Figure 4-6. Confinement volume cleanup rate as a function of system time constant, F/V, assuming an exponential dilution rate

DOE-HDBK-1129-99

100

Q(t)=Q(i) e-t/(F/V)

Note that the quantity of tritium remaining in the

confinement volume decreases by a factor of 10

for each 2.3 time constants, i.e. when t=2.3 x F/V

0.00 0.30 0.60 0.90 1.20 1.50 1.80 2.10 2.40 2.70 3.00 3.30 3.60 3.90 4.20 4.50 4.80 5.10 5.40 5.70 6.00

t/(V/F) = Number of System Time Constants (F/V)

FIGURE 4-6. Confinement volume cleanup rate as a function of system time constant,

F/V, assuming an exponential dilution rate

The fourth consideration is the system leak rate. While the tritium removal system is in operation,

some of the gases will leak out of the system to the environment. The barrier must be leak tight

enough to prevent a significant release of tritium to the environment while the tritium is being

removed. A high flow rate tritium removal system can be used to help offset a leaky system, but

will significantly increase the cost of the removal system.

The quantity of tritium released to the environment due to the leak rate can be calculated.

Assuming exponential dilution, the concentration of tritium in the gas C T2(t) is

CT2(t) = CT2(i)e -t/(F/V)

where CT2(i) =

initial concentration of tritium in the system

t =

time

V =

volume of the system

F =

flow rate of the tritium removal system

Note, CT2(i) = QT2/V where QT2 is the quantity of tritium released.