The simplest type of tritium removal system can be found in those applications
where high-quality primary containment systems are enclosed in high-quality
secondary containment systems. In most applications, the high-quality
secondary containment systems are operated under vacuum conditions when
the primary and secondary containment systems are actually in service. The
tritium removal systems, in this case, can be as simple as a vacuum transfer
system designed to move any tritium that escapes from the primary system to
an appropriate collection point for later processing. Under such circumstances,
the actual transfer of the tritium can be allowed to proceed quite slowly
because, at an allowable leakage rate of 10 -6 to 10-7 cm3/sec from the
secondary, the total leakage rate from the secondary system should be less
than 0.25 Ci/day.
More complex approaches should be taken when the primary systems are
enclosed in intermediate-quality, secondary containment systems (e.g., a
glovebox) because, in these types of applications, the ingress of tritium into the
glovebox atmosphere is not the only factor that should be considered.
Additional consideration should also be given to the maintenance of the
glovebox operational atmosphere, the total volume of the containment system,
the total volume of the cleanup system, the ability of the cleanup system to
remove tritium from the glovebox atmosphere as a function of flow rate, the
overall leakage rates into and out of the glovebox, the overall leakage rates
into and out of the cleanup system, and operating temperature requirements
for each of the operational components.
One example of this type of cleanup system that has been used extensively in
several different tritium facilities works as follows:
Tritium is released into the secondary containment system (i.e., the
glovebox) as a result of a primary system failure.
The cleanup system is started and the tritium-containing gases captured
in the glovebox are circulated through the cleanup system.