wants to know 
about them are (a) chemical and bio- 
logical stability, (b) site and extent of 
absorption, (c) translocation and distri- 
bution in body fluids and organs as 
functions of time, (d) biological half- 
life, (e) places of permanent or semi- 
permanent storage, (f) biological trans- 
formations and methods of excretion 
and (e) modes of biochemical and 
pharmacological action. 
Tritium labeling by exchange meth- 
ods is possible with most drugs. 
Testing is performed largely in animal 
experiments, and assay is by liquid- 
scintillator counting and radioauto- 
graphs. 
In new-drug studies, tests to find an 
appropriate labeling technique and 
then to test the quality of the label are 
always fundamental. A label can 
arrive at a spot through movement of 
the whole molecule, transfer of part of 
the molecule in a metabolic process or 
merely by exchange of the tritium atom 
with the hydrogen of another molecule. 
One must also evaluate isotopic 
effects. Tritium can move preferen- 
tially in chemical or biological systems 
as the result of two things: (a) the dif- 
ferent strengths of hydrogen and 
tritium bonds and (b) the different 
mobilities exhibited by atoms con- 
taining hydrogen and their counter- 
parts containing tritium. 
Petroleum Engineering 
Oil geologists find tritium useful in 
studying fluid flow in both laboratory 
experiments and underground explora- 
tion. Tritium has several advantages 
over other tracers: (a) a cost that is a 
small fraction of the total cost of a 
test, (b) weak radiation that presents 
no health hazard, (c) relatively long 
life, (d) detection techniques that can 
be used in the field, (e) absence of 
quantitative | 
3-|Zn, 400°C 
reduction 
— 7.| Concentration | 4-|Mg, 650°C yl 
Aqueous [by electrolysis] 5-|Mg-Hg, 400°C "| Ho 
ample 6-|Ca, 25°C | 
7-|LIAIH,, 25°C | 
Organic {Quantitative | 8-|CH3Mgl, 100°° | 
SE Mel, CH 
sample | combustion TT combustion 3-[Al,C4, 120°C | = th, 
CO, 10-|CaC,_ 25°C | cH, 
Organic 1-|CgHoMgBr, 120°C] ————> CH 
or ' quantitative |_| H.C 
aqueous FE PETE NAD BAIT: for hy drogen | mixture 
sample 
FIG. 3. Conversion methods for gas counting of tritium. 
next page list users, methods, and publications, 
References should not be confused with story 
above appear in fifth column of the table. 
bibliography on this page 
appreciable tritium in naturally occur- 
ring gases and (f) the ability to in- 
corporate it as a label in the fluid that is 
to be traced, which is usually water or 
a hydrocarbon. 
In a “‘five-spot’”’ technique oil is 
taken from a central producing well 
while four other wells are used as in- 
jection wells. Water or gas forced 
down an injection well will force oil to 
the site of the production well. Dif- 
ferent tracers, used together, indicate 
which of the injection wells are 
effective. Tritium-labeled gases that 
are useful are tritium itself, CH? and 
C.H%. Other radioactive gases that 
are frequently used are C'H,, C}*H, 
and Kr®®. Dilution factors as great as 
103 are currently usable. 
Many nonradioactive gas tracers 
have been used in the past. They 
include dyes, boron compounds, am- 
monia, salts, helium and carbon mon- 
oxide. However, such tracers present 
many difficulties: (a) failure to behave 
as the fluid to be traced, (b). lack of 
sensitivity, (c) high cost and (d) need 
for laboratory techniques that cannot 
be used in the field. In the use of 
helium there is inconvenient back- 
ground due to naturally occurring 
helium. Carbon monoxide presents a 
special health hazard. 
If the flooding fluid is water, tritium- 
labeled water is the ideal tracer. 
Other long-lived tracers are usable if 
they are chemically complex so that 
they do not react with the materials 
they encounter. 
Another special problem is the 
labeling of gases held in underground 
storage reservoirs. The technique is 
appropriate for measuring the size of 
the reservoir and finding leaks that can 
Table and references on the 
Numbers associated with conversions 
waste the stored gas or poison nearby 
mines. Currently reservoirs are tagged 
at levels that permit tracing their 
gas for 25-30 yr. This requires about 
1 ¢ per million cubic feet. 
Cost of homogeneous labeling is $2-3 
per million cubic feet. The cost per 
injection includes similar costs of a 
few hundred dollars for isotope pro- 
curement and calibration, respectively, 
and an injection cost of a few thousand 
dollars. 
* * * 
This article is based on material presented 
at the Symposium on Tritium in Tracer 
Applications, Hotel Statler, New York, 
November 22, 1957. 
The speakers were F. Marott Sinez, chair- 
man, Boston University School of Medicine, 
Kenneth E. Wilzbach, Argonne National 
Laboratory, Seymour Rothchild, New England 
Nuclear Corp., James R. Arnold, Princeton 
University, Charles V. Robinson, New Eng- 
land Medical Center, John S. Handloser, 
Brookhaven National Laboratory, Jay F. 
Snell, Pfizer Therapeutic Institute, Donald R. 
Carr, Isotopes, Inc., Maxwell Eidinoff, Sloan 
Kettering Institute, Walter L. Hughes, 
Brookhaven National Laboratory. 
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189 
