Tritium Cleanup and Removal Systems

DOE-HDBK-1129-99

4.1.2 Tritium Cleanup and Removal Systems

Current designs employ tritium removal systems. When tritium is released into a secondary, the

associated cleanup system starts, and the gases containing tritium are circulated through the

cleanup system, and the tritium is removed. See Figure 4-5 for a diagram of a typical gas-to-water

conversion tritium removal system.

FIGURE 4-5. Typical gas-to-water tritium removal system flow schematic

If the cleanup system is associated with a high quality barrier (leak rate of less than 1 Ci of tritium

in a period of 4 to 40 days) then tritium transfer to another container can take several days to

complete without a significant release of tritium to the environment. If the cleanup system is

associated with a medium quality barrier (leak rate of less than 1 Ci in 3 to 30 hours), then the

cleanup system flow rate needs to be high enough to remove tritium within a few hours in order to

prevent a significant release of tritium to the environment. If the cleanup system is associated with

a low quality barrier, (leak rate of 8 Ci or more per minute), then the cleanup system flow rate

needs to be very high so that tritium is removed from the gas before it is released to the

environment.

The captured tritium is generally removed by circulating the gas through a system that removes

tritium down to the part-per-billion level. Typical present-day cleanup systems remove tritium by

cracking the molecules on a hot catalyst. The free hydrogen atoms combine in the catalytic

reactor with the oxygen present to form water. The tritiated water is then removed from the gas by

molecular sieve traps. Depending upon the tritium species, the concentration reduction of these

systems can be from one million to one hundred million in a single pass.

The tritium released to the environment during this process is a function of the quantity of tritium

released, the volume, and leak rate of the container, and the cleanup rate of the tritium removal

system.